Features
Dual, Fast, Analog Loops with Digital Interface
for
Control and Monitoring
nn Wide Input Voltage Range: 4.5V to 17V
nn Output Voltage Range: 0.5V to 5.5V
nn ±0.5% Maximum DC Output Error Over Temperature
nn ±2.5% Current Readback Accuracy at 10A Load
nn 400kHz PMBus-Compliant I2C Serial Interface
nn Integrated 16-Bit ∆Σ ADC
nn Supports Telemetry Polling Rates Up to 125Hz
nn Constant Frequency Current Mode Control
nn Parallel and Current Share Multiple Modules
nn All 7-Bit Slave Addresses Supported
nn Rail and Global Addressing Supported
nn 16mm × 16mm × 5.01mm BGA Package
Readable Data:
LTM4676A
Dual 13A or Single 26A
µModule Regulator with Digital
Power System Management
Description
The LTM®4676A is a dual 13A or single 26A step-down
µModule® (micromodule) DC/DC regulator with 70ms
turn-on time. It features remote configurability and
telemetry-monitoring of power management parameters
over PMBus— an open standard I2C-based digital interface
protocol . The LTM4676A is comprised of fast analog
control loops, precision mixed-signal circuitry, EEPROM,
power MOSFETs, inductors and supporting components.
nn
The LTM4676A’s 2-wire serial interface allows outputs to
be margined, tuned and ramped up and down at programmable slew rates with sequencing delay times. Input and
output currents and voltages, output power, temperatures,
uptime and peak values are readable. At start-up, output
voltages, switching frequency, and channel phase angle
assignments can be set by pin-strapping resistors. The
LTpowerPlay™ GUI and DC1613 USB-to-PMBus converter
and demo kits are available.
Input and Output Voltages, Currents, and Temperatures
Running Peak Values, Uptime, Faults and Warnings
nn Onboard EEPROM Fault Log Record
Writable Data and Configurable Parameters:
nn
nn
PART
NUMBER
PINVOUT RANGE (V)
COMPATIBLE
0.5V to 4 (CH0)
LTM4676
170
4.5 to 26.5
0.5 to 5.4 (CH1)
Yes
70
4.5 to 17 0.5 to 5.5 (Both CH)
LTM4676A
See Table 1 and page 22 for more on LTM4676A’s enhancements over
LTM4676's feature set.
Output Voltage, Voltage Sequencing and Margining
Digital Soft-Start/Stop Ramp
nn OV/UV/OT, UVLO, Frequency and Phasing
nn
nn
System Optimization, Characterization and Data Mining in Prototype, Production and Field Environments
Click to view associated Video Design Idea.
Typical Application
Using PMBus and LTpowerPlay to Monitor Telemetry and Margin
VOUT0/VOUT1 During Load Pattern Tests. 10Hz Polling Rate. 12VIN
Dual 13A µModule Regulator with Digital
Interface for Control and Monitoring*
WP
VOUT1
LOAD1
GND
SGND
SCL
SDA
ALERT
4676A TA01a
*FOR COMPLETE CIRCUIT, SEE FIGURE 62
VOUT1,
ADJUSTABLE
UP TO 13A
VOSNS1
SYNC
SHARE_CLK
100µF
×7
I2C/SMBus I/F WITH
PMBus COMMAND SET
TO/FROM IPMI OR OTHER
BOARD MANAGEMENT
CONTROLLER
0.9
1.7
0.8
0
3
6
TIME (SEC)
9
10
5
5
0
3
6
TIME (SEC)
1.6
0.5
0.8
0
3
4676A TA01b
10
0
1.0
0
1.6
12
Output Current Readback, Varying Load Pattern
15
15
9
0
12
4676A TA01c
2.4
IIN0 (A)
VOUT0 (V)
100µF
×7
CHANNEL 0 TEMP (°C)
REGISTER WRITE
PROTECTION
GPIO0
GPIO1
LOAD0
1.8
IOUT1 (A)
PWM CLOCK AND
TIME-BASE
SYNCHRONIZATION
VOSNS0
LTM4676A
–
1.0
Input Current Readback
60
6
TIME (SEC)
9
0
12
4676A TA01d
Power Stage Temperature Readback
60
57
57
54
54
51
0
3
6
TIME (SEC)
9
51
12
CHANNEL 1 TEMP (°C)
FAULT INTERRUPTS,
POWER SEQUENCING
RUN0
RUN1
VOUT0
VOSNS0+
IOUT0 (A)
ON/OFF CONTROL
VIN0
VIN1
SVIN
1.5
IIN1 (A)
22µF
×3
Output Voltage Readback, VOUT Margined 7.5% Low
1.1
1.9
VOUT0,
ADJUSTABLE
UP TO 13A
VOUT1 (V)
VIN
5.75V TO 17V
VIN RANGE
(V)
L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule and PolyPhase are registered
trademarks and LTpowerPlay is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258, 7420359, 8163643.
Licensed under U.S. Patent 7000125 and other related patents worldwide.
Applications
nn
TURN-ON
START-UP TIME
(MAX) (ms)
4676A TA01e
4676af
For more information www.linear.com/LTM4676A
1
LTM4676A
Table of Contents
Features............................................................ 1
Applications....................................................... 1
Typical Application ............................................... 1
Description........................................................ 1
Absolute Maximum Ratings..................................... 3
Order Information................................................. 3
Pin Configuration................................................. 3
Electrical Characteristics........................................ 4
Typical Performance Characteristics......................... 11
Pin Functions..................................................... 13
Simplified Block Diagram...................................... 18
Decoupling Requirements...................................... 18
Functional Diagram............................................. 19
Test Circuits...................................................... 20
Operation......................................................... 22
Power Module Introduction.............................................22
Power Module Configurability and
Readback Data................................................................ 24
Time-Averaged and Peak Readback Data........................ 26
Power Module Overview.................................................30
EEPROM..........................................................................33
Serial Interface................................................................34
Device Addressing..........................................................35
Fault Detection and Handling..........................................35
Responses to VOUT and IOUT Faults................................36
Responses to Timing Faults............................................ 37
Responses to SVIN OV Faults.......................................... 37
Responses to OT/UT Faults............................................. 37
Responses to External Faults .........................................38
Fault Logging..................................................................38
Bus Timeout Protection..................................................38
PMBus Command Summary................................... 39
PMBus Commands ........................................................ 39
VIN to VOUT Step-Down Ratios........................................50
Input Capacitors..............................................................50
Output Capacitors...........................................................50
Light Load Current Operation..........................................50
Switching Frequency and Phase..................................... 51
Minimum On-Time Considerations..................................53
Variable Delay Time, Soft-Start and Output Voltage
Ramping..........................................................................53
Digital Servo Mode.........................................................54
Soft Off (Sequenced Off)................................................55
Undervoltage Lockout.....................................................55
2
Fault Detection and Handling..........................................56
Open-Drain Pins..............................................................56
Phase-Locked Loop and Frequency Synchronization..... 57
RCONFIG Pin-Straps (External Resistor
Configuration Pins).........................................................58
Voltage Selection............................................................58
Connecting the USB to the I2C/SMBus/PMBus Controller
to the LTM4676A In System...........................................58
LTpowerPlay: An Interactive GUI for Digital Power System
Management................................................................... 62
PMBus Communication and Command Processing........63
Thermal Considerations and
Output Current Derating..................................................64
EMI Performance............................................................ 71
Safety Considerations..................................................... 72
Layout Checklist/Example............................................... 72
Typical Applications............................................. 73
Appendix A........................................................ 79
Similarity Between PMBus, SMBus and I2C
2-Wire Interface.............................................................. 79
Appendix B........................................................ 80
PMBus Serial Digital Interface........................................80
Appendix C: PMBus Command Details....................... 84
Addressing and Write Protect.........................................84
General Configuration Registers.....................................86
On/Off/Margin................................................................. 87
PWM Config.................................................................... 89
Voltage............................................................................ 91
Current............................................................................94
Temperature.................................................................... 97
Timing.............................................................................99
Fault Response.............................................................. 101
Fault Sharing................................................................. 108
Scratchpad.................................................................... 110
Identification................................................................. 110
Fault Warning and Status...............................................111
Telemetry...................................................................... 118
NVM (EEPROM) Memory Commands........................... 121
Package Description.......................................... 127
Package Photograph.......................................... 128
Package Description.......................................... 129
Typical Application............................................ 130
Design Resources............................................. 130
Related Parts................................................... 130
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Absolute Maximum Ratings
Pin Configuration
(Note 1)
Terminal Voltages:
VINn (Note 4), SVIN...................................... –0.3V to 20V
VOUTn............................................................ –0.3V to 6V
VOSNS0+, VORB0+, VOSNS1, VORB1, INTVCC..... –0.3V to 6V
RUNn, SDA, SCL, ALERT............................ –0.3V to 5.5V
FSWPHCFG, VOUTnCFG, V TRIMnCFG, ASEL... –0.3V to 2.75V
VDD33, GPIOn, SYNC, SHARE_CLK, WP,
COMPna, VOSNS0 –, VORB0 –......................... –0.3V to 3.6V
SGND......................................................... –0.3V to 0.3V
Temperatures
Internal Operating Temperature Range
(Notes 2, 3)............................................. –40°C to 125°C
Storage Temperature Range................... –55°C to 125°C
Peak Package Body Temperature During Reflow... 245°C
1
2
3
4
5
TOP VIEW
6
7
8
9
10
11
12
A
B
C
GND
VOUT0
VIN0
GND
D
E
F
GND
G
GND
H
J
K
L
VOUT1
GND
VIN1
GND
M
BGA PACKAGE
144-LEAD (16mm × 16mm × 5.01mm)
TJMAX = 125°C, θJCtop = 8.8°C/W, θJCbottom = 0.8°C/W, θJB = 1.3°C/W, θJA = 10.3°C/W
θ VALUES DETERMINED PER JESD51-12
WEIGHT = 3.3 GRAMS
Order Information
PART NUMBER
PAD OR BALL FINISH
PART MARKING*
DEVICE
FINISH CODE
PACKAGE
TYPE
MSL
RATING
TEMPERATURE RANGE
(See Note 2)
LTM4676AEY#PBF
SAC305 (RoHS)
LTM4676AY
e1
BGA
4
–40°C to 125°C
LTM4676AIY#PBF
SAC305 (RoHS)
LTM4676AY
e1
BGA
4
–40°C to 125°C
LTM4676AIY
SnPb (63/37)
LTM4676AY
e0
BGA
4
–40°C to 125°C
Consult Marketing for parts specified with wider operating temperature
ranges. *Device temperature grade is indicated by a label on the shipping
container. Pad or ball finish code is per IPC/JEDEC J-STD-609.
• Recommended LGA and BGA PCB Assembly and Manufacturing
Procedures:
www.linear.com/umodule/pcbassembly
• Terminal Finish Part Marking:
www.linear.com/leadfree
• LGA and BGA Package and Tray Drawings:
www.linear.com/packaging
4676af
For more information www.linear.com/LTM4676A
3
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VIN
Input DC Voltage
Test Circuit 1
Test Circuit 2; VIN_OFF < VIN_ON = 4.25V
VOUTn
Range of Output Voltage
Regulation
VOUT0 Differentially Sensed on VOSNS0+/VOSNS0– Pin-Pair;
VOUT1 Differentially Sensed on VOSNS1/SGND Pin-Pair;
Commanded by Serial Bus or with Resistors Present at Start-Up on
VOUTnCFG and/or VTRIMnCFG
VOUTn(DC)
Output Voltage, Total
Variation with Line and
Load
(Note 5)
VOUTn Low Range (MFR_PWM_MODEn [1]=1b),
FREQUENCY_SWITCH = 250kHz
Digital Servo Engaged (MFR_PWM_MODEn[6] = 1b)
Digital Servo Disengaged (MFR_PWM_MODEn[6] = 0b)
MAX
UNITS
l
l
5.75
4.5
MIN
TYP
17
5.75
V
V
l
l
0.5
0.5
5.5
5.5
V
V
l
0.995
0.985
1.005
1.015
V
V
1.000
1.000
Input Specifications
IINRUSH(VIN)
Input Inrush Current at
Start-Up
IQ(SVIN)
Input Supply Bias Current Forced Continuous Mode, MFR_PWM_MODEn [0] = 1b
RUNn = 5V, RUN1-n = 0V
Shutdown, RUN0 = RUN1 = 0V
IS(VINn,PSM)
Input Supply Current in
Pulse-Skipping Mode
Operation
IS(VINn,FCM)
Input Supply Current in
Forced Continuous Mode, MFR_PWM_MODEn[0] = 1b
Forced-Continuous Mode IOUTn = 100mA
Operation
IOUTn = 13A
IS(VINn,SHUTDOWN) Input Supply Current in
Shutdown
Test Circuit 1, VOUTn =1V, VIN = 12V; No Load Besides Capacitors;
TON_RISEn = 3ms
Pulse-Skipping Mode, MFR_PWM_MODEn[0] = 0b,
IOUTn = 100mA
Shutdown, RUNn = 0V
400
mA
40
20
mA
mA
20
mA
40
1.37
mA
A
50
µA
Output Specifications
IOUTn
Output Continuous
Current Range
∆VOUTn(LINE)
Line Regulation Accuracy Digital Servo Engaged (MFR_PWM_MODEn[6] = 1b)
l
Digital Servo Disengaged (MFR_PWM_MODEn[6] = 0b)
SVIN and VINn Electrically Shorted Together and INTVCC Open Circuit;
IOUTn = 0A, 5.75V ≤ VIN ≤ 17V, VOUT Low Range
(MFR_PWM_MODEn[1] = 1b) FREQUENCY_SWITCH = 250kHz
(Referenced to 12VIN) (Note 5)
0.03
0.03
±0.2
%
%/V
Load Regulation
Accuracy
0.03
0.2
0.5
%
%
VOUTn
∆VOUTn(LOAD)
VOUTn
(Note 6)
Digital Servo Engaged (MFR_PWM_MODEn[6] = 1b)
Digital Servo Disengaged (MFR_PWM_MODEn[6] = 0b)
0A ≤ IOUTn ≤ 13A, VOUT Low Range, (MFR_PWM_MODEn[1] = 1b)
FREQUENCY_SWITCH = 250kHz (Note 5)
VOUTn(AC)
Output Voltage Ripple
fS (Each Channel)
VOUTn Ripple Frequency
FREQUENCY_SWITCH Set to 500kHz (0xFBE8)
∆VOUTn(START)
Turn-On Overshoot
TON_RISEn = 3ms (Note 12)
tSTART
Turn-On Start-Up Time
Time from VIN Toggling from 0V to 12V to Rising Edge of GPIOn.
TON_DELAYn = 0ms, TON_RISEn = 3ms,
MFR_GPIO_PROPAGATEn = 0x0100,
MFR_GPIO_RESPONSEn = 0x0000
4
0
l
13
10
l
462.5
500
mVP-P
537.5
8
l
60
A
kHz
mV
70
ms
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tDELAY(0ms)
Turn-On Delay Time
Time from First Rising Edge of RUNn to Rising Edge of GPIOn.
TON_DELAYn = 0ms, TON_RISEn = 3ms,
MFR_GPIO_PROPAGATEn = 0x0100,
MFR_GPIO_RESPONSEn = 0x0000.
VIN Having Been Established for at Least 70ms
∆VOUTn(LS)
Peak Output Voltage
Deviation for Dynamic
Load Step
Load: 0A to 6.5A and 6.5A to 0A at 6.5A/µs, Figure 62 Circuit,
VOUTn = 1V, VIN = 12V (Note 12)
50
mV
tSETTLE
Settling Time for
Dynamic Load Step
Load: 0A to 6.5A and 6.5A to 0A at 6.5A/µs, Figure 62 Circuit,
VOUTn = 1V, VIN = 12V (Note 12)
35
µs
IOUTn(OCL_PK)
Output Current Limit,
Peak
Cycle-by-Cycle Inductor Peak Current Limit Inception
22.5
A
IOUTn(OCL_AVG)
Output Current Limit,
Time Averaged
Time-Averaged Output Inductor Current Limit Inception Threshold,
Commanded by IOUT_OC_FAULT_LIMITn (Note 12)
l
MIN
TYP
MAX
2.75
3.1
3.5
UNITS
ms
15.6A; See IO-RB-ACC
Specification (Output Current
Readback Accuracy)
Control Section
VFBCM0
VFBCM1
Channel 0 Feedback Input VOSNS0– Valid Input Range (Referred to SGND)
Common Mode Range
VOSNS0+ Valid Input Range (Referred to SGND)
Channel 1 Feedback Input SGND Valid Input Range (Referred to GND)
Common Mode Range
VOSNS1 Valid Input Range (Referred to SGND)
l
l
–0.1
0.3
5.7
V
V
l
l
–0.3
0.3
5.7
V
V
Full-Scale Command
Voltage, Range 0
(Notes 7, 15)
VOUTn Commanded to 5.500V, MFR_PWM_MODEn [1] = 0b
Resolution
LSB Step Size
Full-Scale Command
Voltage, Range 1
(Notes 7, 15)
VOUTn Commanded to 2.750V, MFR_PWM_MODEn [1] = 1b
Resolution
LSB Step Size
RVSENSE0+
VOSNS0+ Impedance to
SGND
0.05V ≤ VVOSNS0+ – VSGND ≤ 5.5V
41
kΩ
RVSENSE1
VOSNS1 Impedance to
SGND
0.05V ≤ VVOSNS1 – VSGND ≤ 5.5V
37
kΩ
tON(MIN)
Minimum On-Time
(Note 8 )
90
ns
VOUT-RNG0
VOUT-RNG1
5.422
2.711
12
1.375
12
0.6875
5.576
V
Bits
mV
2.788
V
Bits
mV
Analog OV/UV (Overvoltage/Undervoltage) Output Voltage Supervisor Comparators (VOUT_OV/UV_FAULT_LIMIT and VOUT_OV/UV_WARN_LIMIT Monitors)
NOV/UV_COMP
Resolution, Output
Voltage Supervisors
(Note 15)
VOV-RNG
Output OV Comparator
Threshold Detection
Range
(Note 15)
High Range Scale, MFR_PWM_MODEn [1] = 0b
Low Range Scale, MFR_PWM_MODEn [1] = 1b
VOU-STP
Output OV and UV
Comparator Threshold
Programming LSB Step
Size
(Note 15)
High Range Scale, MFR_PWM_MODEn [1] = 0b
Low Range Scale, MFR_PWM_MODEn [1] = 1b
8
1
0.5
Bits
5.6
2.7
22
11
V
V
mV
mV
4676af
For more information www.linear.com/LTM4676A
5
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VOV-ACC
Output OV Comparator
Threshold Accuracy
(See Note 14)
2V ≤ VVOSNS0+ – VVOSNS0– ≤ 5.6V, MFR_PWM_MODE0[1] = 0b
1V ≤ VVOSNS0+ – VVOSNS0– ≤ 2.7V, MFR_PWM_MODE0[1] = 1b
0.5V ≤ VVOSNS0+ – VVOSNS0– < 1V, MFR_PWM_MODE0[1] = 1b
2V ≤ VVSENSE1 – VSGND ≤ 5.6V, MFR_PWM_MODE1[1] = 0b
1.5V ≤ VVSENSE1 – VSGND ≤ 2.7V, MFR_PWM_MODE1[1] = 1b
0.5V ≤ VVSENSE1 – VSGND < 1.5V, MFR_PWM_MODE1[1] = 1b
VUV-RNG
Output UV Comparator
Threshold Detection
Range
(Note 15)
High Range Scale, MFR_PWM_MODEn[1] = 0b
Low Range Scale, MFR_PWM_MODEn[1] = 1b
VUV-ACC
Output UV Comparator
Threshold Accuracy
(See Note 14)
2V ≤ VVSENSE0+ – VVSENSE0– ≤ 5.4V, MFR_PWM_MODE0[1] = 0b
1V ≤ VVSENSE0+ – VVSENSE0– ≤ 2.7V, MFR_PWM_MODE0[1] = 1b
0.5V ≤ VVSENSE0+ – VVSENSE0– < 1V, MFR_PWM_MODE0[1] = 1b
2V ≤ VVOSNS1 – VSGND ≤ 5.4V, MFR_PWM_MODE1[1] = 0b
1.5V ≤ VVOSNS1 – VSGND ≤ 2.7V, MFR_PWM_MODE1[1] = 1b
0.5V ≤ VVOSNS1 – VSGND < 1.5V, MFR_PWM_MODE1[1] = 1b
tPROP-OV
Output OV Comparator
Response Times
tPROP-UV
Output UV Comparator
Response Times
MIN
TYP
MAX
UNITS
±2
±2
±20
±2
±2
±30
%
%
mV
%
%
mV
5.4
2.7
V
V
±2
±2
±20
±2
±2
±30
%
%
mV
%
%
mV
Overdrive to 10% Above Programmed Threshold
35
µs
Underdrive to 10% Below Programmed Threshold
50
µs
l
l
l
l
l
l
1
0.5
l
l
l
l
l
l
Analog OV/UV SVIN Input Voltage Supervisor Comparators (Threshold Detectors for VIN_ON and VIN_OFF)
NSVIN-OV/UV-COMP
SVIN OV/UV Comparator
Threshold-Programming
Resolution
(Note 15)
SVIN-OU-RANGE
SVIN OV/UV Comparator
Threshold-Programming
Range
SVIN-OU-STP
SVIN OV/UV Comparator
Threshold-Programming
LSB Step Size
(Note 15)
SVIN-OU-ACC
SVIN OV/UV Comparator
Threshold Accuracy
9V < SVIN ≤ 20V
4.5V ≤ SVIN ≤ 9V
8
l
4.5
Bits
20
V
82
mV
l
l
±2.5
±225
%
mV
tPROP-SVIN-HIGH-VIN SVIN OV/UV Comparator Test Circuit 1, and:
Response Time, High VIN
VIN_ON = 9V; SVIN Driven from 8.775V to 9.225V
Operating Configuration
VIN_OFF = 9V; SVIN Driven from 9.225V to 8.775V
l
l
35
35
µs
µs
tPROP-SVIN-LOW-VIN SVIN OV/UV Comparator
Response Time, Low VIN
Operating Configuration
l
l
35
35
µs
µs
Test Circuit 2, and:
VIN_ON = 4.5V; SVIN Driven from 4.225V to 4.725V
VIN_OFF = 4.5V; SVIN Driven from 4.725V to 4.225V
Channels 0 and 1 Output Voltage Readback (READ_VOUTn)
NVO-RB
Output Voltage Readback (Note 15)
Resolution and LSB Step
Size
VO-F/S
Output Voltage Full-Scale VRUNn = 0V (Notes 7, 15)
Digitizable Range
VO-RB-ACC
Output Voltage Readback Channel 0: 1V ≤ VVOSNS0+ – VVOSNS0– ≤ 5.5V
Accuracy
Channel 0: 0.6V ≤ VVOSNS0+ – VVOSNS0– < 1V
Channel 1: 1V ≤ VVOSNS1 – VSGND ≤ 5.5V
Channel 1: 0.6V ≤ VVOSNS1 – VSGND < 1V
6
16
244
Bits
µV
8
l
l
l
l
V
Within ±0.5% of Reading
Within ±5mV of Reading
Within ±0.5% of Reading
Within ±5mV of Reading
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tCONVERT-VO-RB
Output Voltage Readback MFR_ADC_CONTROL=0x00 (Notes 9, 15)
Update Rate
MFR_ADC_CONTROL=0x0D (Notes 9, 15)
MFR_ADC_CONTROL=0x05 or 0x09 (Notes 9, 15)
MIN
TYP
MAX
UNITS
100
27
8
ms
ms
ms
Input Voltage (SVIN) Readback (READ_VIN)
NSVIN-RB
Input Voltage Readback
Resolution and LSB Step
Size
(Notes 10, 15)
10
15.625
Bits
mV
SVIN-F/S
Input Voltage Full-Scale
Digitizable Range
(Notes 11, 15)
38.91
V
SVIN-RB-ACC
Input Voltage Readback
Accuracy
READ_VIN, 4.5V ≤ SVIN ≤ 17V
tCONVERT-SVIN-RB
Input Voltage Readback
Update Rate
MFR_ADC_CONTROL=0x00 (Notes 9, 15)
MFR_ADC_CONTROL=0x01 (Notes 9, 15)
l
Within ±2% of Reading
100
8
ms
ms
Channels 0 and 1 Output Current (READ_IOUTn), Duty Cycle (READ_DUTY_CYCLEn), and Computed Input Current (MFR_READ_IINn) Readback
NIO-RB
Output Current Readback (Notes 10, 12)
Resolution and LSB Step
Size
10
15.6
Bits
mA
IO-F/S, II-F/S
Output Current Full-Scale (Note 12)
Digitizable Range and
Input Current Range of
Calculation
±40
A
IO-RB-ACC
Output Current, Readback READ_IOUTn, Channels 0 and 1, 0 ≤ IOUTn ≤ 10A,
Accuracy
Forced-Continuous Mode, MFR_PWM_MODEn[1:0] = 10b
IO-RB(13A)
Full Load Output Current
Readback
NII-RB
Computed Input Current, (Notes 10, 12)
Readback Resolution and
LSB Step Size
II-RB-ACC
Computed Input Current,
Readback Accuracy,
Neglecting ISVIN
tCONVERT-IO-RB
Output Current Readback MFR_ADC_CONTROL=0x00 (Notes 9, 15)
Update Rate
MFR_ADC_CONTROL=0x0D (Notes 9, 15)
MFR_ADC_CONTROL=0x06 or 0x0A (Notes 9, 15)
100
27
8
ms
ms
ms
tCONVERT-II-RB
Computed Input Current,
Readback Update Rate
MFR_ADC_CONTROL=0x00 (Notes 9, 15)
100
ms
NDUTY-RB
Resolution, Duty Cycle
Readback
(Notes 10, 15)
10
Bits
DRB-ACC
Duty Cycle TUE
READ_DUTY_CYCLEn, 16.3% Duty Cycle (Note 15)
tCONVERT-DUTY-RB
Duty Cycle Readback
Update Rate
MFR_ADC_CONTROL=0x00 (Notes 9, 15)
l
IOUTn = 13A (Note 12). See Histograms in Typical Performance
Characteristics
MFR_READ_IINn, Channels 0 and 1, 0 ≤ IOUTn ≤ 10A,
Forced-Continuous Mode, MFR_PWM_MODEn[1:0] = 10b,
MFR_IIN_OFFSETn = 0mA
l
Within 250mA of Reading
13.1
A
10
1.95
Bits
mA
Within 150mA of Reading
±3
%
100
ms
Temperature Readback for Channel 0, Channel 1, and Controller (Respectively: READ_TEMPERATURE_10, READ_TEMPERATURE_11,
and READ_TEMPERATURE_2)
TRES-RB
Temperature Readback
Resolution
Channel 0, Channel 1, and Controller (Note 15)
TRB-CH-ACC(72mV)
Channel Temperature
Channels 0 and 1, PWM Inactive, RUNn = 0V,
TUE, Switching Action Off ∆VTSNSna = 72mV
0.0625
l
°C
Within ±3°C of Reading
4676af
For more information www.linear.com/LTM4676A
7
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
TRB-CH-ACC(ON)
Channel Temperature
READ_TEMPERATURE_1n, Channels 0 and 1,
TUE, Switching Action On PWM Active, RUNn = 5V (Note 12)
Within ±3°C of Reading
TRB-CTRL-ACC(ON)
Control IC Die
Temperature TUE,
Switching Action On
READ_TEMPERATURE_2, PWM Active, RUN0 = RUN1 = 5V
(Note 12)
Within ±1°C of Reading
tCONVERT-TEMP-RB
Temperature Readback
Update Rate
MFR_ADC_CONTROL=0x00 (Notes 9, 15)
MFR_ADC_CONTROL=0x06 or 0x0A (Notes 9, 15)
VINTVCC
Internal VCC Voltage No
Load
6V ≤ VIN ≤ 17V
∆VINTVCC(LOAD)
INTVCC Load Regulation
0mA ≤ IINTVCC ≤ 50mA
100
8
UNITS
ms
ms
INTVCC Regulator
4.8
5
5.2
V
0.5
±2
%
3.3
3.4
V
VINTVCC
VDD33 Regulator
VVDD33
Internal VDD33 Voltage
3.2
ILIM(VDD33)
VDD33 Current Limit
VDD33 Electrically Short-Circuited to GND
70
mA
VVDD33_OV
VDD33 Overvoltage
Threshold
(Note 15)
3.5
V
VVDD33_UV
VDD33 Undervoltage
Threshold
(Note 15)
3.1
V
2.5
V
50
mA
VDD25 Regulator
VVDD25
Internal VDD25 Voltage
ILIM(VDD25)
VDD25 Current Limit
VDD25 Electrically Short-Circuited to GND
Oscillator and Phase-Locked Loop (PLL)
fOSC
Oscillator Frequency
Accuracy
fSYNC
PLL SYNC Capture Range FREQUENCY_SWITCH Set to Frequency Slave Mode (0x0000);
MFR_CONFIG_ALL[4]=1b; SYNC Driven by External Clock; 3.3VOUT
VTH,SYNC
SYNC Input Threshold
VSYNC Rising (Note 15)
VSYNC Falling (Note 15)
VOL,SYNC
SYNC Low Output
Voltage
ISYNC = 3mA
ISYNC
SYNC Leakage Current in 0V ≤ VSYNC ≤ 3.6V
Frequency Slave Mode
MFR_CONFIG_ALL[4]=1b
θSYNC-θ0
SYNC-to-Channel 0
Phase Relationship, Lag
from Falling Edge of Sync
to Rising Edge of Top
MOSFET (MT0) Gate
(Note 15)
MFR_PWM_CONFIG[2:0] = 000b, 01Xb
MFR_PWM_CONFIG[2:0] = 101b
MFR_PWM_CONFIG[2:0] = 001b
MFR_PWM_CONFIG[2:0] = 1X0b
0
60
90
120
Deg
Deg
Deg
Deg
θSYNC-θ1
SYNC-to-Channel 1
Phase Relationship, Lag
from Falling Edge of Sync
to Rising Edge of Top
MOSFET (MT1) Gate
(Note 15)
MFR_PWM_CONFIG[2:0] = 011b
MFR_PWM_CONFIG[2:0] = 000b
MFR_PWM_CONFIG[2:0] = 010b, 10Xb
MFR_PWM_CONFIG[2:0] = 001b
MFR_PWM_CONFIG[2:0] = 110b
120
180
240
270
300
Deg
Deg
Deg
Deg
Deg
8
FREQUENCY_SWITCH = 500kHz (0xFBE8)
250kHz ≤ FREQUENCY_SWITCH ≤ 1MHz (Note 15)
l
l
225
±7.5
±7.5
%
%
1100
kHz
1.5
1
l
0.3
l
V
V
0.4
V
±5
µA
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Electrical Characteristics
The l denotes the specifications which apply over the specified internal
operating temperature range (Note 2). Specified as each individual output channel (Note 4). TA = 25°C, VIN = 12V, RUNn = 5V,
FREQUENCY_SWITCH = 500kHz and VOUTn commanded to 1.000V unless otherwise noted. Configured with factory-default EEPROM
settings and per Test Circuit 1, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
EEPROM Characteristics
Endurance
(Note 13)
0°C ≤ TJ ≤ 85°C During EEPROM Write Operations (Note 3)
l 10,000
Retention
(Note 13)
TJ < TJ(MAX), with Most Recent EEPROM Write Operation Having
Occurred at 0°C ≤ TJ ≤ 85°C (Note 3)
l
Mass_Write
Mass Write Operation
Time
Execution of STORE_USER_ALL Command, 0°C ≤ TJ ≤ 85°C
(ATE-Tested at TJ = 25°C) (Notes 3, 13)
VIH
Input High Threshold
Voltage
SCL, SDA, RUNn, GPIOn (Note 15)
SHARE_CLK, WP (Note 15)
VIL
Input Low Threshold
Voltage
SCL, SDA, RUNn, GPIOn (Note 15)
SHARE_CLK, WP (Note 15)
VHYST
Input Hysteresis
SCL, SDA (Note 15)
VOL
Output Low Voltage
SCL, SDA, ALERT, RUNn, GPIOn, SHARE_CLK:
ISINK = 3mA
Cycles
10
Years
440
4100
ms
Digital I/Os
IOL
Input Leakage Current
SDA, SCL, ALERT, RUNn: 0V ≤ VPIN ≤ 5.5V
GPIOn and SHARE_CLK: 0V ≤ VPIN ≤ 3.6V
tFILTER
Input Digital Filtering
RUNn (Note 15)
GPIOn (Note 15)
CPIN
Input Capacitance
SCL, SDA, RUNn, GPIOn, SHARE_CLK, WP (Note 15)
2.0
1.8
V
V
1.4
0.6
80
0.3
l
l
l
V
V
mV
0.4
V
±5
±2
µA
µA
10
3
µs
µs
10
pF
400
kHz
PMBus Interface Timing Characteristics
fSMB
Serial Bus Operating
Frequency
(Note 15)
10
tBUF
Bus Free Time Between
Stop and Start
(Note 15)
1.3
μs
tHD,STA
Hold Time After Repeated Time Period After Which First Clock Is Generated (Note 15)
Start Condition
0.6
µs
tSU,STA
Repeated Start Condition
Setup Time
(Note 15)
0.6
μs
tSU,STO
Stop Condition Setup
Time
(Note 15)
0.6
μs
tHD,DAT
Data Hold Time
Receiving Data (Note 15)
Transmitting Data (Note 15)
0
0.3
tSU,DAT
Data Setup Time
Receiving Data (Note 15)
0.1
tTIMEOUT_SMB
Stuck PMBus Timer
Timeout
Measured from the Last PMBus Start Event:
Block Reads, MFR_CONFIG_ALL[3]=0b (Note 15)
Non-Block Reads, MFR_CONFIG_ALL[3]=0b (Note 15)
MFR_CONFIG_ALL[3]=1b (Note 15)
tLOW
Serial Clock Low Period
(Note 15)
1.3
tHIGH
Serial Clock High Period
(Note 15)
0.6
0.9
µs
µs
μs
150
32
250
ms
ms
ms
10000
μs
μs
4676af
For more information www.linear.com/LTM4676A
9
LTM4676A
Electrical Characteristics
Note 1: Stresses beyond those listing under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating conditions for extended periods may affect device
reliability and lifetime.
Note 2: The LTM4676A is tested under pulsed-load conditions such that
TJ ≈ TA. The LTM4676AE is guaranteed to meet performance specifications
over the 0°C to 125°C internal operating temperature range. Specifications
over the –40°C to 125°C internal operating temperature range are assured
by design, characterization and correlation with statistical process
controls. The LTM4676AI is guaranteed to meet specifications over the
full –40°C to 125°C internal operating temperature range. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
Note 3: The LTM4676A’s EEPROM temperature range for valid write
commands is 0°C to 85°C. To achieve guaranteed EEPROM data retention,
execution of the “STORE_USER_ALL” command—i.e., uploading RAM
contents to NVM—outside this temperature range is not recommended.
However, as long as the LTM4676A’s EEPROM temperature is less than
130°C, the LTM4676A will obey the STORE_USER_ALL command. Only
when EEPROM temperature exceeds 130°C, the LTM4676A will not act
on any STORE_USER_ALL transactions: instead, the LTM4676A NACKs
the serial command and asserts its relevant CML (communications,
memory, logic) fault bits. EEPROM temperature can be queried prior
to commanding STORE_USER_ALL; see the Applications Information
section.
Note 4: The two power inputs—VIN0 and VIN1—and their respective power
outputs—VOUT0 and VOUT1—are tested independently in production. A
shorthand notation is used in this document that allows these parameters
to be refered to by “VINn” and “VOUTn”, where n is permitted to take on a
value of 0 or 1. This italicized, subscripted “n ” notation and convention
is extended to encompass all such pin names, as well as register names
with channel-specific, i.e., paged data. For example, VOUT_COMMANDn
refers to the VOUT_COMMAND command code data located in Pages 0
and 1, which in turn relate to Channels 0 (VOUT0) and Channel 1 (VOUT1).
Registers containing non-page-specific data, i.e., whose data is “global” to
the module or applies to both of the module's Channels lack the italicized,
subscripted “n ”, e.g., FREQUENCY_SWITCH.
Note 5: VOUTn (DC) and line and load regulation tests are performed in
production with digital servo disengaged (MFR_PWM_MODEn[6] = 0b)
and low VOUTn range selected (MFR_PWM_MODEn [1]) = 1b. The digital
servo control loop is exercised in production (setting MFR_PWM_
MODEn[6] = 1b), but convergence of the output voltage to its final settling
value is not necessarily observed in final test—due to potentially long
time constants involved—and is instead guaranteed by the output voltage
readback accuracy specification. Evaluation in application demonstrates
capability; see the Typical Performance Characteristics section.
10
Note 6: See output current derating curves for different VIN, VOUT, and TA,
located in the Applications Information section.
Note 7: Even though VOUT0 and VOUT1 are specified for 6V absolute
maximum, the maximum recommended regulation-command voltage is:
5.5V for a high-VOUT range setting of MFR_PWM_MODEn [1]=0b; 2.5V for
a low-VOUT range setting of MFR_PWM_MODEn [1]=1b.
Note 8: Minimum on-time is tested at wafer sort.
Note 9: Data conversion is performed in round-robin (cyclic) fashion.
All telemetry signals are continuously digitized, and reported data is
based on measurements not older than 100ms, typical. Some telemetry
parameters can be digitized at a faster update rate by configuring MFR_
ADC_CONTROL.
Note 10: The following telemetry parameters are formatted in PMBusdefined “Linear Data Format”, in which each register contains a word
comprised of 5 most significant bits—representing a signed exponent, to
be raised to the power of 2—and 11 least significant bits—representing
a signed mantissa: input voltage (on SVIN), accessed via the READ_VIN
command code; output currents (IOUTn), accessed via the READ_IOUTn
command codes; module input current (IVIN0 + IVIN1 + ISVIN), accessed via
the READ_IIN command code; channel input currents (IVINn + 1/2 • ISVIN),
accessed via the MFR_READ_IINn command codes;and duty cycles of
channel 0 and channel 1 switching power stages, accessed via the
READ_DUTY_CYCLEn command codes. This data format limits the
resolution of telemetry readback data to 10 bits even though the internal
ADC is 16 bits and the LTM4676A’s internal calculations use 32-bit words.
Note 11: The absolute maximum rating for the SVIN pin is 20V. Input
voltage telemetry (READ_VIN) is obtained by digitizing a voltage scaled
down from the SVIN pin.
Note 12: These typical parameters are based on bench measurements and
are not production tested.
Note 13: EEPROM endurance and retention are guaranteed by wafer-level
testing for data retention. The minimum retention specification applies
for devices whose EEPROM has been cycled less than the minimum
endurance specification, and whose EEPROM data was written to at
0°C ≤ TJ ≤ 85°C. Downloading NVM contents to RAM by executing
the RESTORE_USER_ALL or MFR_RESET commands is valid over the
entire operating temperature range and does not influence EEPROM
characteristics.
Note 14: Channel 0 OV/UV comparator threshold accuracy for
MFR_PWM_MODE0[1] = 1b tested in ATE at VVOSNS0+ – VVOSNS0– =
0.5V and 2.7V. 1V condition tested at IC-Level, only. Channel 1 OV/UV
comparator threshold accuracy for MFR_PWM_MODE1[1] = 1b tested
in ATE with VVOSNS1-VSGND = 0.5V and 2.7V. 1.5V condition tested at
IC-level, only.
Note 15: Tested at IC-level ATE.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Typical Performance Characteristics
Efficiency vs Load Current at 8VIN
100
100
95
95
95
90
90
90
85
80
3.3VOUT, 425kHz
2.5VOUT, 425kHz
1.8VOUT, 425kHz
1.5VOUT, 350kHz
1.2VOUT, 350kHz
1.0VOUT, 350kHz
0.9VOUT, 350kHz
75
70
65
60
85
80
5.0VOUT, 500kHz
3.3VOUT, 575kHz
2.5VOUT, 500kHz
1.8VOUT, 425kHz
1.5VOUT, 350kHz
1.2VOUT, 350kHz
1.0VOUT, 350kHz
0.9VOUT, 350kHz
75
70
65
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
EFFICIENCY (%)
100
EFFICIENCY (%)
EFFICIENCY (%)
Efficiency vs Load Current at 5VIN
TA = 25°C, 12VIN to 1VOUT, unless otherwise noted.
85
80
5.0VOUT, 750kHz
3.3VOUT, 650kHz
2.5VOUT, 575kHz
1.8VOUT, 500kHz
1.5VOUT, 425kHz
1.2VOUT, 350kHz
1.0VOUT, 350kHz
0.9VOUT, 350kHz
75
70
65
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
4676A G01
Efficiency vs Load Current at 12VIN
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
4676A G02
Single Phase Single Output
Pulse-Skipping (Discontinuous)
Mode Efficiency,
VIN = SVIN = VINn, INTVCC Open,
MFR_PWM_MODEn [0] = 0b
4676A G03
Dual Phase Single Output Load
Transient Response,12VIN to 1VOUT
Single Phase Single Output Load
Transient Response,12VIN to 1VOUT
90
EFFICIENCY (%)
80
VOUT
50mV/DIV
AC-COUPLED
VOUT0
50mV/DIV
AC-COUPLED
IOUT
8A/DIV
IOUT
4A/DIV
70
60
50
40
12VIN TO 1.5VOUT, 425kHz
4676A G05
40µs/DIV
FIGURE 29 CIRCUIT AT 12VIN, INTVCC PIN
OPEN CIRCUIT AND VOUT_COMMANDn SET
TO 1.000V. 0A TO 20A LOAD STEP AT 20A/µs
40µs/DIV
FIGURE 62 CIRCUIT AT 12VIN
0A TO 10A LOAD STEP AT 10A/µs
Dual Output Concurrent Rail
Start-Up/Shutdown
Dual Output Start-Up/Shutdown
with a Pre-Biased Load
4676A G06
0 1 2 3 4 5 6 7 8 9 10 11 12 13
OUTPUT CURRENT (A)
4676A G04
Dual Phase Single Output Load
Transient Response, 5VIN to 1VOUT
VOUT
50mV/DIV
AC-COUPLED
IOUT
8A/DIV
40µs/DIV
FIGURE 29 CIRCUIT AT 5VIN,
VOUT_COMMANDn SET TO 1.000V.
0A TO 20A LOAD STEP AT 20A/µs
4676A G07
VOUT0,
VOUT1
500mV/DIV
VOUT0, VOUT1
500mV/DIV
IOUT0
5A/DIV
IDIODE
1mA/DIV
RUN0, RUN1
5V/DIV
RUN0, RUN1
5V/DIV
4676A G08
2ms/DIV
FIGURE 62 CIRCUIT AT 12VIN, 77mΩ LOAD
ON VOUT0, NO LOAD ON VOUT1.
TON_RISE0 = 3ms, TON_RISE1 = 5.297ms,
TOFF_DELAY1 = 0ms, TOFF_DELAY0 = 2.43ms,
TOFF_FALL1 = 5.328ms, TOFF_FALL0 = 3ms,
ON_OFF_CONFIGn = 0x1E
4676A G09
2ms/DIV
FIGURE 62 CIRCUIT AT 12VIN, 77mΩ LOAD ON
VOUT0, 500Ω ON VOUT1. VOUT1 PRE-BIASED
THROUGH A DIODE. TON_RISE0 = 3ms,
TON_RISE1 = 5.297ms, TOFF_DELAY1 = 0ms,
TOFF_DELAY0 = 2.43ms, TOFF_FALL1 = 5.328ms,
TOFF_FALL0 = 3ms, ON_OFF_CONFIG1 = 0x1F
ON_OFF_CONFIG0 = 0x1E
4676af
For more information www.linear.com/LTM4676A
11
LTM4676A
Typical Performance Characteristics
Single Phase Single Output Short-Circuit Protection at No Load
Single Phase Single Output ShortCircuit Protection at Full Load
VOUT0
200mV/DIV
VOUT0
200mV/DIV
IIN0
1A/DIV
IIN0
1A/DIV
10µs/DIV
FIGURE 62 CIRCUIT AT 12VIN,
77mΩ LOAD ON VOUT0 PRIOR TO
APPLICATION OF SHORT CIRCUIT
4676A G10
10µs/DIV
FIGURE 62 CIRCUIT AT 12VIN,
NO LOAD ON VOUT0 PRIOR TO APPLICATION
OF SHORT CIRCUIT
300
20
SPECIFIED UPPER LIMIT
10
MEASUREMENT ERROR (mA)
MEASUREMENT ERROR (mV)
30
CHANNEL 0
0
CHANNEL 1
–10
–20
–30
0.5
SPECIFIED LOWER LIMIT
1.5
3.5
2.5
VOUT (V)
4.5
1.0
SPECIFIED UPPER LIMIT
100
0
CHANNEL 0
–100
CHANNEL 1
–200
SPECIFIED LOWER LIMIT
3.25
0
6.50
IOUT (A)
READ_TEMPERATURE_2
(Control IC Temperature Error) vs
Junction Temperature, RUNn = 0V
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
9.75
13.00
–1.0
–45 –25 –5 15 35 55 75 95 115
ACTUAL TEMPERATURE (°C)
4676A G13
4676A G12
4676A G14
MFR_READ_IINn (Input Current
Readback) Error vs (IVINn + ISVIN),
MFR_PWM_MODEn [0]=1b, IOUTn
Swept from 0A to 13A, One
Channel at a Time, RUN1-n = 0V
READ_VIN (Input Voltage
Readback Telemetry) Error vs
SVIN, RUNn = 0V
400
200
SPECIFIED UPPER LIMIT
MEASUREMENT ERROR (mA)
SPECIFIED UPPER LIMIT
MEASUREMENT ERROR (mV)
4676A G11
0.8
200
–300
5.5
READ_IOUTn (Output Current
Readback) Error vs IOUTn
MEASUREMENT ERROR (°C)
READ_VOUTn (Output Voltage
Readback) Error vs VOUTn
IOUTn = No Load, RUN1-n = 0V
TA = 25°C, 12VIN to 1VOUT, unless otherwise noted.
200
0
100
CHANNEL 1
0
CHANNEL 0
–100
–200
SPECIFIED LOWER LIMIT
SPECIFIED LOWER LIMIT
–400
4
8
12
SVIN (V)
16
20
–200
0
0.2
4676A G15
12
0.4
0.6 0.8 1.0
IINn + ISVIN (A)
1.2
1.4
4676A G21
4676af
For more information www.linear.com/LTM4676A
LTM4676A
READ_OUT of 20 LTM4676As
(DC1811B-B) 12VIN, 1VOUT,
TJ = 25°C, IOUTn = 13A, System
Having Reached Thermally
Steady-State Condition, No Airflow
READ_OUT of 20 LTM4676As
(DC1811B-B) 12VIN, 1VOUT,
TJ = 125°C, IOUTn = 13A, System
Having Reached Thermally
Steady-State Condition, No Airflow
12
10
10
10
READ_IOUT CHANNEL READBACK (A)
4676A G22
READ_IOUT CHANNEL READBACK (A)
4676A G23
13.21875
13.18750
12.96875
13.25000
13.21875
13.18750
13.15625
13.12500
13.09375
13.06250
13.03125
13.00000
13.37500
13.34375
13.31250
0
13.28125
0
13.25000
0
13.21875
2
13.18750
2
13.15625
2
13.15625
4
13.12500
4
6
13.09375
4
6
8
13.06250
6
8
13.03125
8
NUMBER OF CHANNELS
12
NUMBER OF CHANNELS
12
13.12500
NUMBER OF CHANNELS
READ_OUT of 20 LTM4676As
(DC1811B-B) 12VIN, 1VOUT,
TJ = –40°C, IOUTn = 13A, System
Having Reached Thermally
Steady-State Condition, No Airflow
TA = 25°C, 12VIN to 1VOUT, unless otherwise noted.
13.00000
Typical Performance Characteristics
READ_IOUT CHANNEL READBACK (A)
4676A G24
Pin Functions
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
GND (A4, A6-10, B4-B9, C4, C6-C9, D4, D7, E3, F3,
F10, G3, G10-12, H3, H10, J4, J10, K4, K7-9, L4-9, M4,
M6-10): Power Ground of the LTM4676A. Power return
for VOUT0 and VOUT1.
VOUT0 (A1-3, B1-3, C1-3, D1-3): Channel 0 Output Voltage.
VOSNS0+ (D9): Channel 0 Positive Differential Voltage Sense
Input. Together, VOSNS0+ and VOSNS0– serve to kelvin-sense
the VOUT0 output voltage at VOUT0’s point of load (POL)
and provide the differential feedback signal directly to
Channel 0’s control loop and voltage supervisor circuits.
VOUT0 can regulate up to 5.5V output. Command VOUT0’s
target regulation voltage by serial bus. Its initial command
value at SVIN power-up is dictated by NVM (non-volatile
memory) contents (factory default: 1.000V)—or, optionally, may be set by configuration resistors; see VOUT0CFG,
VTRIM0CFG and the Applications Information section.
VOSNS0– (E9): Channel 0 Negative Differential Voltage
Sense Input. See VOSNS0+.
VORB0+ (D10): Channel 0 Positive Readback Pin. Shorted to
VOSNS0+ internal to the LTM4676A. If desired, place a test
point on this node and measure its impedance to VOUT0
on one’s hardware (e.g., motherboard, during in circuit
test (ICT) post-assembly process) to provide a means of
verifying the integrity of the feedback signal connection
between VOSNS0+ and VOUT0.
VORB0– (E10): Channel 0 Negative Readback Pin. Shorted
to VOSNS0– internal to the LTM4676A. If desired, place
a test point on this node and measure its impedance to
GND on one’s hardware (e.g., motherboard, during ICT
post-assembly process) to provide a means of verifying
the integrity of the feedback signal connection between
VOSNS0– and GND (VOUT0 power return).
VOUT1 (J1-3, K1-3, L1-3, M1-3): Channel 1 Output Voltage.
VOSNS1 (H9): Channel 1 Positive Voltage Sense Input.
Connect VOSNS1 to VOUT1 at the POL. This provides the
feedback signal for Channel 1's control loop and voltage
supervisor circuits. VOUT1 can regulate up to 5.5V output.
Command VOUT1’s target regulation voltage by serial bus.
Its initial command value at SVIN power-up is dictated by
NVM (non-volatile memory) contents (factory default:
4676af
For more information www.linear.com/LTM4676A
13
LTM4676A
Pin Functions
1.000V)—or, optionally, may be set by configuration
resistors; see VOUT1CFG, VTRIM1CFG and the Applications
Information section.
action of Channel 0, if desired, but do not route near any
sensitive signals; otherwise, leave electrically isolated
(open).
SGND (F7-8, G7-8): Channel 1 Negative Voltage Sense
Input. See VOSNS1. Additionally, SGND is the signal ground
return path of the LTM4676A. If desired, one may place a
test point on one of the four SGND pins and measure its
impedance to GND on one’s hardware (e.g., motherboard,
during ICT post-assembly process) to provide a means
of verifying the integrity of the feedback signal connection between the other three SGND pins and GND (VOUT1
power return). SGND is not electrically connected to GND
internal to the LTM4676A. Connect SGND to GND local
to the LTM4676A.
SW1 (L10): Switching Node of Channel 1 Step-Down
Converter Stage. Used for test purposes or EMI-snubbing
heavier than that supported by SNUB1. May be routed a
short distance to a local test point to monitor switching
action of Channel 1, if desired, but do not route near any
sensitive signals; otherwise, leave open.
VORB1 (J9): Channel 1 Positive Readback Pin. Shorted to
VOSNS1 internal to the LTM4676A. At one’s option, place
a test point on this node and measure its impedance to
VOUT1 on one’s hardware (e.g., motherboard, during ICT
post-assembly process) to provide a means of verifying
the integrity of the feedback signal connection between
VOUT1 and VOSNS1.
VIN0 (A11-12, B11-12, C11-12, D11-12, E12): Positive
Power Input to Channel 0 Switching Stage. Provide sufficient decoupling capacitance in the form of multilayer
ceramic capacitors (MLCCs) and low ESR electrolytic (or
equivalent) to handle reflected input current ripple from the
step-down switching stage. MLCCs should be placed as
close to the LTM4676A as physically possible. See Layout
Recommendations in the Applications Information section.
VIN1 (H12, J11-12, K11-12, L11-12, M11-12): Positive
Power Input to Channel 1 Switching Stage. Provide sufficient decoupling capacitance in the form of MLCCs and
low ESR electrolytic (or equivalent) to handle reflected
input current ripple from the step-down switching stage.
MLCCs should be placed as close to the LTM4676A as
physically possible. See Layout Recommendations in the
Applications Information section.
SW0 (B10): Switching Node of Channel 0 Step-Down
Converter Stage. Used for test purposes or EMI-snubbing
heavier than that supported by SNUB0. May be routed a
short distance to a local test point to monitor switching
14
SNUB0 (A5): Access to Channel 0 Switching Stage Snubber
Capacitor. Connecting an optional resistor from SNUB0 to
GND can reduce radiated EMI, with only a minor penalty
towards power conversion efficiency. See the Applications
Information section. Pin should otherwise be left open.
SNUB1 (M5): Access to Channel 1 Switching Stage Snubber
Capacitor. Connecting an optional resistor from SNUB0 to
GND can reduce radiated EMI, with only a minor penalty
towards power conversion efficiency. See the Applications
Information section. Pin should otherwise be left open.
SVIN (F11-12): Input Supply for LTM4676A’s Internal
Control IC. In most applications, SVIN connects to VIN0
and/or VIN1, in which case no external decoupling beyond
that already allocated for VIN0/VIN1 is required. If SVIN is
operated from an auxiliary supply separate from VIN0/VIN1,
decouple this pin to GND with a capacitor (0.1μF to 1μF).
INTVCC (F9, G9): Internal Regulator, 5V Output. When
operating the LTM4676A from 5.75V ≤ SVIN ≤ 17V, an LDO
generates INTVCC from SVIN to bias internal control circuits
and the MOSFET drivers of the LTM4676A. No external
decoupling is required. INTVCC is regulated regardless of
the RUNn pin state. When operating the LTM4676A with
4.5V ≤ SVIN < 5.75V, INTVCC must be electrically shorted
to SVIN.
VDD33 (J7): Internally Generated 3.3V Power Supply
Output Pin. This pin should only be used to provide external current for the pull-up resistors required for GPIOn,
SHARE_CLK, and SYNC, and may be used to provide
external current for pull-up resistors on RUNn, SDA, SCL
and ALERT. No external decoupling is required.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Pin Functions
VDD25 (J6): Internally Generated 2.5V Power Supply Output
Pin. Do not load this pin with external current; it is used
strictly to bias internal logic and provides current for the
internal pull-up resistors connected to the configurationprogramming pins. No external decoupling is required.
ASEL (G4): Serial Bus Address Configuration Pin. On any
given I2C/SMBus serial bus segment, every device must
have its own unique slave address. If this pin is left open,
the LTM4676A powers up to its default slave address of
0x4F (hexadecimal), i.e., 1001111b (industry standard
convention is used throughout this document: 7-bit slave
addressing). The lower four bits of the LTM4676A’s slave
address can be altered from this default value by connecting
a resistor from this pin to SGND. Minimize capacitance—
especially when the pin is left open—to assure accurate
detection of the pin state.
FSWPHCFG (H4): Switching Frequency, Channel PhaseInterleaving Angle and Phase Relationship to SYNC
Configuration Pin. If this pin is left open—or, if the
LTM4676A is configured to ignore pin-strap (RCONFIG)
resistors, i.e., MFR_CONFIG_ALL[6] = 1b—then the
LTM4676A’s switching frequency (FREQUENCY_SWITCH)
and channel phase relationships (with respect to the SYNC
clock; MFR_PWM_CONFIG[2:0]) are dictated at SVIN
power-up according to the LTM4676A’s NVM contents.
Default factory values are: 500kHz operation; Channel 0
at 0°; and Channel 1 at 180°C (convention throughout
this document: a phase angle of 0° means the channel’s
switch node rises coincident with the falling edge of
the SYNC pulse). Connecting a resistor from this pin
to SGND (and using the factory-default NVM setting of
MFR_CONFIG_ALL[6] = 0b) allows a convenient way to
configure multiple LTM4676As with identical NVM contents
for different switching frequencies of operation and phase
interleaving angle settings of intra- and extra-moduleparalleled channels—all, without GUI intervention or the
need to “custom pre-program” module NVM contents.
(See the Applications Information section.) Minimize
capacitance—especially when the pin is left open—to
assure accurate detection of the pin state.
VOUT0CFG (G5): Output Voltage Select Pin for VOUT0, Coarse
Setting. If the VOUT0CFG and VTRIM0CFG pins are both left
open—or, if the LTM4676A is configured to ignore pin-
strap (RCONFIG) resistors, i.e., MFR_CONFIG_ALL[6] =
1b—then the LTM4676A’s target VOUT0 output voltage
setting (VOUT_COMMAND0) and associated powergood and OV/UV warning and fault thresholds are
dictated at SVIN power-up according to the LTM4676A’s
NVM contents. A resistor connected from this pin to
SGND—in combination with resistor pin settings on
VTRIM0CFG, and using the factory-default NVM setting of
MFR_CONFIG_ALL[6] = 0b—can be used to configure
the LTM4676A’s Channel 0 output to power-up to a
VOUT_COMMAND value (and associated output voltage
monitoring and protection/fault-detection thresholds)
different from those of NVM contents. (See the Applications
Information section.) Connecting resistor(s) from VOUT0CFG
to SGND and/or VTRIM0CFG to SGND in this manner allows
a convenient way to configure multiple LTM4676As
with identical NVM contents for different output voltage
settings—all without GUI intervention or the need to
“custom-pre-program” module NVM contents. Minimize
capacitance—especially when the pin is left open—to
assure accurate detection of the pin state. Note that use
of RCONFIGs on VOUT0CFG/VTRIM0CFG can affect the VOUT0
range setting (MFR_PWM_MODE0[1]) and loop gain.
VTRIM0CFG (H5): Output Voltage Select Pin for VOUT0, Fine
Setting. Works in combination with VOUT0CFG to affect
the VOUT_COMMAND (and associated output voltage
monitoring and protection/fault-detection thresholds)
of Channel 0, at SVIN power-up. (See VOUT0CFG and the
Applications Information section.) Minimize capacitance—
especially when the pin is left open—to assure accurate
detection of the pin state. Note that use of RCONFIGs on
VOUT0CFG/VTRIM0CFG can affect the VOUT0 range setting
(MFR_PWM_MODE0[1]) and loop gain.
VOUT1CFG (G6): Output Voltage Select Pin for VOUT1, Coarse
Setting. If the VOUT1CFG and VTRIM1CFG pins are both left
open—or, if the LTM4676A is configured to ignore pinstrap (RCONFIG) resistors, i.e., MFR_CONFIG_ALL[6] =
1b—then the LTM4676A’s target VOUT1 output voltage
setting (VOUT_COMMAND1) and associated OV/UV
warning and fault thresholds are dictated at SVIN power-up
according to the LTM4676A’s NVM contents, in precisely
the same fashion that the VOUT0CFG and VTRIM0CFG pins
affect the respective settings of VOUT0 /Channel 0. (See
4676af
For more information www.linear.com/LTM4676A
15
LTM4676A
Pin Functions
VOUT0CFG, VTRIM0CFG and the Applications Information
section.) Minimize capacitance—especially when the pin
is left open—to assure accurate detection of the pin state.
Note that use of RCONFIGs on VOUT1CFG/VTRIM1CFG can
affect the VOUT1 range setting (MFR_PWM_MODE1[1])
and loop gain.
VTRIM1CFG (H6): Output Voltage Select Pin for VOUT1, Fine
Setting. Works in combination with VOUT1CFG to affect
the VOUT_COMMAND (and associated output voltage
monitoring and protection/fault-detection thresholds)
of Channel 1, at SVIN power-up. (See VOUT1CFG and the
Applications Information section.) Minimize capacitance—
especially when the pin is left open—to assure accurate
detection of the pin state. Note that use of RCONFIGs on
VOUT1CFG/VTRIM1CFG can affect the VOUT1 range setting
(MFR_PWM_MODE1[1]) and loop gain.
SYNC (E7): PWM Clock Synchronization Input and OpenDrain Output Pin. The setting of the FREQUENCY_SWITCH
command dictates whether the LTM4676A is a “sync
master” or “sync slave” module. When the LTM4676A
is a sync master, FREQUENCY_SWITCH contains the
commanded switching frequency of Channels 0 and 1—in
PMBus linear data format—and it drives its SYNC pin low
for 500ns at a time, at this commanded rate. In contrast,
a sync slave uses MFR_CONFIG_ALL[4]=1b and does not
pull its SYNC pin low. The LTM4676A’s PLL synchronizes
the LTM4676A’s PWM clock to the waveform present on
the SYNC pin—and therefore, a resistor pull-up to 3.3V
is required in the application, regardless of whether the
LTM4676A is a sync master or slave. EXCEPTION: driving
the SYNC pin with an external clock is permissible; see
the Applications Information section for details.
SCL (E6): Serial Bus Clock Open-Drain Input (Can Be an
Input and Output, if Clock Stretching is Enabled). A pull-up
resistor to 3.3V is required in the application for digital
communication to the SMBus master(s) that nominally
drive this clock. The LTM4676A will never encounter
scenarios where it would need to engage clock stretching
unless SCL communication speeds exceed 100kHz—and
even then, LTM4676A will not clock stretch unless clock
stretching is enabled by means of setting MFR_CONFIG_
ALL[1] = 1b. The factory-default NVM configuration
setting has MFR_CONFIG_ALL[1] = 0b: clock stretching
16
disabled. If communication on the bus at clock speeds
above 100kHz is required, the user’s SMBus master(s)
need to implement clock stretching support to assure
solid serial bus communications, and only then should
MFR_CONFIG_ALL[1] be set to 1b. When clock stretching is enabled, SCL becomes a bidirectional, open-drain
output pin on LTM4676A.
SDA (D6): Serial Bus Data Open-Drain Input and Output.
A pull-up resistor to 3.3V is required in the application.
ALERT (E5): Open-Drain Digital Output. A pull-up resistor
to 3.3V is required in the application only if SMBALERT
interrupt detection is implemented in one’s SMBus system.
SHARE_CLK (H7): Share Clock, Bidirectional OpenDrain Clock Sharing Pin. Nominally 100kHz. Used for
synchronizing the time base between multiple LTM4676As
(and any other Linear Technology devices with a SHARE_
CLK pin)—to realize well-defined rail sequencing and rail
tracking. Tie the SHARE_CLK pins of all such devices
together; all devices with a SHARE_CLK pin will synchronize
to the fastest clock. A pull-up resistor to 3.3V is only required when synchronizing the time base between devices.
GPIO 0, GPIO 1 (E4 and F4, Respectively): Digital,
Programmable General Purpose Inputs and Outputs.
Open-drain outputs and/or high impedance inputs. The
LTM4676A’s factory-default NVM configurations for
MFR_GPIO_PROPAGATEn—0x6893—and MFR_GPIO_
RESPONSEn—0xC0—are such that: (1) when a channelspecific fault condition is detected—such as channel OT
(overtemperature) or output UV/OV—the respective GPIOn
pin pulls logic low; (2) when a non-channel specific fault
condition is detected—such as input OV or control IC
OT—both GPIOn pins pull logic low; (3) the LTM4676A
ceases switching action on Channel 0 and 1 when its
respective GPIOn pin is logic low. Most significantly, this
default configuration provides for graceful integration and
inter-operation of LTM4676A with paralleled channel(s) of
other LTM4676A(s)—in terms of properly coordinating
efforts in starting, ceasing, and resuming switching
action and output voltage regulation, in unison—all
without GUI intervention or the need to “custompreprogram” module NVM contents. Pull-up resistors
from GPIOn to 3.3V are required for proper operation in
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Pin Functions
the vast majority of applications. (Only if the LTM4676A’s
MFR_GPIO_RESPONSEn value were set to 0x00 might
pull-ups be unnecessary. See the Applications Information
section for details.)
WP (K6): Write Protect Pin, Active High. An internal
10μA current source pulls this pin to VDD33. If WP is
open circuit or logic high, only I2C writes to PAGE,
OPERATION, CLEAR_FAULTS, MFR_CLEAR_PEAKS and
MFR_EE_UNLOCK are supported. Additionally, individual
faults can be cleared by writing 1b’s to bits of interest in
registers prefixed with “STATUS”. If WP is low, I2C writes
are unrestricted.
RUN0, RUN1 (F5 and F6, Respectively): Enable Run Input
for Channels 0 and 1, Respectively. Open-drain input and
output. Logic high on these pins enables the respective
outputs of the LTM4676A. These open-drain output pins
hold the pin low until the LTM4676A is out of reset and
SVIN is detected to exceed VIN_ON. A pull-up resistor to
3.3V is required in the application. Do not pull RUN logic
high with a low impedance source.
TSNS0a, TSNS0b (D5 and C5, Respectively): Channel 0
Temperature Excitation/Measurement and Thermal Sensor
Pins, Respectively. Connect TSNS0a to TSNS0b. This allows
the LTM4676A to monitor the Power Stage Temperature
of Channel 0.
TSNS1a, TSNS1b (J5 and K5, Respectively): Channel 1
Temperature Excitation/Measurement and Thermal Sensor
Pins, Respectively. In most applications, connect TSNS1a
to TSNS1b. This allows the LTM4676A to monitor the
Power Stage Temperature of Channel 1. See the Applications Information section for information on how to use
TSNS1a to monitor a temperature sensor external to the
module, e.g., a PN junction on the die of a microprocessor.
ISNS0a+, ISNS0b+ (F2 and F1, Respectively): Channel 0
Positive Current Sense and Kelvin Sense Pins, Respectively.
Connect ISNS0a+ to ISNS0b+.
ISNS1a+, ISNS1b+ (H2 and H1, Respectively): Channel 1
Positive Current Sense and Kelvin Sense Pins, Respectively.
Connect ISNS1a+ to ISNS1b+.
ISNS0a–, ISNS0b– (E2 and E1, Respectively): Channel 0
Negative Current Sense and Kelvin Sense Pins, Respectively. Connect ISNS0a– to ISNS0b–.
ISNS1a–, ISNS1b– (G2 and G1, Respectively): Channel 1
Negative Current Sense and Kelvin Sense Pins, Respectively. Connect ISNS1a– to ISNS1b–.
COMP0a, COMP1a (E8 and H8, Respectively): Current
Control Threshold and Error Amplifier Compensation Nodes
for Channels 0 and 1, Respectively. The trip threshold
of each channel’s current comparator increases with a
respective rise in COMPna voltage. Small filter capacitors
(22pF) internal to the LTM4676A on these COMP pins
(terminated to SGND) introduce high frequency roll off of
the error-amplifier response, yielding good noise rejection
in the control loop. See COMP0b/COMP1b.
COMP0b, COMP1b (D8 and J8, Respectively): Internal
Loop Compensation Networks for Channels 0 and 1, Respectively. For the vast majority of applications, the internal,
default loop compensation of the LTM4676A is suitable to
apply “as is”, and yields very satisfactory results: apply the
default loop compensation to the control loops of Channels 0 and 1 by simply connecting COMP0a to COMP0b
and COMP1a to COMP1b, respectively. In contrast, when
more specialized applications require a personal touch the
optimization of control loop response, this can be easily
accomplished by connecting (an) R-C network(s) from
COMP0a and/or COMP1a—terminated to SGND—and
leaving COMP0b and/or COMP1b open, as desired.
DNC (C10, E11, H11, K10): Do not connect these pins
to external circuitry. Solder these pins only to mounting
pads on the PC board for mechanical integrity. These pads
must remain electrically open circuit.
4676af
For more information www.linear.com/LTM4676A
17
LTM4676A
Simplified Block Diagram
VIN
5.75V TO 17V
+
CINL
CINH
VIN0
SNUB0
VOUT0
ADJUSTABLE
UP TO 5.5V
UP TO 13A
2.2nF
COUT0HF
COUT0LF
GND
2.2µF
ISNS0b–
VIN1
POWER CONTROL
ANALOG SECTION
600nH
THERMAL
SENSOR
2.2nF
1µF
MT0
VOUT0
INTVCC VDD33
1µF
SW0
+
SVIN
MB0
SNUB1
MT1
600nH
VOUT1
2.2µF
THERMAL
SENSOR
MB1
ISNS1a–
TSNS0b
TSNS1b
TSNS0a
TSNS1a
VORB0+
VORB1[+]
VOSNS0–
VORB0–
+
x1
–
TO ERROR
AMPLIFIER
VOSNS1[+]
ANALOG
READBACK
SIGNALS
CONTROLLER SIGNAL GND
COMP1a
INTERNAL
COMP
ADC
COMP1b
INTERNAL
COMP
SCL
5V TOLERANT; PULL-UP
RESISTORS NOT SHOWN
3.3V TOLERANT; PULL-UP
RESISTOR NOT NEEDED
5V TOLERANT; PULL-UP
RESISTORS NOT SHOWN
3.3V TOLERANT; PULL-UP
RESISTORS NOT SHOWN
SYNC
SDA
3.3V TOLERANT; PULL-UP
RESISTOR NOT SHOWN
VDD25
SPI
SLAVE
ALERT
WP
RUN0
LOCAL
HIGH
LOAD1
FREQ
MLCCs
SGND [VOSNS1–]
COMP0a
COMP0b
COUT1HF
ISNS1a+
THERMAL
SENSOR
ISNS0a–
VOSNS0+
COUT1LF
ISNS1b+
ISNS0a+
LOCAL
HIGH
FREQ
MLCCs
+
GND
ISNS1b–
ISNS0b+
LOAD0
VOUT1
ADJUSTABLE
UP TO 5.5V
UP TO 13A
SW1
ASEL
POWER MANAGEMENT
DIGITAL SECTION
SPI
MASTER
RUN1
GPIO0
ROM
DIGITAL ENGINE
GPIO1
RAM
EEPROM
SYNC
DRIVER
FSWPHCFG
VOUT0CFG
CONFIGURATION
RESISTORS TERMINATING
TO SGND NOT SHOWN
VTRIM0CFG
OSC
(32MHz)
VOUT1CFG
VTRIM1CFG
SHARE_CLK
4676 F01
Figure 1. Simplified LTM4676A Block Diagram
Decoupling Requirements
TA = 25°C. Using Figure 1 configuration.
SYMBOL
PARAMETER
CONDITIONS
CINH
External High Frequency Input Capacitor Requirement
(5.75V ≤ VIN ≤ 17V, VOUTn Commanded to 1.000V)
IOUT0 = 13A, 3 × 22μF, or 4 × 10μF
IOUT1 = 13A, 3 × 22μF, or 4 × 10μF
COUTnHF
External High Frequency Output Capacitor Requirement
(5.75V ≤ VIN ≤ 17V, VOUTn Commanded to 1.000V)
IOUT0 = 13A
IOUT1 = 13A
18
MIN
TYP
MAX
UNITS
40
66
µF
400
400
µF
µF
4676af
For more information www.linear.com/LTM4676A
For more information www.linear.com/LTM4676A
+
COUT0LF
LOCAL
HIGH
FREQ
MLCCs
3.3V Tolerant; Pull-Up
Resistors Not Shown
5V Tolerant; Pull-Up
Resistors Not Shown
3.3V Tolerant; Pull-Up
Resistor Not Needed
5V Tolerant; Pull-Up
Resistors Not Shown
(LOAD0 Power Consumption
Telemetry: READ_POUT0)
LOAD0
COUT0HF
RSNUB0
UP TO
2W
(VOUT0 Telemetry:
READ_VOUT0 and
MFR_VOUT_PEAK0)
VOUT0
ADJUSTABLE
UP TO 5.5V
UP TO 13A
Optional Snubber
Resistor for Moderate
Reduction in EMI
(Size: EIA0603 ~EIA2512)
–
R
R
VOSNS0–
SHARE_CLK
GPIO1
GPIO0
RUN1
RUN0
WP
ALERT
SDA
SCL
COMP0b
COMP0a
R
+
A=1
–
R
CHANNEL TIMING
MANAGEMENT
I
INTERFACE WITH PMBus
COMMAND SET
(10kHz TO 400kHz
COMPATIBLE)
2C-BASED SMBus
VDD33
ZCOMP0b
UVLO
TMUX
ROM
PROGRAM
16-BIT
ADC
VTSNS
30µA
RAM
22pF
MB1
EEPROM
ZISNS1a
ZISNS1b+
ZISNS1b–
+ –
VORB1[+]
TSNS1a
TSNS1b
ISNS1a–
ISNS1a+
ISNS1b+
ISNS1b–
GND
VOUT1
CONFIG
DETECT
SYNC
DRIVER
1nF + 20kΩ
ZCOMP1b
SW1
SNUB1
COMP1a
COMP1b
14.3k
×6
VTRIM1CFG
VOUT1CFG
VTRIM0CFG
VOUT0CFG
FSWPHCFG
ASEL
VDD25
(Switching Frequency Telemetry:
READ_FREQUENCY) SYNC
Channel 1 Internal Loop Compensation
Channel 1 Current Demand Signal
SGND [VOSNS1–]
VOSNS1[+]
Channel 1 (VOUT1) Voltage Feedback Signal
(Differential when Terminating SGND at LOAD1 as Shown)
Channel 1 Current Sense Signal, ∆ISNS1a
Channel 1 Thermal Sensor
(Telemetry: READ_TEMPERATURE_11
and MFR_TEMPERATURE_1_PEAK1)
(IOUT1 Telemetry: READ_IOUT1
and MFR_IOUT_PEAK1)
Controller Signal GND
OSC
(32MHz)
SINC3
SPI
MASTER
SPI
SLAVE
DACs, OV/UV
Comparators,
Other
8:1 MUX
DIGITAL ENGINE, MAIN CONTROL
VDD33
COMPARE
VDD33
1nF + 20kΩ
22pF
TO E/A
2µA
CURRENT MODE
PWM CTRL. LOOPS,
LIN. REGULATORS,
DACs ADC, UV/OV
COMPARATORS,
VCO AND PLL,
MOSFET DRIVERS
AND POWER
SWITCH LOGIC
MT1
(PWM1 Telemetry:
READ_DUTY_CYCLE1)
VDD33 VIN1
(Computed Channel 1 Input Current, IVIN1 + 1/2 • ISVIN: MFR_READ_IIN1)
POWER CONTROL
ANALOG SECTION
INT
FILTER
SVIN INTVCC
POWER MANAGEMENT
DIGITAL SECTION
DIGITAL ENGINE, INCLUDING:
ROM, RAM, NVM AND OSCILLATOR
10µA
Channel 0 Internal Loop Compensation
Channel 0 (VOUT0) Voltage Feedback Signal
Channel 0 Current Demand Signal
VORB0–
MB0
MT0
–
VIN0
Power Controller Thermal Sensor
(Telemetry: READ_TEMPERATURE_2)
∆ISNS0a, Channel 0 Current Sense Signal
Channel 0 Thermal Sensor
(Telemetry: READ_TEMPERATURE_10
and MFR_TEMPERATURE_1_PEAK0)
(IOUT0 Telemetry: READ_IOUT0
and MFR_IOUT_PEAK0)
∆VOSNS0, Differential Feedback Signal
ZISNS0a
ZISNS0b
+
ZISNS0b–
– +
VOSNS0+
VORB0+
TSNS0a
TSNS0b
ISNS0a–
ISNS0a
+
ISNS0b+
ISNS0b
GND
VOUT0
SW0
SNUB0
(PWM0 Telemetry:
READ_DUTY_CYCLE0)
(SVIN Telemetry:
READ_VIN and MFR_VIN_PEAK)
(Computed Total Input Current, IVINO + IVIN1 + ISVIN: READ_IIN)
+
CINH
(Computed Channel 0 Input Current, IVIN0 + 1/2 • ISVIN: MFR_READ_IIN0)
CINL
∆VOSNS0
VOSNS1
∆ISNS0a
∆ISNS1a
SVIN÷39
+
PWM0
PWM1
VIN
5.75V TO 17V
(LOAD1 Power Consumption
Telemetry: READ_POUT1)
LOCAL
HIGH
FREQ
MLCCs
LOAD1
COUT1HF
VOUT1
ADJUSTABLE
UP TO 5.5V
UP TO 13A
(VOUT1 Telemetry:
READ_VOUT1 and
MFR_VOUT_PEAK1)
COUT1LF
4676A FD
Configuration
Resistors Terminating
to SGND Not Shown
3.3V Tolerant; Pull-Up
Resistor Not Shown
+
RSNUB1
UP TO
2W
Optional Snubber
Resistor for Moderate
Reduction in Radiated EMI
(Size: EIA0603 ~EIA2512)
LTM4676A
Functional Diagram
4676af
19
LTM4676A
Test Circuits
VIN
5.75V TO 17V
+
CINL
150µF
VIN0
VIN1
SVIN
VDD33
CINH
10µF
×6
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL,
FAULT MANAGEMENT AND
POWER SEQUENCING
PWM CLOCK SYNCH
TIME BASE SYNCH
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
Test Circuit 1. LTM4676A ATE High VIN Operating Range Configuration, 5.75V ≤ VIN ≤ 17V
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
LTM4676A
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
GND
(PULL-UP RESISTORS ON DIGITAL
I/O PINS NOT SHOWN)
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VORB0+
VOSNS0+
VOSNS0–
VORB0–
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
+
COUTL0
OPT*
COUTH0 VOUT0
100µF 1V ADJUSTABLE
×4
UP TO 13A
LOAD0
+
COUTL1
OPT*
VOUT1
COUTH1
1V ADJUSTABLE
100µF
UP TO 13A
×4
LOAD1
4676A TC01
RTH0
30.1k
CTH0
470pF
20
RTH1
30.1k
CTH1
470pF
*COUTL0, COUTL1 NOT USED IN ATE TESTING
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Test Circuits
VIN
4.5V TO 5.75V
+
CINL
150µF
VIN0
VIN1
SVIN
VDD33
CINH
10µF
×6
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
Test Circuit 2. LTM4676A ATE Low VIN Operating Range Configuration, 4.5V ≤ VIN ≤ 5.75V
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL,
FAULT MANAGEMENT AND
POWER SEQUENCING
PWM CLOCK SYNCH
TIME BASE SYNCH
LTM4676A
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
GND
(PULL-UP RESISTORS ON DIGITAL
I/O PINS NOT SHOWN)
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VORB0+
VOSNS0+
VOSNS0–
VORB0–
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
+
COUTL0
OPT*
COUTH0 VOUT0
100µF 1V ADJUSTABLE
×4
UP TO 13A
LOAD0
+
COUTL1
OPT*
VOUT1
COUTH1
1V ADJUSTABLE
100µF
UP TO 13A
×4
LOAD1
4676A TC02
RTH0
30.1k
CTH0
470pF
RTH1
30.1k
CTH1
470pF
*COUTL0, COUTL1 NOT USED IN ATE TESTING
4676af
For more information www.linear.com/LTM4676A
21
LTM4676A
Operation
Power Module Introduction
The LTM4676A is a highly configurable dual 13A output standalone nonisolated switching mode step-down
DC/DC power supply with built-in EEPROM NVM (nonvolatile memory) and I2C-based PMBus/SMBus 2-wire
serial communication interface capable of 400kHz SCL
bus speed. Two output voltages can be regulated (VOUT0,
VOUT1—collectively, VOUTn) with a few external input and
output capacitors and pull-up resistors. Readback telemetry
data of average input and output voltages and currents,
Channel PWM duty cycles, and module temperatures are
continually digitized cyclically by an integrated 16-bit ADC
(analog-to-digital converter). Many fault thresholds and
responses are customizable. Data can be autonomously
saved to EEPROM when a fault occurs, and the resulting
fault log can be retrieved over I2C at a later time, for analysis.
The LTM4676A provides precisely regulated output voltages
between 0.6VDC to 5.5VDC (±0.5% above 1VDC, ±5mV
below 1VDC). The target output voltage can be set according
to pin-strapping resistors (VOUTn CFG and VTRIMn CFG pins),
NVM/register settings, and altered on the fly via the I2C
interface. The NVM factory-default switching frequency is
500kHz and the phase-interleaving angle between its two
channels is 180°. Channel switching frequency, phase
angle, and phase relationship with respect to the falling edge
of the SYNC pin waveform can be configured according
to a pin-strap resistor (FSWPHCFG pin) and NVM/register
settings—though, not on the fly during regulation. The
7-bit I2C slave address of the module defaults to the value
retrieved from MFR_ADDRESS[6:0] at power-up (factory
default: 0x4F), but the least significant four bits of the
address are set by resistor pin-strapping the ASEL pin.
Bits[6:4] of MFR_ADDRESS can be written and stored to
EEPROM. Between the ASEL resistor pin-strap and userconfigurable MFS_ADDRESS[6:4], the LTM4676A can take
on any 7-bit slave address desired. With the exception of
the ASEL pin, the module can be configured to ignore all
pin-strap resistors, if desired (see MFR_CONFIG_ALL[6]).
The LTM4676A is very similar to its predecessor, the
LTM4676. Note that the supported input voltage range of
the LTM4676A is 20V absolute maximum (17V maximum
22
operating)—and that this is lower than the voltage range
supported by the LTM4676. The major improvements
are as follows:
Tighter output voltage regulation accuracy (total DC
error): ±0.5% rather than ±1%, for VOUTn ≥ 1V; ±5mV
rather than ±1%, for 0.6V ≤ VOUTn < 1V.
n
The module’s turn-on start-up time (see tSTART in the
Electrical Characteristics table) has been reduced to
60ms (70ms, maximum, over temperature).
n
VOUT0 and VOUT1 are both configurable for up to 5.5VOUT.
n
An LTM4676A synchronizing to an external SYNC clock
can be configured for better fault tolerance, i.e., the
behavior of a “sync slave”-configured LTM4676A can
be set to automatically operate at its nominal target
switching frequency in the absence of a SYNC clock,
rather than operate at the lower-end of its PLL synccapture range.
n
MFR_ADC_CONTROL and MFR_ADC_TELEMETRY_
STATUS are new commands, enabling faster telemetry
update rates—up to 125Hz in LTM4676A, compared
to 10Hz in LTM4676, nominal.
n
PMBus compliance to Version 1.2 of Part I and Part II
of PMBus Specifications documents. The LTM4676A
supports the PAGE_PLUS_READ, PAGE_PLUS_WRITE
and SMBALERT_MASK commands.
n
Improved fault logging. See Appendix C, PMBus Command Details.
n
For parallel-output applications, the differential amplifier
sensing VOSNS0+/VOSNS0– can be used to regulate the
paralleled VOUT0 and VOUT1 outputs. VOSNS1 can be
connected to VOSNS0+ and SGND can be connected
to power GND local to the module rather than at the
point of load sensing-point, for routing convenience
(MFR_PWM_CONFIG[7]).
n
Any 7-bit slave address can be assigned to the
LTM4676A. Bits [6:4] of MFR_ADDRESS are userconfigurable and can be stored to EEPROM. The least
significant nibble of MFR_ADDRESS is assigned by the
resistor pin-strap setting on the ASEL pin.
n
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
Table 1 provides a summary of LTM4676A’s supported
PMBus commands, as well as a direct comparison to those
of the LTM4676. For details on the supported commands,
payloads and data formats see Appendix C: PMBus Command Details.
For introductory information about the PMBus Specification, see Appendix A: Similarity Between PMBus, SMBus
and I2C 2-Wire Interface. For information about the data
communication link layer and timing diagrams, see Appendix B: PMBus Serial Digital Interface.
Output Current Limit and Overvoltage Protection.
n
Three Integrated Temperature Sensors, Over/Undertemperature Protection.
n
Constant Frequency Peak Current Mode Control.
n
Configurable Switching Frequency, 250kHz to 1MHz;
Synchronizable to External Clock; Seven Configurable
Channel Phase Interleaving Settings.
n
Internal Loop Compensation Provided; External Loop
Compensation Can Be Applied, if Preferred.
n
Major features of the LTM4676A strictly from a DC/DC
converter power delivery point of view are as follows:
n
Up to 13A Output Current Delivery from Each of Two
Integrated Power Stages (See Front Page Figure)—or
Up to 26A Output, Combined (See Figure 29 and
Figure 36).
n
Integrated Snubber Capacitors Enable EMI Reduction
by Placing External Snubber Resistors Adjacent to the
Module (see Figures 32 and 33).
n
Low Profile (16mm × 16mm × 5.01mm) BGA Package
Power Solution Requires Only Input and Output Capacitors; at Most, Nine Pull-Up Resistors for Open-Drain
Digital Signals; at Most, Six Pull-Down Resistors to
Configure All Possible Pin-Strapping Options.
Wide Input Voltage Range: DC/DC Step-Down Conversion from 5.75V to 17V Input (See Figure 62).
n
DC/DC Step-Down Conversion from 4.5V to 5.75V Input,
Connecting SVIN to INTVCC (See Figure 29).
n
DC/DC Step-Down Conversion Possible from Less Than
4.5V Input When an Auxiliary 5V Bias Supply Powers
SVIN and INTVCC (See Figure 31).
n
Output Voltage Range: 0.5V to 5.5V on both VOUT0 and
VOUT1.
n
Differential Remote Sensing of VOUT0 (VOSNS0+/
VOSNS0–). For paralleled outputs, the VOSNS0+/VOSNS0–
pin-pair can be configured as the feedback path for
both VOUT0 and VOUT1 (see Figure 36 and, optionally,
MFR_PWM_CONFIG[7]).
n
Start-Up Into a Pre-Biased Load Without Sinking
Current.
n
Four LTM4676As Can Be Paralleled to Deliver Up to
100A (See Figure 33).
n
One LTM4676A Can Be Paralleled with Three LTM4620A
or LTM4630 Modules to Deliver Up to 130A; Infer
Rail Status and Telemetry of Paralleled LTM4620A or
LTM4630 via the Sole LTM4676A (See Figure 34).
n
Discontinuous Mode Operation Available for Higher
Light-Load Efficiency (MFR_PWM_MODEn [0]).
n
Features of the LTM4676A that enable power system
management, rail sequencing, and fault monitoring and
reporting are as follows:
I2C-based PMBus/SMBus 2-Wire Serial Communication
Interface (SDA, SCL) with ALERT Interrupt Pin, SCL
Clock Capable of 400kHz Bus Communication Speeds
with Clock Low Extending—or 100kHz, Otherwise.
n
Configurable Output Voltage.
n
Configurable Input Undervoltage Comparators
(UVLO Rising, UVLO Falling).
n
Configurable Switching Frequency.
n
Configurable Current Limit.
n
Configurable Output Over/Undervoltage Comparators.
n
Configurable Turn-On and Turn-Off Delay Times.
n
Configurable Output Ramp Rise and Fall Times.
n
Non-Volatile Configuration Memory (NVM EEPROM) to
Configure Aforementioned Settings, and More—Yielding Standalone Operation, if Desired, and Also Enabling
In-Situ Changes to the LTM4676A’s Configuration in
Embedded Designs.
n
For more information www.linear.com/LTM4676A
4676af
23
LTM4676A
Operation
Monitoring and Reporting of Telemetry Data: Average
Output and Input Currents and Voltages, Internal Temperatures, and Power Stage Duty Cycles—Continuously
Digitized Cyclically by a 16-Bit ADC.
n
• Peak Observed Output Current and Voltage, Input
Voltage, and Module Temperatures Can Be Polled
and Cleared/Reset.
• ADC Latency Not Greater Than 100ms, Nominal.
• Option to Monitor One External Temperature in Lieu of
Channel 1 (VOUT1) Module Power Stage Temperature.
Monitoring, Reporting, and Configurable Response
to Latching and Non-Latching Individual Fault and/or
Warning Status, Including but Not Limited to:
Time-Base Interconnect (SHARE_CLK, 100kHz Heartbeat) for Synchronization in the Time Domain Between
Multiple LTM4676As.
n
Optional External Configuration Resistors (RCONFIGs)
for Setting Start-Up Output Voltages, Switching Frequency and Channel-to-Channel Phase Interleaving
Angle.
n
Any 7-Bit Slave Address Can Be Assigned to the
LTM4676A (0x4F Default), Configured by Resistor Pin
Strapping the ASEL Pin and User-Editable Bits [7:4] of
MFR_ADDRESS.
n
n
• Output Over/Undervoltages.
• Input (SVIN) Over/Undervoltages.
• Module Input and Power Stage Output Overcurrents.
• Module Power Stage Over/Undertemperatures.
• Internal Control IC Overtemperature.
• Communication, Memory and Logic (CML) Faults.
Fault Logging Upon Detection of a Fault Condition. The
LTM4676A Can Be Configured to Automatically Upload a
Fault Log to Its NVM, Consisting of: an Uptime Counter,
Peak Observed Telemetry, Telemetry Gathered from the
Six Most Recent Rounds of Cyclical ADC Data Leading
Up to the Detection of the Fault That Triggered Fault Log
Writing, and Fault Status Associated with That ADC
History.
n
Two Configurable Open-Drain General Purpose Input/
Output Pins (GPIO0, GPIO1), Which Can Be Used for:
n
• Fault Reporting, e.g., as a System Interrupt Signal.
• Coordinating Turn-On/Off of the LTM4676A in Multiphase/Multirail Systems.
• Propagating an Unfiltered Power Good Signal (Output
of a VOUTn Undervoltage Comparator) to Command
Turn-On/Off of a Downstream Rail.
A Write Protect (WP) Pin and Configurable WRITE_
PROTECT Register to Protect the Internal Configuration
of RAM and NVM Against Unintended Changes via I2C.
n
24
Power Module Configurability and
Readback Data
This section of the data sheet describes all the configurable
features and readable data of the LTM4676A accessible
via I2C. The relevant command code name(s) are indicated
by use of all capital letters, e.g., “VIN_ON”. Refer to Table
1 and Appendix C: PMBus Command Details of this data
sheet for details of the command code, payload size, data
format and factory-default value. Specific register bits of
some registers are indicated with the use of brackets, i.e.,
“[” and “]”. The least significant bit (LSB) of a register is
bit number zero, indicated by “[0]”. The most significant
bit of a byte-long (8-bit-long) register is bit number seven,
indicated by “[7]”. The most significant bit (MSB) of a
word-long (16-bit-long) register is bit number fifteen,
indicated by “[15]”. Multiple bits of a register can be
alluded to with the use of a colon, e.g., bits 2, 1 and
0 of the MFR_PWM_CONFIG register are indicated by
“MFR_PWM_CONFIG[2:0]”. Bits can take on values of 0b
or 1b. The subscripted “b” suffix indicates the number’s
value is in binary. Values in hexadecimal are indicated with
a “0x” prefix. For example, decimal value “89” is indicated
by 0x59 and 01011001b (8-bit-long values), as well as
0x0059 and 0000000001011001b (16-bit-long values).
One further shorthand notion the reader will notice is the
italicized “n” or “n”. “n” can take on a value of 0 or 1—and
provides an easy way to refer to registers which are paged
commands, i.e., register names which have the same
command code value but can be configured independently
(or yield channel-specific telemetry) for Channel 0 (Page
0, or 0x00) vs Channel 1 (Page 1, or 0x01). Registers
For more information www.linear.com/LTM4676A
4676af
LTM4676A
Operation
lacking an “n” are therefore easily identified as being
global in nature, i.e., common to both Channels/Outputs.
For example, the switching frequency setting commanded
by register FREQUENCY_SWITCH is common to both
channels, and lacks “n”. Another example: the READ_VIN
register contains the digitized input voltage as seen at
the SVIN pin, and SVIN is unique, i.e., common to both
Channels. In contrast, the nominal commanded output
voltage is indicated by the register VOUT_COMMANDn.
The “n” indicates that VOUT_COMMAND can be set differently for Channel 0 vs Channel 1. Executing the PAGE
Command (Command Code 0x00) with payload 0x00 sets
the LTM4676A to write/read data pertaining to Channel 0 in
all subsequent I2C transactions until the Page is changed.
Executing the PAGE Command with payload 0x01 sets the
LTM4676A to write/read data pertaining to Channel 1 in
all subsequent I2C transactions until the Page is changed.
Executing the PAGE Command with payload 0xFF sets the
LTM4676A to write data pertaining to Channels 0 and 1
in all subsequent I2C write transactions until the Page is
changed. Reads from and writes to global registers do
not require setting the Page to 0xFF. Reads from channelspecific (i.e., non-global) registers when the Page is set to
0xFF result in the LTM4676A reporting the value on Page
0x00 (i.e., Channel 0-specific data).
The list below itemizes aspects of the LTM4676A relating
to power supply functions that are configurable by I2C
communications—provided the state of the WP (write
protect) pin and the WRITE_PROTECT register value permit
the I2C writes—and by EEPROM settings:
Output start-up voltages (VOUT_COMMANDn), the
maximum commandable output voltages (VOUT_MAXn),
output margin high (VOUT_MARGIN_HIGHn) and margin
low (VOUT_MARGIN_LOWn) command voltages, and
output over/undervoltage warning and fault thresholds
(VOUT_OV_WARN_LIMITn , VOUT_OV_FAULT_LIMITn ,
VOUT_UV_WARN_LIMITn , and VOUT_UV_FAULT_
LIMITn). Additionally, these values can be configured
at SVIN power-up according to resistor-pin strapping of
the VOUT0CFG, VTRIM0CFG, VOUT1CFG and/or VTRIM1CFG
pins, provided MFR_CONFIG_ALL[6] = 0b.
n
Output voltages, on the fly, including transition rate
(∆V/∆t), VOUT_TRANSITION_RATEn — either by I2C
n
writes to the VOUT_COMMANDn , VOUT_MARGIN_
HIGHn , or VOUT_MARGIN_LOWn registers, and/or to
the OPERATIONn register.
Input undervoltage-lockout, rising (VIN_ON) and input
undervoltage lockout, falling (VIN_OFF), based on the
SVIN pin voltage.
n
Switching frequency (FREQUENCY_SWITCH) and channel
phase-interleaving angle (MFR_PWM_CONFIG[2:0]).
However, these parameters can be changed via I2C
communications only when the LTM4676A’s channels
are off, i.e., not switching. The LTM4676A synchronizes
its switching frequency to a clock signal supplied to
its SYNC pin when MFR_CONFIG_ALL[4]=1b. These
parameters can be configured at SVIN power-up according
to resistor-pin strapping of the FSWPHCFG pin, provided
MFR_CONFIG_ALL[6] = 0b.
n
Output voltage turn-on and turn-off sequencing and
associated watchdog timers, namely:
n
• Output voltage turn-on delay time (the time delay
from the LTM4676A being commanded to turn on,
e.g., by the RUNn pin toggling from logic low to high,
before switching action commences. TON_DELAYn).
• Output voltage soft-start ramp-up time (TON_RISEn).
• The amount of time (TON_MAX_FAULT_LIMITn)
permitted to elapse after the LTM4676A is
commanded to turn on, e.g., by the RUNn pin toggling
from logic low to high, after which, if the output voltage
fails to exceed the output undervoltage fault threshold
(VOUT_UV_FAULT_LIMITn), the LTM4676A’s output
(VOUTn) is declared to have not come up in a timely
manner.
• The LTM4676A’s response to any such aforementioned TON_MAX_FAULT_LIMIT n event
(TON_MAX_FAULT_RESPONSEn).
• Output voltage soft-stop ramp-down time
(TOFF_FALLn).
• Output voltage turn-off delay time (the time delay
from the LTM4676A being commanded to turn off,
e.g., by the RUNn pin toggling from logic high to low,
before switching action ceases. TOFF_DELAYn).
4676af
For more information www.linear.com/LTM4676A
25
LTM4676A
Operation
• When commanded to turn off its output—or,
when turning off its output in response to a fault—
configuring whether the LTM4676A's output (VOUTn)
becomes high impedance (“High-Z” or “three
state”—turning off both MTn and MBn in the power
stage). (“Immediate Off”, ON_OFF_CONFIGn[0] =
1b vs configuring the output voltage to be ramped
down according to TOFF_FALLn and/or TOFF_DELAYn
settings, ON_OFF_CONFIGn[0] = 0b).
• The amount of time (TOFF_MAX_WARN_LIMITn)
permitted to elapse after the LTM4676A is supposed
to have turned off its output, i.e., at the end of the
period dictated by TOFF_FALLn , after which, If the
output voltage has not fallen below 12.5% of the
former target voltage of regulation, the LTM4676A’s
output (VOUTn) is declared to have not powered down
in a timely manner.
Configurable output voltage restart time. Subsequent to
the RUNn pin being pulled low, the LTM4676A pulls RUNn
logic low, itself, and the output cannot be restarted until a
minimum time has elapsed—the restart delay time. This
delay assures proper sequencing of all system rails. The
minimum restart delay processed by the LTM4676A is
the longer of (TOFF_DELAYn + TOFF_FALLn + 136ms)
vs the commanded MFR_RESTART_DELAYn register
value. At the end of this delay, the LTM4676A releases
its RUNn pin.
n
Configurable fault-hiccup retry delay time. When a
fault occurs in which the LTM4676A’s fault response
behavior to that fault is to reattempt power-up of its
output voltage after said fault ceases to be present (e.g.,
“Infinite Retry”), the delay time for the LTM4676A to
re-engage switching action is the longer of the MFR_
RETRY_DELAYn time vs the time required for the output
to decay below 12.5% of the formerly commanded
output voltage value (unless this lattermost criteria, i.e.,
requiring the output to decay below 12.5% is negated by
the setting of MFR_CHAN_CONFIGn [0] to “1b”—which
is the LTM4676A’s factory-NVM default setting).
n
Output over/undervoltage fault responses (VOUT_OV_
FAULT_RESPONSEn, VOUT_UV_FAULT_RESPONSEn).
n
Time-averaged current limit warning and instantaneous
peak (cycle-by-cycle) fault thresholds, and fault response
(IOUT_OC_WARN_LIMITn, IOUT_OC_FAULT_LIMITn,
IOUT_OC_FAULT_RESPONSEn).
n
Channel (VOUT0, VOUT1) overtemperature warning and
fault thresholds, and fault response (OT_WARN_LIMITn,
OT_FAULT_LIMITn, OT_FAULT_RESPONSEn).
n
Channel (V OUT0, V OUT1) undertemperature fault
thresholds and fault response (UT_FAULT_LIMITn,
UT_FAULT_RESPONSEn).
n
Input overvoltage fault threshold and response
(VIN_OV_FAULT_LIMIT, VIN_OV_FAULT_RESPONSE),
based on the SVIN pin voltage.
n
Input undervoltage warning threshold (VIN_UV_WARN_
LIMIT) based on the SVIN pin voltage.
n
Module input overcurrent warning threshold
(IIN_OC_WARN_LIMIT)
n
The control IC within the LTM4676A module ceases
switching action if control IC temperature exceeds 160°C
(Note 12). The control IC resumes operation after a 10°C
cool-down hysteresis. Note that these typical parameters
are based on measurements in a lab oven and are not
production tested. This overtemperature protection is
intended to protect the device during momentary overload
conditions. The maximum rated junction temperature will
be exceeded when this protection is active. Continuous
operation above the specified absolute maximum operating junction temperature may impair device reliability or
permanently damage the device.
Time-Averaged and Peak Readback Data
Time-averaged telemetry readback data accessible via I2C
communications follow:
Channel output current (READ_IOUTn) and peak
observed value of READ_IOUTn (MFR_IOUT_PEAKn).
n
Channel output voltage (READ_VOUTn) and peak
observed value of READ_VOUTn (MFR_VOUT_PEAKn).
n
Channel output power (READ_POUTn).
n
Channel input current (MFR_READ_IINn) and module
input current (READ_IIN).
n
26
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
Channel temperatures (READ_TEMPERATURE_1n) and
peak observed values of READ_TEMPERATURE_1n
(MFR_TEMPERATURE_1_PEAKn).
n
Control IC temperature (READ_TEMPERATURE_2) and
peak observed value (MFR_TEMPERATURE_2_PEAK).
n
Input voltage (READ_VIN), based on the voltage of
the SVIN pin, and peak observed value of READ_VIN
(MFR_VIN_PEAK).
n
Channel topside power MOSFET (MTn) duty cycle
(READ_DUTY_CYCLEn)
n
Digitized cyclical telemetry is available at a 10Hz update
rate, typical. Through the use of the MFR_ADC_CONTROL
command, some signals of interest can be digitized more
frequently—up to a 125Hz update rate, typical. Availability
of newly digitized telemetry data can be made known via
the MFR_ADC_TELEMETRY_STATUS command.
Peak observed values of telemetry readback data can
be cleared with the MFR_CLEAR_PEAKS I2C command,
provided the WRITE_PROTECT register value permits it.
(Executing MFR_CLEAR_PEAKS can be performed regardless of the state of the WP pin.)
Details on the LTM4676A’s Fault Log Feature follow:
Fault logging is enabled when MFR_CONFIG_ALL[7] = 1b.
n
A fault log is present in NVM when STATUS_MFR_
SPECIFICn [3]Reports “1b”, which is propagated to the
MFR Bit (Bit 12) of the STATUS_WORD register.
n
Retrieving fault log data, if present, is performed with
the MFR_FAULT_LOG command. 147 bytes of data
are retrieved using the PMBus-defined variant to the
SMBus block read protocol.
n
The fault log contents in NVM, if present, are cleared
by executing the MFR_FAULT_LOG_CLEAR command.
n
The fault log will not be written if a fault log is already
present in NVM.
n
The LTM4676A can be forced to write a fault log to
its NVM by executing the MFR_FAULT_LOG_STORE
command; the LTM4676A will behave as if a channel
faulted off. Note the command is NACKed and a CML
fault is reported if a fault log is already present at the
time of executing MFR_FAULT_LOG_STORE.
n
When an external stimulus pulls the LTM4676A’s
GPIOn pin(s) logic low, the respective channel (VOUTn)
either: takes no action on it, i.e., ignores it completely—
if MFR_GPIO_RESPONSEn = 0x00; or, turns off immediately,
i.e., the power stage(s) become high impedance (“inhibited”)—
if MFR_GPIO_RESPONSEn = 0xC0.
The MFR_GPIO_PROPAGATEn register contents configure which fault(s) cause the LTM4676A to pull its GPIOn
pin(s) logic low.
I2C communications are originated by the user’s (system’s)
I2C master device. Writes/reads to/from Channel 0 of the
LTM4676A (VOUT0: PAGE 0x00), to/from Channel 1 of the
LTM4676A (VOUT1: PAGE 0x01), or writes to both Channels
0 and 1 of the LTM4676A (VOUT0 and VOUT1: PAGE 0xFF)
are possible. The target channel(s) of interest are selected
by the I2C master by executing the PAGE command and
sending the appropriate argument (0x00, 0x01, 0xFF) in
the payload. The PAGE command is unrestricted, i.e.,
not affected by the WP pin or WRITE_PROTECT register
settings.
The LTM4676A always responds to its global slave addresses, 0x5A and 0x5B. Commands sent to the global
address 0x5A act the same as if the PAGE command were
set to 0xFF, i.e., received commands are written to both
channels simultaneously. Commands sent to the global
address 0x5B are applied to the PAGE active at the time of
the global address transaction, i.e., allows channel-specific
command of all LTM4676A devices on the bus.
I2C commands not listed above that relate to Fault Status
and EEPROM NVM Operations follow. Writing of the
following is possible provided the state of the WP (write
protect) pin and the WRITE_PROTECT register value
permits the I2C writes:
Soliciting (reading) module fault status and clearing
(writing) module fault status (CLEAR_FAULTS, STATUS_
BYTEn, STATUS_WORDn, STATUS_VOUTn, STATUS_
IOUTn, STATUS_INPUT, STATUS_TEMPERATUREn,
STATUS_CML [communications, memory, and/or
logic], and STATUS_MFR_SPECIFICn [miscellaneous]).
n
Storing the LTM4676A’s user-writable RAM register
data to the EEPROM NVM (STORE_USER_ALL).
n
For more information www.linear.com/LTM4676A
4676af
27
LTM4676A
Operation
An alternate means to the STORE_USER_ALL
command to directly erase and write the LTM4676A’s
EEPROM contents, protected by unlock keys, to
facilitate programming of the LTM4676A EEPROM in
environments such as ICT (in-circuit test) and bulk
programming by, e.g., embedded hardware or by the
LTpowerPlay GUI. Also, a means to directly read the
LTM4676A EEPROM contents (MFR_EE_UNLOCK,
MFR_EE_ERASE, MFR_EE_DATA).
n
Instigating a soft reset of the LTM4676A without powercycling SVIN power (MFR_RESET). The MFR_RESET
command triggers the download of EEPROM NVM data
to RAM registers, as if SVIN power had been cycled.
n
Forcing a download of EEPROM NVM data to
RAM registers (RESTORE_USER_ALL). This is
indistinguishable from executing MFR_RESET.
n
Other data that can be obtained from the LTM4676A via
I2C communications are as follows:
Soliciting the LTM4676A for its PMBus capabilities, as
defined by PMBus (CAPABILITY):
n
• PEC (packet error checking). Note, the LTM4676A
requires valid PEC in I2C communications when
MFR_CONFIG_ALL[2] = 1b. The NVM factory-default
configuration is MFR_CONFIG_ALL[2] = 0b, i.e., PEC
not required.
• I2C communications can be supported at up to 400kHz
SCL bus speed. Note, clock low extending (clock
stretching) must be enabled on the LTM4676A to
ensure robust communications above 100kHz SCL
bus speeds, i.e., MFR_CONFIG_ALL[1] = 1b. The
NVM factory-default configuration is MFR_CONFIG_
ALL[1] = 0b, i.e. Clock stretching is disabled.
• The LTM4676A has an SMBALERT (ALERT) pin
and does support the SMBus ARA (alert response
address) protocol.
Soliciting the module for the maximum output voltage
it can be commanded to produce (MFR_VOUT_MAXn).
n
Soliciting the device for the data format of its output
voltage-related registers (VOUT_MODEn).
n
28
Soliciting the device for the revisions of PMBus specifications that it supports (Part I: Rev. 1.2; Part II: Rev 1.2).
n
Soliciting the device for the identification of the
manufacturer of the LTM4676A, “LTC” (MFR_ID) and
the manufacturer code representing the LTM4676A and
revision, 0x47EX (MFR_SPECIAL_ID).
n
Soliciting the device for its part number, “LTM4676A”
(MFR_MODEL).
n
Soliciting the module for its serial umber
(MFR_SERIAL).
n
The digital status of the LTM4676A’s I/O pads and
validity of the ADC (MFR_PADS) and WP pin status
(MFR_COMMON[0]).
n
The following list indicates other aspects of the LTM4676A
relating to power system management and power
sequencing that are configurable by I2C communications—
provided the state of the WP (write protect) pin and the
WRITE_PROTECT register value permit the I2C writes—and
by EEPROM settings:
Providing multiple means to read/write data directly
to a particular channel of the LTM4676A by assigning
additional slave address for channels 0 and 1 (MFR_
RAIL_ADDRESSn), the benefit of which is that it reduces
page command usage and associated I2C traffic. It
also facilitates altering the same register of multiple
LTM4676A in unison without invoking the PMBus group
command protocol. See also PAGE_PLUS_READ and
PAGE_PLUS_WRITE.
n
Configuring the output voltage to be on or off by means
other than the RUNn pin (ON_OFF_CONFIGn [3], OPERATION commands).
n
Configuring whether the LTM4676A performs a
CLEAR_FAULTS command upon itself when either
RUNn pin toggles from logic low to logic high.
(MFR_CONFIG_ALL[0]).
n
Configuring whether the LTM4676A pulls RUNn logic
low when the LTM4676A is commanded off by other
means (MFR_CHAN_CONFIGn[4]).
n
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
Configuring the response of the LTM4676A when it is
commanded to turn on its output prior to the completion
of processing TOFF_DELAYn and TOFF_FALLn powerdown sequencing (MFR_CHAN_CONFIGn[3]).
n
Configuring whether the LTM4676A’s output is
disabled when SHARE_CLK is held low (MFR_CHAN_
CONFIGn[2]).
n
Configuring whether the ALERT pin is pulled low when
GPIOn is pulled low by external stimulus (MFR_CHAN_
CONFIGn[1]).
n
Setting the value of the MFR_IIN_OFFSETn registers,
representing an estimate of the current drawn by the
SVIN pin. The SVIN pin current is not measured by
the LTM4676A but the MFR_IIN_OFFSETn is used in
computing and reporting channel and total module
input currents (MFR_READ_IINn , READ_IIN).
n
Three words (six bytes) of the LTM4676A’s EEPROM that
are available for storing user data. (USER_DATA_03n,
USER_DATA_04).
n
Invoking or releasing several levels of I2C write protection
(WRITE_PROTECT).
n
Configuring the bus timeout for 255ms (MFR_CONFIG_
ALL[3]=1b) if the host needs more time to complete
I2C transactions.
n
Determining whether the user-editable RAM register
values are identical to the contents of the user NVM
(MFR_COMPARE_USER_ALL).
n
Setting the programmable output voltage range of VOUT
to a narrower range (0.5V to 2.75V) in order to achieve
a higher resolution of VOUT adjustment than is available
by default (MFR_PWM_MODEn[1]). MFR_PWM_MODE
cannot be changed on the fly; switching action must
be off. Note that altering the VOUT range alters the gain
of the control loop and may therefore require loop
compensation to be adjusted.
n
Altering the temperature coefficient of the LTM4676A’s
current sensing elements, if needed (MFR_IOUT_CAL_
GAIN_TCn) (uncommon to alter this parameter from its
NVM-Factory default setting).
n
Altering the gain or offset of the power stage sensors
(MFR_TEMP_1_GAINn and MFR_TEMP_1_OFFSETn)—
or that of the external temperature sensor, when an
external temperature sensor is used on the TSNS1a
pin. (Uncommon to alter this parameter from its NVMfactory default setting).
n
Configuring whether the LTM4676A Pulls SHARE_CLK
logic low when SVIN has fallen outside Its UVLO
thresholds (MFR_PWM_CONFIG[4]). MFR_PWM_
CONFIG cannot be changed on the fly; switching action
must be off (uncommon to alter this parameter from
its NVM-factory default setting).
n
Configuring whether the LTM4676A’s output voltage
digital servos are active vs disengaged (MFR_PWM_
MODEn[6]. Uncommon to alter this parameter from its
NVM-factory default settings).
n
Configuring whether the LTM4676A’s current limit
range is set to high range vs low range. (MFR_PWM_
MODEn[7]. Not recommended to alter this parameter
from its NVM-factory default settings).
n
Remaining LTM4676A status that can be queried over I2C
communications follow:
Access to three “hand-shaking” status bits (MFR_COMMON[6:4]) to ease implementation of PMBus busy
protocols, i.e., enabling fast and robust system level
communication through polling of these bits to infer
LTM4676A’s readiness to act on subsequent I2C writes.
(See PMBus communication and command processing,
in the Applications Information section.)
n
Providing a means to determine whether the LTM4676A
NVM download to RAM has occurred (“NVM Initialized,”
MFR_COMMON[3]).
n
Providing a means other than ARA protocol to determine whether the LTM4676A is pulling ALERT low
(MFR_COMMON[7]).
n
Detecting a SHARE_CLK timeout event
(MFR_COMMON[1]).
n
Verifying or Altering the Slave Address of the LTM4676A
(MFR_ADDRESS).
n
4676af
For more information www.linear.com/LTM4676A
29
LTM4676A
Operation
Power Module Overview
A dedicated remote-sense amplifier precisely kelvin-senses
VOUT0’s load via the differential pin-pair formed by VOSNS0+
and VOSNS0–. VOUT0 can be commanded to between 0.5VDC
and 5.5VDC. VOUT1 is sensed via the pin-pair formed by
VOSNS1 and signal ground of the module’s SGND. VOUT1
can be commanded to between 0.5VDC and 5.5VDC.
Output voltage readback telemetry is available over I2C
(READ_VOUTn registers). Peak output voltage readback
telemetry is accessible in the MFR_READ_VOUT_PEAKn
registers. If VOSNS0– exceeds VOSNS+, no phase reversal
of the differentially-sensed output voltage feedback signal
occurs (Note 12). Similarly, no phase reversal occurs when
SGND exceeds VOSNS1(Note 12). For added flexibility, the
VOSNSO+/VOSNSO– feedback pins can be configured as the
control loop feedback path for both VOUT0 and VOUT1 by
setting MFR_PWM_CONFIG[7]=1b. (See Figure 36).
The typical application schematic is shown in Figure 62
on the back page of this data sheet.
The LTM4676A can operate from input voltages between
5.75V and 17V (see front page figure). In this con-figuration,
INTVCC MOSFET driver and control IC bias is generated
internally by an LDO fed from SVIN to produce 5V at up to
100mA peak output current. Additional internal LDOs—
3.3V (VDD33), derived from INTVCC, and 2.5V (VDD25),
derived from VDD33—bias the LTM4676A’s digital circuitry.
When INTVCC is connected to SVIN, the LTM4676A can
operate from input voltages between 4.5V and 5.75V (see
Figure 29). Control IC bias (SVIN) is routed independent
of the inputs to the power stages (VIN0, VIN1); this enables step-down DC/DC conversion from less than 4.5V
input (see Figure 31), so long as auxiliary power (4.5V
~ 17V) is available to bias the control IC appropriately.
Furthermore, the inputs of the two power stages are not
connected together internal to the module; therefore, DC/
DC step-down conversion from two different source power
supplies can be performed.
Per Note 6 of the Electrical Characteristics section, the
output current may require derating for some operating
scenarios. Detailed derating guidance is provided in the
Applications Information section.
30
The LTM4676A contains dual integrated constant frequency
current mode control buck regulators (Channel 0 and
Channel 1) whose built-in power MOSFETs are capable of
fast switching speed. The factory NVM-default switching
frequency clocks SYNC at 500kHz, to which the regulators synchronize their switching frequency. The default
phase-interleaving angle between the channels is 180°.
A pin-strapping resistor on FSWPHCFG configures the frequency of the SYNC clock (switching frequency) and the
channel phase relationship of the channels to each other
and with respect to the falling edge of the SYNC signal.
(Not all possible combinations of switching frequency
and phase-angle assignments are settable by resistor pin
programming; see Table 4. Configure the LTM4676A’s
NVM to implement settings not available by resistor-pin
strapping.) When a FSWPHCFG pin-strap resistor sets the
channel phase relationship of the LTM4676A’s channels,
the SYNC clock is not driven by the module; instead, SYNC
becomes strictly a high impedance input and channel
switching frequency is then synchronized to SYNC provided
by an externally-generated clock or sibling LTM4676A with
pull-up resistor to VDD33. Switching frequency and phase
relationship can be altered via the I2C interface, but only
when switching action is off, i.e., when the module is not
regulating either output. See the Applications Information
section for details.
Internal feedback loop compensation for Regulator 0 is
available by connecting COMP0a to COMP0b. (For Regulator 1, the connection is from COMP1a to COMP1b.) With
current mode control and internal feedback loop compensation, the LTM4676A module has sufficient stability
margins and good transient performance with a wide
range of output capacitors—even all-ceramic MLCCs.
Table 20 provides guidance on input and output capacitors
recommended for many common operating conditions.
The Linear Technology μModule Power Design Tool is
available for transient and stability analysis. Furthermore,
expert users who prefer to not make use of the module’s
internal feedback loop compensation—but instead, tailor
the feedback loop compensation specifically for his/her
application—may do so by not connecting COMPn a to
COMPn b: the personalized loop compensation network
can be applied externally, i.e., from COMPn a to SGND,
and leaving COMPn b open circuit.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
The LTM4676A has two general purpose input/output
pins, named GPIO0 and GPIO1. The behavior of these pins
is configurable via registers MFR_GPIO_PROPAGATEn
and MFR_GPIO_RESPONSEn. The GPIOn pins are high
impedance during NVM-download-to-RAM initialization.
These pins are intended to perform one of two primary
functions, or a hybrid of the two: behave as open- drain,
active low fault/warning indicators; and/or, behave as
auxiliary RUN pins for their respective VOUTs. In the former
case, the pins can be configured as interrupt pins, pulling
active low when output under/overvoltage, input under/
overvoltage, input/output overcurrent, overtemperature,
and/or communication, memory or logic (CML) fault or
warning events are detected by the LTM4676A. Factory
NVM-default settings configure the LTM4676A for the
latter case, enabling the GPIOn to be bussed to paralleled
siblings (paralleled LTM4676A channels and/or modules),
for purposes of coordinating orderly power-up and powerdown, i.e., in unison. The LTM4676A DC/DC regulator does
not feature a traditional “power good” (PGOOD) indicator pin
to indicate when the output voltage is within a few percent
of the target regulation point. However, the GPIOn pin can
be configured as a PGOOD indicator. If used for eventbased sequencing of downstream rails, configure GPIOn
as the unfiltered output of the VOUT_UV_FAULT_LIMITn
comparator, setting Bit 12 of MFR_GPIO_PROPAGATEn to
“1b”; do not set Bits 9 and 10 of MFR_GPIO_PROPAGATEn
for this purpose, since the propagation of power good in
those latter instances is subject to supervisor filtering and
comparator latency. If it is necessary to have the desired
PGOOD polarity appear on the GPIOn pin immediately
upon SVIN power-up—given that the pin will initially be
high impedance, until NVM contents have downloaded
to RAM—a pull-down Schottky diode is needed between
the RUNn pin of the LTM4676A and the respective GPIOn
pin. (see Figure 2). If the GPIOn pin is configured as a
PGOOD indicator, the MFR_GPIO_RESPONSEn must be
set to “ignore” (0x00), or else the LTM4676A cannot start
up due to the latch-off conditions imposed.
The RUNn pin is a bidirectional open-drain pin. This means
it should never be driven logic high from a low impedance
source. Instead, simply provide a 10k pull-up resistor from
the RUNn pins to VDD33. The LTM4676A pulls its RUNn
pin logic low during NVM-download-to-RAM initialization,
Voltage Based Sequencing by Cascading GPIOn Pins Into RUNn Pins
(MFR_GPIO_PROPAGATE = XXX1X00XX00XXXXXb and MFR_GPIO_RESPONSE = 0x00)
*
START
GPIO0 = VOUT0_UVUF
RUN0
LTM4676A
RUN1
GPIO1 = VOUT1_UVUF
*
*
RUN0
GPIO0 = VOUT0_UVUF
LTM4676A
GPIO1 = VOUT1_UVUF
RUN1
*
4676A F02
TO NEXT CHANNEL
IN THE SEQUENCE
NOTE: RESISTOR OR RC PULL-UPS ON RUNn AND GPIOn PINS NOT SHOWN
*OPTIONAL SIGNAL SCHOTTKY DIODE. ONLY NEEDED WHEN ACCURATE PGOOD
(POWER GOOD) INDICATION IS REQURED BY THE SYSTEM/USER IMMEDIATELY
AT SVIN POWER UP
Figure 2. Event (Voltage) Based Sequencing
when SVIN is below the commanded undervoltage lockout
voltage (VIN_ON, rising and VIN_OFF, falling), and
subsequent to external stimulus pulling RUN low—for
a minimum time dictated by MFR_RESTART_DELAYn.
Bussing the respective RUNn and GPIOn pins to sibling
LTM4676A modules enables coordinated power-up/powerdown to be well orchestrated, i.e., performing turn-on and
turn-off in a unified fashion.
When RUNn exceeds 2V, the LTM4676A initially idles for
a time dictated by the TON_DELAYn register. After the
TON_DELAYn time expires, the module begins ramping
up the respective control loop’s internal reference,
starting from 0V. In the absence of a pre-biased VOUTn
condition, the output voltage is ramped linearly from 0V
to the commanded target voltage, with a ramp-up time
dictated by the TON_RISEn register. In the presence of a
pre-biased VOUTn condition, the output voltage is brought
into regulation in the same manner as aforementioned,
with the exception that inductor current is prevented from
going negative (the module’s controller is operated in
discontinuous mode operation during start-up). In both
cases, the output voltage reaches regulation in a consistent
time, as measured with respect to RUNn toggling high.
See start-up oscilloscope shots in the Typical Performance
Characteristics section.
4676af
For more information www.linear.com/LTM4676A
31
LTM4676A
Operation
Pulling the RUNn pin below 1.4V turns off the DC/DC
converter, i.e., forces the respective regulator into a
shutdown state. Factory NVM-default settings configure
the LTM4676A to turn off its power stage MOSFETs
immediately, thereby becoming high impedance. The
output voltage then decays according to whatever output
capacitance and load impedance is present. Alternatively,
NVM/register settings can configure the LTM4676A to
actively discharge VOUTn when RUNn is pulled logic low,
according to prescribed TOFF_DELAYn delay and TOFF_
FALLn ramp-down times. See the Applications Information section for details. The LTM4676A does not feature
an explicit, analog TRACK pin. Rail-to-rail tracking and
sequencing is handled digitally, as explained previously.
Bussing the open-drain SHARE_CLK pins of all LTM4676As
(and providing a pull-up resistor to VDD33) provides a means
for all LTM4676As in the system to synchronize their timebase (or “heartbeat”) to the fastest SHARE_CLK clock.
Sharing the heartbeat amongst all LTM4676A ensures
that all rails are sequenced according to expectations;
it negates timing errors that could otherwise materialize
due to SHARE_CLK (time-base) tolerance and part-to-part
variation.
Electrically connect adjacent pins ISNS0a+ to ISNS0b+; ISNS0a–
to ISNS0b–; ISNS1a+ to ISNS1b+; and ISNS1a– to ISNS01b–.
Current sense information is derived from across the
power inductors (ISNSnb+/ISNSn b– pin-pairs) internal to the
LTM4676A and made available to the internal control IC’s
current control loops and ADC sensors (ISNSn a+/ISNSn a–) by
the aforementioned connections. Output current readback
telemetry is available over I2C (READ_IOUTn registers).
Peak output current readback telemetry is available in the
MFR_READ_IOUT_PEAKn registers.
Output power readback is computed by the LTM4676A
according to:
READ_POUTn = READ_VOUTn • READ_IOUTn
Alternating excitation currents of 2µA and 30µA are
sourced from each of the TSNS0a and TSNS1a pins.
Connecting TSNS0a to TSNS0b, and then TSNS1a to TSNS1b,
temperature sensing of the Channel 0 and Channel 1 power
stages is realized by the LTM4676A digitizing the voltages
that appear at the PNP transistor temperature sensors
32
that reside at pins TSNS0b and TSNS1b, respectively.
The LTM4676A performs what is known in the industry
as delta VBE (∆VBE) computations and makes channel
(power stage) temperature telemetry available over I2C
(READ_TEMPERATURE_1n). The junction temperature
of the control IC within the LTM4676A is also available
over I2C (READ_TEMPERATURE_2). Observed peak
Channel temperatures can be read back in registers
READ_MFR_TEMPERATURE_1_PEAKn. Observed peak
temperature of the control IC can be read back in register
MFR_READ_TEMPERATURE_2_PEAK.
For a fixed load current, the amplitude of the current
sense information changes over temperature due to the
temperature coefficient of copper (inductor DCR), which
is approximately 3900ppm/°C. This would introduce significant current readback error over the operating range
of the module if not for the fact that the LTM4676A’s
temperature readback information is used in conjunction
with the perceived current sense signal to yield temperaturecorrected current readback data.
If desired, it is possible to use only the temperature
readback information derived from the TSNS0a/TSNS0b
pins to yield temperature-corrected current readback data
for both Channels 0 and 1. This frees up the Channel 1
temperature sensor to monitor a temperature sensor
external to the LTM4676A. This is achieved by setting
MFR_PWM_MODE0[4] = 1b (the NVM-factory default
value is 0b). This degrades the current readback accuracy
of Channel 1—more so when Channel 0 and Channel 1
are not paralleled outputs. However, the TSNS1a pin
becomes available to be connected to an external diodeconnected small-signal PNP transistor (such as 2N3906)
and 10nF X7R capacitor, i.e., an external temperature
sensor, whose temperature readback data and peak value
are available over I2C (READ_TEMPERATURE_11, MFR_
READ_TEMPERATURE_1_PEAK1). Implementation of the
aforementioned is as follows: (1) local to the LTM4676A,
electrically connect a 10nF X7R capacitor directly from
TSNS1a to SGND; (2) differentially route a pair of traces
from the LTM4676A's TSNS1a and SGND pins to the target PNP transistor; (3) electrically connect the emitter of
the PNP transistor to TSNS1a; (4) electrically connect the
collector and base of the PNP transistor to SGND.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
Power stage duty cycle readback telemetry is available over
I2C (READ_DUTY_CYCLEn registers). Computed channel
input current readback is computed by the LTM4676A as:
MFR_READ_IINn = READ_DUTY_CYCLEn • READ_IOUTn
+ MFR_IIN_OFFSETn
Computed module input current readback is computed
by the LTM4676A as:
READ_IIN=MFR _READ_IIN0 +MFR _READ_IIN1
where MFR_IIN_OFFSETn is a register value representing
the SVIN input bias current. The SVIN current is not digitized by the module. The factory NVM-default value of
MFR_IIN_OFFSET n is 30.5mA, representing the
contribution of current drawn by each of the module’s
channels on the SVIN pin, when the power stages are
operating in forced continuous mode at the factorydefault switching frequency of 500kHz. See Table 8 in
the Applications Information section for recommended
MFR_IIN_OFFSETn setting vs Switching Frequency. The
aforementioned method by which input current is calculated
yields an accurate current readback value even at light load
currents, but only as long as the module is configured for
forced continuous operation (NVM-factory default). SVIN
and peak SVIN readback telemetry is accessible via I2C in
the READ_VIN and MFR_VIN_PEAK registers, respectively.
The power stage switch nodes are brought out on the SWn
pin for functional operation monitoring and for optional
installation of a resistor-capacitor snubber circuit (terminated to GND) for reduced EMI. Internal 2.2nF snubber
capacitors connected directly to the switch nodes further
facilitate implementation of a snubber network, if desired.
See the Application Information section for details.
The LTM4676A features a write protect (WP) pin. If WP is
open circuit or logic high, I2C writes are severely restricted:
only I2C writes to the PAGE, OPERATION, CLEAR_FAULTS,
MFR_CLEAR_PEAKS, and MFR_EE_UNLOCK commands
are supported, with the exception that individual fault bits
can be cleared by writing a “1b” to the respective bits in the
STATUS_* registers. Register reads are never restricted.
Not to be confused with the WP pin, the LTM4676A
features a WRITE_PROTECT register, which is also used to
restrict I2C writes to register contents. Refer to Appendix
C: PMBus Command Details for details. The WP pin and
the WRITE_PROTECT register provide a level of protection
against accidental changes to RAM and EEPROM contents.
The LTM4676A supports all possible 7-bit slave addresses.
The factory NVM-default slave address is 0x4F. The lower
four bits of the LTM4676A’s slave address can be altered
from this default value by connecting a resistor from
the ASEL pin to SGND. See Table 5 in the Applications
Information section for details. Bits[6:4] can be altered by
writing to the SLAVE_ADDRESS command. The value of
the SLAVE_ADDRESS command can be stored to NVM,
however, the lower four bits of the SLAVE_ADDRESS is
always dictated by the ASEL resistor pin-strap setting.
Up to four LTM4676A modules (8 channels) can be paralleled, suitable for powering ~100A loads such as CPUs and
GPUs. (See Figure 33) The LTM4676A can be paralleled with
LTM4620A or LTM4630 modules, as well (see Figure 34
and Figure 35).
EEPROM
The LTM4676A’s control IC contains an internal EEPROM
(non-volatile memory, NVM) to store configuration settings
and fault log information. EEPROM endurance retention
and mass write operation time are specified in the Electrical Characteristics and Absolute Maximum Ratings
sections. Write operations at TJ < 0°C or at TJ > 85°C are
possible although the Electrical Characteristics are not
guaranteed and the EEPROM retention characteristics
may be degraded. Read operations performed at junction
temperatures between –40°C and 125°C do not degrade
the EEPROM. The fault logging function, which is useful
in debugging system problems that may occur at high
temperatures, only writes to fault log-specific EEPROM
locations (partitions). If occasional writes to these registers occur above 85°C junction, the slight degradation in
the data retention characteristics of the fault log does not
undermine the usefulness of the function.
It is recommended that the EEPROM not be written when
the control IC die temperature is greater than 85°C. If the
die temperature exceeds 130°C, the LTM4676A’s control
IC disables all EEPROM write operations. EEPROM write
operations are subsequently re-enabled when the die
temperature drops below 125°C.
4676af
For more information www.linear.com/LTM4676A
33
LTM4676A
Operation
The degradation in EEPROM retention for temperatures
>125°C can be approximated by calculating the dimensionless acceleration factor using the following equation:
⎡⎛ Ea ⎞ ⎛
⎞⎤
1
1
–
⎢⎜ ⎟•⎜
⎟⎥
⎣⎝ k ⎠ ⎝ TUSE +273 TSTRESS +273 ⎠⎦
AF = e
where:
AF = acceleration factor
Ea = activation energy = 1.4eV
K = 8.617 • 10–5 eV/°K
TUSE = 125°C specified junction temperature
TSTRESS = actual junction temperature in °C
Example: Calculate the effect on retention when operating
at a junction temperature of 135°C for 10 hours.
TSTRESS = 130°C
set in the STATUS_BYTE and STATUS_WORD commands,
the appropriate bit is set in the STATUS_MFR_SPECIFIC
command, and the ALERT pin will be pulled low. EEPROM
repair can be attempted by writing the desired configuration
to the controller and executing a STORE_USER_ALL
command followed by a CLEAR_FAULTS command.
The LTM4676A manufacturing section of the EEPROM
is mirrored. The LTM4676A has the ability to operate if
either one of the two sections of the manufacturing section of the EEPROM configuration becomes corrupted.
If a discrepancy is detected, the “NVM CRC Fault” in the
STATUS_MFR_SPECIFIC command is set. If this bit
remains set after being cleared by issuing a CLEAR_FAULTS
or writing a 1 to this bit, an irrecoverable internal fault has
occurred. There are no provisions for field repairing unrecoverable EEPROM faults in the manufacturing section.
Serial Interface
TUSE = 125°C
AF= e[(1.4/8.617 • 10
–5)
• (1/398 – 1/403)] = 1.66
The equivalent operating time at 125°C = 16.6 hours.
Thus the overall retention of the EEPROM was degraded
by 6.6 hours as a result of operating at a junction temperature of 130°C for 10 hours. The effect of the overstress
is negligible when compared to the overall EEPROM
retention rating of 87,600 hours at a maximum junction
temperature of 125°C.
The LTM4676A serial interface is a PMBus compliant slave
device and can operate at any frequency between 10kHz
and 400kHz. The address is configurable using either
the EEPROM or an external resistor divider. In addition
the LTM4676A always responds to the global broadcast
address of 0x5A (7 bit) or 0x5B (7 bit). Address 0x5A
is not paged and is performed on both channels. 0x5B
respects the page command. Because address 0x5A
does not support page, it can not be used for any paged
reading commands.
The integrity of the EEPROM is checked with a CRC
calculation each time its data is read, such as after a
power-on reset or execution of a RESTORE_USER_ALL or
MFR_RESET command. If CRC error occurs, the MFR bit is
set in the STATUS_BYTE and STATUS_WORD commands.
The NVM CRC error bit in the STATUS_MFR_SPECIFIC
command is set and the ALERT and RUN pins are pulled
low disabling the output as a safety measure. The device
will only respond at special address 0x7C or global addresses 0x5A and 0x5B.
The serial interface supports the following protocols
defined in the PMBus specifications: 1) send command,
2) write byte, 3) write word, 4) group, 5) read byte, 6)
read word and 7) read block 8) PAGE_PLUS_READ,
9) PAGE_PLUS_WRITE 10) SMBALERT_MASK read,
11) SMBALERT_MASK write. All read operations will
return a valid PEC if the PMBus master requests it. If the
PEC_REQUIRED bit is set in the MFR_CONFIG_ALL command, the PMBus write operations will not be acted upon
until a valid PEC has been received by the LTM4676A.
CRC Protection
Communication Protection
The integrity of the EEPROM memory is checked after a
power-on reset. A CRC error will prevent the controller from
leaving the OFF state. If a CRC error occurs, the CML bit is
34
PEC write errors (if PEC_REQUIRED is active), attempts
to access unsupported commands, or writing invalid data
to supported commands will result in a CML fault. The
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Operation
CML bit is set in the STATUS_BYTE and STATUS_WORD
commands, the appropriate bit is set in the STATUS_CML
command, and the ALERT pin is pulled low.
Device Addressing
Fault Detection and Handling
A variety of fault and warning reporting and handling
mechanisms are available. Fault and warning detection
capabilities include:
Input OV/FAULT Protection and UV Warning
n
The LTM4676A offers four different types of addressing
over the PMBus interface, specifically: 1) global, 2) device,
3) rail addressing and 4) alert response address (ARA).
Global addressing provides a means of the PMBus master to
address all LTM4676A devices on the bus. The LTM4676A
global address is fixed 0x5A (7 bit) or 0xB4 (8 bit) and cannot be disabled. Commands sent to the global address act
the same as if PAGE is set to a value of 0xFF. Commands
sent are written to both channels simultaneously. Global
command 0x5B (7 bit) or 0xB6 (8 bit) is paged and allows
channel specific command of all LTM4676A devices on the
bus. Other LTC device types may respond at one or both of
these global addresses; therefore do not read from global
addresses.
Rail addressing provides a means for the bus master to
simultaneously communicate with all channels connected
together to produce a single output voltage (PolyPhase®).
While similar to global addressing, the rail address can
be dynamically assigned with the paged MFR_RAIL_ADDRESS command, allowing for any logical grouping of
channels that might be required for reliable system control.
Do not read from rail addresses because multiple LTC
devices may respond.
Device addressing provides the standard means of the
PMBus master communicating with a single instance of
an LTM4676A. The value of the device address is set by a
combination of the ASEL0 and ASEL1 configuration pins
and the MFR_ADDRESS command. When this addressing
means is used, the PAGE command determines the channel
being acted upon. Device addressing can be disabled by
writing a value of 0x80 to the MFR_ADDRESS.
All four means of PMBus addressing require the user to
employ disciplined planning to avoid addressing conflicts.
Communication to LTM4676A devices at global and rail
addresses should be limited to command write operations.
Average Input OC Warn
n
Output OV/UV Fault and Warn Protection
n
Output OC Fault and Warn Protection
n
Internal and External Overtemperature Fault and Warn
Protection
n
External Undertemperature Fault Protection
n
CML Fault (Communication, Memory or Logic)
n
External Fault Detection via the Bidirectional GPIOn
Pins.
n
In addition, the LTM4676A can map any combination of fault
indicators to their respective GPIOn pin using the propagate
GPIOn response commands, MFR_GPIO_PROPAGATEn.
Typical usage of a GPIO pin is as a driver for an external
crowbar device, overtemperature alert, overvoltage alert
or as an interrupt to cause a microcontroller to poll the
fault commands. Alternatively, the GPIOn pins can be
used as inputs to detect external faults downstream of the
controller that require an immediate response. The GPIO0
and/or GPIO1 pins can also be configured as power good
outputs. Power good indicates the controller output is
within the OV/UV fault thresholds. At power-up the pin will
initially be three-state. If it is necessary to have the desired
polarity on the pin at power-up in this configuration, attach
a Schottky diode between the RUN pin of the propagated
power good signal and the GPIO pin. The Cathode must
be attached to RUN and the Anode to the GPIO pin (see
Figure 2). If the GPIO pin is set to a power good status,
the MFR_GPIO_RESPONSE must be ignore otherwise a
latched off condition exists.
As described in the Soft-Start section, it is possible to
control start-up through concatenated events. If GPIOn
is used to drive the RUN pin of another controller, the
unfiltered VOUT_UV fault limit should be mapped to the
GPIO pin.
4676af
For more information www.linear.com/LTM4676A
35
LTM4676A
Operation
Any fault or warning event will cause the ALERT pin to assert
low unless the ALERT is masked by the SMBALERT_MASK
command. The pin will remain asserted low until the
CLEAR_FAULTS command is issued, the fault bit is written
to a 1, the PMBus master successfully reads the device
ARA register, bias power is cycled or a MFR_RESET or
RESTORE_USER_ALL command is issued. Channel specific
faults are cleared if the RUN pins are toggled OFF/ON or
the part is commanded OFF/ON via PMBus. If bit 0 of MFR_
CONFIG_ALL is set to a 1, toggling the RUN pins OFF/ON or
commanding the part OFF/ON via PMBus clears all faults.
The MFR_GPIO_PROPAGATEn command determines if the
GPIO pins are pulled low when a fault is detected; however,
the ALERT pin is always pulled low if a fault or warning is
detected and the status bits are updated unless the ALERT
pin is masked using the SMBALERT_MASK command.
Output and input fault event handling is controlled by the
corresponding fault response byte as specified in Table 24
to Table 28. Shutdown recovery from these types of faults
can either be autonomous or latched. For autonomous
recovery, the faults are not latched, so if the fault condition
is not present after the retry interval has elapsed, a new
soft-start is attempted. If the fault persists, the controller
will continue to retry. The retry interval is specified by the
MFR_RETRY_DELAY command and prevents damage to
the regulator components by repetitive power cycling. The
MFR_RETRY_DELAY must be greater than 120ms. It can
not exceed 83.88 seconds.
Channel-to-channel fault dependencies can be created
by connecting GPIOn pins together. In the event of an
internal fault, one or more of the channels is configured
to pull the bussed GPIOn pins low. The other channels
are then configured to shut down when the GPIOn pins
are pulled low. For autonomous group retry, the faulted
channel is configured to release the GPIOn pin(s) after a
retry interval, assuming the original fault has cleared. All
the channels in the group then begin a soft-start sequence.
If the fault response is LATCH_OFF, the GPIO pin remains
asserted low until either the RUN pin is toggled OFF/ON
or the part is commanded OFF/ON. The toggling of the
RUN either by the pin or OFF/ON command will clear
faults associated with the channel. If it is desired to have
all faults cleared when either RUN pin is toggled, set bit 0
of MFR_CONFIG_ALL to a 1.
36
The status of all faults and warnings is summarized in the
STATUS_WORD and STATUS_BYTE commands.
Responses to VOUT and IOUT Faults
VOUT OV and UV conditions are monitored by comparators.
The OV and UV limits are set in three ways.
As a Percentage of the VOUT if Using the Resistor Configuration Pins
n
In EEPROM if Either Programmed at the Factory or
Through the GUI
n
By PMBus Command
n
The IIN and IOUT overcurrent monitors are performed by
ADC readings and calculations. Thus these values are
based on average currents and can have a nominal time
latency of up to 100ms. The IOUT calculation accounts for
the power inductor DCR and the temperature coefficient of
the inductor's copper winding. The input current is equal to
the sum of output current times the respective channel duty
cycle plus the input offset current for each channel. If this
calculated input current exceeds the IIN_OC_WARN_LIMIT
the ALERT pin is pulled low and the IIN_OC_WARN bit is
asserted in the STATUS_INPUT register.
The LTM4676A provides the ability to ignore the fault,
shut down and latch off or shut down and retry indefinitely
(hiccup). The retry interval is set in MFR_RETRY_DELAYn
and can be from 120ms to 83.88 seconds in 1ms increments. The shutdown for OV/UV and OC can be done
immediately or after a user selectable deglitch time.
Output Overvoltage Fault Response
A programmable overvoltage comparator (OV) guards
against transient overshoots as well as long-term overvoltages at the output. In such cases, the top MOSFET is
turned off and the bottom MOSFET is turned on until the
overvoltage condition is cleared regardless of the PMBus
VOUT_OV_FAULT_RESPONSEn command byte value. This
hardware level fault response delay is typically 2µs from
the overvoltage condition to BG asserted high. Using the
VOUT_OV_FAULT_RESPONSEn command, the user can
select any of the following behaviors:
OV Pull-Down Only (OV cannot be ignored)
n
For more information www.linear.com/LTM4676A
4676af
LTM4676A
Operation
Shut Down (Stop Switching) Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
Either the Latch Off or Retry fault responses can be deglitched in increments of (0 to 7) • 10µs. See Table 24.
Output Undervoltage Response
The response to an undervoltage comparator output can
be either:
Ignore
condition is predicated upon detection of the VOUT_UV_
FAULT_LIMITn as the output is undergoing a SOFT_START
sequence. The TON_MAX_FAULT_LIMITn time is started
after TON_DELAYn has been reached and a SOFT_START
sequence is started. The resolution of the TON_MAX_
FAULT_LIMITn is 10µs. If the VOUT_UV_FAULT_LIMITn
is not reached within the TON_MAX_FAULT_LIMITn time,
the response of this fault is determined by the value of
the TON_MAX_FAULT_RESPONSEn command value. This
response may be one of the following:
Ignore
n Shut Down (Stop Switching) Immediately—Latch Off
n Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
Either the Latch Off or Retry fault responses can be deglitched in increments of (0 to 7) • 10µs. See Table 25.
Peak Output Overcurrent Fault Response
Due to the current mode control algorithm, peak inductor
current is always limited on a cycle by cycle basis. The
value of the peak current limit is specified in the Electrical
Characteristics table. The current limit circuit operates by
limiting the COMPna maximum voltage. DCR sensing is
used so the COMPna maximum voltage has a temperature
dependency directly proportional to the TC of the DCR
of the inductor. The LTM4676A automatically monitors
the power stage temperature sensors and modifies the
maximum allowed COMPna to compensate for this term.
The overcurrent fault processing circuitry can execute the
following behaviors:
Current Limit Indefinitely
n Shut Down Immediately—Latch Off
n Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
The overcurrent responses can be deglitched in increments
of (0 to 7) • 16ms. See Table 26.
Responses to Timing Faults
TON_MAX_FAULT_LIMITn is the time allowed for VOUT to
rise and settle at start-up. The TON_MAX_FAULT_LIMITn
This fault response is not deglitched. A value of 0 in
TON_MAX_FAULT_LIMITn means the fault is ignored. The
TON_MAX_FAULT_LIMITn should be set longer than the
TON_RISEn time. It is recommended TON_MAX_FAULT_
LIMITn always be set to a non-zero value, otherwise the
output may never come up and no flag will be set to the
user.
See Table 28.
Responses to SVIN OV Faults
SVIN overvoltage is measured with the ADC; therefore,
the response is naturally deglitched by up to the 100ms
typical response time of the ADC. The fault responses are:
Ignore
n Shut Down Immediately—Latch Off
n Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
See Table 28.
Responses to OT/UT Faults
Internal Overtemperature Fault/Warn Response
An internal temperature sensor protects against EEPROM
damage. Above 85°C, no writes to EEPROM are recommended. Above 130°C, the internal over temperature warn
threshold is exceeded and the part disables EEPROM writes
4676af
For more information www.linear.com/LTM4676A
37
LTM4676A
Operation
and does not re-enable until the temperature has dropped
to 125°C. When the die temperature exceed 160°C the
internal over temperature fault response is enabled and
the PWM is disabled until the die temperature drops below
150°C. Temperature is measured by the ADC. Internal
temperature faults cannot be ignored. Internal temperature
limits cannot be adjusted by the user.
See Table 27.
External Overtemperature and Undertemperature
Fault Response
Two temperature sensors within the LTM4676A are
used to sense power stage temperature. The OT_FAULT_
RESPONSEn and UT_FAULT_RESPONSEn commands are
used to determine the appropriate response to an overtemperature and undertemperature condition, respectively.
The fault responses are:
Ignore
n Shut Down Immediately—Latch Off
n Shut Down Immediately—Retry Indefinitely using the
Time Interval Specified in MFR_RETRY_DELAYn
n
See Table 28.
Responses to External Faults
When either GPIOn pin is pulled low, the OTHER bit is set
in the STATUS_WORD command, the appropriate bit is set
in the STATUS_MFR_SPECIFC command, and the ALERT
pin is pulled low. Responses are not deglitched. Each
channel can be configured to ignore or shut down then
retry in response to its GPIOn pin going low by modifying
the MFR_GPIO_RESPONSEn command. To avoid the
ALERT pin asserting low when GPIO is pulled low, assert
bit 1 of MFR_CHAN_CONFIGn, or mask the ALERT using
the SMBALERT_MASK command.
Fault Logging
The LTM4676A has fault logging capability. Data is logged
into memory in the order shown in Table 30. The data to
be stored in the fault log is being continuously stored in
internal volatile memory. When a fault event occurs, the
recording into internal volatile memory is halted, the fault
38
log information is available from the MFR_FAULT_LOG
command, and the contents of the internal memory
are copied into EEPROM. Fault logging is allowed at
temperatures above 85°C; however, retention of 10 years is
not guaranteed. When the die temperature exceeds 130°C
the fault logging is delayed until the die temperature drops
below 125°C. After the fault condition that created the fault
log event has been removed, clear the fault before the fault
log data is erased, or else the part will immediately issue
another fault log.
When the LTM4676A powers-up, it checks the EEPROM
for a valid fault log. If a valid fault log exists in EEPROM,
the “Valid Fault Log” bit in the STATUS_MFR_SPECIFIC
command will be set and an ALERT event will be generated.
Also, fault logging will be blocked until the LTM4676A has
received a MFR_FAULT_LOG_CLEAR command before
fault logging will be re-enabled.
The information is stored in EEPROM in the event of any fault
that disables the controller on either channel. An external
GPIOn pulling low will not trigger a fault logging event.
Bus Timeout Protection
The LTM4676A implements a timeout feature to avoid
hanging the serial interface. The data packet timer begins
at the first START event before the device address write
byte. Data packet information must be completed within
25ms or the LTM4676A will three-state the bus and ignore
the given data packet. If more time is required, assert
bit 3 of MFR_CONFIG_ALL to allow typical bus timeouts
of 255ms. Data packet information includes the device
address byte write, command byte, repeat start event
(if a read operation), device address byte read (if a read
operation), all data bytes and the PEC byte if applicable.
The LTM4676A allows longer PMBus timeouts for block
read data packets. This timeout is proportional to the
length of the block read. The additional block read timeout
applies primarily to the MFR_FAULT_LOG command. In
no circumstances will the timeout period be less than the
tTIMEOUT_SMB specification of 32ms (typical).
The user is encouraged to use as high a clock rate as possible
to maintain efficient data packet transfer between all devices
sharing the serial bus interface. The LTM4676A supports
the full PMBus frequency range from 10kHz to 400kHz.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
PMBus Command Summary
PMBus Commands
Table 1 lists supported PMBus commands and
manufacturer specific commands. A complete description
of these commands can be found in the “PMBus Power
System Management Protocol Specification – Part
II – Revision 1.2." Users are encouraged to reference
this specification. Exceptions or manufacturer specific
implementations are listed in Table 1.
All commands from 0xD0 through 0xFF not listed in this
table are implicitly reserved by the manufacturer. Users
should avoid blind writes within this range of commands
to avoid undesired operation of the part. All commands
from 0x00 through 0xCF not listed in this table are implicitly
not supported by the manufacturer. Attempting to access
non-supported or reserved commands may result in a CML
command fault event. All output voltage settings and
measurements are based on the VOUT_MODE setting of
0x14. This translates to an exponent of 2–12.
If PMBus commands are received faster than they are being
processed, the part may become too busy to handle new
commands. In these circumstances the part follows the
protocols defined in the PMBus Specification v1.2, Part
II, Section 10.8.7, to communicate that it is busy.
The part includes handshaking features to eliminate busy
errors and simplify error handling software while ensuring
robust communication and system behavior. Please refer
to the PMBus Communication and Command Processing
subsection in the Applications Information section for details.
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
PAGE
0x00
Channel or page currently targeted No difference: 0x00, read/write, non-paged, not stored in NVM.
for paged communications.
84
OPERATIONn
0x01
Operating mode control. On/off,
margin high and margin low.
No difference: 0x80, read/write, paged, stored in user-editable NVM.
88
ON_OFF_CONFIGn
0x02
RUNn pin and On/Off
Configuration.
No difference: 0x1F, read/write, paged, stored in user-editable NVM.
87
CLEAR_FAULTS
0x03
Clear any fault bits that have been
set.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
111
PAGE_PLUS_WRITE
0x05
Write a command directly to a
specified page.
Default value not applicable, write-only, nonpaged, not stored in NVM.
Command not supported.
84
PAGE_PLUS_READ
0x06
Read a command directly from a
specified page.
Default value not applicable, read/write, nonpaged, not stored in NVM.
Command not supported.
85
WRITE_PROTECT
0x10
Level of protection provided by the No difference: 0x00, read/write, non-paged, stored in user-editable NVM.
device against accidental changes.
85
STORE_USER_ALL
0x15
Store user operating memory to
EEPROM (user-editable NVM).
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
122
RESTORE_USER_
ALL
0x16
Restore user operating memory
from EEPROM.
Default value not applicable, send byte only,
non-paged, not stored in NVM.
Identical to MFR_RESET command (0xFD).
122
CAPABILITY
0x19
Summary of PMBus optional
communication protocols
supported by this device.
No difference: 0xB0, read-only, non-paged, not stored in NVM.
110
SMBALERT_MASKn
0x1B
Mask ALERT activity.
Command not supported.
Default mask values: STATUS_
VOUTn =0x00, STATUS_IOUTn =0x00,
STATUS_INPUT=0x00, STATUS_
TEMPERATUREn =0x00, STATUS_CML=0x00,
STATUS_MFR_SPECIFICn =0x11.
Read/write, paged as indicated, 10 bytes
total, stored in NVM
112
Reserved. Execute MFR_
RESET command (0xFD),
instead.
4676af
For more information www.linear.com/LTM4676A
39
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
VOUT_MODEn
0x20
Output voltage format/exponent.
No difference: 0x14 (2–12), read-only, paged, not stored in NVM.
92
VOUT_COMMANDn
0x21
Nominal output voltage set point.
No difference: 0x1000 (1.000V), read/write, paged, stored in user-editable
NVM.
93
VOUT_MAXn
0x24
The upper limit on the
commandable output voltage.
Page 0x00: 0x599A (5.600V)
Page 0x01: 0x599A (5.600V)
Read/write, paged, stored in user-editable
NVM.
92
VOUT_MARGIN_
HIGHn
0x25
Margin high output voltage set
point. Must be greater than
VOUT_COMMANDn.
No difference: 0x10CD (1.050V), read/write, paged, stored in user-editable
NVM.
93
VOUT_MARGIN_
LOWn
0x26
Margin low output voltage set
point. Must be less than
VOUT_COMMANDn.
No difference: 0x0F33 (0.950V), read/write, paged, stored in user-editable
NVM.
94
VOUT_TRANSITION_
RATEn
0x27
The rate at which the output
voltage changes when VOUTn is
commanded to a new value via
I2C.
No difference: 0x8042 (0.001V/ms), read/write, paged, stored in usereditable NVM.
99
FREQUENCY_
SWITCH
0x33
The switching frequency setting.
No difference: 0xFBE8 (500kHz), read/write, non-paged, stored in usereditable NVM.
91
VIN_ON
0x35
The undervoltage lockout (UVLO)- No difference: 0xCAC0 (5.500V), as monitored on the “SVIN” pin, read/
write, non-paged, stored in user-editable NVM.
rising threshold.
92
VIN_OFF
0x36
The undervoltage lockout (UVLO)- No difference: 0xCAA0 (5.250V) , as monitored on the “SVIN” pin, read/
write, non-paged, stored in user-editable NVM.
falling threshold.
92
IOUT_CAL_GAINn
0x38
The ratio of the voltage at the
control IC’s current-sense pins
to the sensed current, in mΩ, at
25°C.
Trimmed at ATE, read/write, paged, stored in
factory-only NVM. Writes to this register not
recommended.
95
VOUT_OV_FAULT_
LIMITn
0x40
Output overvoltage fault limit.
No difference: 0x119A (1.100V), read/write, paged, stored in user-editable
NVM.
93
VOUT_OV_FAULT_
RESPONSEn
0x41
Action to be taken by the device
when an output overvoltage fault
is detected.
No difference: 0x7A (20µs glitch filter; non-latching shutdown;
autonomous restart upon fault removal), read/write, paged, stored in
user-editable NVM.
102
VOUT_OV_WARN_
LIMITn
0x42
Output overvoltage warning
threshold.
0x1133 (1.075V), read/write, paged, stored in 0x111F (1.070V), read/
user-editable NVM.
write, paged, stored in
user-editable NVM.
93
VOUT_UV_WARN_
LIMITn
0x43
Output undervoltage warning
threshold.
0x0ECD (0.925V), read/write, paged, stored
in user-editable NVM.
94
VOUT_UV_FAULT_
LIMITn
0x44
Output undervoltage fault limit.
No difference: 0x0E66 (0.900V), read/write, paged, stored in user-editable
NVM.
VOUT_UV_FAULT_
RESPONSEn
0x45
Action to be taken by the device
No difference: 0xB8 (non-latching shutdown; autonomous restart upon
when an output undervoltage fault fault removal), read/write, paged, stored in user-editable NVM.
is detected.
103
IOUT_OC_FAULT_
LIMITn
0x46
Output overcurrent fault threshold No difference: 0xDADB (22.84A), read/write, paged, stored in user(cycle-by-cycle inductor peak
editable NVM.
current).
96
40
Page 0x00: 0x4000
(4.000V).
Page 0x01: 0x5666
(5.400V).
Read/write, paged, stored
in user-editable NVM.
Trimmed at ATE, readonly, paged, stored in
factory-only NVM.
0x0EE1 (0.930V), read/
write, paged, stored in
user-editable NVM.
94
4676af
For more information www.linear.com/LTM4676A
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
IOUT_OC_FAULT_
RESPONSEn
0x47
Action to be taken by the device
when an output overcurrent fault
is detected.
No difference: 0x00 (try to regulate through the fault condition/event;
limit the cycle-by-cycle peak of the inductor current to not exceed the
commanded IOUT_OC_FAULT_LIMIT), read/write, paged, stored in usereditable NVM.
IOUT_OC_WARN_
LIMITn
0x4A
Output overcurrent warning
No difference: 0xD3E6 (15.59A), read/write, paged, stored in user-editable
threshold (time-averaged inductor NVM.
current).
97
OT_FAULT_LIMITn
0x4F
Overtemperature fault threshold.
No difference: 0xF200 (128°C), read/write, paged, stored in user-editable
NVM.
98
OT_FAULT_
RESPONSEn
0x50
Action to be taken by the device
when an overtemperature fault is
detected via TSNSn a.
No difference: 0xB8 (non-latching shutdown; autonomous restart upon
fault removal), read/write, paged, stored in user-editable NVM.
107
OT_WARN_LIMITn
0x51
Overtemperature warning
threshold.
No difference: 0xEBE8 (125°C), read/write, paged, stored in user-editable
NVM.
98
UT_FAULT_LIMITn
0x53
Undertemperature fault threshold. No difference: 0xE530 (–45°C), read/write, paged, stored in user-editable
NVM.
98
UT_FAULT_
RESPONSEn
0x54
Response to undertemperature
fault events.
No difference: 0x00 (ignore; continue without interruption), read/write,
paged, stored in user-editable NVM, read/write, paged, stored in usereditable NVM.
107
VIN_OV_FAULT_
LIMIT
0x55
Input supply (SVIN) overvoltage
fault limit.
0xDA2E (17.44V), read/write, non-paged,
stored in user-editable NVM.
91
VIN_OV_FAULT_
RESPONSEn
0x56
Response to input overvoltage
fault events.
No difference: 0xB8 (non-latching shutdown; autonomous restart upon
fault removal), read/write, paged, stored in user-editable NVM.
101
VIN_UV_WARN_
LIMIT
0x58
Input undervoltage warning
threshold.
No difference: 0xCAA6 (5.297V), read/write, non-paged, stored in usereditable NVM.
91
IIN_OC_WARN_
LIMIT
0x5D
Input supply overcurrent warning
threshold.
No difference: 0xD300 (12A), read/write, non-paged, stored in usereditable NVM.
95
POWER_GOOD_ONn
0x5E
Output voltage at or above which a Not supported.
power good should be asserted.
PGOOD thresholds
set by VOUT_OV/UV_
FAULT_LIMITs. 0x0EE1
(0.9299V), read/write,
paged, stored in usereditable NVM.
N/A
POWER_GOOD_OFFn
0x5F
Output voltage at or below which
a power good should be deasserted.
Not supported.
PGOOD thresholds
set by VOUT_OV/UV_
FAULT_LIMITs. 0x0EB8
(0.9199V), read/write,
paged, stored in usereditable NVM.
N/A
TON_DELAYn
0x60
Time from RUNn and/or
OPERATIONn on to output rail
turn-on.
No difference: 0x8000 (0ms), read/write, paged, stored in user-editable
NVM.
99
TON_RISEn
0x61
Time from when the output
voltage reference starts to rise
until it reaches its commanded
setting.
No difference: 0xC300 (3ms), read/write, paged, stored in user-editable
NVM.
99
0xDB60 (27.0V), read/
write, non-paged, stored
in user-editable NVM.
105
4676af
For more information www.linear.com/LTM4676A
41
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
TON_MAX_FAULT_
LIMITn
0x62
Turn-on watchdog timeout fault
threshold (time permitted for
VOUTn to reach or exceed VOUT_
UV_FAULT_LIMITn after turn-on
command is received).
No difference: 0xCA80 (5ms), read/write, paged, stored in user-editable
NVM.
99
TON_MAX_FAULT_
RESPONSEn
0x63
Action to be taken by the device
when a TON_MAX_FAULTn event
is detected.
No difference: 0xB8 (non-latching shutdown; autonomous restart upon
fault removal), read/write, paged, stored in user-editable NVM.
104
TOFF_DELAYn
0x64
Time from RUN and/or Operation
off to the start of TOFF_FALLn
ramp.
No difference: 0x8000 (0ms), read/write, paged, stored in user-editable
NVM.
100
TOFF_FALLn
0x65
Time from when the output
No difference: 0xC300 (3ms), read/write, paged, stored in user-editable
voltage reference starts to fall until NVM.
it reaches 0V.
100
TOFF_MAX_WARN_
LIMITn
0x66
Turn-off watchdog timeout fault
threshold (time permitted for
VOUTn to decay to or below
12.5% of the commanded VOUTn
value at the time of receiving a
turn-off command).
No difference: 0x8000 (no limit; warning is disabled), read/write, paged,
stored in user-editable NVM.
100
STATUS_BYTEn
0x78
One byte summary of the unit’s
fault condition.
No difference: default value not applicable, read/write, paged, not stored
in NVM.
113
STATUS_WORDn
0x79
Two byte summary of the unit’s
fault condition.
No difference: default value not applicable, read/write, paged, not stored
in NVM.
113
STATUS_VOUTn
0x7A
Output voltage fault and warning
status.
No difference: default value not applicable, read/write, paged, not stored
in NVM.
114
STATUS_IOUTn
0x7B
Output current fault and warning
status.
No difference: default value not applicable, read/write, paged, not stored
in NVM.
114
STATUS_INPUT
0x7C
Input supply (SVIN) fault and
warning status.
No difference: default value not applicable, read/write, non-paged, not
stored in NVM.
114
STATUS_
TEMPERATUREn
0x7D
TSNSn a -sensed temperature fault
and warning status for READ_
TEMERATURE_1n .
No difference: default value not applicable, read/write, paged, not stored
in NVM.
115
STATUS_CML
0x7E
Communication and memory fault No difference: default value not applicable, read/write, non-paged, not
and warning status.
stored in NVM.
115
STATUS_MFR_
SPECIFICn
0x80
Manufacturer specific fault and
state information.
No difference: default value not applicable, read/write, paged, not stored
in NVM.
115
READ_VIN
0x88
Measured input supply (SVIN)
voltage.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
118
READ_IIN
0x89
Calculated total input supply
current.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
118
READ_VOUTn
0x8B
Measured output voltage.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
118
READ_IOUTn
0x8C
Measured output current.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
READ_
TEMPERATURE_1n
0x8D
Measurement of TSNSn a-sensed
temperature.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
42
4676af
For more information www.linear.com/LTM4676A
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
READ_
TEMPERATURE_2
0x8E
Measured control IC junction
temperature.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
119
READ_DUTY_
CYCLEn
0x94
Measured duty cycle of MTn .
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
READ_POUTn
0x96
Calculated output power.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
PMBUS_REVISION
0x98
PMBus revision supported by this
device.
0x22 (Revision 1.2 of Part I and Revision 1.2 0x11 (Revision 1.1 of Part
of Part II of PMBus Specification documents), I and Revision 1.1 of Part
read-only, non-paged, not stored in NVM.
II of PMBus Specification
documents), read-only,
non-paged, not stored in
NVM.
110
MFR_ID
0x99
Manufacturer identification, in
ASCII
No difference: “LTC”, read-only, non-paged.
110
MFR_MODEL
0x9A
Manufacturer’s part number, in
ASCII
LTM4676A, read-only, non-paged.
MFR_SERIAL
0x9E
Serial number of this specific unit. Up to nine bytes of custom-formatted data that identify the unit’s
configuration, read-only, non-paged.
111
MFR_VOUT_MAXn
0xA5
Maximum allowed output voltage.
0x5B34 (5.700V) on both channels. Read0x4189 (4.096V) on
only, paged, not stored in user-editable NVM. Channel 0, 0x5800
(5.500V) on Channel 1.
Read-only, paged, not
stored in user-editable
NVM.
94
USER_DATA_00
0xB0
OEM reserved data.
Read/write, non-paged, stored in usereditable NVM. Recommended against
altering.
Read/write, non-paged,
stored in user-editable
NVM. Recommended
against altering.
110
USER_DATA_01n
0xB1
OEM reserved data.
Read/write, paged, stored in user-editable
NVM. Recommended against altering.
Read/write, paged, stored
in user-editable NVM.
Recommended against
altering.
110
USER_DATA_02
0xB2
OEM reserved data.
Read/write, non-paged, stored in usereditable NVM. Recommended against
altering.
Read/write, non-paged,
stored in user-editable
NVM. Recommended
against altering.
110
USER_DATA_03n
0xB3
User-editable words available for
the user.
No difference: 0x0000, read/write, paged, stored in user-editable NVM.
110
USER_DATA_04
0xB4
A user-editable word available for
the user.
No difference: 0x0000, read/write, non-paged, stored in user-editable
NVM.
110
MFR_EE_UNLOCK
0xBD
Unlock user EEPROM for access
No difference: default value not applicable, read/write, non-paged, not
by MFR_EE_ERASE and MFR_EE_ stored in NVM.
DATA commands.
126
MFR_EE_ERASE
0xBE
Initialize user EEPROM for bulk
programming by MFR_EE_DATA.
No difference: default value not applicable, read/write, non-paged, not
stored in NVM.
126
MFR_EE_DATA
0xBF
Data transferred to and from
EEPROM using sequential PMBus
word reads or writes. Supports
bulk programming.
No difference: default value not applicable, read/write, non-paged, not
stored in NVM.
126
LTM4676, read-only,
non-paged.
111
4676af
For more information www.linear.com/LTM4676A
43
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
MFR_CHAN_
CONFIG_*n
0xD0
Channel-specific configuration
bits.
No difference: 0x1F, read/write, paged, stored in user-editable NVM.
Register is named “MFR_CHAN_CONFIG” and referred to as “MFR_
CHAN_CONFIG_LTM467X” in LTpowerPlay.
MFR_CONFIG_ALL_*
0xD1
Global configuration bits, i.e.,
common to both VOUT channels
0 and 1.
Same as LTM4676 except: Bit 4 configures
whether the SYNC drive circuit is active (0b)
or inactive (1b); Bit 3 configures whether the
Stuck PMBus Timer Timeout is 150ms for
Block Reads and 32ms for Non-Block Reads
(0b) or 250ms for all Reads (1b).
MFR_GPIO_
PROPAGATE_*n
0xD2
Configuration bits for propagating No difference: 0x6893, read/write, paged, stored in user-editable NVM.
faults to the GPIOn pins.
Register is named “MFR_GPIO_PROPAGATE” and referred to as “MFR_
GPIO_PROPAGATE_LTM467X” in LTpowerPlay.
108
MFR_PWM_
MODE_*n
0xD4
Configuration for the PWM engine 0xC1, read/write, paged, stored in userof each VOUT channel.
editable NVM. Bit 1 commands whether the
output is in high range (0b) or low range
(1b). Bit 0 commands whether the output is
operating in Forced Continuous Conduction
Mode (1b) or Discontinuous Mode (0b).
89
Command is named MFR_PWM_MODE and
referred to as MFR_PWM_MODE_LTM467X
in LTpowerPlay.
0x09, read/write,
non-paged, stored in
user-editable NVM.
Register is named
“MFR_CONFIG_ALL”
and referred to as “MFR_
CONFIG_ALL_LTM467X”
in LTpowerPlay. Bit 4 is
reserved.
0xC2, read/write, paged,
stored in user-editable
NVM.
86
87
Bits 1:0 command the
operating mode of the
output. Command is
named MFR_PWM_MODE
and referred to as MFR_
PWM_MODE_LTM467X
in LTpowerPlay.
MFR_GPIO_
RESPONSEn
0xD5
Action to be taken by the device
when the GPIOn pin is asserted
low by circuitry external to the
unit.
No difference: 0xC0 (make the respective output’s power stage high
impedance, i.e., three-stated; autonomous restart upon fault removal),
read/write, paged, stored in user-editable NVM.
109
MFR_OT_FAULT_
RESPONSE
0xD6
Action to be taken by the device
when a control IC junction
overtemperature fault is detected.
No difference: 0xC0 (make the respective output’s power stage high
impedance, i.e., three-stated; autonomous restart upon fault removal),
read-only, non-paged, not stored in user-editable NVM.
106
MFR_IOUT_PEAKn
0xD7
Maximum measured value of
READ_IOUTn since the last MFR_
CLEAR_PEAKS.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
120
MFR_ADC_
CONTROL
0xD8
ADC telemetry parameter for
repeated fast ADC readback.
0x00, read/write, not paged, not stored in
NVM. Allows telemetry readback rates up to
125Hz instead of 10Hz, nominal. Use PAGE_
PLUS_READ/WRITE commands instead of
the LTM4676's former MFR_CHANNEL_
ADDRESSn command.
0x80, read/write, paged,
stored in user-editable
NVM. MFR_CHANNEL_
ADDRESSn, the slave
address to the PAGEactivated channel.
120
MFR_ADC_
TELEMETRY_
STATUS
0xDA
ADC status during short-loop.
Default value not applicable, read/write,
not paged, not stored in NVM. ADC status
indicating most recently digitized telemetry
when engaged in short round-robin loop
(MFR_ADC_CONTROL=0x0D)
Command not supported.
121
MFR_RETRY_
DELAYn
0xDB
Retry interval during fault-retry
mode.
No difference: 0xF3E8 (250ms), read/write, paged, stored in user-editable
NVM.
101
MFR_RESTART_
DELAYn
0xDC
Minimum interval (nominal) the
RUNn pin is pulled logic low by
internal circuitry.
No difference: 0xF258 (150ms), read/write, paged, stored in user-editable
NVM.
101
44
4676af
For more information www.linear.com/LTM4676A
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
MFR_VOUT_PEAKn
0xDD
Maximum measured value of
READ_VOUTn since the last
MFR_CLEAR_PEAKS.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
MFR_VIN_PEAK
0xDE
Maximum measured value of
READ_VIN since the last MFR_
CLEAR_PEAKS.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
120
MFR_
TEMPERATURE_1_
PEAKn
0xDF
Maximum value of TSNSna
measured temperature since the
last MFR_CLEAR_PEAKS.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
120
MFR_CLEAR_PEAKS
0xE3
Clears all peak values.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
112
MFR_PADS
0xE5
Digital status of the I/O pads.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
116
MFR_ADDRESS
0xE6
LTM4676A's I2C slave address,
right-justified.
0x4F, read/write, non-paged, stored in usereditable NVM. Bits[6:4] represent the userconfigurable upper 3 bits of the 7-bit slave
address of the device. Bits[3:0] are dictated
by the ASEL resistor pin-strap setting. Setting
this command to 0x80 disables devicespecific addressing.
MFR_SPECIAL_ID
0xE7
Manufacturer code representing IC 0x47EX, read-only, non-paged.
silicon and revision
MFR_IIN_OFFSETn
0xE9
Coefficient used in calculations of No difference: 0x8BE7 (0.0305A), read/write, paged, stored in userREAD_IIN and MFR_READ_IINn , editable NVM.
representing the contribution of
input current drawn by the control
IC, including the MOSFET drivers.
95
MFR_FAULT_LOG_
STORE
0xEA
Commands a transfer of the fault
log from RAM to EEPROM. This
causes the part to behave as if a
channel has faulted off.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
123
MFR_FAULT_LOG_
CLEAR
0xEC
Initialize the EEPROM block
reserved for fault logging and
clear any previous fault logging
locks.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
126
MFR_READ_IINn
0xED
Calculated input current, by
channel.
No difference: default value not applicable, read-only, paged, not stored
in NVM.
119
MFR_FAULT_LOG
0xEE
Fault log data bytes. This
sequentially retrieved data is used
to assemble a complete fault log.
No difference: default value not applicable, read-only, non-paged, stored
in fault-log NVM.
122
MFR_COMMON
0xEF
Manufacturer status bits that are
common across multiple LTC ICs/
modules.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
116
MFR_COMPARE_
USER_ALL
0xF0
Compares current command
contents (RAM) with NVM.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM.
122
MFR_
TEMPERATURE_2_
PEAK
0xF4
Maximum measured control IC
junction temperature since last
MFR_CLEAR_PEAKS.
No difference: default value not applicable, read-only, non-paged, not
stored in NVM.
120
0x4F, read-only,
non-paged, stored in
factory-only NVM. Least
significant four bits
augmented by ASEL
resistor pin-strap. Cannot
take on value 0x80;
device-specific addressing
cannot be disabled.
86
0x448X, read-only, nonpaged.
111
4676af
For more information www.linear.com/LTM4676A
45
LTM4676A
PMBus Command Summary
Table 1. Summary of Supported Commands and Feature Differences Between the LTM4676A and the LTM4676 (Items of Greatest
Significance Indicated by Gray-Shaded Cells; Common Commands, Values and Attributes Indicated by Non-Shaded, Merged Cells)
LTM4676 NVM FACTORYDEFAULT VALUE AND/OR
ATTRIBUTES
PAGE
PMBus COMMAND CMD CODE COMMAND OR FEATURE
NAME, OR FEATURE (REGISTER) DESCRIPTION
LTM4676A NVM FACTORY-DEFAULT VALUE
AND/OR ATTRIBUTES
MFR_PWM_
CONFIG_*
0xF5
Configuration bits for setting
the phase interleaving angles of
Channels 0 and 1, SHARE_CLK
behavior in UVLO, and using
the fully differential amplifier
to regulate paralleled output
channels.
0x10, read/write, non-paged, stored in usereditable NVM. When bit 7 is 0b, Channel 1's
output is regulated by the VOSNS1 and SGND
feedback signals. When bit 7 is 1b, Channel
1's output is regulated by the VOSNS0+ and
VOSNS0– feedback signals. Only set bit 7 to 1b
for PolyPhase rail applications. The command
is named MFR_PWM_CONFIG and referred
to as MFR_PWM_CONFIG_LTM467X in
LTpowerPlay.
MFR_IOUT_CAL_
GAIN_TCn
0xF6
Temperature coefficient of the
current sensing element.
No difference: 0x0F14 (3860ppm/°C), read/write, paged, stored in usereditable NVM.
95
MFR_TEMP_1_
GAINn
0xF8
Sets the slope of the temperature
sensors that interface to TSNSna.
0x3FAE (0.995, in custom units), read/write,
paged, stored in user-editable NVM.
97
MFR_TEMP_1_
OFFSETn
0xF9
Sets the offset of the TSNSna
temperature sensor with respect
to –273.1°C.
No difference: 0x8000 (0.0), read/write, paged, stored in NVM.
97
MFR_RAIL_
ADDRESSn
0xFA
Common address for PolyPhase
outputs to adjust common
parameters.
No difference: 0x80, read/write, paged, stored in NVM.
86
MFR_RESET
0xFD
Commanded reset without
requiring a power down.
No difference: default value not applicable, send byte only, non-paged, not
stored in NVM. Identical to RESTORE_USER_ALL.
89
46
0x10, read/write, nonpaged, stored in usereditable NVM. Channel 1
output regulated strictly
by VOSNS1 and SGND
feedback signals. Bit 7
reserved and must be 0b.
The command is named
MFR_PWM_CONFIG
and referred to as MFR_
PWM_CONFIG_LTM467X
in LTpowerPlay.
0x4000 (1.000 in custom
units), read/write, paged,
stored in user-editable
NVM.
90
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
Table 2. VOUTn CFG Pin Strapping Look-Up Table for the
LTM4676A's Output Voltage, Coarse Setting (Not Applicable if
MFR_CONFIG_ALL[6] = 1b)
RVOUTn CFG*
(kΩ)
VOUTn (V) SETTING
COARSE
MFR_PWM_MODEn[1] BIT
Open
NVM
NVM
32.4
See Table 3
See Table 3
22.6
3.3
0
18.0
3.1
0
15.4
2.9
0
12.7
2.7
0
10.7
2.5
0, if VTRIMn > 0mV
1, if VTRIMn ≤ 0mV
9.09
2.3
1
7.68
2.1
1
6.34
1.9
1
5.23
1.7
1
4.22
1.5
1
3.24
1.3
1
2.43
1.1
1
1.65
0.9
1
0.787
0.7
1
0
0.5
1
*RVOUTn CFG value indicated is nominal. Select RVOUTn CFG from a resistor
vendor such that its value is always within 3% of the value indicated in
the table. Take into account resistor initial tolerance, T.C.R. and resistor
operating temperatures, soldering heat/IR reflow, and endurance of the
resistor over its lifetime. Thermal shock/cycling, moisture (humidity) and
other effects (depending on one’s specific application) could also affect
RVOUTn CFG’s value over time. All such effects must be taken into account
in order for resistor pin strapping to yield the expected result at every
SVIN power-up and/or every execution of MFR_RESET or RESTORE_
USER_ALL, over the lifetime of one’s product.
Table 3. VTRIMnCFG Pin Strapping Look-Up Table for the
LTM4676A's Output Voltage, Fine Adjustment Setting (Not
Applicable if MFR_CONFIG_ALL[6] = 1b)
VTRIM (mV) FINE
ADJUSTMENT
TO VOUTn
SETTING WHEN
RESPECTIVE
RVOUTnCFG ≠
RVTRIMnCFG*
(kΩ)
32.4kΩ
Open
0
32.4
99
22.6
86.625
18.0
74.25
15.4
61.875
VOUTn OUTPUT
VOLTAGE
SETTING
(V) WHEN
VOUTnCFG PIN
USES RCFG =
32.4kΩ
NVM
MFR_PWM_
MODEn[1] BIT
0, if VOUT_OV_
FAULT_LIMITn
> 2.75V
1, if VOUT_OV_
FAULT_LIMITn
≤ 2.75V
12.7
49.5
10.7
37.125
5.50
0
9.09
24.75
5.25
0
7.68
12.375
5.00
0
6.34
–12.375
4.75
0
5.23
–24.75
4.50
0
4.22
–37.125
4.25
0
3.24
–49.5
4.00
0
2.43
–61.875
3.75
0
1.65
–74.25
3.63
0
0.787
–86.625
3.50
0
0
–99
3.46
0
*RVTRIMnCFG value indicated is nominal. Select RVTRIMnCFG from a
resistor vendor such that its value is always within 3% of the value
indicated in the table. Take into account resistor initial tolerance,
T.C.R. and resistor operating temperatures, soldering heat/IR reflow,
and endurance of the resistor over its lifetime. Thermal shock/cycling,
moisture (humidity) and other effects (depending on one’s specific
application) could also affect RVTRIMnCFG’s value over time. All such
effects must be taken into account in order for resistor pin strapping to
yield the expected result at every SVIN power-up and/or every execution
of MFR_RESET or RESTORE_USER_ALL, over the lifetime of one’s
product.
4676af
For more information www.linear.com/LTM4676A
47
LTM4676A
Applications Information
Table 4. FSWPHCFG Pin Strapping Look-Up Table to Set the LTM4676A's Switching Frequency and Channel Phase-Interleaving
Angle (Not Applicable if MFR_CONFIG_ALL[6] = 1b)
RFSWPHCFG*
(kΩ)
SWITCHING
FREQUENCY (kHz)
θSYNC TO θ0
θSYNC TO θ1
bits [2:0] of
MFR_PWM_CONFIG
bit [4] of
MFR_CONFIG_ALL
Open
NVM; LTM4676A
Default = 500
NVM; LTM4676A
Default = 0°
NVM; LTM4676A
Default = 180°
NVM; LTM4676A
Default = 000b
NVM; LTM4676A
Default = 0b
32.4
250
0°
180°
000b
0b
22.6
350
0°
180°
000b
0b
18.0
425
0°
180°
000b
0b
15.4
575
0°
180°
000b
0b
12.7
650
0°
180°
000b
0b
10.7
750
0°
180°
000b
0b
9.09
1000
0°
180°
000b
0b
7.68
500
120°
240°
100b
0b
6.34
500
90°
270°
001b
0b
5.23
External**
0°
240°
010b
1b
4.22
External**
0°
120°
011b
1b
3.24
External**
60°
240°
101b
1b
2.43
External**
120°
300°
110b
1b
1.65
External**
90°
270°
001b
1b
0.787
External**
0°
180°
000b
1b
0
External**
120°
240°
100b
1b
*RFSWPHCFG value indicated is nominal. Select RFSWPHCFG from a resistor vendor such that its value is always within 3% of the value indicated in
the table. Take into account resistor initial tolerance, T.C.R. and resistor operating temperatures, soldering heat/IR reflow, and endurance of the
resistor over its lifetime. Thermal shock/cycling, moisture (humidity) and other effects (depending on one’s specific application) could also affect
RFSWPHCFG’s value over time. All such effects must be taken into account in order for resistor pin-strapping to yield the expected result at every
SVIN power-up and/or every execution of MFR_RESET or RESTORE_USER_ALL, over the lifetime of one’s product.
**"External" setting corresponds to the FREQUENCY_SWITCH (Command 0x33) value set to 0x0000; the device synchronizes its switching
frequency to that of the clock provided on the SYNC pin, provided MFR_CONFIG_ALL[4]=1b.
48
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
Table 5. ASEL Pin Strapping Look-Up Table to Set the
LTM4676A's Slave Address (Applicable Regardless of
MFR_CONFIG_ALL[6] Setting)
RASEL* (kΩ)
SLAVE ADDRESS
Open
100_1111_R/W
32.4
100_1111_R/W
22.6
100_1110_R/W
18.0
100_1101_R/W
15.4
100_1100_R/W
12.7
100_1011_R/W
10.7
100_1010_R/W
9.09
100_1001_R/W
7.68
100_1000_R/W
6.34
100_0111_R/W
5.23
100_0110_R/W
4.22
100_0101_R/W
3.24
100_0100_R/W
2.43
100_0011_R/W
1.65
100_0010_R/W
0.787
100_0001_R/W
0
100_0000_R/W
Table 6. LTM4676A MFR_ADDRESS Command Examples
Expressed in 7- and 8-Bit Addressing
HEX DEVICE
ADDRESS BIT BIT BIT BIT BIT BIT BIT BIT
DESCRIPTION 7 BIT 8 BIT 7 6 5 4 3 2 1 0 R/W
Rail4
0x5A 0xB4
0
1
0
1
1
0
1
0
0
Global4
0x5B 0xB6
0
1
0
1
1
0
1
1
0
Default
0x4F 0x9E
0
1
0
0
1
1
1
1
0
Example 1
0x40 0x80
0
1
0
0
0
0
0
0
0
Example 2
0x41 0x82
0
1
0
0
0
0
0
1
0
1
0
0
0
0
0
0
0
0
Disabled2,3
Note 1: This table can be applied to the MFR_RAIL_ADDRESSn command,
but not the MFR_ADDRESS command.
Note 2: A disabled value in one command does not disable the device, nor
does it disable the Global address.
Note 3: A disabled value in one command does not inhibit the device from
responding to device addresses specified in other commands.
Note 4: It is not recommended to write the value 0x00, 0x0C
(7 bit), 0x5A (7 bit), 0x5B (7 bit), or 0x7C (7 bit) to the MFR_RAIL_
ADDRESSn or MFR_ADDRESS commands.
where:
R/W = Read/Write bit in control byte.
All PMBus device addresses listed in the specification are 7 bits wide
unless otherwise noted.
Note: The LTM4676A will always respond to slave address 0x5A and
0x5B regardless of the NVM or ASEL resistor configuration values.
*RCFG value indicated is nominal. Select RCFG from a resistor vendor
such that its value is always within 3% of the value indicated in the
table. Take into account resistor initial tolerance, T.C.R. and resistor
operating temperatures, soldering heat/IR reflow, and endurance of the
resistor over its lifetime. Thermal shock cycling, moisture (humidity)
and other effects (depending on one’s specific application) could
also affect RCFG’s value over time. All such effects must be taken into
account in order for resistor pin-strapping to yield the expected result
at every SVIN power-up and/or every execution of MFR_RESET or
RESTORE_USER_ALL, over the lifetime of one’s product.
4676af
For more information www.linear.com/LTM4676A
49
LTM4676A
Applications Information
VIN to VOUT Step-Down Ratios
Output Capacitors
There are restrictions in the maximum VIN and VOUT stepdown ratio that can be achieved for a given input voltage.
Each output of the LTM4676A is capable of 95% duty
cycle at 500kHz, but the VIN to VOUT minimum dropout
is still a function of its load current and will limit output
current capability related to high duty cycle on the topside
switch. Minimum on-time tON(MIN) is another consideration
in operating at a specified duty cycle while operating at
a certain frequency due to the fact that tON(MIN) < D/fSW,
where D is duty cycle and fSW is the switching frequency.
tON(MIN) is specified in the electrical parameters as 90ns.
See Note 6 in the Electrical Characteristics section for
output current guideline.
The LTM4676A is designed for low output voltage ripple
noise and good transient response. The bulk output
capacitors defined as COUT are chosen with low enough
effective series resistance (ESR) to meet the output voltage ripple and transient requirements. COUT can be a low
ESR tantalum capacitor, a low ESR polymer capacitor or
ceramic capacitor. The typical output capacitance range
for each output is from 400µF to 700µF. Additional output
filtering may be required by the system designer, if further
reduction of output ripple or dynamic transient spikes
is required. Table 20 shows a matrix of different output
voltages and output capacitors to minimize the voltage
droop and overshoot during a 6.5A/µs transient. The table
optimizes total equivalent ESR and total bulk capacitance
to optimize the transient performance. Stability criteria are
considered in the Table 20 matrix, and the Linear Technology
µModule Power Design Tool will be provided for stability
analysis. Multiphase operation reduces effective output
ripple as a function of the number of phases. Application
Note 77 discusses this noise reduction versus output
ripple current cancellation, but the output capacitance
should be considered carefully as a function of stability
and transient response. The Linear Technology µModule
Power Design Tool can calculate the output ripple reduction as the number of implemented phases increases by N
times. A small value 10Ω resistor can be placed in series
from VOUTn to the VOSNS0+ or VOSNS1 pin to allow for a
bode plot analyzer to inject a signal into the control loop
and validate the regulator stability.
Input Capacitors
The LTM4676A module should be connected to a low acimpedance DC source. For the regulator input four 22µF
input ceramic capacitors are used to handle the RMS
ripple current. A 47µF to 100µF surface mount aluminum
electrolytic bulk capacitor can be used for more input bulk
capacitance. This bulk input capacitor is only needed if
the input source impedance is compromised by long inductive leads, traces or not enough source capacitance.
If low impedance power planes are used, then this bulk
capacitor is not needed.
For a buck converter, the switching duty-cycle can be
estimated as:
Dn =
VOUTn
VINn
Light Load Current Operation
Without considering the inductor current ripple, for each
output, the RMS current of the input capacitor can be
estimated as:
ICINn (RMS) =
IOUTn (MAX)
η%
• Dn • (1−Dn )
The LTM4676A has two modes of operation: high efficiency,
discontinuous conduction mode or forced continuous
conduction mode. The mode of operation is configured by
bit 0 of the MFR_PWM_MODEn command (discontinuous
conduction is always the start-up mode, forced continuous
is the default running mode).
In the above equation, η% is the estimated efficiency of the
power module. The bulk capacitor can be a switcher-rated
electrolytic aluminum capacitor, or a Polymer capacitor.
50
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
If a channel is enabled for discontinuous mode operation,
the inductor current is not allowed to reverse. The reverse
current comparator, IREV , turns off the bottom MOSFET
(MBn) just before the inductor current reaches zero,
preventing it from reversing and going negative. Thus, the
controller can operate in discontinuous (pulse-skippng)
operation. In forced continuous operation, the inductor
current is allowed to reverse at light loads or under
large transient conditions. The peak inductor current
is determined solely by the voltage on the COMPna pin.
In this mode, the efficiency at light loads is lower than
discontinuous mode operation. However, continuous
mode exhibits lower output ripple and less interference
with audio circuitry. Forced continuous conduction mode
may result in reverse inductor current, which can cause
the input supply to boost. The VIN_OV_FAULT_LIMIT can
detect this (if SVIN is connected to VIN0 and/or VIN1) and
turn off the offending channel. However, this fault is based
on an ADC read and can nominally take up to 100ms to
detect. If there is a concern about the input supply boosting, keep the part in discontinuous conduction operation.
Switching Frequency and Phase
The switching frequency of the LTM4676A’s channels is
established by its analog phase-locked-loop (PLL) locking
on to the clock present at the module’s SYNC pin. The
clock waveform on the SYNC pin can be generated by the
LTM4676A’s internal circuitry when an external pull-up
resistor to 3.3V (e.g., VDD33) is provided, in combination
with the LTM4676A control IC’s FREQUENCY_SWITCH
command being set to one of the following supported
values: 250kHz, 350kHz, 425kHz, 500kHz, 575kHz,
650kHz, 750kHz, 1MHz (see Table 8 for hexadecimal
values). In this configuration, the module is called a
“sync master”: using the factory-default setting of
MFR_CONFIG_ALL[4]=0b, SYNC becomes a bidirectional
open-drain pin, and the LTM4676A pulls SYNC logic low
for nominally 500ns at a time, at the prescribed clock
rate. The SYNC signal can be bused to other LTM4676A
modules (configured as “sync slaves”), for purposes of
synchronizing switching frequencies of multiple modules
within a system—but only one LTM4676A should be
configured as a “sync master”; the other LTM4676A(s)
should be configured as “sync slaves”.
There are two recommended ways to configure an
LTM4676A as a “sync slave”:
• The most straightforward way is to set its FREQUENCY_
SWITCH command to 0x0000 and MFR_CONFIG_
ALL[4]=1b. This can be easily implemented with resistor
pin-strap settings on the FSWPHCFG pin (see Table 4).
Using MFR_CONFIG_ALL[4]=1b, the LTM4676A’s
SYNC pin becomes a high impedance input, only—i.e.,
it does not drive SYNC low. The module synchronizes
its frequency to that of the clock applied to its SYNC
pin. The only shortcoming of this approach is: in the
absence of an externally applied clock, the switching
frequency of the module will default to the low end of
its frequency-synchronization capture range (~225kHz).
• If fault-tolerance to the loss of an externally applied
SYNC clock is desired, the FREQUENCY_SWITCH
command of a “sync slave” can be left at the nominal
target switching frequency of the application, and
not 0x0000 (see Table 7). However, it is then still
necessary to configure MFR_CONFIG_ALL[4]=1b. With
this combination of configurations, the LTM4676A’s
SYNC pin becomes a high impedance input and the
module synchronizes its frequency to that of the
externally applied clock, provided that the frequency of
the externally applied clock exceeds ~½ of the target
frequency (FREQUENCY_SWITCH). If the SYNC clock is
absent, the module responds by operating at its target
frequency, indefinitely. If and when the SYNC clock
is restored, the module automatically phase-locks to
the SYNC clock as normal. The only shortcoming of
this approach is: the EEPROM must be configured per
above guidance; resistor pin-strapping options on the
FSWPHCFG pin alone cannot provide fault-tolerance to
the absence of the SYNC clock.
The FREQUENCY_SWITCH command can be altered
via I2C commands, but only when switching action is
disengaged, i.e., the module’s outputs are turned off. The
FREQUENCY_SWITCH command takes on the value stored
in NVM at SVIN power-up, but is overridden according
to a resistor pin-strap applied between the FSWPHCFG pin
and SGND only if the module is configured to respect
resistor pin-strap settings (MFR_CONFIG_ALL[6] = 0b).
4676af
For more information www.linear.com/LTM4676A
51
LTM4676A
Applications Information
Table 4 highlights available resistor pin-strap and
corresponding FREQUENCY_SWITCH settings.
The relative phasing of all active channels in a PolyPhase
rail should be optimally phased. The relative phasing of
each rail is 360°/n, where n is the number of phases in
the rail. MFR_PWM_CONFIG[2:0] configures channel
relative phasing with respect to the SYNC pin. Phase
relationship values are indicated with 0° corresponding
to the falling edge of SYNC being coincident with the
turn-on of the top MOSFETs, MTn.
The MFR_PWM_CONFIG command can be altered
via I2C commands, but only when switching action is
disengaged, i.e., the module’s outputs are turned off. The
MFR_PWM_CONFIG command takes on the value stored
in NVM at SVIN power-up, but is overridden according to
a resistor pin-strap applied between the FSWPHCFG pin and
SGND only if the module is configured to respect resistor
pin-strap settings (MFR_CONFIG_ALL[6] = 0b). Table 4
highlights available resistor pin-strap and corresponding
MFR_PWM_CONFIG[2:0] settings.
Some combinations of FREQUENCY_SWITCH and
MFR_PWM_CONFIG[2:0] are not available by resistor
pin-strapping the FSWPHCFG pin. All combinations
of supported values for FREQUENCY_SWITCH and
MFR_PWM_CONFIG[2:0] can be configured by NVM
programming—or, I2C transactions, provided switching
action is disengaged, i.e., the module’s outputs are
turned off.
Care must be taken to minimize capacitance on SYNC
to assure that the pull-up resistor versus the capacitor
load has a low enough time constant for the application
to form a “clean” clock. (See “Open-Drain Pins”, later
in this section.)
When an LTM4676A is configured as a sync slave, it is
permissible for external circuitry to drive the SYNC pin
from a current-limited source (less than 10mA), rather
than using a pull-up resistor. Any external circuitry must
not drive high with arbitrarily low impedance at SVIN
power-up, because the SYNC output can be low impedance
until NVM contents have been downloaded to RAM.
52
Recommended LTM4676A switching frequencies of
operation for many common VIN-to-VOUT applications
are indicated in Table 7. When the two channels of an
LTM4676A are stepping input voltage(s) down to output
voltages whose recommended switching frequencies
in Table 7 are significantly different, operation at the
higher of the two recommended switching frequencies
is preferable, but minimum on-time must be considered.
(See Minimum On-Time Considerations section.) For
example, consider an application in which it is desired for
an LTM4676A to step-down 12VIN to 1VOUT on Channel 0,
and 12VIN to 3.3VOUT on Channel 1: according to Table 7,
the recommended switching frequency is 350kHz and
650kHz, respectively. However, the switching frequency
setting of the LTM4676A is common to both channels.
Based on the aforementioned guidance, operation at
650kHz would be preferred—in order to keep inductor
ripple currents reasonable—however, it is then realized
that the on-time for a 12VIN-to-1VOUT condition at
650kHz is only 128ns, which is marginal. Therefore, for
this particular example, the recommended switching
frequency becomes 575kHz.
Table 7. Recommended Switching Frequency for Various
VIN-to-VOUT Step-Down Scenarios
5VIN
8VIN
12VIN
0.9VOUT
350kHz
350kHz
350kHz
1.0VOUT
350kHz
350kHz
350kHz
1.2VOUT
350kHz
350kHz
350kHz
1.5VOUT
350kHz
350kHz
425kHz
1.8VOUT
425kHz
425kHz
500kHz
2.5VOUT
425kHz
500kHz
575kHz
3.3VOUT
425kHz
575kHz
650kHz
5.0VOUT
N/A
500kHz
750kHz
The current drawn by the SVIN pin of the LTM4676A is not
digitized or computed. A value representing the estimated
SVIN current is located in the MFR_IIN_OFFSETn command,
and is used in the computations of input current readback
telemetry, namely READ_IIN and and MFR_READ_IINn.
The recommended setting of MFR_IIN_OFFSETn is
found in Table 8. The same value should be used for
MFR_IIN_OFFSET0 and MFR_IIN_OFFSET1 (i.e., Pages
0x00 and 0x01).
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
Table 8. Recommended MFR_IIN_OFFSETn Setting vs
Switching Frequency Setting
SWITCHING
FREQUENCY
(kHz)
FREQUENCY_
SWITCH
COMMAND
VALUE (HEX.)
RECOMMENDED RECOMMENDED
MFR_IIN_
MFR_IIN_
OFFSETn
OFFSETn
SETTING (mA) SETTING (HEX.)
250
0xF3E8
20.3
0x8A99
350
0xFABC
24.4
0x8B20
425
0xFB52
27.4
0x8B82
500
0xFBE8
30.5
0x8BE7
575
0x023F
33.6
0x9227
650
0x028A
36.7
0x9259
750
0x02EE
40.8
0x929C
1000
0x03E8
51.0
0x9344
Sync. to
External Clock,
fSYNC
0x0000
0.041 • fSYNC +
10.037
*
*See Appendix C: PMBus Command Details, L11 data format.
Minimum On-Time Considerations
Minimum on-time, tON(MIN), is the smallest time duration that the LTM4676A is capable of turning on the top
MOSFET. It is determined by internal timing delays and the
gate charge required to turn on the top MOSFET. Low duty
cycle applications may approach this minimum on-time
limit and care should be taken to ensure that:
tON(MIN) <
VOUTn
VINn • fOSC
If the duty cycle falls below what can be accommodated
by the minimum on-time, the controller will begin to skip
cycles. The output voltage will continue to be regulated,
but the ripple voltage and current will increase.
The minimum on-time for the LTM4676A is 90ns, nominal,
guardband to 130ns.
Variable Delay Time, Soft-Start and Output
Voltage Ramping
The LTM4676A must enter its run state prior to soft-start.
The RUNn pins are released after the part initializes and
SVIN is greater than the VIN_ON threshold. If multiple
LTM4676As are used in an application, they should be
configured to share the same RUNn pins. They all hold
their respective RUNn pins low until all devices initialize
and SVIN exceeds the VIN_ON threshold for all devices.
The SHARE_CLK pin assures all the devices connected to
the signal use the same time base.
After the RUNn pin releases, the controller waits for the
user-specified turn-on delay (TON_DELAYn) prior to
initiating an output voltage ramp. Multiple LTM4676As and
other LTC parts can be configured to start with variable
delay times. To work correctly, all devices use the same
timing clock (SHARE_CLK) and all devices must share
the RUNn pin. This allows the relative delay of all parts
to be synchronized. The actual variation in the delay will
be dependent on the highest clock rate of the devices
connected to the SHARE_CLK pin (all Linear Technology
ICs are configured to allow the fastest SHARE_CLK signal
to control the timing of all devices). The SHARE_CLK signal
can be ±7.5% in frequency, thus the actual time delays
will have some variance.
Soft-start is performed by actively regulating the load
voltage while digitally ramping the target voltage from 0V
to the commanded voltage set point. The rise time of the
voltage ramp can be programmed using the TON_RISEn
command to minimize inrush currents associated with the
start-up voltage ramp. The soft-start feature is disabled
by setting TON_RISEn to any value less than 0.250ms.
The LTM4676A performs the necessary math internally to
assure the voltage ramp is controlled to the desired slope.
However, the voltage slope can not be any faster than the
fundamental limits of the power stage. The number of steps
in the ramp is equal to TON_RISE/0.1ms. Therefore, the
shorter the TON_RISEn time setting, the more jagged the
soft-start ramp appears.
The LTM4676A PWM always operates in discontinuous
mode during the TON_RISEn operation. In discontinuous
mode, the bottom MOSFET (MBn) is turned off as soon
as reverse current is detected in the inductor. This allows
the regulator to start up into a pre-biased load.
There is no analog tracking feature in the LTM4676A;
however, two outputs can be given the same TON_RISEn and
TON_DELAYn times to achieve ratiometric rail tracking.
Because the RUNn pins are released at the same time and
both units use the same time base (SHARE_CLK), the
outputs track very closely. If the circuit is in a PolyPhase
configuration, all timing parameters must be the same.
4676af
For more information www.linear.com/LTM4676A
53
LTM4676A
Applications Information
Coincident rail tracking can be achieved by setting two
outputs to have the same turn-on/off slew rates, identical
turn-on delays, and appropriately chosen turn-off delays:
and
filter should be complimented with an externally applied
capacitor between GPIOn and ground—to further filter
the waveform. The RC time-constant of the filter should
be set sufficiently fast to assure no appreciable delay is
incurred. For most applications, a value of 300µs to 500µs
will provide sufficient filtering without significantly delaying the trigger event.
VOUT _COMMANDRAIL1 VOUT _COMMANDRAIL2
=
TOFF _FALLRAIL1
TOFF _FALLRAIL2
Digital Servo Mode
VOUT _COMMANDRAIL1 VOUT _COMMANDRAIL2
=
TON_RISERAIL1
TON_RISERAIL2
and
TON_DELAYRAIL1 = TON_DELAYRAIL2
and (if VOUT_COMMANDRAIL2 ≥ VOUT_COMMANDRAIL1)
TOFF _DELAYRAIL1 =
⎛ VOUT _COMMANDRAIL1 ⎞
TOFF _DELAYRAIL2 + ⎜1–
⎟
⎝ VOUT _COMMANDRAIL2 ⎠
•TOFF _FALLRAIL2
or else (VOUT_COMMANDRAIL2 < VOUT_COMMANDRAIL1)
TOFF _DELAYRAIL2 =
⎛ VOUT _COMMANDRAIL2 ⎞
TOFF _DELAYRAIL1 + ⎜1–
⎟
⎝ VOUT _COMMANDRAIL1 ⎠
•TOFF _FALLRAIL1
The described method of start-up sequencing is time based.
For concatenated events it is possible to control the RUN
pin based on the GPIOn pin of a different controller (see
Figure 2). The GPIOn pin can be configured to release
when the output voltage of the converter is greater than
the VOUT_UV_FAULT_LIMITn. It is recommended to use
the unfiltered VOUT UV fault limit because there is little
appreciable time delay between the converter crossing the
UV threshold and the GPIOn pin releasing. The unfiltered
output can be enabled by the MFR_GPIO_PROPAGATEn[12]
setting. (Refer to the MFR section of the PMBus commands
in Appendix C: PMBus Command Details). The unfiltered
signal may have some glitching as the VOUT signal
transitions through the comparator threshold. A small
digital filter of 250µs internally deglitches the GPIOn pins.
If the TON_RISE time is greater than 100ms, the deglitch
54
For maximum accuracy in the regulated output voltage,
enable the digital servo loop by asserting bit 6 of the
MFR_PWM_MODEn command. In digital servo mode,
the LTM4676A adjusts the regulated output voltage
based on the ADC voltage reading. Every 100ms the
digital servo loop steps the LSB of the DAC (nominally
1.375mV or 0.6875mV depending on the voltage range bit,
MFR_PWM_MODEn[1]) until the output is at the correct
ADC reading. At power-up this mode engages after TON_
MAX_FAULT_LIMITn unless the limit is set to 0 (infinite).
If the TON_MAX_FAULT_LIMITn is set to 0 (infinite), the
servo begins after TON_RISEn is complete and VOUTn has
exceeded VOUT_UV_FAULT_LIMITn and IOUT_OCn is
not present. This same point in time is when the output
changes from discontinuous to the mode commanded by
MFR_PWM_MODEn [0]. Refer to Figure 3 for details on
the VOUTn waveform under time based sequencing.
RUNn
DIGITAL SERVO
MODE ENABLED FINAL OUTPUT
VOLTAGE REACHED
TON_MAX_FAULT_LIMITn
VOUT_UV_FAULT_LIMITn
DAC VOLTAGE
ERROR (NOT
TO SCALE)
VOUTn
TON_DELAYn
TON_RISEn
TIME DELAY OF
MANY SECONDS
TIME
4676A F03
Figure 3. Timing Controlled VOUT Rise
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
If the TON_MAX_FAULT_LIMITn is set to a value greater
than 0 and the TON_MAX_FAULT_RESPONSEn is set to
ignore (0x00), the servo begins:
1.After the TON_RISEn sequence is complete
2.After the TON_MAX_FAULT_LIMITn time is reached;
and
3.After the VOUT_UV_FAULT_LIMITn has been exceed
or the IOUT_OC_FAULT_LIMITn is no longer active.
If the TON_MAX_FAULT_LIMITn is set to a value greater
than 0 and the TON_MAX_FAULT_RESPONSEn is not set
to ignore (0X00), the servo begins:
1.After the TON_RISEn sequence is complete;
2.After the TON_MAX_FAULT_LIMITn time has expired
and both VOUT_UV_FAULTn and IOUT_OC_FAULTn are
not present.
The maximum rise time is limited to 1.3 seconds.
In a PolyPhase configuration it is recommended only one
of the control loops have the digital servo mode enabled.
This will assure the various loops do not work against each
other due to slight differences in the reference circuits.
Soft Off (Sequenced Off)
In addition to a controlled start-up, the LTM4676A also
supports controlled turn-off. The TOFF_DELAYn and
TOFF_FALLn functions are shown in Figure 4. TOFF_FALLn
is processed when the RUNn pin goes low or if the module
is commanded off. If the module faults off or GPIOn is
pulled low externally and the module is programmed to
RUNn
VOUTn
TOFF_DELAYn
TOFF_FALLn
TIME
Figure 4. TOFF_DELAYn and TOFF_FALLn
4676A F04
respond to this (MFR_GPIO_RESPONSEn = 0xC0), the
output three-states (becomes high impedance) rather than
exhibiting a controlled ramp. The output then decays as
a function of the load.
The output voltage operates as shown in Figure 4 so long as
the part is in forced continuous mode and the TOFF_FALLn
time is sufficiently slow that the power stage can achieve
the desired slope. The TOFF_FALLn time can only be met if
the power stage and controller can sink sufficient current
to assure the output is at zero volts by the end of the fall
time interval. If the TOFF_FALLn time is set shorter than
the time required to discharge the load capacitance, the
output will not reach the desired zero volt state. At the end
of TOFF_FALLn, the controller ceases to sink current and
VOUTn decays at the natural rate determined by the load
impedance. If the controller is in discontinuous mode, the
controller does not pull negative current and the output
becomes pulled low by the load, not the power stage. The
maximum fail time is limited to 1.3 seconds. The number of
steps in the ramp is equal to TOFF_FALL/0.1ms.Therefore,
the shorter the TOFF_FALLn setting, the more jagged the
TOFF_FALLn ramp appears.
Undervoltage Lockout
The LTM4676A is initialized by an internal thresholdbased UVLO where SVIN must be approximately 4V and
INTVCC, VDD33, VDD25 must be within approximately
20% of the regulated values. In addition, VDD33 must
be within approximately 7% of the targeted value before
the LTM4676A releases its RUNn pins. After the part has
initialized, an additional comparator monitors SVIN. The
VIN_ON threshold must be exceeded before the power
sequencing can begin. When SVIN drops below the VIN_OFF
threshold, the LTM4676A pulls its RUNn pins low and
SVIN must increase above the VIN_ON threshold before
the controller will restart. The normal start-up sequence
will be allowed after the VIN_ON threshold is crossed.
It is possible to program the contents of the NVM in
the application if the VDD33 supply is externally driven.
This activates the digital portion of the LTM4676A
without engaging the high voltage sections. PMBus
communications are valid in this supply configuration. If SVIN has not been applied to the LTM4676A,
4676af
For more information www.linear.com/LTM4676A
55
LTM4676A
Applications Information
MFR_COMMON[3] will be asserted low, indicating that
NVM has not initialized. If this condition is detected, the
part will only respond to addresses 0x5A and 0x5B. To
initialize the part issue the following set of commands:
global address 0x5B command 0xBD data 0x2B followed
by global address 0x5B command 0xBD and data 0xC4.
The part will now respond to the correct address. Configure
the part as desired then issue a STORE_USER_ALL. When
SVIN is applied a MFR_RESET or RESTORE_USER_ALL,
command must be issued to allow the PWM to be enabled
and valid ADC conversions to be read.
Fault Detection and Handling
The LTM4676A GPIOn pins are configurable to indicate a
variety of faults including OV/UV, OC, OT, timing faults,
peak overcurrent faults. In addition the GPIOn pins can be
pulled low by external sources to indicate to the LTM4676A
the presence of a fault in some other portion of the system.
The fault response is configurable via PMBus Command
Code names with a _RESPONSE suffix and allows the
following options:
Ignore
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAYn
n
Refer to Appendix C and the PMBus specification for
more details.
The OV response is automatic and rapid. If an OV is detected, MTn is turned off and BGn is turned on, until the
OV condition clears.
Fault logging is available on the LTM4676A. The fault
logging is configurable to automatically store data when
a fault occurs that causes the unit to fault off. The header
portion of the fault logging table contains peak values. It
is possible to read these values at any time. This data will
be useful while troubleshooting the fault.
If the LTM4676A internal temperature is in excess of 85°C
or below 0°C, the write into the NVM is not recommended.
The data will still be held in RAM, unless the 3.3V supply
UVLO threshold is reached. If the die temperature exceeds
130°C all NVM communication is disabled until the die
56
temperature drops below 125°C, with the exception of
the RESTORE_USER_ALL command, which is valid at
any temperature.
Open-Drain Pins
Note that up to nine pull-up resistors are required for
proper operation of the LTM4676A:
• Three for the SMBus/I2C interface (the SCL, SDA, and
ALERT pins); two, only if the system SMBus host does
not make use of the ALERT interrupt. (These are 5V
tolerant).
• One each for the RUN0 and RUN1 pins (or, just one
to RUN0 and RUN1, if RUN0 and RUN1 are electrically
connected together). (These are 5V tolerant).
• One each for GPIO0 and GPIO1 (or, just one to GPIO0
and GPIO1, if GPIO0 and GPIO1 are electrically connected
together). (These are 3.3V tolerant).
• One on SHARE_CLK, required, for the LTM4676A to
establish a heartbeat time base for timing-related operations and functions (output voltage ramp-up timing,
voltage margining transition timing, SYNC open-drain
drive frequency). (SHARE CLK is 3.3V tolerant).
• One on SYNC, in order for the LTM4676A to phase lock
to the frequency generated by the open-drain output
of its digital engine. EXCEPTION: in some applications,
it is desirable to drive the LTM4676A’s SYNC pin
with a hard-driven (low impedance) external clock.
This is the only scenario where the LTM4676A does
not require a pull-up resistor on SYNC. However, be
aware that the SYNC pin can be low impedance during
NVM initialization, i.e., during download of EEPROM
contents to RAM (for ~50ms [Note 12] after SVIN
power is applied). Therefore, the hard-driven clock
signal should only be applied to the LTM4676A SYNC
pin through a series resistor whose impedance limits
current into the SYNC pin during NVM initialization to
less than 10mA. If FREQUENCY_SWITCH=0x0000, any
clock signal should be provided prior to the RUNn pins
toggle from logic low to logic high, or else the switching frequency of the LTM4676A will start off at the low
end of its PLL-capture range (~225kHz) until the SYNC
clock becomes established. (SYNC is 3.3V tolerant).
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
All the above pins interface to pull-down transistors within
the module that can sink 3mA at 0.4V. The low threshold
on the pins is 1.4V; thus, plenty of margin on the digital
signals with 3mA of current. For 3.3V pins, 3mA of current
is a 1.1k resistor. Unless there are transient speed issues
associated with the RC time constant of the resistor pullup and parasitic capacitance to ground, a 10k resistor or
larger is generally recommended.
For high speed signals such as the SDA, SCL and SYNC,
a lower value resistor may be required. The RC time constant should be set to 1/3 to 1/5 the required rise time
to avoid timing issues. For a 100pF load and a 400kHz
PMBus communication rate, the rise time must be less
than 300ns. The resistor pull-up on the SDA and SCL pins
with the time constant set to 1/3 the rise time:
RPULLUP =
tRISE
=1k
3 •100pF
Be careful to minimize parasitic capacitance on the SDA and
SCL pins to avoid communication problems. To estimate
the loading capacitance, monitor the signal in question
and measure how long it takes for the desired signal to
reach approximately 63% of the output value. This is one
time constant.
The SYNC pin interfaces to a pull-down transistor within the module whose output is held low for
nominally 500ns per switching period. If the internal
oscillator is set for 500kHz and the load is 100pF and a
3x time constant is required, the resistor calculation is
as follows:
RPULLUP =
2µs – 500ns
= 5k
3 •100pF
The closest 1% resistor is 4.99k.
If timing errors are occurring or if the SYNC frequency is
not as fast as desired, monitor the waveform and determine
if the RC time constant is too long for the application. If
possible reduce the parasitic capacitance. If not reduce
the pull up resistor sufficiently to assure proper timing.
Phase-Locked Loop and Frequency
Synchronization
The LTM4676A has a phase-locked loop (PLL) comprised
of an internal voltage-controlled oscillator (VCO) and a
phase detector. The PLL is locked to the falling edge of
the SYNC pin. The phase relationship between channel 0,
channel 1 and the falling edge of SYNC is controlled by
the lower 3 bits of the MFR_PWM_CONFIG command. For
PolyPhase applications, it is recommended all the phases
be spaced evenly. Thus for a 2-phase system the signals
should be 180° out of phase and a 4-phase system should
be spaced 90°.
The phase detector is an edge-sensitive digital type that
provides a known phase shift between the external and
internal oscillators. This type of phase detector does not
exhibit false lock to harmonics of the external clock.
The output of the phase detector is a pair of complementary current sources that charge or discharge the internal
filter network. The PLL lock range is guaranteed between
225kHz and 1.1MHz.
The PLL has a lock detection circuit. If the PLL should lose
lock during operation, bit 4 of the STATUS_MFR_SPECIFIC
command is asserted and the ALERT pin is pulled low.
The fault can be cleared by writing a 1 to the bit. If the
user does not wish to see the PLL_FAULT, even if a
synchronization clock is not available at power up, bit 3
of the MFR_CONFIG_ALL command must be asserted.
If the SYNC signal is not clocking in the application, the
PLL runs at the lowest free running frequency of the VCO.
This will be well below the intended PWM frequency of
the application and may cause undesirable operation of
the converter.
If the PWM (SWn) signal appears to be running at too
high a frequency, monitor the SYNC pin. Extra transitions
on the falling edge will result in the PLL trying to lock on
to noise instead of the intended signal. Review routing of
digital control signals and minimize crosstalk to the SYNC
signal to avoid this problem. Multiple LTM4676As are
required to share the SYNC pin in PolyPhase configurations;
4676af
For more information www.linear.com/LTM4676A
57
LTM4676A
Applications Information
for other configurations, it is optional. If the SYNC pin
is shared between LTM4676As, only one LTM4676A
can be programmed with a frequency output. All the
other LTM4676As must be configured for external clock
(MFR_CONFIG_ALL[4]=1b, and/or see Table 4).
Voltage Selection
When an output voltage is set using the RCONFIG pins on
VOUTn_CFG and VTRIMn_CFG (MFR_CONFIG_ALL[6] =
0b), the following parameters are set as a percentage of
the output voltage:
RCONFIG Pin-Straps (External Resistor
Configuration Pins)
• VOUT_OV_FAULT_LIMIT
The LTM4676A default NVM is programmed to respect
the RCONFIG pins. If a user wishes the output voltage,
PWM frequency and phasing and the address to be set
without programming the part or purchasing specially
programmed parts, the RCONFIG pins can be used to
establish these parameters—provided MFR_CONFIG_
ALL[6] = 0b. The RCONFIG pins only require a resistor
terminating to SGND of the LTM4676A. The RCONFIG pins
are only monitored at initial power up and during a reset
(MFR_RESET or RESTORE_USER_ALL) so modifying their
values perhaps using a DAC after the part is powered will
have no effect. To assure proper operation, the value of
RCONFIG resistors applied to the LTM4676A pin-strapping
pins must not deviate more than ±3% away from the target
nominal values indicated in lookup Table 2 to Table 5,
over the lifetime of the product. Thin film, 1% tolerance
(or better), ±50ppm/°C-T.C.R. rated (or better) resistors
from vendors such as KOA Speer, Panasonic, Vishay and
Yageo are good candidates. Noisy clock signals should
not be routed near these pins. Note that bits [3:0] of
MFR_ADDRESS are dictated by the ASEL pin-strap resistor
regardless of the setting of MFR_CONFIG_ALL[6].
• VOUT_MAX+7.5%
58
+10%
• VOUT_OV_WARN+7.5%
• VOUT_MARGIN_HI+5%
• VOUT_MARGIN_LO–5%
• VOUT_UV_WARN
–6.5%
• VOUT_UV_FAULT_LIMIT
–7%
Connecting the USB to the I2C/SMBus/PMBus
Controller to the LTM4676A In System
The LTC USB to I2C/SMBus/PMBus controller can be
interfaced to the LTM4676A on the user’s board for programming, telemetry and system debug. The controller,
when used in conjunction with LTpowerPlay, provides a
powerful way to debug an entire power system. Faults are
quickly diagnosed using telemetry, fault status registers
and the fault log. The final configuration can be quickly
developed and stored to the LTM4676A EEPROM.
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
Figure 5 and Figure 6 illustrate the application schematics
for powering, programming and communicating with
one or more LTM4676As via the LTC I2C/SMBus/PMBus
controller regardless of whether or not system power is
present. If system power is not present the dongle will
power the LTM4676A through the VDD33 supply pin. To
initialize the part when SVIN is not applied and the VDD33
pin is powered use global address 0x5B command 0xBD
data 0x2B followed by address 0x5B command 0xBD data
0xC4. The part can now be communicated with, and the
project file updated. To write the updated project file to
the NVM issue a STORE_USER_ALL command. When
SVIN is applied, a MFR_RESET or RESTORE_USER_ALL
must be issued to allow the PWM to be enabled and valid
ADCs to be read.
Because of the controllers limited current sourcing capability, only the LTM4676As, their associated pull-up resistors
and the I2C pull-up resistors should be powered from the
ORed 3.3V/3.4V supply. In addition, any device sharing
the I2C bus connections with the LTM4676A must not
have body diodes between the SDA/SCL pins and their
respective VDD node because this will interfere with bus
communication in the absence of system power. In Figure 5,
the dongle will not bias the LTM4676As when SVIN is
present. It is recommended the RUNn pins be held low
to avoid providing power to the load until the part is fully
configured.
The LTC controller/adapter I2C connections are opto-isolated from the PC USB. The 3.3V/3/4V from the controller/
adapter and the LTM4676A VDD33 pin must be driven to
each LTM4676A with a separate PFET or diode, according
to Figure 5 and Figure 6. Only when SVIN is not applied is it
permissible for the VDD33 pins to be electrically in parallel
because the INTVCC LDO is off. The DC1613’s 3.3V current
limit is 100mA but typical VDD33 currents are under 15mA.
The VDD33 does back drive the INTVCC pin. Normally this
is not an issue if SVIN is open. The DC2086 is capable of
delivering 3.4V at 2A.
Using a 4-pin header in Figure 5 or Figure 6 maximizes
flexibility to alter the LTM4676A’s NVM contents at any
stage of the user’s product development and production
cycles. If the LTM4676A’s NVM is “pre-programmed”, i.e.,
contains its finalized configuration, prior to being soldered
to the user’s PCB/motherboard—or, if other means have
been provided for altering the LTM4676A's NVM contents
in the user’s system—then the 3.3V/3.4V pin on the header
is not needed, and a 3-pin header is sufficient to establish
GUI communications. The LTM4676A can be purchased
with customized NVM contents; consult factory for details.
Alternatively, the NVM contents of the LTM4676A can be
configured in a mass production environment by designing for it in ICT (in-circuit test), or by providing a means
of applying SVIN while holding the LTM4676A’s RUN pins
low. Communication to the module must be made possible
via the SCL and SDA pins/nets in all NVM programming
scenarios. Recommended headers are found in Table 9
and Table 10.
4676af
For more information www.linear.com/LTM4676A
59
LTM4676A
Applications Information
VIN
MODULE PROGRAMMING
AND COMMUNICATION
INTERFACE HEADER
100k
100k
SVIN
ISOLATED 3.4V
(USUALLY NEEDED)
SEE TABLES 9-13 FOR
CONNECTOR AND
PINOUT OPTIONS
VDD33
TP0101K
SOT-23
SCL
10k
SDA
10k
TO LTC DC2086 DIGITAL
POWER PROGRAMMING
ADAPTER (REQUIRES LTC
DC1613 USB TO I2C/SMBus/
PMBus CONTROLLER)
VGS MAX ON THE TP0101K IS 8V. IF VIN > 16V,
CHANGE THE RESISTOR DIVIDER ON THE PFET GATE
ALTERNATE PFETS/PACKAGES:
SOT-723: GOOD-ARK SEMI SSF2319GE
ON SEMI NTK3139PT1G
ROHM RZM002P02T2L
SOT-523: DIODES INC. DMG1013T-7
GOOD-ARK SEMI SSF2319GD
SOT-563: DIODES INC. DMP2104V-7
ON SEMI NTZS3151PT1G
SOT-323: DIODES INC. DMG1013UW-7
ON SEMI NTS2101PT1G
VISHAY Si1303DL-T1-E3
VDD25
LTM4676A
SCL
SDA
WP SGND
SVIN
VDD33
TP0101K
SOT-23
VDD25
LTM4676A
•
•
•
SCL
SDA
WP SGND
•
•
•
4676A F05
Figure 5. Circuit Suitable for Programming EEPROM/NVM of LTM4676A and Other LTC
PSM Modules/ICs in Vast Systems, Even When VIN Power is Absent, 0°C < TJ ≤ 85°C
MODULE PROGRAMMING
AND COMMUNICATION
INTERFACE HEADER
SEE TABLES 9-13 FOR
CONNECTOR AND
PINOUT OPTIONS
VIN
SVIN
ISOLATED 3.4V
(USUALLY NEEDED)
SCL
VDD33
D1
SOD882
SDA
TO LTC DC2086 DIGITAL
POWER PROGRAMMING
ADAPTER (REQUIRES LTC
DC1613 USB TO I2C/SMBus/
PMBus CONTROLLER)
10k
10k
D2
SOD882
SCL
SDA
WP SGND
SVIN
VDD33
•
•
•
D1, D2: NXP PMEG2005AEL OR PMEG2005AELD.
DIODE SELECTION IS NOT ARBITRARY.
USE VF < 210mV AT IF = 20mA
VDD25
LTM4676A
SCL
SDA
WP SGND
•
•
•
60
VDD25
LTM4676A
4676A F06
Figure 6. Circuit Suitable for Programming EEPROM/NVM of LTM4676A and Other LTC PSM
Modules/ICs in Vast Systems, Even When VIN Power is Absent, TA > 20°C and TJ < 85°C
For more information www.linear.com/LTM4676A
4676af
LTM4676A
Applications Information
Table 9. 4-Pin Headers, 2mm Pin-to-Pin Spacing, Gold Flash or Plating, Compatible with DC2086 Cables
MOUNTING
STYLE
INSERTION
ANGLE
INTERFACE STYLE
Shrouded and Keyed Header
VENDOR PART NUMBER
Hirose DF3DZ-4P-2V(51)
DF3DZ-4P-2V(50)
DF3Z-4P-2V(50)
3M
951104-2530-AR-PR
Hirose DF3DZ-4P-2H(51)
DF3DZ-4P-2H(50)
FCI
10112684-G03-04ULF
Vertical
Non Shrouded, Non-Keyed Header
Shrouded and Keyed Header
Surface Mount
Right Angle
Vertical
Through-Hole
Right Angle
Non Shrouded. Cable-to-Header/PCB
Mechanics Yield Keying Effect
Shrouded and Keyed Header
Non Shrouded, Non-Keyed Header
Shrouded and Keyed Header
Non Shrouded. Cable-to-Header/PCB
Mechanics Yield Keying Effect
Hirose
Harwin
Samtec
Sullins
Hirose
Norcomp
Harwin
Samtec
DF3-4P-2DSA(01)
M22-2010405
TMM-104-01-LS
NRPN041PAEN-RC
DF3-4P-2DS(01)
27630402RP2
M22-2030405
TMM-104-01-L-S-RA
PINOUT STYLE (SEE TABLE 11)
Type A
Type A and B Supported. Reversible/Not Keyed
Type A
Type B. Keying Achieved by PCB Surface
Type A
Type A and B Supported. Reversible/Not Keyed
Type A
Type B. Keying Achieved by Intentional PCB
Interference
Table 10. 3-Pin Headers, 2mm Pin-to-Pin Spacing, Gold Flash or Plating, Compatible with DC2086 Cables
MOUNTING
STYLE
INSERTION
ANGLE
INTERFACE STYLE
Shrouded and Keyed Header
VENDOR PART NUMBER
Hirose DF3DZ-3P-2V(51)
DF3DZ-3P-2V(50)
DF3Z-3P-2V(50)
3M
951103-2530-AR-PR
Hirose DF3DZ-3P-2H(51)
DF3DZ-3P-2H(50)
FCI
10112684-G03-03LF
Vertical
Non Shrouded, Non-Keyed Header
Shrouded and Keyed Header
Surface Mount
Right Angle
Vertical
Through-Hole
Right Angle
Non Shrouded. Cable-to-Header/PCB
Mechanics Yield Keying Effect
Shrouded and Keyed Header
Non Shrouded, Non-Keyed Header
Shrouded and Keyed Header
Non Shrouded. Cable-to-Header/PCB
Mechanics Yield Keying Effect
Hirose
Harwin
Samtec
Sullins
Hirose
Norcomp
Harwin
Samtec
Table 11. Recommended 4-Pin Header Pinout (Pin Numbering
Scheme Adheres to Hirose Conventions). Interfaces to DC2086
Cables
PINOUT STYLE (SEE TABLE 12)
Type A
Type A and B Supported. Reversible/Not Keyed
Type A
Type B. Keying Achieved by PCB Surface
DF3-3P-2DSA(01)
M22-2010305
TMM-103-01-LS
NRPN031PAEN-RC
DF3-3P-2DS(01)
27630302RP2
M22-2030305
TMM-103-01-L-S-RA
Type A
Type A and B Supported. Reversible/Not Keyed
Type A
Type B. Keying Achieved by Intentional PCB
Interference
Table 12. Recommended 3-Pin Header Pinout (Pin Numbering
Scheme Adheres to Hirose Conventions). Interfaces to DC2086
Cables
PIN NUMBER
PINOUT STYLE “A”
(SEE TABLE 9)
PINOUT STYLE “B”
(SEE TABLE 9)
PIN NUMBER
PINOUT STYLE “A”
(SEE TABLE 10)
PINOUT STYLE “B”
(SEE TABLE 10)
1
SDA
Isolated 3.3V/3.4V
1
SDA
SCL
2
GND
SCL
2
GND
GND
3
SCL
GND
3
SCL
SDA
4
Isolated 3.3V/3.4V
SDA
4676af
For more information www.linear.com/LTM4676A
61
LTM4676A
Applications Information
Table 13. 4-Pin Male-to-Male Shrouded and Keyed Adapter
(Optional. Eases Creation of Adapter Cables, if Deviating from
Recommended Connectors/Connector Pinouts). Interfaces to
DC2086 Cables
Vendor
Part Number
Website
Hirose
DF3-4EP-2A
www.hirose.com, www.hirose.co.jp
LTpowerPlay: An Interactive GUI for Digital
Power System Management
LTpowerPlay is a powerful Windows-based development
environment that supports Linear Technology digital
power ICs including the LTM4676A. The software supports a variety of different tasks. LTpowerPlay can be
used to evaluate Linear Technology ICs by connecting to
a demo board or the user application. LTpowerPlay can
also be used in an offline mode (with no hardware pres-
ent) in order to build multiple IC configuration files that
can be saved and reloaded at a later time. LTpowerPlay
provides unprecedented diagnostic and debug features.
It becomes a valuable diagnostic tool during board bringup to program or tweak the power system or to diagnose
power issues when bringing up rails. LTpowerPlay utilizes
Linear Technology’s USB-to-I2C/SMBus/PMBus controller
to communication with one of the many potential targets
including the DC1811B-B (single LTM4676A) or DC1989
(dual, triple, quad LTM4676) demo boards, or a customer
target system. The software also provides an automatic
update feature to keep the revisions current with the latest
set of device drivers and documentation. A great deal of context sensitive help is available with LTpowerPlay along with
several tutorial demos. Complete information is available at
http://www.linear.com/ltpowerplay
Figure 7. LTPowerPlay
62
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
CMD
PMBus
WRITE
WRITE COMMAND
DATA BUFFER
DECODER
PAGE
CMDS
DATA
MUX
CALCULATIONS
PENDING
S
R
•
•
•
VOUT_COMMAND
0x00
0x21
•
•
•
MFR_RESET
INTERNAL
PROCESSOR
FETCH,
CONVERT
DATA
AND
EXECUTE
0xFD
x1
4676A F08
Figure 8. Write Command Data Processing
PMBus Communication and Command
Processing
The LTM4676A has one deep buffer to hold the last data
written for each supported command prior to processing
as shown in Figure 8; Write Command Data Processing.
When the part receives a new command from the bus,
it copies the data into the Write Command Data Buffer,
indicates to the internal processor that this command
data needs to be fetched, and converts the command to
its internal format so that it can be executed.
Two distinct parallel blocks manage command buffering
and command processing (fetch, convert, and execute)
to ensure the last data written to any command is never
lost. Command data buffering handles incoming PMBus writes by storing the command data to the Write
Command Data Buffer and marking these commands for
future processing. The internal processor runs in parallel
and handles the sometimes slower task of fetching, converting and executing commands marked for processing.
Some computationally intensive commands (e.g., timing
parameters, temperatures, voltages and currents) have
internal processor execution times that may be long
relative to PMBus timing. If the part is busy processing a
command, and new command(s) arrive, execution may
be delayed or processed in a different order than received.
The part indicates when internal calculations are in process
via bit 5 of MFR_COMMON (‘calculations not pending’).
When the part is busy calculating, bit 5 is cleared. When
this bit is set, the part is ready for another command. An
example polling loop is provided in Figure 8 which ensures
that commands are processed in order while simplifying
error handling routines.
When the part receives a new command while it is busy,
it will communicate this condition using standard PMBus
protocol. Depending on part configuration it may either
NACK the command or return all ones (0xFF) for reads. It
may also generate a BUSY fault and ALERT notification,
or stretch the SCL clock low. For more information refer
to PMBus Specification v1.2, Part II, Section 10.8.7 and
SMBus v2.0 section 4.3.3. Clock stretching can be enabled
by asserting bit 1 of MFR_CONFIG_ALL. Clock stretching
will only occur if enabled and the bus communication
speed exceeds 100kHz.
PMBus busy protocols are well accepted standards, but
can make writing system level software somewhat complex. The part provides three ‘hand shaking’ status bits
which reduce complexity while enabling robust system
level communication.
The three hand shaking status bits are in the MFR_
COMMON register. When the part is busy executing an
internal operation, it will clear bit 6 of MFR_COMMON
(‘module not busy’). When the part is busy specifically
because it is in a transitional VOUT state (margining hi/lo,
power off/on, moving to a new output voltage set point,
etc.) it will clear bit 4 of MFR_COMMON (‘output not in
transition’). When internal calculations are in process, the
part will clear bit 5 of MFR_COMMON (‘calculations not
pending’). These three status bits can be polled with a
PMBus read byte of the MFR_COMMON register until all
three bits are set. A command immediately following the
status bits being set will be accepted without NACKing or
generating a BUSY fault/ALERT notification. The part can
NACK commands for other reasons, however, as required
by the PMBus spec (for instance, an invalid command or
data). An example of a robust command write algorithm
for the VOUT_COMMANDn register is provided in Figure 9.
// wait until bits 6, 5, and 4 of MFR_COMMON are all set
do
{
mfrCommonValue = PMBUS_READ_BYTE(0xEF);
partReady = (mfrCommonValue & 0x68) == 0x68;
}while(!partReady)
// now the part is ready to receive the next command
PMBUS_WRITE_WORD(0x21, 0x2000); //write VOUT_COMMAND to 2V
Figure 9. Example of a Command Write of VOUT_COMMAND
4676af
For more information www.linear.com/LTM4676A
63
LTM4676A
Applications Information
It is recommended that all command writes (write byte,
write word, etc.) be preceded with a polling loop to avoid
the extra complexity of dealing with busy behavior and
unwanted ALERT notification. A simple way to achieve this
is by creating SAFE_WRITE_BYTE() and SAFE_WRITE_
WORD() subroutines. The above polling mechanism allows
one’s software to remain clean and simple while robustly
communicating with the part. For a detailed discussion
of these topics and other special cases please refer to
the application note section located at www.linear.com/
designtools/app_notes.
When communicating using bus speeds at or below
100kHz, the polling mechanism shown here provides a
simple solution that ensures robust communication without
clock stretching. At bus speeds in excess of 100kHz, it is
strongly recommended that the part be configured to enable clock stretching. This requires a PMBus master that
supports clock stretching. System software that detects
and properly recovers from the standard PMBus NACK/
BUSY faults as described in the PMBus Specification v1.2,
Part II, Section 10.8.7 is required to communicate above
100kHz without clock stretching. Clock stretching will not
extend the PMBus speed beyond the specified 400kHz.
Thermal Considerations and
Output Current Derating
The thermal resistances reported in the Pin Configuration section of this data sheet are consistent with those
parameters defined by JESD51-12 and are intended for
use with finite element analysis (FEA) software modeling
tools that leverage the outcome of thermal modeling,
simulation, and correlation to hardware evaluation performed on a µModule package mounted to a hardware
test board defined by JESD51-9 (“Test Boards for Area
Array Surface Mount Package Thermal Measurements”).
The motivation for providing these thermal coefficients is
found in JESD51-12 (“Guidelines for Reporting and Using
Electronic Package Thermal Information”).
Many designers may opt to use laboratory equipment and a
test vehicle such as the demo board to predict the µModule
regulator’s thermal performance in their application at
various electrical and environmental operating conditions
to compliment any FEA activities. Without FEA software,
64
the thermal resistances reported in the Pin Configuration
section are in-and-of themselves not relevant to providing
guidance of thermal performance; instead, the derating
curves provided later in this data sheet can be used in
a manner that yields insight and guidance pertaining to
one’s application-usage, and can be adapted to correlate
thermal performance to one’s own application.
The Pin Configuration section gives four thermal coefficients explicitly defined in JESD51-12; these coefficients
are quoted or paraphrased below:
1 θJA, the thermal resistance from junction to ambient, is
the natural convection junction-to-ambient air thermal
resistance measured in a one cubic foot sealed enclosure. This environment is sometimes referred to as
“still air” although natural convection causes the air to
move. This value is determined with the part mounted
to a JESD51-9 defined test board, which does not reflect
an actual application or viable operating condition.
2 θJCbottom, the thermal resistance from junction to the
bottom of the product case, is determined with all of
the component power dissipation flowing through the
bottom of the package. In the typical µModule regulator,
the bulk of the heat flows out the bottom of the package, but there is always heat flow out into the ambient
environment. As a result, this thermal resistance value
may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
3 θJCtop, the thermal resistance from junction to top of
the product case, is determined with nearly all of the
component power dissipation flowing through the top of
the package. As the electrical connections of the typical
µModule regulator are on the bottom of the package, it
is rare for an application to operate such that most of
the heat flows from the junction to the top of the part.
As in the case of θJCbottom, this value may be useful
for comparing packages but the test conditions don’t
generally match the user’s application.
4 θJB, the thermal resistance from junction to the printed
circuit board, is the junction-to-board thermal resistance where almost all of the heat flows through the
bottom of the µModule regulator and into the board,
and is really the sum of the θJCbottom and the thermal
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
resistance of the bottom of the part through the solder
joints and through a portion of the board. The board
temperature is measured a specified distance from the
package, using a two sided, two layer board. This board
is described in JESD51-9.
A graphical representation of the aforementioned thermal
resistances is given in Figure 10; blue resistances are
contained within the µModule regulator, whereas green
resistances are external to the µModule package.
As a practical matter, it should be clear to the reader that
no individual or sub-group of the four thermal resistance
parameters defined by JESD51-12 or provided in the Pin
Configuration section replicates or conveys normal operating conditions of a µModule regulator. For example,
in normal board-mounted applications, never does 100%
of the device’s total power loss (heat) thermally conduct
exclusively through the top or exclusively through bottom of the µModule package—as the standard defines
for θJCtop and θJCbottom, respectively. In practice, power
loss is thermally dissipated in both directions away from
the package—granted, in the absence of a heat sink and
airflow, a majority of the heat flow is into the board.
Within the LTM4676A, be aware there are multiple power
devices and components dissipating power, with a consequence that the thermal resistances relative to different
junctions of components or die are not exactly linear with
respect to total package power loss. To reconcile this
complication without sacrificing modeling simplicity—but
also, not ignoring practical realities—an approach has been
taken using FEA software modeling along with laboratory
testing in a controlled-environment chamber to reasonably define and correlate the thermal resistance values
supplied in this data sheet: (1) Initially, FEA software is
used to accurately build the mechanical geometry of the
LTM4676A and the specified PCB with all of the correct
material coefficients along with accurate power loss source
definitions; (2) this model simulates a software-defined
JEDEC environment consistent with JSED 51-9 and
JESD51-12 to predict power loss heat flow and temperature
readings at different interfaces that enable the calculation of
the JEDEC-defined thermal resistance values; (3) the model
and FEA software is used to evaluate the LTM4676A with
heat sink and airflow; (4) having solved for and analyzed
these thermal resistance values and simulated various
operating conditions in the software model, a thorough
laboratory evaluation replicates the simulated conditions
with thermocouples within a controlled environment
chamber while operating the device at the same power
loss as that which was simulated. The outcome of this
process and due diligence yields the set of derating curves
provided in later sections of this data sheet, along with
well-correlated JESD51-12-defined θ values provided in
the Pin Configuration section of this data sheet.
The 1V, 1.8V and 3.3V power loss curves in Figure 11,
Figure 12 and Figure 13 respectively can be used in
coordination with the load current derating curves in
Figures 14 to 25 for calculating an approximate θJA
thermal resistance for the LTM4676A with various heat
sinking and air flow conditions. These thermal resistances
represent demonstrated performance of the LTM4676A
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)
RESISTANCE
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION
JUNCTION-TO-CASE
CASE (BOTTOM)-TO-BOARD
(BOTTOM) RESISTANCE
RESISTANCE
AMBIENT
BOARD-TO-AMBIENT
RESISTANCE
4676A F10
µMODULE DEVICE
Figure 10. Graphical Representation of JESD51-12 Thermal Coefficients
4676af
For more information www.linear.com/LTM4676A
65
LTM4676A
Applications Information
on DC1811B-B hardware; a 4-layer FR4 PCB measuring
99mm × 133mm × 1.6mm using outer and inner copper
weights of 2oz and 1oz, respectively. The power loss
curves are taken at room temperature, and are increased
with multiplicative factors with ambient temperature.
These approximate factors are listed in Table 14.
(Compute the factor by interpolation, for intermediate
temperatures.) The derating curves are plotted with the
LTM4676A’s paralleled outputs initially sourcing up to 26A
and the ambient temperature at 30°C. The output voltages
are 1V, 1.8V and 3.3V. These are chosen to include the
lower and higher output voltage ranges for correlating
the thermal resistance. Thermal models are derived
from several temperature measurements in a controlled
temperature chamber along with thermal modeling
analysis. The junction temperatures are monitored while
ambient temperature is increased with and without air
flow, and with and without a heat sink attached with
thermally conductive adhesive tape. The BGA heat sinks
evaluated in Table 18 (and attached to the LTM4676A
with thermally conductive adhesive tape listed in Table
19) yield very comparable performance in laminar airflow
despite being visibly different in construction and form
factor. The power loss increase with ambient temperature
change is factored into the derating curves. The junctions
are maintained at 120°C maximum while lowering output
current or power while increasing ambient temperature.
The decreased output current decreases the internal
module loss as ambient temperature is increased. The
monitored junction temperature of 120°C minus the
ambient operating temperature specifies how much module
temperature rise can be allowed. As an example in Figure 15,
the load current is derated to ~19A at ~80°C ambient
with 400LFM airflow and no heat sink and the room
66
temperature (25°C) power loss for this 12VIN to 1VOUT
at 19AOUT condition is ~4W. A 4.8W loss is calculated by
multiplying the ~4W room temperature loss from the 12VIN
to 1VOUT power loss curve at 19A (Figure 11), with the 1.2
multiplying factor at 80°C ambient (from Table 14). If the
80°C ambient temperature is subtracted from the 120°C
junction temperature, then the difference of 40°C divided
by 4.8W yields a thermal resistance, θJA, of 8.3°C/W—in
good agreement with Table 15. Table 15, Table 16 and
Table 17 provide equivalent thermal resistances for 1V, 1.8V
and 3.3V outputs with and without air flow and heat sinking.
The derived thermal resistances in Table 15, Table 16
and Table 17 for the various conditions can be multiplied
by the calculated power loss as a function of ambient
temperature to derive temperature rise above ambient,
thus maximum junction temperature. Room temperature
power loss can be derived from the efficiency curves
in the Typical Performance Characteristics section and
adjusted with ambient temperature multiplicative factors
from Table 14.
Table 14. Power Loss Multiplicative Factors vs Ambient
Temperature
AMBIENT TEMPERATURE
POWER LOSS MULTIPLICATIVE
FACTOR
Up to 40°C
1.00
50°C
1.05
60°C
1.10
70°C
1.15
80°C
1.20
90°C
1.25
100°C
1.30
110°C
1.35
120°C
1.40
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
Table 15. 1.0V Output
DERATING CURVE
Figures 14, 15
Figures 14, 15
Figures 14, 15
Figures 16, 17
Figures 16, 17
Figures 16, 17
VIN (V)
5, 12
5, 12
5, 12
5, 12
5, 12
5, 12
POWER LOSS CURVE
Figure 11
Figure 11
Figure 11
Figure 11
Figure 11
Figure 11
AIRFLOW (LFM)
0
200
400
0
200
400
HEAT SINK
None
None
None
BGA Heat Sink
BGA Heat Sink
BGA Heat Sink
θJA (°C/W)
10.6
9.5
8.5
9.8
8.2
7.1
VIN (V)
5, 12
5, 12
5, 12
5, 12
5, 12
5, 12
POWER LOSS CURVE
Figure 12
Figure 12
Figure 12
Figure 12
Figure 12
Figure 12
AIRFLOW (LFM)
0
200
400
0
200
400
HEAT SINK
None
None
None
BGA Heat Sink
BGA Heat Sink
BGA Heat Sink
θJA (°C/W)
10.7
9.4
8.4
9.9
8.3
7.1
VIN (V)
5, 12
5, 12
5, 12
5, 12
5, 12
5, 12
POWER LOSS CURVE
Figure 13
Figure 13
Figure 13
Figure 13
Figure 13
Figure 13
AIRFLOW (LFM)
0
200
400
0
200
400
HEAT SINK
None
None
None
BGA Heat Sink
BGA Heat Sink
BGA Heat Sink
θJA (°C/W)
10.6
9.3
8.4
10.0
8.4
7.3
Table 16. 1.8V Output
DERATING CURVE
Figures 18, 19
Figures 18, 19
Figures 18, 19
Figures 20, 21
Figures 20, 21
Figures 20, 21
Table 17. 3.3V Output
DERATING CURVE
Figure 22, 23
Figure 22, 23
Figure 22, 23
Figure 24, 25
Figure 24, 25
Figure 24, 25
Table 18. Heat Sink Manufacturer (Thermally Conductive Adhesive Tape Pre-Attached)
HEAT SINK MANUFACTURER
PART NUMBER
WEBSITE
Aavid Thermalloy
375424B00034G
www.aavid.com
Cool Innovations
4-050503PT411
www.coolinnovations.com
Wakefield Engineering
LTN20069
www.wakefield.com
Table 19. Thermally Conductive Adhesive Tape Vendor
THERMALLY CONDUCTIVE ADHESIVE
TAPE MANUFACTURER
PART NUMBER
WEBSITE
Chomerics
T411
www.chomerics.com
4676af
For more information www.linear.com/LTM4676A
67
LTM4676A
Applications Information
Table 20. LTM4676A Channel Output Voltage Response vs Component Matrix. 6.5A Load-Stepping at 6.5A/µs. Typical Measured Values
COUTH VENDORS PART NUMBER
COUTL
VENDORS
AVX
12106D107MAT2A (100μF, 6.3V, 1210 Case Size)
Sanyo POSCAP 6TPF330M9L (330μF, 6.3V, 9mΩ ESR, D3L Case Size)
Murata
GRM32ER60J107ME20L (100μF, 6.3V, 1210 Case Size) Sanyo POSCAP 6TPD470M (470μF, 6.3V, 10mΩ ESR, D4D Case Size)
Taiyo Yuden
JMK325BJ107MM-T (100μF, 6.3V, 1210 Case Size)
TDK
C3225X5R0J107MT (100μF, 6.3V, 1210 Case Size)
PART NUMBER
Sanyo POSCAP 2R5TPE470M9 (470μF, 2.5V, 9mΩ ESR, D2E Case Size)
FSWPHCFG
PINSTRAP,
CONNECT
RTHn CTHn
RESISTOR
(EXT (EXT
COUTLn
COMPn a TO
COUTHn
TO SGND
LOOP LOOP
(CERAMIC (BULK
COMPn b?
OUTPUT OUTPUT (INTERNAL LOOP COMP) COMP) fSW (Table 4)
VOUTn VINn
REF.
(kΩ)
(kΩ) (nF) (kHz)
CAP)
CAP)
COMP)
(V) (V) CIRCUIT*
VOUTn CFG
PINSTRAP
RESISTOR
TO SGND
(Table 2)
(kΩ)
VTRIMn CFG
PINSTRAP,
RESISTOR
TO SGND
(Table 3)
(kΩ)
TRANSIENT
DROOP
(0A TO
6.5A)
(mV)
PK-PK
DEVIATION
(0A TO RECOV6.5A
ERY
TO 0A) TIME
(mV)
(µs)
0.9
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
1.65
None
42
79
45
0.9
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
4.12
2.2
350
22.6
1.65
None
91
162
40
0.9
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
1.65
None
42
79
45
0.9
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
4.12
2.2
350
22.6
1.65
None
91
162
40
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
2.43
0
44
85
45
1
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
4.22
2.2
350
22.6
2.43
0
90
160
40
1
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
2.43
0
44
85
45
1
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
4.22
2.2
350
22.6
2.43
0
90
160
40
1
1.2
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
3.24
0
45
85
45
1.2
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
4.42
2.2
350
22.6
3.24
0
89
149
40
1.2
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
3.24
0
45
85
45
1.2
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
4.42
2.2
350
22.6
3.24
0
89
149
40
1.5
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
4.22
None
45
85
45
1.5
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
4.75
2.2
350
22.6
4.22
None
89
149
40
1.5
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
350
22.6
4.22
None
45
85
45
1.5
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
4.75
2.2
350
22.6
4.22
None
89
149
40
1.8
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
425
18.0
6.34
0
45
85
45
1.8
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
4.99
2.2
500
None
6.34
0
88
144
40
1.8
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
500
None
6.34
0
45
85
45
1.8
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
4.99
2.2
500
None
6.34
0
88
144
40
2.5
5
Test Ckt. 2 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
425
18.0
10.7
None
46
86
45
2.5
5
Test Ckt. 2 100µF × 3
330µF
No. Use RTH, CTH
5.62
2.2
575
15.4
10.7
None
89
148
40
2.5
12 Test Ckt. 1 100µF × 7
None
Yes, cf. Figure 62
N/A
N/A
575
15.4
10.7
None
46
86
45
2.5
12 Test Ckt. 1 100µF × 3
330µF
No. Use RTH, CTH
5.62
2.2
575
15.4
10.7
None
90
150
40
3.3
5
Test Ckt. 2 100µF × 5
None
Yes, cf. Figure 62
N/A
N/A
425
18.0
22.6
None
56
110
45
3.3
12 Test Ckt. 1 100µF × 5
None
Yes, cf. Figure 62
N/A
N/A
650
12.7
22.6
None
60
112
45
5
12 Test Ckt. 1 100µF × 5
None
Yes, cf. Figure 62
N/A
N/A
750
10.7
32.4
7.68
62
125
50
*For all conditions: CINH input capacitance is 10µF × 3, per channel (VIN0, VIN1). CINL bulk input capacitance of 150µF is optional if VIN has very low input
impedance.
68
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information-Derating Curves
See also Figure 37, 12VIN to 5VOUT Derating Curves.
8
10
7
9
12VIN
3
2
6
5
12VIN
4
3
5VIN
5VIN
2
1
1
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
40
400LFM
200LFM
0LFM
30
40
Figure 13. 3.3VOUT Power Loss Curve
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
26
24
22
20
18
16
14
12
10
8
6
4
2
0
400LFM
200LFM
0LFM
30
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F17
Figure 17. 12V to 1V Derating
Curve, BGA Heat Sink
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F15
MAXIMUM LOAD CURRENT (A)
MAXIMUM LOAD CURRENT (A)
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
4676A F16
Figure 16. 5V to 1V Derating
Curve, BGA Heat Sink
Figure 15. 12V to 1V Derating Curve,
No Heat Sink
400LFM
200LFM
0LFM
40
5VIN
4676A F13
MAXIMUM LOAD CURRENT (A)
MAXIMUM LOAD CURRENT (A)
MAXIMUM LOAD CURRENT (A)
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Figure 14. 5V to 1V Derating
Curve, No Heat Sink
30
12VIN
4
Figure 12. 1.8VOUT Power Loss Curve
4676A F14
26
24
22
20
18
16
14
12
10
8
6
4
2
0
6
4676A F12
26
24
22
20
18
16
14
12
10
8
6
4
2
0
MAXIMUM LOAD CURRENT (A)
30
8
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26
OUTPUT CURRENT (A)
Figure 11. 1VOUT Power Loss Curve
400LFM
200LFM
0LFM
10
2
4676A F11
26
24
22
20
18
16
14
12
10
8
6
4
2
0
POWER LOSS (W)
5
4
7
POWER LOSS (W)
POWER LOSS (W)
12
8
6
0
14
400LFM
200LFM
0LFM
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F18
Figure 18. 5V to 1.8V Derating
Curve, No Heat Sink
26
24
22
20
18
16
14
12
10
8
6
4
2
0
400LFM
200LFM
0LFM
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F19
Figure 19. 12V to 1.8V Derating
Curve, No Heat Sink
4676af
For more information www.linear.com/LTM4676A
69
LTM4676A
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
400LFM
200LFM
0LFM
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F20
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F23
Figure 23. 12V to 3.3V Derating
Curve, No Heat Sink
70
400LFM
200LFM
0LFM
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F22
Figure 21. 12V to 1.8V Derating
Curve, with Heat Sink
MAXIMUM LOAD CURRENT (A)
MAXIMUM LOAD CURRENT (A)
400LFM
200LFM
0LFM
26
24
22
20
18
16
14
12
10
8
6
4
2
0
4676A F21
Figure 20. 5V to 1.8V Derating
Curve, with Heat Sink
26
24
22
20
18
16
14
12
10
8
6
4
2
0
MAXIMUM LOAD CURRENT (A)
400LFM
200LFM
0LFM
26
24
22
20
18
16
14
12
10
8
6
4
2
0
26
24
22
20
18
16
14
12
10
8
6
4
2
0
400LFM
200LFM
0LFM
30
40
Figure 22. 5V to 3.3V Derating
Curve, No Heat Sink
MAXIMUM LOAD CURRENT (A)
26
24
22
20
18
16
14
12
10
8
6
4
2
0
MAXIMUM LOAD CURRENT (A)
MAXIMUM LOAD CURRENT (A)
Applications Information-Derating Curves
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F24
Figure 24. 5V to 3.3V Derating
Curve, with Heat Sink
26
24
22
20
18
16
14
12
10
8
6
4
2
0
400LFM
200LFM
0LFM
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F25
Figure 25. 12V to 3.3V Derating
Curve, with Heat Sink
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Applications Information
The SWn pin provides access to the midpoint of the power
MOSFETs in LTM4676A’s power stages.
Connecting an optional series RC network from SWn to
GND can dampen high frequency (~30MHz+) switch node
ringing caused by parasitic inductances and capacitances
in the switched-current paths. The RC network is called
a snubber circuit because it dampens (or “snubs”) the
resonance of the parasitics, at the expense of higher
power loss.
To use a snubber, choose first how much power to allocate
to the task and how much PCB real estate is available to
implement the snubber. For example, if PCB space allows a low inductance 1W resistor to be used—derated
conservatively to 600mW (PSNUB)—then the capacitor in
the snubber network (CSW) is computed by:
PSNUB
VINn (MAX)2 • fSW
The snubber resistor (RSW) value is then given by:
60
50
40
30
20
10
0
–10
30
226.2
814.8
422.4 618.6
FREQUENCY (MHz)
1010
4676A F26
where VINn(MAX) is the maximum input voltage that the
input to the power stage (VINn ) will see in the application,
and fSW is the DC/DC converter’s switching frequency
of operation. CSW should be NPO, C0G or X7R-type (or
better) material.
RSW
70
5nH
=
CSW
The snubber resistor should be low ESL and capable of
withstanding the pulsed currents present in snubber circuits. A value between 0.7Ω and 4.2Ω is normal.
For ease of snubber implementation, integrated 2.2nF
snubber capacitors connect to each of the LTM4676A’s
channel switch nodes via a low inductance path. The
electrically floating ends of these snubber capacitors are
made available on the SNUBn pins of the LTM4676A. Using the aforementioned guidance on snubber selection,
a properly sized snubber resistor can be conveniently
connected directly between SNUBn and GND.
Figure 26. Radiated Emissions Scan of the LTM4676A
Producing 1VOUT at 26A, from 12VIN. DC1811B-B Hardware
with Outputs Paralleled. No Snubbers Applied. fSW =
350kHz. Measured in a 10m Chamber. Peak Detect Method
70
60
SIGNAL AMPLITUDE (dB µV/m)
CSW =
EMI performance of the LTM4676A (on DC1811B-B)
with and without a snubber is compared and contrasted
in Figure 26 and Figure 27. The snubber resistors applied
to the SNUBn pins reduce EMI signal amplitude by several
dBµV/m.
SIGNAL AMPLITUDE (dB µV/m)
EMI Performance
50
40
30
20
10
0
–10
30
226.2
814.8
422.4 618.6
FREQUENCY (MHz)
1010
4676A F27
Figure 27. Radiated Emissions Scan of the LTM4676A
Producing 1VOUT at 26A, from 12VIN. DC1811B-B Hardware
with Outputs Paralleled. 1Ω (1/4W rated) Snubber
Resistors Applied from SNUBn to GND. fSW = 350kHz.
Measured in a 10m Chamber. Peak Detect Method
4676af
For more information www.linear.com/LTM4676A
71
LTM4676A
Applications Information
Safety Considerations
The LTM4676A modules do not provide galvanic isolation
from VIN to VOUT. There is no internal fuse. If required,
a slow blow fuse with a rating twice the maximum input
current needs to be provided to protect each unit from
catastrophic failure.
The fuse or circuit breaker should be selected to limit the
current to the regulator during overvoltage in case of an
internal top MOSFET fault. If the internal top MOSFET fails,
then turning it off will not resolve the overvoltage, thus the
internal bottom MOSFET will turn on indefinitely trying to
protect the load. Under this fault condition, the input voltage will source very large currents to ground through the
failed internal top MOSFET and enabled internal bottom
MOSFET. This can cause excessive heat and board damage depending on how much power the input voltage can
deliver to this system. A fuse or circuit breaker can be used
as a secondary fault protector in this situation. The device
does support over current and overtemperature protection.
Layout Checklist/Example
The high integration of LTM4676A makes the PCB board
layout very simple and easy. However, to optimize its
electrical and thermal performance, some layout considerations are still necessary.
VIN0
GND
• Place high frequency ceramic input and output capacitors next to the VINn , GND and VOUTn pins to minimize
high frequency noise.
• Place a dedicated power ground layer underneath the
module.
• To minimize the via conduction loss and reduce module
thermal stress, use multiple vias for interconnection
between top layer and other power layers.
• Do not put vias directly on pads, unless they are capped
or plated over.
• Use a separate SGND copper plane for components
connected to signal pins. Connect SGND to GND local
to the LTM4676A.
• For parallel modules, tie the VOUTn, VOSNS0+/VOSNS– and/
or VOSNS1/SGND voltage-sense differential pair lines,
RUNn, GPIOn, COMPna, SYNC and SHARE_CLK pins
together—as shown in Figure 33.
• Bring out test points on the signal pins for monitoring.
Figure 28 gives a good example of the recommended layout.
12
VIN1
CIN0
• Use large PCB copper areas for high current paths,
including VINn , GND and VOUTn . It helps to minimize
the PCB conduction loss and thermal stress.
CIN1
12
VIN0
11
VIN1
GND
10
11
9
10
9
GND
8
GND
SGND
7
COUT0 6
COUT1
5
GND
7
6
5
4
GND
4
3
2
3
1
2
VOUT0
GND
8
A
B
C
D
E
F G
CNTRL
H
J
K
L
M
VOUT1
4676A F28a
GND
VOUT0
VOUT1
1
A
B
C
D
E
F
G
H
J
K
L
M
Figure 28. Recommended PCB Layout Package Top View
72
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Typical Applications
VIN0
VIN1
SVIN
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
+
V
VDD33
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
PWM CLOCK SYNCH.
TIME BASE SYNCH.
• SLAVE ADDRESS = 1001010_R/W (0X4A)
• 350kHz SWITCHING FREQUENCY
• NO GUI CONFIGURATION AND
NO PART-SPECIFIC PROGRAMMING REQUIRED EXCEPT:
VIN_OFF < VIN_UV_WARN_LIMIT < VIN_ON < 4.3V
IN MULTI-MODULE SYSTEMS, CONFIGURING RAIL_ADDRESS
IS RECOMMENDED
• SETTING MFR_PWM_CONFIG[7] = 1b CONFIGURES THE VOUT1
CONTROL LOOP TO USE THE VOSNS0+/VOSNS0– DIFFERENTIAL-SENSE
PIN-PAIR AS THE FEEDBACK SIGNAL FOR REGULATING VOUT1.
10.7k
1%
±50ppm/°C
COUT
100µF
×14
ORB0
LTM4676A
VOUT, 1.5V
ADJUSTABLE
UP TO 26A
LOAD
VOSNS0+
VOSNS0–
–
V
ORB0
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
FSWPHCFG
10k
×7
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
CINH
22µF
×3
CINL
220µF
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
+
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
VIN
4.5V to 5.75V
4676A F29
2.1k
1%
±50ppm/°C
22.6k
1%
±50ppm/°C
14
14
12
12
CHANNEL OUTPUT CURRENT (A)
CHANNEL OUTPUT CURRENT (A)
Figure 29. 26A, 1.5V Output DC/DC µModule Regulator with I2C/SMBus/PMBus Serial Interface
10
8
IOUT1
6
IOUT0
4
2
0
–2
0
4
20
24
16
12
TOTAL OUTPUT CURRENT (A)
8
28
10
IOUT1
8
IOUT0
6
4
2
0
–2
0
4
20
24
8
16
12
TOTAL OUTPUT CURRENT (A)
4676A F30a
(30a) 5VIN, Figure 29 Circuit
28
4676A F30b
(30b) 12VIN, Figure 29 Circuit with INTVCC
Open and VOUT Commanded to 1V
Figure 30. Current Sharing Performance of the LTM4676A's Channels
4676af
For more information www.linear.com/LTM4676A
73
LTM4676A
Typical Applications
CINL
220µF
CINH
22µF
×3
VIN0
VIN1
SVIN
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
+
V
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
VDD33
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
PWM CLOCK SYNCH.
TIME BASE SYNCH.
• SLAVE ADDRESS = 1001111_R/W (0X4F)
• 350kHz SWITCHING FREQUENCY
• NO GUI CONFIGURATION AND
NO PART-SPECIFIC PROGRAMMING REQUIRED EXCEPT:
VIN_OFF < VIN_UV_WARN_LIMIT < VIN_ON < 4.5V
IN MULTI-MODULE SYSTEMS, CONFIGURING RAIL_ADDRESS
IS RECOMMENDED
ORB0
VOSNS0+
VOSNS0–
–
V
LTM4676A
22.6k
1%
±50ppm/°C
COUT0
100µF
×7
VOUT0, 1.2V
ADJUSTABLE
UP TO 13A
LOAD0
ORB0
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
10k
×9
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
+
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
5V
LOW POWER BIAS
<100mA
3.3VIN
NOMINAL
3.24k
1%
±50ppm/°C
COUT1
100µF
×7
VOUT1, 2.5V
ADJUSTABLE
UP TO 13A
LOAD1
4676A F31
10.7k
1%
±50ppm/°C
Figure 31. 13A, 1.2V and 2.5V Outputs Generated from 3.3V Power Input and Providing I2C/SMBus/PMBus Serial Interface
VOUT1
50mV/DIV
VOUT1
50mV/DIV
VOUT0
50mV/DIV
VOUT0
50mV/DIV
SCL
5V/DIV
SDA
5V/DIV
SCL
5V/DIV
SDA
5V/DIV
4ms/DIV
4ms/DIV
4676A F38a
(32a) PMBus Operation (Reg. 0x01): 0x80 → 0xA8 (Margin High)
VOUT1
50mV/DIV
4676A F38b
(32b) PMBus Operation (Reg. 0x01): 0xA8 → 0x80 (Margin Off)
VOUT1
50mV/DIV
VOUT0
50mV/DIV
SCL
5V/DIV
SDA
5V/DIV
VOUT0
50mV/DIV
SCL
5V/DIV
SDA
5V/DIV
4ms/DIV
4676A F38c
(32c) PMBus Operation (Reg. 0x01): 0x80 → 0x98 (Margin Low)
4ms/DIV
4676A F38d
(32d) PMBus Operation (Reg. 0x01): 0x98 → 0x80 (Margin Off)
Figure 32. Output Voltage Margining, Figure 31 Circuit
74
4676af
For more information www.linear.com/LTM4676A
LTM4676A
10k
×7
U1
LTM4676A
VINO
VIN1
SVIN
CIN2
10µF
×4
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
VDD33
SVIN
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
VINO
VIN1
CIN3
10µF
×4
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
U2
LTM4676A
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
VDD33
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
VINO
VIN1
SVIN
CIN4
10µF
×4
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
U3
LTM4676A
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
VDD33
PWM CLOCK SYNCH.
TIME BASE SYNCH.
RTH
1.65k
CTH
3.3nF
U4
LTM4676A
CTHP
220pF
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VOSNS0+
VOSNS0–
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
COUT(BULK)
330µF
×10
VOUT, 1V
COUT(MLCC)
ADJUSTABLE
100µF
UP TO 100A
×10
LOAD
GND
VINO
VIN1
SVIN
VDD33
CIN1
10µF
×4
22.6k
1%
±50ppm/°C
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VOSNS0+
VOSNS0–
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
CIN5
150µF
787Ω
1%
±50ppm/°C
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VOSNS0+
VOSNS0–
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
1.65k
1%
±50ppm/°C
GND
+
1.65k
1%
±50ppm/°C
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VOSNS0+
VOSNS0–
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
VIN
5.75V TO 16V
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
Typical Applications
3.24k
1%
±50ppm/°C
U1: SLAVE ADDRESS = 1000000_R/W (0X40)
U2: SLAVE ADDRESS = 1000001_R/W (0X41)
U3: SLAVE ADDRESS = 1000010_R/W (0X42)
U4: SLAVE ADDRESS = 1000011_R/W (0X43)
350kHz SWITCHING FREQUENCY WITH
INTERLEAVING
NO GUI CONFIGURATION AND NO PART-SPECIFIC
PROGRAMMING REQUIRED
IN MULTI-MODULE SYSTEMS, CONFIGURING
RAIL_ADDRESS IS RECOMMENDED
ELECTRICALLY UNCONNECTED PINS
VORB0+, VORB0– AND VORB1 NOT SHOWN
4676A F39
1.21k
1%
±50ppm/°C
SETTING MFR_PWM_CONFIG[7] = 1b CONFIGURES
THE VOUT1 CONTROL LOOP TO USE THE
VOSNS0+/VOSNS0– DIFFERENTIAL-SENSE PIN-PAIR
AS THE FEEDBACK SIGNAL FOR REGULATING VOUT1.
Figure 33. Four Paralleled LTM4676A Producing 1VOUT at Up to 100A. Integrated Power System Management Features Accessible
Over 2-Wire I2C/SMBus/PMBus Serial Interface. Evaluated on DC1989A-C, Custom-Stuffed with LTM4676A Modules
4676af
For more information www.linear.com/LTM4676A
75
LTM4676A
Typical Applications
CIN5
150µF
VINO
VIN1
SVIN
VDD33
CIN1
10µF
×4
10k
×6
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
PWM CLOCK SYNCH.
TIME BASE SYNCH.
U1
LTM4676A
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VOSNS0+
VOSNS0–
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
COUT(BULK)
470µF
×10
U1: SLAVE ADDRESS = 1000000_R/W (0x40)
500kHz SWITCHING FREQUENCY WITH INTERLEAVING
NO GUI CONFIGURATION AND NO PART-SPECIFIC
PROGRAMMING REQUIRED EXCEPT:
IOUT_OC_WARN_LIMITn =18A
MFR_GPIO_RESPONSEn = 0x00
IN MULTI-MODULE SYSTEMS, CONFIGURING
RAIL_ADDRESS IS RECOMMENDED
RTH*
RTEMP3
121k
TEMP
EXTVCC
PHASMD
RTEMP4
121k
TEMP
EXTVCC
PHASMD
SGND
INTVCC
GND
CINTVCC3
4.7µF
PGOOD1
VOUT1
VOUTS1
VFB1
CINTVCC4
4.7µF
DIFFP
DIFFN
DIFFOUT
VOUT2
VOUTS2
VFB2
U4*
CLKOUT
RFSET4
121k
COMP1
COMP2
fSET
SGND
CLKOUT
RUN1
RUN2
TRACK1
TRACK2
PGOOD1
VOUT1
VOUTS1
VFB1
PGOOD2
SW1
CIN4
10µF
×4
RVFB
8.25k
DIFFN
DIFFOUT
VOUT2
VOUTS2
VFB2
U3*
MODE_PLLIN
RFSET3
121k
SETTING MFR_PWM_CONFIG[7] = 1b CONFIGURES
THE VOUT1 CONTROL LOOP TO USE THE VOSNS0+/VOSNS0–
DIFFERENTIAL-SENSE PIN-PAIR AS THE FEEDBACK SIGNAL
FOR REGULATING VOUT1.
DIFFP
RUN1
RUN2
TRACK1
TRACK2
COMP1
COMP2
fSET
ELECTRICALLY UNCONNECTED PINS
VORB0+, VORB0– AND VORB1 NOT SHOWN
GND
CIN3
10µF
×4
SW2
RFSET2
121k
CINTVCC2
4.7µF
PGOOD2
SW2
–
COMP1
COMP2
fSET
DIFFN
DIFFOUT
VOUT2
VOUTS2
VFB2
U2*
SW1
U5B
1/2 LT1801
SW2
SW1
RUN1
RUN2
TRACK1
TRACK2
+
PGOOD1
VOUT1
VOUTS1
VFB1
DIFFP
4676A F40
PGOOD2
SGND
TEMP
EXTVCC
PHASMD
CLKOUT
RDIV2*
VIN
MODE_PLLIN
RDIV1*
RTEMP2
121k
MODE_PLLIN
M1
2N7002A
–
CIN2
10µF
×4
1.2k
1%
±50ppm/°C
INTVCC
U5A
1/2 LT1801
6.34k
1%
±50ppm/°C
INTVCC
RCLK
200Ω
+
GND
CTH*
VOUT, 1V
COUT(MLCC)
ADJUSTABLE
100µF
UP TO 100A~130A
×20
LOAD
GND
+
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
12VIN ±20%
*STUFFING OPTIONS
DEMO BOARD OUTPUT CURRENT U2, U3, U4 RDIV1 RDIV2 RTH CTH
DC2106B-A
UP TO 100A
LTM4620A 23.2k 76.8k 6.98k 4.7nF
20k 80.6k 7.15k 2.2nF
DC2106B-B
UP TO 130A
LTM4630
Figure 34. One LTM4676A Operating In Parallel with 3xLTM4620A or 3xLTM4630 (See Demo Boards DC2106B-A, DC2106B-B)
Producing 1VOUT at up to 100A ~ 130A. Power System Management Features Accessible Through LTM4676A. See Figure 35
76
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Typical Applications
CHANNEL OUTPUT CURRENT (A)
14
12
10
U1-LTM4676A-IOUT0
U1-LTM4676A-IOUT1
U2-LTM4620A-IOUT1
U2-LTM4620A-IOUT2
U3-LTM4620A-IOUT1
U3-LTM4620A-IOUT2
U4-LTM4620A-IOUT1
U4-LTM4620A-IOUT2
8
6
4
2
0
–2
0
10 20 30 40 50 60 70 80 90 100
TOTAL OUTPUT CURRENT (A)
4676A F41a
Figure 35a. LTM4676A Paralleled with 3x LTM4620A (Up to 100A Output)
CHANNEL OUTPUT CURRENT (A)
21
18
15
U1-LTM4676A-IOUT0
U1-LTM4676A-IOUT1
U2-LTM4630-IOUT1
U2-LTM4630-IOUT2
U3-LTM4630-IOUT1
U3-LTM4630-IOUT2
U4-LTM4630-IOUT1
U4-LTM4630-IOUT2
12
9
6
3
0
–3
0
20
40
80 100 120
60
TOTAL OUTPUT CURRENT (A)
140
4676A F41b
Figure 35b. LTM4676A Paralleled with 3x LTM4630 (Up to 130A Output)
Figure 35. Current Sharing Performance of Figure 34 Circuit at 12VIN
4676af
For more information www.linear.com/LTM4676A
77
LTM4676A
Typical Applications
RSET1
13.3k
GND REF/BYP
RSET2
1.62k
10k
×7
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
PWM CLOCK SYNCH.
TIME BASE SYNCH.
• SLAVE ADDRESS = 1000101_R/W (0X45)
VIN0
VIN1
SVIN
VDD33
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
U1
LTM4676A
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
CINH
22µF
×3
FSWPHCFG
CINL
220µF
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
+
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
VIN
5.75V to 17V
OPTIONAL: INSTALLING U2 AWAY FROM HEAT SOURCES
ALLOWS INTVCC LDO LOSSES NORMALLY INCURRED BY
THE LTM4676A TO BE DISSIPATED INSTEAD BY THE LT3060.
THERMAL-DERATING CAN THUS BE IMPROVED
• 750kHz SWITCHING FREQUENCY
• NO GUI CONFIGURATION AND NO
PART-SPECIFIC PROGRAMMING REQUIRED
IN MULTI-MODULE SYSTEMS, CONFIGURING
RAIL_ADDRESS IS RECOMMENDED.
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VORB0+
VOSNS0+
VOSNS0–
–
V
COUT
100µF
×10
VOUT, 5V
ADJUSTABLE
UP TO 26A
LOAD
ORB0
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
OUT
U2
LT3060
SHDN
ADJ
IN
4676A F42
4.22k
1%
±50ppm/°C
5.36k
1%
±50ppm/°C
32.4k
1%
±50ppm/°C
7.68k
1%
±50ppm/°C
• SETTING MFR_PWM_CONFIG[7]=1b CONFIGURES THE VOUT1
CONTROL LOOP TO USE THE VOSNS0+/VOSNS0– DIFFERENTIAL-SENSE
PIN-PAIR AS THE FEEDBACK SIGNAL FOR REGULATING VOUT1.
MAXIMUM LOAD CURRENT (A)
Figure 36. 26A, 5V Output DC/DC µModule Regulator with Serial Interface
26
24
22
20
18
16
14
12
10
8
6
4
2
0
400LFM, WITH U2, RSET1 AND RSET2 INSTALLED: θJA = 6.2°C/W
200LFM, WITH U2, RSET1 AND RSET2 INSTALLED: θJA = 7.9°C/W
400LFM, WITH U2, RSET1 AND RSET2 NOT USED: θJA = 7.3°C/W
200LFM, WITH U2, RSET1 AND RSET2 NOT USED: θJA = 8.9°C/W
30
40
50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4676A F43
Figure 37. Output Derating Curve of Figure 36 Circuit Tested on DC1811B-B, 12VIN, No Heat Sink
78
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix A
Similarity Between PMBus, SMBus and I2C
2-Wire Interface
PMBus reads. If a general purpose I2C controller is used,
check that repeat start is supported.
The PMBus 2-wire interface is an incremental extension
of the SMBus. SMBus is built upon I2C with some minor
differences in timing, DC parameters and protocol. The
PMBus/SMBus protocols are more robust than simple I2C
byte commands because PMBus/SMBus provide time-outs
to prevent bus errors and optional packet error checking
(PEC) to ensure data integrity. In general, a master device
that can be configured for I2C communication can be
used for PMBus communication with little or no change
to hardware or firmware. Repeat start (restart) is not
supported by all I2C controllers but is required for SMBus/
For a description of the minor extensions and exceptions
PMBus makes to SMBus, refer to PMBus Specification
Part 1 Revision 1.2: Paragraph 5: Transport.
For a description of the differences between SMBus and
I2C, refer to System Management Bus (SMBus) Specification Version 2.0: Appendix B—Differences Between
SMBus and I2C.
PMBus data format terminology and abbreviations used in
LTC data sheets (see Appendix C, for example), application
notes, and the LTpowerPlay GUI are indicated in Table 21.
Table 21. Data Format Terminology
MEANING
TERMINOLOGY FOR: SPECS, GUI,
APPLICATION NOTES
ABBREVIATIONS FOR SUMMARY
COMMAND TABLE
Linear
Linear
Linear_5s_11s
L11
Linear (for Voltage Related
Commands)
Linear
Linear_16u
L16
Direct-Manufacturer Customized
DirectMfr
CF
PMBus TERMINOLOGY
Direct
Hex
ASCII
Register Fields
Hex
I16
ASCII
ASC
Reg
Reg
Handshaking features are included to ensure robust system communication. Please refer to the PMBus Communication and Command Processing
subsection of the Applications Information section for further details.
4676af
For more information www.linear.com/LTM4676A
79
LTM4676A
Appendix B
PMBus Serial Digital Interface
supports 255 bytes of returned data. For this reason, the
PMBus timeout may be extended when reading the fault log.
The LTM4676A communicates with a host (master) using the standard PMBus serial bus interface. The Timing
Diagram, Figure 38, shows the timing relationship of the
signals on the bus. The two bus lines, SDA and SCL,
must be high when the bus is not in use. External pull-up
resistors or current sources are required on these lines.
Figure 39 is a key to the protocol diagrams in this section.
PEC is optional.
A value shown below a field in the following figures is a
mandatory value for that field.
The data formats implemented by PMBus are:
The LTM4676A is a slave device. The master can communicate with the LTM4676A using the following formats:
Master transmitter transmits to slave receiver. The
transfer direction in this case is not changed.
n
Master transmitter, slave receiver
n
Master reads slave immediately after the first byte. At
the moment of the first acknowledgment (provided by
the slave receiver) the master transmitter becomes a
master receiver and the slave receiver becomes a slave
transmitter.
n
Master receiver, slave transmitter
n
The following PMBus protocols are supported:
Write Byte, Write Word, Send Byte, Block Write
n
Read Byte, Read Word, Block Read
n
Combined format. During a change of direction within
a transfer, the master repeats both a start condition
and the slave address but with the R/W bit reversed.
In this case, the master receiver terminates the transfer
by generating a NACK on the last byte of the transfer
and a STOP condition.
n
Block Write -- Block Read Process Call
n
Alert Response Address
n
Figure 40 to Figure 56 illustrate the aforementioned PMBus
protocols. All transactions support PEC (parity error check)
and GCP (group command protocol). The Block Read
SDA
tf
tLOW
tr
tSU(DAT)
tHD(SDA)
tf
tSP
tr
tBUF
SCL
tHD(STA)
START
CONDITION
tHD(DAT)
tHIGH
tSU(STA)
tSU(STO)
4676A F38
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Figure 38. Timing Diagram
80
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix B
1
1
7
1
8
1
1
DATA BYTE
A
P
S
SLAVE ADDRESS Wr A
S
START CONDITION
Sr
REPEATED START CONDITION
Rd
READ (BIT VALUE OF 1)
Wr
WRITE (BIT VALUE OF 0)
x
SHOWN UNDER A FIELD INDICATES THAT THAT
FIELD IS REQUIRED TO HAVE THE VALUE OF x
A
ACKNOWLEDGE (THIS BIT POSITION MAY BE 0
FOR AN ACK OR 1 FOR A NACK)
P
STOP CONDITION
x
x
PEC PACKET ERROR CODE
MASTER TO SLAVE
SLAVE TO MASTER
...
CONTINUATION OF PROTOCOL
4676A F39
Figure 39. PMBus Packet Protocol Diagram Element Key
1
7
S
1
1
SLAVE ADDRESS Rd/Wr A
1
P
4676A F40
Figure 40. Quick Command Protocol
1
S
1
1
SLAVE ADDRESS Wr A COMMAND CODE A
7
1
1
8
P
4676A F41
Figure 41. Send Byte Protocol
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
1
PEC
A
P
4676A F42
Figure 42. Send Byte Protocol with PEC
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
1
DATA BYTE
A
P
4676A F43
Figure 43. Write Byte Protocol
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
8
1
1
DATA BYTE
A
PEC
A
P
4676A F44
Figure 44. Write Byte Protocol with PEC
4676af
For more information www.linear.com/LTM4676A
81
LTM4676A
Appendix B
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
8
1
1
DATA BYTE LOW
A
DATA BYTE HIGH
A
P
4676A F45
Figure 45. Write Word Protocol
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
8
1
8
1
1
DATA BYTE LOW
A
DATA BYTE HIGH
A
PEC
A
P
4676A F46
Figure 46. Write Word Protocol with PEC
1
S
7
1
1
8
1
1
7
1
1
8
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
1
DATA BYTE
1
NA P
4676A F47
Figure 47. Read Byte Protocol
1
S
7
1
1
8
1
7
1
1
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
8
1
8
1
1
DATA BYTE
A
PEC
A
P
4676A F48
Figure 48. Read Byte Protocol with PEC
1
S
7
1
1
8
1
1
SLAVE ADDRESS Wr A COMMAND CODE A
7
1
1
Sr SLAVE ADDRESS Rd A
8
1
DATA BYTE LOW
A
8
1
1
DATA BYTE HIGH NA P
4676A F49
Figure 49. Read Word Protocol
1
S
7
1
1
8
1
1
7
1
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
8
1
DATA BYTE LOW
A
8
1
DATA BYTE HIGH A
8
1
1
PEC
A
P
4676A F50
Figure 50. Read Word Protocol with PEC
1
S
7
1
1
8
1
7
1
1
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
8
1
8
DATA BYTE 1
A
DATA BYTE 2
1
8
A …
8
1
DATA BYTE N
1
BYTE COUNT = N A
…
1
NA P
4676A F51
Figure 51. Block Read Protocol
1
S
7
1
1
8
1
1
7
1
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
8
1
8
DATA BYTE 1
A
DATA BYTE 2
1
A …
8
1
BYTE COUNT = N A
8
1
8
DATA BYTE N
A
PEC
1
…
1
NA P
4676A F52
Figure 52. Block Read Protocol with PEC
82
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix B
1
S
7
1
1
8
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A BYTE COUNT = M A
8
1
1
7
1
8
A …
DATA BYTE 2
1
Sr SLAVE ADDRESS Rd A
8
1
8
A …
DATA BYTE 1
A
…
1
BYTE COUNT = N A
1
DATA BYTE 2
1
A …
DATA BYTE M
8
8
8
1
DATA BYTE 1
A
1
1
DATA BYTE N
…
NA P
4676A F53
Figure 53. Block Write – Block Read Process Call
1
S
7
1
1
8
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A BYTE COUNT = M A
8
1
DATA BYTE 2
1
7
1
1
Sr SLAVE ADDRESS Rd A
8
1
DATA BYTE 2
8
A …
A …
1
A
…
1
DATA BYTE M
8
8
DATA BYTE 1
A …
1
BYTE COUNT = N A
8
1
DATA BYTE 1
A
8
1
8
1
DATA BYTE N
A
PEC
…
1
NA P
4676A F54
Figure 54. Block Write – Block Read Process Call with PEC
1
7
1
1
7
1
1
S ALERT RESPONSE Rd A DEVICE ADDRESS NA P
ADDRESS
4676A F55
Figure 55. Alert Response Address Protocol
1
7
1
1
7
1
S ALERT RESPONSE Rd A DEVICE ADDRESS A
ADDRESS
8
PEC
1
1
NA P
4676A F56
Figure 56. Alert Response Address Protocol with PEC
4676af
For more information www.linear.com/LTM4676A
83
LTM4676A
Appendix C: PMBus Command Details
Addressing and Write Protect
COMMAND NAME
CMD
CODE DESCRIPTION
DATA
PAGED FORMAT
PAGE
0x00
Channel (page) presently selected for any
paged command.
PAGE_PLUS_WRITE
0x05
Write a command directly to a specified page.
PAGE_PLUS_READ
0x06
Read a command directly from a specified
page.
WRITE_PROTECT
0x10
Protect the device against unintended PMBus
modifications.
R/W Byte
N
Reg
Y
MFR_ADDRESS
0xE6
Specify right-justified 7-bit device address.
R/W Byte
N
Reg
Y
0x4F
MFR_RAIL_ADDRESS
0xFA
Specify unique right-justified 7-bit address
for channels comprising a PolyPhase output.
R/W Byte
Y
Reg
Y
0x80
TYPE
R/W Byte
N
W Block
N
Block R/W
Process
N
UNITS NVM
Reg
DEFAULT
VALUE
0x00
0x00
Related commands: MFR_COMMON.
PAGE
The PAGE command provides the ability to configure, control and monitor both PWM channels through only one
physical address, either the MFR_ADDRESS or GLOBAL device address. Each PAGE contains the operating memory
for one PWM channel.
Pages 0x00 and 0x01 correspond to channel 0 and channel 1, respectively, in this device.
Setting PAGE to 0xFF applies any following paged commands to both outputs. With PAGE set to 0xFF the LTM4676A
will respond to read commands as if PAGE were set to 0x00 (channel 0 results).
This command has one data byte.
PAGE_PLUS_WRITE
The PAGE_PLUS_WRITE command provides a way to set the page within a device, send a command and then send
the data for the command, all in one communication packet. Commands allowed by the present write protection level
may be sent with PAGE_PLUS_WRITE.
The value stored in the PAGE command is not affected by PAGE_PLUS_WRITE. If PAGE_PLUS_WRITE is used to send
a non-paged command, the Page Number byte is ignored.
This command uses Write Block protocol. An example of the PAGE_PLUS_WRITE command with PEC sending a command that has two data bytes is shown in Figure 57.
1
7
S
SLAVE
ADDRESS
1
1
W
PAGE_PLUS
A
A
COMMAND CODE
8
8
LOWER DATA
BYTE
1
8
BLOCK COUNT
(= 4)
1
8
A
PAGE
NUMBER
1
8
1
8
1
1
A
UPPER DATA
BYTE
A
PEC BYTE
A
P
1
8
1
A
COMMAND
CODE
A
…
4676A F57
Figure 57. Example of PAGE_PLUS_WRITE
84
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
PAGE_PLUS_READ
The PAGE_PLUS_READ command provides the ability to set the page within a device, send a command and then read
the data returned by the command, all in one communication packet .
The value stored in the PAGE command is not affected by PAGE_PLUS_READ. If PAGE_PLUS_READ is used to access
data from a non-paged command, the Page Number byte is ignored.
This command uses Block Write – Block Read Process Call protocol. An example of the PAGE_PLUS_READ command
with PEC is shown in Figure 58.
NOTE: PAGE_PLUS commands cannot be nested. A PAGE_PLUS command cannot be used to read or write another
PAGE_PLUS command. If this is attempted, the LTM4676A will NACK the entire PAGE_PLUS packet and issue a CML
fault for Invalid/Unsupported Data.
1
7
S
SLAVE
ADDRESS
1
7
Sr
SLAVE
ADDRESS
1
1
W
PAGE_PLUS
A
A
COMMAND CODE
1
R
8
1
8
A
BLOCK COUNT
(= 2)
1
8
BLOCK COUNT
(= 2)
1
8
A
LOWER DATA
BYTE
1
8
A
PAGE
NUMBER
1
8
1
A
COMMAND
CODE
A
1
8
1
8
A
UPPER DATA
BYTE
A
PEC BYTE
1
…
1
NA P
4676A F58
Figure 58. Example of PAGE_PLUS_READ
WRITE_PROTECT
The WRITE_PROTECT command is used to control writing to the LTM4676A device. This command does not indicate
the status of the WP pin which is defined in the MFR_COMMON command. The WP pin takes precedence over the
value of this command unless the WRITE_PROTECT command is more stringent.
BYTE MEANING
0x80 Disable all writes except to the WRITE_PROTECT, PAGE, MFR_
EE_UNLOCK and STORE_USER_ALL command
0x40 Disable all writes except to the WRITE_PROTECT, PAGE,
MFR_EE_UNLOCK, MFR_CLEAR_PEAKS, STORE_USER_ALL,
OPERATION and CLEAR_FAULTS command. individual fault
bits can be cleared by writing a 1 to the respective bits in the
STATUS registers.
0x20 Disable all writes except to the WRITE_PROTECT, OPERATION,
MFR_EE_UNLOCK, MFR_CLEAR_PEAKS, CLEAR_FAULTS,
PAGE, ON_OFF_CONFIG, VOUT_COMMAND and STORE_USER_
ALL. Individual fault bits can be cleared by writing a 1 to the
respective bits in the STATUS registers.
0x10 Reserved, must be 0
0x08 Reserved, must be 0
0x04 Reserved, must be 0
0x02 Reserved, must be 0
0x01 Reserved, must be 0
Enable writes to all commands when WRITE_PROTECT is set to 0x00.
This command has one data byte.
4676af
For more information www.linear.com/LTM4676A
85
LTM4676A
Appendix C: PMBus Command Details
If WP pin is high, PAGE, OPERATION, MFR_CLEAR_PEAKS, MFR_EE_UNLOCK and CLEAR_FAULTS commands are
supported. Individual fault bits can be cleared by writing a 1 to the respective bits in the STATUS registers.
MFR_ADDRESS
The MFR_ADDRESS command byte sets the 7 bits of the PMBus slave address for this device.
Setting this command to a value of 0x80 disables device addressing. The GLOBAL device address, 0x5A and 0x5B,
cannot be deactivated. If RCONFIG is set to ignore (MFR_CONFIG_ALL[6]=1b), the ASEL pin is still used to determine
the LSB of the channel address. If the ASEL pin is open, the LTM4676A will use the four LSBs of the MFR_ADDRESS
stored in EEPROM. Values of 0x5A, 0x5B, 0x0C, and 0x7C are not recommended.
This command has one data byte.
MFR_RAIL_ADDRESS
The MFR_RAIL_ADDRESS command enables direct device address access to the PAGE activated channel. The value
of this command should be common to all devices attached to a single power supply rail.
The user should only perform command writes to this address. If a read is performed from this address and the rail
devices do not respond with EXACTLY the same value, the LTM4676A will detect bus contention and set a CML communications fault.
Setting this command to a value of 0x80 disables rail device addressing for the channel.
This command has one data byte.
General Configuration Registers
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
DATA
PAGED FORMAT UNITS
NVM
DEFAULT
VALUE
MFR_CHAN_CONFIG
0xD0
Configuration bits that are channel specific.
R/W Byte
Y
Reg
Y
0x1F
MFR_CONFIG_ALL
0xD1
Configuration bits that are common to all
pages.
R/W Byte
N
Reg
Y
0x09
MFR_CHAN_CONFIG
General purpose configuration command common to multiple LTC products.
BIT
MEANING
7
Reserved
6
Reserved
5
Reserved
4
Disable RUN Low. When asserted the RUN pin is not pulsed low if commanded OFF
3
Short Cycle. When asserted the output will immediate off if commanded ON while waiting for TOFF_DELAY or TOFF_FALL. TOFF_MIN of 120ms
is honored then the part will command ON.
2
SHARE_CLOCK control, if SHARE_CLOCK is held low, the output is disabled
1
No GPIO ALERT, ALERT is not pulled low if GPIO is pulled low externally. Assert this bit if either POWER_GOOD or VOUT_UVUF are propagated
on GPIO
0
Disables the VOUT decay value requirement for MFR_RETRY_TIME processing. When this bit is set to a 0, the output must decay to less than
12.5% of the programmed value for any action that turns off the rail including a fault, an OFF/ON command, or a toggle of RUN from high to low
to high.
This command has one data byte.
86
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
MFR_CONFIG_ALL
General purpose configuration command common to multiple LTC products
BIT
MEANING
7
Enable Fault Logging
6
Ignore Resistor Configuration Pins
5
Disable CML fault for Quick Command message
4
Disable SYNC out
3
Enable 255ms Time Out
2
A valid PEC required for PMBus writes to be accepted. If this bit is not set,
the part will accept commands with invalid PEC.
1
Enable the use of PMBus clock stretching
0
Enables a low to high transition on either RUN pin to issue a
CLEAR_FAULTS command
This command has one data byte.
On/Off/Margin
COMMAND NAME
CMD
CODE
DESCRIPTION
TYPE
DATA
PAGED FORMAT UNITS
NVM
DEFAULT
VALUE
ON_OFF_CONFIG
0x02
RUN pin and PMBus bus on/off command configuration.
R/W Byte
Y
Reg
Y
0x1F
OPERATION
0x01
Operating mode control. On/off, margin high and margin
low.
R/W Byte
Y
Reg
Y
0x80
MFR_RESET
0xFD
Commanded reset without requiring a power-down.
Identical to RESTORE_USER_ALL.
Send Byte
N
NA
ON_OFF_CONFIG
The ON_OFF_CONFIG command configures the combination of RUNn pin input and serial bus commands needed to
turn the unit on and off. This includes how the unit responds when power is applied.
The only bits allowed to be changed are as follows:
3: Controls how the unit responds to commands received via the serial bus
0: RUN pin action when commanding the unit to turn off. If bit 0 is set to one, the part will stop transferring power to
the output stage as fast as possible. This will have the effect of the load discharging the output capacitor. Setting
bit 0 to a zero will cause the regulator to use the programmed turn-off delay and fall times. If the part is in continuous mode, the programmed turn-off response may pull the output to zero volts considerably faster than removing
power immediately from the load.
Changing the value of bits 4, 2 or 1, will generate a CML fault.
This command has one data byte.
4676af
For more information www.linear.com/LTM4676A
87
LTM4676A
Appendix C: PMBus Command Details
Table 22. ON_OFF_CONFIG Detailed Register Information
ON_OFF_CONFIG Data Contents
BITS(S) SYMBOL
OPERATION
b[7:5] Reserved
b[3]
Don’t care. Always returns 0.
On_off_config_use_pmbus
Controls how the unit responds to commands received via the serial bus.
0: Unit ignores the Operation command b[7:6].
1: Unit responds to Operation command b[7:6]. The unit also requires the RUNn pin to be asserted for the
unit to start.
b[0] On_off_config_control_fast_off RUNn pin turn off action when commanding the unit to turn off.
0: Use the programmed TOFF_DELAY.
1: Turn off the output and stop transferring energy as quickly as possible. The device does not sink current
in order to decrease the output voltage fall time.
Note: A high on the RUN pin is always required to start power conversion. Power conversion will always stop with a low on RUN.
OPERATION
The OPERATION command is used to turn the unit on and off in conjunction with the input from the RUNn pins. It is
also used to cause the unit to set the output voltage to the upper or lower MARGIN VOLTAGEs. The unit stays in the
commanded operating mode until a subsequent OPERATION command or change in the state of the RUNn pin instructs
the device to change to another mode. If the part is stored in the MARGIN_LOW/HIGH state, the next MFR_RESET
or RESTORE_USER_ALL or SVIN power cycle will ramp to that state. If the OPERATION command is modified, for
example ON is changed to MARGIN_LOW, the output will move at a fixed slope set by the VOUT_TRANSITION_RATE.
The default operation command is sequence off.
Margin High (Ignore Faults) and Margin Low (Ignore Faults) operations are not supported by the LTM4676A.
The part defaults to the Sequence Off state.
This command has one data byte.
Table 23. OPERATION Command Detail Register OPERATION Data Contents
When On_Off_Config_Use_PMBus Enables Operation_Control
SYMBOL
Action
Value
Turn off immediately
0x00
Turn on
0x80
BITS
FUNCTION Margin Low
0x98
Margin High
0xA8
Sequence off
0x40
OPERATION Data Contents When On_Off_Config is Configured Such That
OPERATION Command Is Not Used to Command Channel On or Off
SYMBOL
Action
Value
BITS
Output at Nominal
0x80
FUNCTION Margin Low
0x98
Margin High
0xA8
Note: Attempts to write a reserved value will cause a CML fault.
88
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
MFR_RESET
This command provides a means by which the user can perform a reset of the LTM4676A. Identical to RESTORE_USER_ALL.
This write-only command has no data bytes.
PWM Config
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
DATA
DEFAULT
PAGED FORMAT UNITS NVM VALUE
MFR_PWM_MODE
0xD4
Configuration for the PWM engine of each channel.
R/W Byte
Y
Reg
Y
0xC1
MFR_PWM_CONFIG
0xF5
Set numerous parameters for the DC/DC controller
including phasing.
R/W Byte
N
Reg
Y
0x10
FREQUENCY_SWITCH
0x33
Switching frequency of the controller.
R/W Word
N
L11
Y
500
0xFBE8
kHz
MFR_PWM_MODE
The MFR_PWM_MODE command allows the user to program the PWM controller to use, discontinuous (pulse-skipping
mode), or forced continuous conduction mode.
BIT
MEANING
7
Range of ILIMIT
0 – Low Current Range
1 – High Current Range
6
Enable Servo Mode
5
Reserved
4
Page 0 Only: Use of TSNS1a-Sensed Temperature Telemetry
0 - Temperature sensed via TSNS1a is used to temperature-correct the current-sense information digitized by Channel 1's current sense input,
ISNS1a+/ISNS1a–.
1 - Temperature sensed via TSNS0a is used to temperature-correct the current-sense information digitized by Channel 1's current sense input,
ISNS1a+/ISNS1a–. Telemetry obtained from the thermal sensor connected to TSNS1a can be external to the module, if desired.
3
Reserved
2
Reserved
1
Voltage Range
0 - Hi Voltage Range 5.5 volts max
1 - Lo Voltage Range 2.75 volts max
0
PWM Mode
0 - Discontinuous Mode
1 - Continuous Mode
Whenever the channel is ramping on, the PWM mode will be discontinuous, regardless of the value of this
command.
Bit [7] of this command determines if the part is in high range or low range of the IOUT_OC_FAULT_LIMIT command.
Changing this bit value changes the PWM loop gain and compensation. Changing this bit value whenever an output is
active may have detrimental system results.
4676af
For more information www.linear.com/LTM4676A
89
LTM4676A
Appendix C: PMBus Command Details
Bit [6] The LTM4676A will not servo while the part is OFF, ramping on or ramping off. When set to a one, the output servo
is enabled. The output set point DAC will be slowly adjusted to minimize the difference between the READ_VOUT_ADC
and the VOUT_COMMAND (or the appropriate margined value).
Bit [1] of this command determines if the part is in high range or low voltage range. Changing this bit value changes
the PWM loop gain and compensation. This bit value cannot be changed when an output is active.
This command has one data byte.
MFR_PWM_CONFIG
The MFR_PWM_CONFIG command sets the switching frequency phase offset with respect to the falling edge of the
SYNC signal. The part must be in the OFF state to process this command. Either the RUN pins must be low or the part
must be commanded off. If the part is in the RUN state and this command is written, the command will be ignored and
a BUSY fault will be asserted. Bit 7 allows remote differential voltage sensing for PolyPhase rail applications.
BIT
MEANING
7
EA Connection
0 – Independent EA and Channel Outputs
1 – EA1 uses EA0 input for PolyPhase operation
6
Reserved.
5
Reserved
4
Share Clock Enable : If this bit is 1, the
SHARE_CLK pin will not be released until
SVIN > VIN_ON. The SHARE_CLK pin will be
pulled low when SVIN < VIN_OFF. If this bit is 0, the SHARE_CLK
pin will not be pulled low when SVIN < VIN_OFF except for the
initial application of SVIN.
3
Reserved
BIT [2:0]
CHANNEL 0 (DEGREES)
CHANNEL 1 (DEGREES)
000b
0
180
001b
90
270
010b
0
240
011b
0
120
100b
120
240
101b
60
240
110b
120
300
Do not assert Bit [7] unless it is a PolyPhase application and both VOUT pins are tied together and both COMPna pins
are tied together.
This command has one data byte.
90
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
FREQUENCY_SWITCH
The FREQUENCY_SWITCH command sets the switching frequency, in kHz, of a PMBus device. See Table 7 for recommended values.
Supported Frequencies:
VALUE [15:0]
0x0000
0xF3E8
0xFABC
0xFB52
0xFBE8
0x023F
0x028A
0x02EE
0x03E8
RESULTING FREQUENCY (TYP)
External Oscillator
250kHz
350kHz
425kHz
500kHz
575kHz
650kHz
750kHz
1000kHz
The part must be in the OFF state to process this command. Either the RUN pins must be low or the part must be
commanded off. If the part is in the RUN state and this command is written, the command will be ignored and a BUSY
fault will be asserted. When the part is commanded off and the frequency is changed, a PLL_UNLOCK status may be
detected as the PLL locks onto the new frequency.
This command has two data bytes and is formatted in Linear_5s_11s format.
Voltage
Input Voltage (SVIN) and Limits
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
DATA
DEFAULT
PAGED FORMAT UNITS NVM VALUE
VIN_OV_FAULT_ LIMIT
0x55
Input supply (SVIN) overvoltage fault limit.
R/W Word
N
L11
V
Y
27.0
0xDB60
VIN_UV_WARN_LIMIT
0x58
Input supply (SVIN) undervoltage warning limit.
R/W Word
N
L11
V
Y
5.297
0xCAA6
VIN_ON
0x35
Input voltage (SVIN) at which the unit should start
power conversion.
R/W Word
N
L11
V
Y
5.500
0xCAC0
VIN_OFF
0x36
Input voltage (SVIN) at which the unit should stop
power conversion.
R/W Word
N
L11
V
Y
5.250
0xCAA0
VIN_OV_FAULT_LIMIT
The VIN_OV_FAULT_LIMIT command sets the value of the measured (SVIN) input voltage, in volts, that causes an
input overvoltage fault. The fault is detected with the A/D converter resulting in latency up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
VIN_UV_WARN_LIMIT
The VIN_UV_WARN_LIMIT command sets the value of the SVIN input voltage that causes an SVIN input undervoltage
warning. The warning is detected with the A/D converter resulting in latency up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
4676af
For more information www.linear.com/LTM4676A
91
LTM4676A
Appendix C: PMBus Command Details
VIN_ON
The VIN_ON command sets the SVIN input voltage, in volts, at which the unit should start power conversion.
This command has two data bytes and is formatted in Linear_5s_11s format.
VIN_OFF
The VIN_OFF command sets the SVIN input voltage, in volts, at which the unit should stop power conversion.
This command has two data bytes and is formatted in Linear_5s_11s format.
Output Voltage and Limits
COMMAND NAME
VOUT_MODE
CMD CODE DESCRIPTION
0x20
Output voltage format and exponent (2–12).
VOUT_MAX
0x24
VOUT_OV_FAULT_ LIMIT
TYPE
R Byte
PAGED
Y
DATA
FORMAT UNITS
Reg
NVM
R/W Word
Y
L16
V
Y
0x40
Upper limit on the commanded output voltage
including VOUT_MARGIN_HIGH.
Output overvoltage fault limit.
R/W Word
Y
L16
V
Y
VOUT_OV_WARN_ LIMIT
0x42
Output overvoltage warning limit.
R/W Word
Y
L16
V
Y
VOUT_MARGIN_HIGH
0x25
R/W Word
Y
L16
V
Y
VOUT_COMMAND
0x21
Margin high output voltage set point. Must be
greater than VOUT_COMMAND.
Nominal output voltage set point.
R/W Word
Y
L16
V
Y
VOUT_MARGIN_LOW
0x26
R/W Word
Y
L16
V
Y
VOUT_UV_WARN_ LIMIT
0x43
Margin low output voltage set point. Must be
less than VOUT_COMMAND.
Output undervoltage warning limit.
R/W Word
Y
L16
V
Y
VOUT_UV_FAULT_ LIMIT
0x44
Output undervoltage fault limit.
R/W Word
Y
L16
V
Y
MFR_VOUT_MAX
0xA5
Maximum allowed output voltage including
VOUT_OV_FAULT_LIMIT.
R Word
Y
L16
V
DEFAULT
VALUE
2–12
0x14
5.6
0x599A
1.1
0x119A
1.075
0x1133
1.05
0x10CD
1.0
0x1000
0.95
0x0F33
0.925
0x0ECD
0.9
0x0E66
5.7
0x5B33
VOUT_MODE
The data byte for VOUT_MODE command, used for commanding and reading output voltage, consists of a 3-bit mode
(only linear format is supported) and a 5-bit parameter representing the exponent used in output voltage Read/Write
commands.
This read-only command has one data byte.
VOUT_MAX
The VOUT_MAX command sets an upper limit on any voltage, including VOUT_MARGIN_HIGH, the unit can command
regardless of any other commands or combinations. The maximum allowed value of this command is 5.7 volts. The
maximum output voltage the LTM4676A can produce is 5.5 volts including VOUT_MARGIN_HIGH. However, the
VOUT_OV_FAULT_LIMIT can be commanded as high as 5.7 volts.
This command has two data bytes and is formatted in Linear_16u format.
92
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
VOUT_OV_FAULT_LIMIT
The VOUT_OV_FAULT_LIMIT command sets the value of the output voltage measured at the sense pins, in volts, which
causes an output overvoltage fault.
If the VOUT_OV_FAULT_LIMIT is modified and the switcher is active, allow 10ms after the command is modified to
assure the new value is being honored. The part indicates if it is busy making a calculation. Monitor bits 5 and 6 of
MFR_COMMON. Either bit is low if the part is busy. If this wait time is not met, and the VOUT_COMMAND is modified
above the old overvoltage limit, an OV condition might temporarily be detected resulting in undesirable behavior and
possible damage to the switcher.
If VOUT_OV_FAULT_RESPONSE is set to OV_PULLDOWN, the GPIO pin will not assert if VOUT_OV_FAULT is propagated. The LTM4676A will pull the TG low and assert the BG bit as soon as the overvoltage condition is detected.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_OV_WARN_LIMIT
The VOUT_OV_WARN_LIMIT command sets the value of the output voltage measured at the sense pins, in volts, which
causes an output voltage high warning. The READ_VOUT value will be used to determine if this limit has been exceeded.
In response to the VOUT_OV_WARN_LIMIT being exceeded, the device:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT Overvoltage Warning bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_MARGIN_HIGH
The VOUT_MARGIN_HIGH command loads the unit with the voltage to which the output is to be changed, in volts, when
the OPERATION command is set to “Margin High”. The value must be greater than VOUT_COMMAND. The maximum
guaranteed value on VOUT_MARGIN_HIGH is 5.5 volts.
This command will not be acted on during TON_RISE and TOFF_FALL output sequencing. The VOUT_TRANSITION_RATE
will be used if this command is modified while the output is active and in a steady-state condition.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_COMMAND
The VOUT_COMMAND consists of two bytes and is used to set the output voltage, in volts. The maximum guaranteed
value on VOUT is 5.5 volts.
This command will not be acted on during TON_RISE and TOFF_FALL output sequencing. The VOUT_TRANSITION_RATE
will be used if this command is modified while the output is active and in a steady-state condition.
This command has two data bytes and is formatted in Linear_16u format.
4676af
For more information www.linear.com/LTM4676A
93
LTM4676A
Appendix C: PMBus Command Details
VOUT_MARGIN_LOW
The VOUT_MARGIN_LOW command loads the unit with the voltage to which the output is to be changed, in volts,
when the OPERATION command is set to “Margin Low”. The value must be less than VOUT_COMMAND.
This command will not be acted on during TON_RISE and TOFF_FALL output sequencing. The VOUT_TRANSITION_RATE
will be used if this command is modified while the output is active and in a steady-state condition.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_UV_WARN_LIMIT
The VOUT_UV_ WARN_LIMIT command reads the value of the output voltage measured at the sense pins, in volts,
which causes an output voltage low warning.
In response to the VOUT_UV_WARN_LIMIT being exceeded, the device:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT Undervoltage Warning bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_UV_FAULT_LIMIT
The VOUT_UV_FAULT_LIMIT command reads the value of the output voltage measured at the sense pins, in volts,
which causes an output undervoltage fault.
This command has two data bytes and is formatted in Linear_16u format.
MFR_VOUT_MAX
The MFR_VOUT_MAX command is the maximum output voltage in volts for each channel including VOUT_OV_FAULT_
LIMIT. If the output voltages are set to high range (Bit 1 of MFR_PWM_MODE set to a 0) MFR_VOUT_MAX for channel
0 and 1 is 5.7V. If the output voltages are set to low range (Bit 1 of MFR_PWM_MODE set to a 1) the MFR_VOUT_MAX
for both channels is 2.75V. Entering VOUT_COMMAND values greater than this will result in a CML fault and the output
voltage setting will be clamped to the maximum level.
This read-only command has 2 data bytes and is formatted in Linear_16u format.
Current
Input Current Calibration
COMMAND NAME
MFR_IIN_OFFSET
94
CMD CODE DESCRIPTION
0xE9
Coefficient used to add to the input current to
account for the IQ of the part.
TYPE
R/W
Word
PAGED
Y
DATA
FORMAT
L11
UNITS
A
NVM
Y
DEFAULT
VALUE
0.0305
0x8BE7
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
MFR_IIN_OFFSET
The MFR_IIN_OFFSET command allows the user to set an input current representing the quiescent current of each
channel. For accurate results at low output current, the part should be in continuous conduction mode. (MFR_PWM_
MODE[0]=1b). See Table 8 for recommended values.
This command has 2 data bytes and is formatted in Linear_5s_11s format.
Output Current Calibration
COMMAND NAME
IOUT_CAL_GAIN
MFR_IOUT_CAL_GAIN_TC
CMD
CODE DESCRIPTION
0x38 The ratio of the voltage at the current
sense pins to the sensed current.
0xF6 Temperature coefficient of the current
sensing element.
DATA
TYPE
PAGED FORMAT UNITS
R/W Word
Y
L11
mΩ
R/W Word
Y
CF
DEFAULT
NVM
VALUE
FactoryTrimmed,
Only NVM 3.28mΩ typical
Y
3860
0x0F14
IOUT_CAL_GAIN
The IOUT_CAL_GAIN command is nominally used to set the resistance value of the current sense element, in milliohms.
(see also MFR_IOUT_CAL_GAIN_TC). Writes to this register result in a NACK and do not impact output current readback telemetry.
This command has two data bytes and is formatted in Linear_5s_11s format.
MFR_IOUT_CAL_GAIN_TC
The MFR_IOUT_CAL_GAIN_TC command allows the user to program the temperature coefficient of the IOUT_CAL_GAIN
inductor DCR in ppm/°C.
This command has two data bytes and is formatted in 16-bit 2’s complement integer ppm. N = –32768 to 32767 •
10–6. Nominal temperature is 27°C. The IOUT_CAL_GAIN is multiplied by:
[1.0 + MFR_IOUT_CAL_GAIN_TC • (READ_TEMPERATURE_1‑27)]. DCR sensing will have a typical value of 3900.
The IOUT_CAL_GAIN and MFR_IOUT_CAL_GAIN_TC impact all current parameters including: READ_IOUT, READ_IIN,
IOUT_OC_FAULT_LIMIT and IOUT_OC_WARN_LIMIT. Writes to this register are not recommended; use the factorydefault value.
Input Current
COMMAND NAME
IIN_OC_WARN_LIMIT
CMD CODE DESCRIPTION
0x5D
Input overcurrent warning limit.
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
R/W Word
N
L11
A
Y
DEFAULT
VALUE
12
0xD300
IIN_OC_WARN_LIMIT
The IIN_OC_WARN_LIMIT command sets the value of the input current, in amperes, that causes a warning indicating
the input current is high. The READ_IIN value will be used to determine if this limit has been exceeded.
In response to the IIN_OC_WARN_LIMIT being exceeded, the device:
• Sets the OTHER bit in the STATUS_BYTE
• Sets the INPUT bit in the upper byte of the STATUS_WORD
4676af
For more information www.linear.com/LTM4676A
95
LTM4676A
Appendix C: PMBus Command Details
• Sets the IIN Overcurrent Warning bit in the STATUS_INPUT command, and
• Notifies the host by asserting ALERT pin, unless masked
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
Output Current
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
DEFAULT
VALUE
IOUT_OC_FAULT_LIMIT
0x46
Output overcurrent fault limit.
R/W Word
Y
L11
A
Y
22.84
0xDADB
IOUT_OC_WARN_LIMIT
0x4A
Output overcurrent warning limit.
R/W Word
Y
L11
A
Y
15.59
0xD3E6
IOUT_OC_FAULT_LIMIT
The IOUT_OC_FAULT_LIMIT command sets the value of the peak output current limit, in amperes. When the controller
is in current limit, the overcurrent detector will indicate an overcurrent fault condition. The programmed overcurrent
fault limit value is rounded up to the nearest one of the following set of discrete values:
25mV/IOUT_CAL_GAIN
28.6mV/IOUT_CAL_GAIN
32.1mV/IOUT_CAL_GAIN
35.7mV/IOUT_CAL_GAIN
39.3mV/IOUT_CAL_GAIN
42.9mV/IOUT_CAL_GAIN
46.4mV/IOUT_CAL_GAIN
50mV/IOUT_CAL_GAIN
37.5mV/IOUT_CAL_GAIN
42.9mV/IOUT_CAL_GAIN
48.2mV/IOUT_CAL_GAIN
53.6mV/IOUT_CAL_GAIN
58.9mV/IOUT_CAL_GAIN
64.3mV/IOUT_CAL_GAIN
69.6mV/IOUT_CAL_GAIN
75mV/IOUT_CAL_GAIN
Low Range (1.5x Nominal Loop Gain)
MFR_PWM_MODE [7]=0
High Range (Nominal Loop Gain)
MFR_PWM_MODE [7]=1
Note: This is the peak of the current waveform. The READ_IOUT command returns the average current. The peak output
current limits are adjusted with temperature based on the MFR_IOUT_CAL_GAIN_TC using the equation:
IOUT_OC_FAULT_LIMIT = IOUT_CAL_GAIN • (1 + MFR_IOUT_CAL_GAIN_TC • (READ_TEMPERTURE_1-27.0)).
The LTpowerPlay GUI automatically convert the voltages to currents.
The IOUT range is set with bit 7 of the MFR_PWM_MODE command.
The IOUT_OC_FAULT_LIMIT is ignored during TON_RISE and TOFF_FALL.
This command has two data bytes and is formatted in Linear_5s_11s format.
96
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
IOUT_OC_WARN_LIMIT
This command sets the value of the output current that causes an output overcurrent warning in amperes. The
READ_IOUT value will be used to determine if this limit has been exceeded.
In response to the IOUT_OC_WARN_LIMIT being exceeded, the device:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the IOUT bit in the STATUS_WORD
• Sets the IOUT Overcurrent Warning bit in the STATUS_IOUT command, and
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
The IOUT_OC_FAULT_LIMIT is ignored during TON_RISE and TOFF_FALL.
This command has two data bytes and is formatted in Linear_5s_11s format
Temperature
Power Stage DCR Temperature Calibration
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
DEFAULT
FORMAT UNITS NVM VALUE
MFR_TEMP_1_GAIN
0xF8
Sets the slope of the power stage temperature
sensor.
R/W Word
Y
CF
MFR_TEMP_1_OFFSET
0xF9
Sets the offset of the power stage temperature
sensor with respect to –273.1°C.
R/W Word
Y
L11
C
Y
0.995
0x3FAE
Y
0
0x8000
MFR_TEMP_1_GAIN
The MFR_TEMP_1_GAIN command will modify the slope of the power stage temperature sensor to account for nonidealities in the element and errors associated with the remote sensing of the temperature in the inductor.
This command has two data bytes and is formatted in 16-bit 2’s complement integer. N = 8192 to 32767. The effective
adjustment is N • 2–14. The nominal value is 1.
MFR_TEMP_1_OFFSET
The MFR_TEMP_1_OFFSET command will modify the offset of the power stage temperature sensor to account for
non-idealities in the element and errors associated with the remote sensing of the temperature in the inductor.
This command has two data bytes and is formatted in Linear_5s_11s format. The part starts the calculation with a
value of –273.15 so the default adjustment value is zero.
4676af
For more information www.linear.com/LTM4676A
97
LTM4676A
Appendix C: PMBus Command Details
Power Stage Temperature Limits
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT UNITS
NVM
DEFAULT
VALUE
OT_FAULT_LIMIT
0x4F
Power stage overtemperature fault limit.
R/W Word
Y
L11
C
Y
128
0xF200
OT_WARN_LIMIT
0x51
Power stage overtemperature warning limit.
R/W Word
Y
L11
C
Y
125
0xEBE8
UT_FAULT_LIMIT
0x53
Power stage undertemperature fault limit.
R/W Word
Y
L11
C
Y
–45
0xE530
OT_FAULT_LIMIT
The OT_FAULT_LIMIT command sets the value of the power stage temperature, in degrees Celsius, which causes an
overtemperature fault. The READ_TEMPERATURE_1 value will be used to determine if this limit has been exceeded.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
OT_WARN_LIMIT
The OT_WARN_LIMIT command sets the value of the power stage temperature, in degrees Celsius, which causes an
overtemperature warning. The READ_TEMPERATURE_1 value will be used to determine if this limit has been exceeded.
In response to the OT_WARN_LIMIT being exceeded, the device:
• Sets the TEMPERATURE bit in the STATUS_BYTE
• Sets the Overtemperature Warning bit in the STATUS_TEMPERATURE command, and
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
UT_FAULT_LIMIT
The UT_FAULT_LIMIT command sets the value of the power stage temperature, in degrees Celsius, which causes
an undertemperature fault. The READ_TEMPERATURE_1 value will be used to determine if this limit has been
exceeded.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has two data bytes and is formatted in Linear_5s_11s format.
98
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
Timing
Timing—On Sequence/Ramp
COMMAND NAME
TON_DELAY
CMD CODE DESCRIPTION
0x60
Time from RUN and/or Operation on to output
rail turn-on.
TON_RISE
0x61
Time from when the output starts to rise
until the output voltage reaches the VOUT
commanded value.
TON_MAX_FAULT_LIMIT
0x62
Maximum time from the start of TON_RISE for
VOUT to cross the VOUT_UV_FAULT_LIMIT.
VOUT_TRANSITION_RATE
0x27
Rate the output changes when VOUT
commanded to a new value.
DATA
TYPE
PAGED FORMAT UNITS
R/W Word
Y
L11
ms
NVM
Y
R/W Word
Y
L11
ms
Y
R/W Word
Y
L11
ms
Y
R/W Word
Y
L11
V/ms
Y
DEFAULT
VALUE
0.0
0x8000
3.0
0xC300
5.0
0xCA80
0.001
0x8042
TON_DELAY
The TON_DELAY command sets the time, in milliseconds, from when a start condition is received until the output
voltage starts to rise. Values from 0ms to 83 seconds are valid.
This command has two data bytes and is formatted in Linear_5s_11s format.
TON_RISE
The TON_RISE command sets the time, in milliseconds, from the time the output starts to rise to the time the output
enters the regulation band. Values from 0 to 1.3 seconds are valid. The part will be in discontinuous mode during
TON_RISE events. If TON_RISE is less than 0.25ms, the LTM4676A digital slope will be bypassed. The output voltage
transition will be controlled by the analog performance of the PWM switcher. The maximum allowed slope is 4V/ms.
This command has two data bytes and is formatted in Linear_5s_11s format.
TON_MAX_FAULT_LIMIT
The TON_MAX_FAULT_LIMIT command sets the value, in milliseconds, on how long the unit can attempt to power
up the output without reaching the output undervoltage fault limit.
A data value of 0ms means that there is no limit and that the unit can attempt to bring up the output voltage indefinitely.
The maximum limit is 83 seconds.
This command has two data bytes and is formatted in Linear_5s_11s format.
VOUT_TRANSITION_RATE
When a PMBus device receives either a VOUT_COMMAND or OPERATION (Margin High, Margin Low) that causes the
output voltage to change this command set the rate in V/ms at which the output voltage changes. This commanded
rate of change does not apply when the unit is commanded on or off.
This command has two data bytes and is formatted in Linear_5s_11s format.
4676af
For more information www.linear.com/LTM4676A
99
LTM4676A
Appendix C: PMBus Command Details
Timing—Off Sequence/Ramp
COMMAND NAME
TOFF_DELAY
TOFF_FALL
TOFF_MAX_WARN_LIMIT
DATA
CMD CODE DESCRIPTION
TYPE
PAGED FORMAT UNITS
0x64
Time from RUN and/or Operation off to the start R/W Word
Y
L11
ms
of TOFF_FALL ramp.
0x65
Time from when the output starts to fall until the R/W Word
Y
L11
ms
output reaches zero volts.
0x66
Maximum allowed time, after TOFF_FALL
R/W Word
Y
L11
ms
completed, for the unit to decay below 12.5%.
NVM
Y
Y
Y
DEFAULT
VALUE
0.0
0x8000
3.0
0xC300
0.0
0x8000
TOFF_DELAY
The TOFF_DELAY command sets the time, in milliseconds, from when a stop condition is received until the output
voltage starts to fall. Values from 0 to 83 seconds are valid.
This command is excluded from fault events.
This command has two data bytes and is formatted in Linear_5s_11s format.
TOFF_FALL
The TOFF_FALL command sets the time, in milliseconds, from the end of the turn-off delay time until the output voltage is commanded to zero. It is the ramp time of the VOUT DAC. When the VOUT DAC is zero, the part will three-state.
The part will maintain the mode of operation programmed. For defined TOFF_FALL times, the user should set the part
to continuous conduction mode. Loading the max value indicates the part will ramp down at the slowest possible rate.
The minimum supported fall time is 0.25ms. A value less than 0.25ms will result in a 0.25ms ramp. The maximum fall
time is 1.3 seconds. The maximum allowed slope is 4V/ms.
In discontinuous conduction mode, the controller will not draw current from the load and the fall time will be set by
the output capacitance and load current.
This command has two data bytes and is formatted in Linear_5s_11s format.
TOFF_MAX_WARN_LIMIT
The TOFF_MAX_WARN_LIMIT command sets the value, in milliseconds, on how long the unit can attempt to turn off
the output until a warning is asserted. The output is considered off when the VOUT voltage is less than 12.5% of the
programmed VOUT_COMMAND value. The calculation begins after TOFF_FALL is complete. TOFF_MAX_WARN is not
enabled in VOUT_DECAY is disabled.
A data value of 0ms means that there is no limit and that the unit can attempt to turn off the output voltage indefinitely.
Other than 0, values from 120ms to 524 seconds are valid.
This command has two data bytes and is formatted in Linear_5s_11s format.
Precondition for Restart
COMMAND NAME
MFR_RESTART_ DELAY
100
CMD CODE DESCRIPTION
0xDC
Delay from actual RUN active edge to virtual
RUN active edge.
TYPE
R/W Word
DATA
PAGED FORMAT UNITS
Y
L11
ms
NVM
Y
DEFAULT
VALUE
150
0xF258
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
MFR_RESTART_DELAY
This command specifies the minimum RUN off time in milliseconds. This device will pull the RUN pin low for this length
of time once a falling edge of RUN has been detected. The minimum recommended value is 136ms.
Note: The restart delay is different than the retry delay. The restart delay pulls run low for the specified time, after which
a standard start-up sequence is initiated. The minimum restart delay should be equal to TOFF_DELAY + TOFF_FALL
+ 136ms. Valid values are from 136ms to 65.52 seconds in 16ms increments. To assure a minimum off time, set
the MFR_RESTART_DELAY 16ms longer than the desired time. The output rail can be off longer than the MFR_
RESTART_DELAY after the RUN pin is pulled high if the output decay bit 1 is enabled in MFR_CHAN_CONFIG and the
output takes a long time to decay below 12.5% of the programmed value.
This command has two data bytes and is formatted in Linear_5s_11s format.
Fault Response
Fault Responses All Faults
COMMAND NAME
MFR_RETRY_ DELAY
CMD CODE DESCRIPTION
0xDB
Retry interval during FAULT retry mode.
TYPE
R/W Word
DATA
PAGED FORMAT UNITS
Y
L11
ms
NVM
Y
DEFAULT
VALUE
250
0xF3E8
MFR_RETRY_DELAY
This command sets the time in milliseconds between restarts if the fault response is to retry the controller at specified
intervals. This command value is used for all fault responses that require retry. The retry time starts once the fault has
been detected by the offending channel. Valid values are from 120ms to 83.88 seconds in 10µs increments.
Note: The retry delay time is determined by the longer of the MFR_RETRY_DELAY command or the time required
for the regulated output to decay below 12.5% of the programmed value. If the natural decay time of the output is
too long, it is possible to remove the voltage requirement of the MFR_RETRY_DELAY command by asserting bit 0 of
MFR_CHAN_CONFIG.
This command has two data bytes and is formatted in Linear_5s_11s format.
Fault Responses Input Voltage (SVIN)
COMMAND NAME
VIN_OV_FAULT_RESPONSE
CMD CODE DESCRIPTION
0x56
Action to be taken by the device when an SVIN
input supply overvoltage fault is detected.
TYPE
R/W Byte
DATA
PAGED FORMAT UNITS
Y
Reg
NVM
DEFAULT
VALUE
Y
0xB8
VIN_OV_FAULT_RESPONSE
The VIN_OV_FAULT_RESPONSE command instructs the device on what action to take in response to an (SVIN) input
overvoltage fault. The data byte is in the format given in Table 28.
The device also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Set the INPUT bit in the upper byte of the STATUS_WORD
4676af
For more information www.linear.com/LTM4676A
101
LTM4676A
Appendix C: PMBus Command Details
• Sets the SVIN Overvoltage Fault bit in the STATUS_INPUT command, and
• Notifies the host by asserting ALERT pin, unless masked.
This command has one data byte.
Fault Responses Output Voltage
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT UNITS
NVM
DEFAULT
VALUE
VOUT_OV_FAULT_RESPONSE
0x41
Action to be taken by the device when an
output overvoltage fault is detected.
R/W Byte
Y
Reg
Y
0xB8
VOUT_UV_FAULT_RESPONSE
0x45
Action to be taken by the device when an
output undervoltage fault is detected.
R/W Byte
Y
Reg
Y
0xB8
TON_MAX_FAULT_
RESPONSE
0x63
Action to be taken by the device when a
TON_MAX_FAULT event is detected.
R/W Byte
Y
Reg
Y
0xB8
VOUT_OV_FAULT_RESPONSE
The VOUT_OV_FAULT_RESPONSE command instructs the device on what action to take in response to an output
overvoltage fault. The data byte is in the format given in Table 24.
The device also:
• Sets the VOUT_OV bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT Overvoltage Fault bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin, unless masked.
The only value recognized for this command are:
0x80–The device shuts down (disables the output) and the unit does not attempt to retry. The output remains disabled
until the fault is cleared (PMBus, Part II, Section 10.7).
0xB8–The device shuts down (disables the output) and device attempts retry continuously, without limitation, until
it is commanded OFF (by the RUN pin or OPERATION command or both), bias power is removed, or another fault
condition causes the unit to shut down.
0x4n The device shuts down and the unit does not attempt to retry. The output remains disabled until the part is
commanded OFF then ON or the RUN pin is asserted low then high or MFR_RESET or RESTORE_USER_ALL through the
command or removal of SVIN. The OV fault must remain active for a period of n • 10µs, where n is a value from 0 to 7.
0x78+n The device shuts down and the unit attempts to retry continuously until either the fault condition is cleared or
the part is commanded OFF then ON or the RUN pin is asserted low then high or MFR_RESET or RESTORE_USER_ALL
through the command or removal of SVIN. The OV fault must remain active for a period of n • 10µs, where n is a value
from 0 to 7.
Any other value will result in a CML fault and the write will be ignored.
This command has one data byte.
102
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
Table 24. VOUT_OV_FAULT_RESPONSE Data Byte Contents
BITS
7:6
DESCRIPTION
Response
VALUE
00
For all values of bits [7:6], the LTM4676A:
• Sets the corresponding fault bit in the status commands and
• Notifies the host by asserting ALERT pin, unless masked.
01
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• The device receives a CLEAR_FAULTS command.
• The output is commanded through the RUNn pin, the OPERATION
command, or the combined action of the RUNn pin and
OPERATION command, to turn off and then to turn back on, or
5:3
• Bias power is removed and reapplied to the LTM4676A.
Retry Setting
2:0
Delay Time
10
11
MEANING
Part performs OV pull down only (i.e., turns off the top
MOSFET and turns on lower MOSFET while VOUT is >
VOUT_OV_FAULT)
The PMBus device continues operation for the delay time
specified by bits [2:0] and the delay time unit specified for that
particular fault. If the fault condition is still present at the end of
the delay time, the unit responds as programmed in the Retry
Setting (bits [5:3]).
The device shuts down immediately (disables the output) and
responds according to the retry setting in bits [5:3].
Not supported. Writing this value will generate a CML fault.
000-110 The unit does not attempt to restart. The output remains
disabled until the fault is cleared until the device is commanded
OFF bias power is removed.
111
The PMBus device attempts to restart continuously, without
limitation, until it is commanded OFF (by the RUNn pin or
OPERATION command or both), bias power is removed, or
another fault condition causes the unit to shut down without
retry. Note: The retry interval is set by the MFR_RETRY_DELAY
command.
XXX
The delay time in 10µs increments. This delay time determines
how long the controller continues operating after a fault is
detected. Only valid for deglitched off state
VOUT_UV_FAULT_RESPONSE
The VOUT_UV_FAULT_RESPONSE command instructs the device on what action to take in response to an output
undervoltage fault. The data byte is in the format given in Table 25.
The device also:
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT undervoltage fault bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin, unless masked.
The UV fault and warn are masked until the following criteria are achieved:
1) The TON_MAX_FAULT_LIMIT has been reached
2) The TON_DELAY sequence has completed
3) The TON_RISE sequence has completed
4) The VOUT_UV_FAULT_LIMIT threshold has been reached
5) The IOUT_OC_FAULT_LIMIT is not present
The UV fault and warn are masked whenever the channel is not active.
The UV fault and warn are masked during TON_RISE and TOFF_FALL sequencing.
This command has one data byte.
4676af
For more information www.linear.com/LTM4676A
103
LTM4676A
Appendix C: PMBus Command Details
Table 25. VOUT_UV_FAULT_RESPONSE Data Byte Contents
BITS
7:6
DESCRIPTION
VALUE
Response
MEANING
00
The PMBus device continues operation without interruption.
(Ignores the fault functionally)
01
The PMBus device continues operation for the delay time
specified by bits [2:0] and the delay time unit specified for
that particular fault. If the fault condition is still present at the
end of the delay time, the unit responds as programmed in the
Retry Setting (bits [5:3]).
• The device receives a CLEAR_FAULTS command
10
• The output is commanded through the RUNn pin, the OPERATION
command, or the combined action of the RUNn pin and
OPERATION command, to turn off and then to turn back on, or
The device shuts down (disables the output) and responds
according to the retry setting in bits [5:3].
11
Not supported. Writing this value will generate a CML fault.
For all values of bits [7:6], the LTM4676A:
• Sets the corresponding fault bit in the status commands and
• Notifies the host by asserting ALERT pin, unless masked.
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• Bias power is removed and reapplied to the LTM4676A
5:3
2:0
000-110 The unit does not attempt to restart. The output remains
disabled until the fault is cleared until the device is commanded
OFF bias power is removed.
Retry Setting
Delay Time
111
The PMBus device attempts to restart continuously, without
limitation, until it is commanded OFF (by the RUNn pin or
OPERATION command or both), bias power is removed, or
another fault condition causes the unit to shut down without
retry. Note: The retry interval is set by the MFR_RETRY_DELAY
command.
XXX
The delay time in 10µs increments. This delay time determines
how long the controller continues operating after a fault is
detected. Only valid for deglitched off state.
TON_MAX_FAULT_RESPONSE
The TON_MAX_FAULT_RESPONSE command instructs the device on what action to take in response to a TON_MAX
fault. The data byte is in the format given in Table 28.
The device also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
• Sets the TON_MAX_FAULT bit in the STATUS_VOUT command, and
• Notifies the host by asserting ALERT pin, unless masked.
• A value of 0 disables the TON_MAX_FAULT_RESPONSE. It is not recommended to use 0.
This command has one data byte.
104
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
Fault Responses Output Current
COMMAND NAME
IOUT_OC_FAULT_RESPONSE
CMD CODE DESCRIPTION
0x47
Action to be taken by the device when an
output overcurrent fault is detected.
TYPE
PAGED
DATA
FORMAT
R/W Byte
Y
Reg
UNITS
NVM
DEFAULT
VALUE
Y
0x00
IOUT_OC_FAULT_RESPONSE
The IOUT_OC_FAULT_RESPONSE command instructs the device on what action to take in response to an output
overcurrent fault. The data byte is in the format given in Table 26.
The device also:
• Sets the IOUT_OC bit in the STATUS_BYTE
• Sets the IOUT bit in the STATUS_WORD
• Sets the IOUT Overcurrent Fault bit in the STATUS_IOUT command, and
• Notifies the host by asserting ALERT pin, unless masked.
This command has one data byte.
Table 26. IOUT_OC_FAULT_RESPONSE Data Byte Contents
BITS DESCRIPTION
7:6
VALUE
Response
The LTM4676A continues to operate indefinitely while
maintaining the output current at the value set by IOUT_OC_
FAULT_LIMIT without regard to the output voltage (known as
constant-current or brick-wall limiting).
01
Not supported.
10
The LTM4676A continues to operate, maintaining the output
current at the value set by IOUT_OC_FAULT_LIMIT without
regard to the output voltage, for the delay time set by bits [2:0].
If the device is still operating in current limit at the end of the
delay time, the device responds as programmed by the Retry
Setting in bits [5:3].
11
The LTM4676A shuts down immediately and responds as
programmed by the Retry Setting in bits [5:3].
For all values of bits [7:6], the LTM4676A:
• Sets the corresponding fault bit in the status commands and
• Notifies the host by asserting ALERT pin, unless masked.
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• The device receives a CLEAR_FAULTS command
• The output is commanded through the RUNn pin, the OPERATION
command, or the combined action of the RUNn pin and
OPERATION command, to turn off and then to turn back on, or
• Bias power is removed and reapplied to the LTM4676A.
5:3
2:0
Retry Setting
Delay Time
MEANING
00
000-110 The unit does not attempt to restart. The output remains
disabled until the fault is cleared by cycling the RUNn pin or
removing bias power.
111
The device attempts to restart continuously, without limitation,
until it is commanded OFF (by the RUNn pin or OPERATION
command or both), bias power is removed, or another fault
condition causes the unit to shut down. Note: The retry interval
is set by the MFR_RETRY_DELAY command.
XXX
The number of delay time units in 16ms increments. This
delay time is used to determine the amount of time a unit is
to continue operating after a fault is detected before shutting
down. Only valid for deglitched off state.
4676af
For more information www.linear.com/LTM4676A
105
LTM4676A
Appendix C: PMBus Command Details
Fault Responses IC Temperature
COMMAND NAME
MFR_OT_FAULT_
RESPONSE
CMD CODE DESCRIPTION
0xD6
Action to be taken by the device when an
internal overtemperature fault is detected.
TYPE
PAGED
R Byte
N
DATA
FORMAT UNITS
NVM
DEFAULT
VALUE
Reg
0xC0
MFR_OT_FAULT_RESPONSE
The MFR_OT_FAULT_RESPONSE command byte instructs the device on what action to take in response to an internal
overtemperature fault. The data byte is in the format given in Table 27.
The LTM4676A also:
• Sets the MFR bit in the STATUS_WORD, and
• Sets the Overtemperature Fault bit in the STATUS_MFR_SPECIFIC command
• Notifies the host by asserting ALERT pin, unless masked.
This command has one data byte.
Table 27. Data Byte Contents MFR_OT_FAULT_RESPONSE
BITS DESCRIPTION
7:6
VALUE
MEANING
Response
00
Not supported. Writing this value will generate a CML fault.
For all values of bits [7:6], the LTM4676A:
01
Not supported. Writing this value will generate a CML fault
• Sets the corresponding fault bit in the status commands and
10
The device shuts down immediately (disables the output) and
responds according to the retry setting in bits [5:3].
11
The device’s output is disabled while the fault is present.
Operation resumes and the output is enabled when the fault
condition no longer exists.
000
The unit does not attempt to restart. The output remains
disabled until the fault is cleared.
• Notifies the host by asserting ALERT pin, unless masked.
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• The device receives a CLEAR_FAULTS command
• The output is commanded through the RUNn pin, the OPERATION
command, or the combined action of the RUNn pin and
OPERATION command, to turn off and then to turn back on, or
• Bias power is removed and reapplied to the LTM4676A
5:3
Retry Setting
001-111 Not supported. Writing this value will generate CML fault.
2:0
Delay Time
XXX
Not supported. Value ignored
Fault Responses Power Stage Temperature
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT UNITS
NVM
DEFAULT
VALUE
OT_FAULT_ RESPONSE
0x50
Action to be taken by the device when a power
stage overtemperature fault is detected,
R/W Byte
Y
Reg
Y
0xB8
UT_FAULT_ RESPONSE
0x54
Action to be taken by the device when a power
stage undertemperature fault is detected.
R/W Byte
Y
Reg
Y
0x00
106
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
OT_FAULT_RESPONSE
The OT_FAULT_RESPONSE command instructs the device on what action to take in response to a power stage overtemperature fault. The data byte is in the format given in Table 28.
The device also:
• Sets the TEMPERATURE bit in the STATUS_BYTE
• Sets the Overtemperature Fault bit in the STATUS_TEMPERATURE command, and
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has one data byte.
UT_FAULT_RESPONSE
The UT_FAULT_RESPONSE command instructs the device on what action to take in response to a power stage undertemperature fault. The data byte is in the format given in Table 28.
The device also:
• Sets the TEMPERATURE bit in the STATUS_BYTE
• Sets the Undertemperature Fault bit in the STATUS_TEMPERATURE command, and
• Notifies the host by asserting ALERT pin, unless masked.
This condition is detected by the ADC so the response time may be up to 100ms, typical.
This command has one data byte.
Table 28. Data Byte Contents: TON_MAX_FAULT_RESPONSE, VIN_OV_FAULT_RESPONSE,
OT_FAULT_RESPONSE, UT_FAULT_RESPONSE
BITS DESCRIPTION
7:6
5:3
2:0
VALUE
Response
For all values of bits [7:6], the LTM4676A:
• Sets the corresponding fault bit in the status commands, and
• Notifies the host by asserting ALERT pin, unless masked.
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• The device receives a CLEAR_FAULTS command
• The output is commanded through the RUNn pin, the OPERATION
command, or the combined action of the RUNn pin and
OPERATION command, to turn off and then to turn back on, or
• Bias power is removed and reapplied to the LTM4676A
Retry Setting
Delay Time
MEANING
00
The PMBus device continues operation without interruption.
01
Not supported. Writing this value will generate a CML fault.
10
The device shuts down immediately (disables the output) and
responds according to the retry setting in bits [5:3].
11
Not supported. Writing this value will generate a CML fault.
000-110 The unit does not attempt to restart. The output remains disabled
until the fault is cleared until the device is commanded OFF bias
power is removed.
111
The PMBus device attempts to restart continuously, without
limitation, until it is commanded OFF (by the RUNn pin or
OPERATION command or both), bias power is removed, or another
fault condition causes the unit to shut down without retry. Note:
The retry interval is set by the MFR_RETRY_DELAY command.
XXX
Not supported. Values ignored
4676af
For more information www.linear.com/LTM4676A
107
LTM4676A
Appendix C: PMBus Command Details
Fault Sharing
Fault Sharing Propagation
COMMAND NAME
CMD CODE
DESCRIPTION
MFR_GPIO_ PROPAGATEn
0xD2
Configuration that determines which faults are
propagated to the GPIO pins.
TYPE
R/W Word
DATA
PAGED FORMAT UNITS
Y
NVM
DEFAULT
VALUE
Y
0x6893
Reg
MFR_GPIO_PROPAGATE
The MFR_GPIO_PROPAGATE command enables the faults that can cause the GPIOn pin to assert low. The command is
formatted as shown in Table 29. Faults can only be propagated to the GPIO if they are programmed to respond to faults.
This command has two data bytes.
Table 29. GPIOn Propagate Fault Configuration. The GPIO0 and GPIO1 pins are designed to provide electrical notification of selected events to
the user. Some of these events are common to both output channels. Others are specific to an output channel. They can also be used to share faults
between channels.
BIT(S) SYMBOL
OPERATION
B[15]
VOUT disabled while not decayed.
This is used in a PolyPhase configuration when bit 0 of the MFR_CHAN_CONFIG is a zero. If the
channel is turned off, by toggling the RUN pin or commanding the part OFF, and then the RUN
is reasserted or the part is commanded back on before the output has decayed, VOUT will not
restart until the 12.5% decay is honored. The GPIO pin is asserted during this condition if bit 15
is asserted.
B[14]
Mfr_gpio_propagate_short_CMD_cycle 0: No action
b[13]
Mfr_gpio_propagate_ton_max_fault
1: Asserts low if commanded off then on before the output has sequenced off. Re-asserts high
120ms after sequence off.
0: No action if a TON_MAX_FAULT fault is asserted
1: Associated output will be asserted low if a TON_MAX_FAULT fault is asserted
GPIO0 is associated with page 0 TON_MAX_FAULT faults
Mfr_gpio0_propagate_vout_uvuf,
GPIO1 is associated with page 1 TON_MAX_FAULT faults
Unfiltered VOUT_UV_FAULT_LIMIT comparator output
Mfr_gpio1_propagate_vout_uvuf
GPIO0 is associated with channel 0
b[11]
Mfr_gpio0_propagate_int_ot,
GPIO1 is associated with channel 1
0: No action if the MFR_OT_FAULT_LIMIT fault is asserted
b[10]
Mfr_gpio1_propagate_int_ot
Mfr_pwrgd1_en*
1: Associated output will be asserted low if the MFR_OT_FAULT_LIMIT fault is asserted
0: No action if channel 1 POWER_GOOD is not true
b[12]
1: Associated output will be asserted low if channel 1 POWER_GOOD is not true
b[9]
Mfr_pwrgd0_en*
If this bit is asserted, the GPIO_FAULT_RESPONSE must be ignore. If the GPIO_FAULT_
RESPONSE is not set to ignore, the part will latch off and never be able to start.
0: No action if channel 0 POWER_GOOD is not true
1: Associated output will be asserted low if channel 0 POWER_GOOD is not true
b[8]
Mfr_gpio0_propagate_ut,
If this bit is asserted, the GPIO_FAULT_RESPONSE must be ignore. If the GPIO_FAULT_
RESPONSE is not set to ignore, the part will latch off and never be able to start.
0: No action if the UT_FAULT_LIMIT fault is asserted
Mfr_gpio1_propagate_ut
1: Associated output will be asserted low if the UT_FAULT_LIMIT fault is asserted
GPIO0 is associated with page 0 UT faults
GPIO1 is associated with page 1 UT faults
108
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
Table 29. GPIOn Propagate Fault Configuration. The GPIO0 and GPIO1 pins are designed to provide electrical notification of selected events to
the user. Some of these events are common to both output channels. Others are specific to an output channel. They can also be used to share faults
between channels.
BIT(S) SYMBOL
OPERATION
b[7]
Mfr_gpio0_propagate_ot,
0: No action if the OT_FAULT_LIMIT fault is asserted
Mfr_gpio1_propagate_ot
1: Associated output will be asserted low if the OT_FAULT_LIMIT fault is asserted
GPIO0 is associated with page 0 OT faults
GPIO1 is associated with page 1 OT faults
b[6]
b[5]
b[4]
Reserved
Reserved
Mfr_gpio0_propagate_input_ov,
b[3]
b[2]
Mfr_gpio1_propagate_input_ov
Reserved
Mfr_gpio0_propagate_iout_oc,
0: No action if the IOUT_OC_FAULT_LIMIT fault is asserted
Mfr_gpio1_propagate_iout_oc
1: Associated output will be asserted low if the IOUT_OC_FAULT_LIMIT fault is asserted
0: No action if the VIN_OV_FAULT_LIMIT fault is asserted
1: Associated output will be asserted low if the VIN_OV_FAULT_LIMIT fault is asserted
GPIO0 is associated with page 0 OC faults
b[1]
Mfr_gpio0_propagate_vout_uv,
GPIO1 is associated with page 1 OC faults
0: No action if the VOUT_UV_FAULT_LIMIT fault is asserted
Mfr_gpio1_propagate_vout_uv
1: Associated output will be asserted low if the VOUT_UV_FAULT_LIMIT fault is asserted
GPIO0 is associated with page 0 UV faults
b[0]
Mfr_gpio0_propagate_vout_ov,
GPIO1 is associated with page 1 UV faults
0: No action if the VOUT_OV_FAULT_LIMIT fault is asserted
Mfr_gpio1_propagate_vout_ov
1: Associated output will be asserted low if the VOUT_OV_FAULT_LIMIT fault is asserted
GPIO0 is associated with page 0 OV faults
GPIO1 is associated with page 1 OV faults
*The PWRGD status is designed as an indicator and not to be used for power supply sequencing.
Fault Sharing Response
COMMAND NAME
MFR_GPIO_RESPONSE
CMD CODE DESCRIPTION
TYPE
0xD5
Action to be taken by the device when the GPIO pin R/W Byte
is asserted low.
PAGED
Y
DATA
FORMAT
Reg
UNITS
NVM
Y
DEFAULT
VALUE
0xC0
MFR_GPIO_RESPONSE
This command determines the controller’s response to the GPIOn pin being pulled low by an external source.
VALUE
0xC0
0x00
MEANING
GPIO_INHIBIT The LTM4676A will three-state the output in response to the GPIO pin pulled low.
GPIO_IGNORE The LTM4676A continues operation without interruption.
The device also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the MFR bit in the STATUS_WORD
• Sets the GPIOB bit in the STATUS_MFR_SPECIFIC command, and
• Notifies the host by asserting ALERT pin, unless masked. The ALERT pin pulled low can be disabled by setting bit[1]
of MFR_CHAN_CFG.
This command has one data byte.
4676af
For more information www.linear.com/LTM4676A
109
LTM4676A
Appendix C: PMBus Command Details
Scratchpad
COMMAND NAME
USER_DATA_00
USER_DATA_01
USER_DATA_02
USER_DATA_03
USER_DATA_04
CMD CODE
0xB0
0xB1
0xB2
0xB3
0xB4
DESCRIPTION
OEM reserved. Typically used for part serialization.
Manufacturer reserved for LTpowerPlay.
OEM reserved. Typically used for part serialization.
A NVM word available for the user.
A NVM word available for the user.
TYPE
R/W Word
R/W Word
R/W Word
R/W Word
R/W Word
PAGED
N
Y
N
Y
N
DATA
DEFAULT
FORMAT UNITS NVM VALUE
Reg
Y
NA
Reg
Y
NA
Reg
Y
NA
Reg
Y
0x0000
Reg
Y
0x0000
USER_DATA_00 through USER_DATA_04
These commands are non-volatile memory locations for customer storage. The customer has the option to write any
value to the USER_DATA_nn at any time. However, the LTpowerPlay software and contract manufacturers use some
of these commands for inventory control. Modifying the reserved USER_DATA_nn commands may lead to undesirable
inventory control and incompatibility with these products.
These commands have 2 data bytes and are in register format.
Identification
COMMAND NAME
PMBUS_REVISION
CAPABILITY
MFR_ID
MFR_MODEL
MFR_SERIAL
MFR_SPECIAL_ID
CMD CODE DESCRIPTION
0x98
PMBus revision supported by this device. Current
revision is 1.2.
0x19
Summary of PMBus optional communication protocols
supported by this device.
0x99
The manufacturer ID of the LTM4676A in ASCII.
0x9A
Manufacturer part number in ASCII.
0x9E
Serial number of this specific unit in ASCII.
0xE7
Manufacturer code representing the LTM4676A.
TYPE
R Byte
DATA
PAGED FORMAT UNITS
N
Reg
NVM
DEFAULT
VALUE
0x22
R Byte
N
Reg
0xB0
R String
R String
R Block
R Word
N
N
N
N
ASC
ASC
CF
Reg
LTC
LTM4676A
NA
0x47EX
PMBus_REVISION
The PMBUS_REVISION command indicates the revision of the PMBus to which the device is compliant. The LTM4676A
is PMBus Version 1.2 compliant in both Part I and Part II.
This read-only command has one data byte.
CAPABILITY
This command provides a way for a host system to determine some key capabilities of a PMBus device.
The LTM4676A supports packet error checking, 400kHz bus speeds, and ALERT pin.
This read-only command has one data byte.
MFR_ID
The MFR_ID command indicates the manufacturer ID of the LTM4676A using ASCII characters.
This read-only command is in block format.
110
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
MFR_MODEL
The MFR_MODEL command indicates the manufacturer’s part number of the LTM4676A using ASCII characters.
This read-only command is in block format.
MFR_SERIAL
The MFR_SERIAL command contains up to 9 bytes of custom formatted data used to uniquely identify the LTM4676A
configuration.
This read-only command is in block format.
MFR_SPECIAL_ID
The 16-bit word representing the part name. The 0x47E prefix denotes the part is an LTM4676A, X is adjustable by
the manufacturer.
This read-only command has 2 data bytes.
Fault Warning and Status
COMMAND NAME
CLEAR_FAULTS
SMBALERT_MASK
CMD CODE DESCRIPTION
0x03
Clear any fault bits that have been set.
0x1B
Mask ALERT Activity.
MFR_CLEAR_PEAKS
STATUS_BYTE
0xE3
0x78
STATUS_WORD
STATUS_VOUT
STATUS_IOUT
STATUS_INPUT
STATUS_ TEMPERATURE
0x79
0x7A
0x7B
0x7C
0x7D
STATUS_CML
0x7E
STATUS_MFR_ SPECIFIC
0x80
MFR_PADS
MFR_COMMON
0xE5
0xEF
TYPE
Send Byte
Block R/W
Clears all peaks values.
Send Byte
One byte summary of the unit’s fault
R/W Byte
condition.
Two byte summary of the unit’s fault condition. R/W Word
Output voltage fault and warning status.
R/W Byte
Output current fault and warning status.
R/W Byte
R/W Byte
Input supply (SVIN) fault and warning status.
R/W Byte
TSNSna-sensed fault and warning status for
READ_TEMERATURE_1.
Communication and memory fault and
R/W Byte
warning status.
Manufacturer specific fault and state
R/W Byte
information.
Digital status of the I/O pads.
R Word
Manufacturer status bits that are common
R Byte
across multiple LTC ICs/modules.
N
Y
Reg
DEFAULT
VALUE
NA
See CMD
Details
NA
NA
Y
Y
Y
N
Y
Reg
Reg
Reg
Reg
Reg
NA
NA
NA
NA
NA
N
Reg
NA
Y
Reg
NA
N
N
Reg
Reg
NA
NA
PAGED
N
Y
FORMAT UNITS
Reg
NVM
Y
CLEAR_FAULTS
The CLEAR_FAULTS command is used to clear any fault bits that have been set. This command clears all bits in all
status commands simultaneously. At the same time, the device negates (clears, releases) its ALERT pin signal output
if the device is asserting the ALERT pin signal. If the fault is still present when the bit is cleared, the fault bit will remain
set and the host notified by asserting the ALERT pin low. CLEAR_FAULTS can take up to 10µs to process. If a fault
occurs within that time frame it may be cleared before the status register is set.
This write-only command has no data bytes.
For more information www.linear.com/LTM4676A
4676af
111
LTM4676A
Appendix C: PMBus Command Details
The CLEAR_FAULTS does not cause a unit that has latched off for a fault condition to restart. Units that have shut down
for a fault condition are restarted when:
• The output is commanded through the RUN pin, the OPERATION command, or the combined action of the RUN pin
and OPERATION command, to turn off and then to turn back on, or
• MFR_RESET or RESTORE_USER_ALL command is issued.
• Bias power is removed and reapplied to the integrated circuit
MFR_CLEAR_PEAKS
The MFR_CLEAR_PEAKS command clears the MFR_*_PEAK data values. A MFR_RESET or RESTORE_USER_ALL
will initiate this command.
This write-only command has no data bytes.
SMBALERT_MASK
The SMBALERT_MASK command can be used to prevent a particular status bit or bits from asserting ALERT as they
are asserted.
Figure 59 shows an example of the Write Word format used to set an ALERT mask, in this case without PEC. The bits
in the mask byte align with bits in the specified status register. For example, if the STATUS_TEMPERATURE command
code is sent in the first data byte, and the mask byte contains 0x40, then a subsequent External Overtemperature Warning
would still set bit 6 of STATUS_TEMPERATURE but not assert ALERT. All other supported STATUS_TEMPERATURE
bits would continue to assert ALERT if set.
Figure 60 shows an example of the Block Write – Block Read Process Call protocol used to read back the present state
of any supported status register, again without PEC.
SMBALERT_MASK cannot be applied to STATUS_BYTE, STATUS_WORD, MFR_COMMON or MFR_PADS. Factory default
masking for applicable status registers is shown below. Providing an unsupported command code to SMBALERT_MASK
will generate a CML for Invalid/Unsupported Data.
1
7
S
SLAVE
ADDRESS
1
1
W
A SMBALERT_MASK A
COMMAND CODE
8
1
8
8
1
1
MASK BYTE
A
P
1
STATUS_x
A
COMMAND CODE
4676A F59
Figure 59. Example of Setting SMBALERT_MASK
1
7
1
1
S
SLAVE
ADDRESS
W
A SMBALERT_MASK A
COMMAND CODE
1
7
Sr
SLAVE
ADDRESS
8
1
R
1
8
1
BLOCK COUNT
(= 1)
A
8
1
STATUS_x
A
COMMAND CODE
1
8
1
8
A
BLOCK COUNT
(= 1)
A
MASK BYTE
1
…
1
NA P
4676A F60
Figure 60. Example of Reading SMBALERT_MASK
112
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
SMBALERT_MASK Default Setting: (Refer Also to Summary of the Status Registers, Figure 61)
STATUS RESISTER
ALERT Mask Value MASKED BITS
STATUS_VOUTn
0x00
None
STATUS_IOUTn
0x00
None
STATUS_TEMPERATUREn
0x00
None
STATUS_CML
0x00
None
STATUS_INPUT
0x00
None
STATUS_MFR_SPECIFICn
0x11
Bit 4 (internal PLL unlocked), bit 0 (GPIOn pulled low by external device)
STATUS_BYTE
The STATUS_BYTE command returns a one-byte summary of the most critical faults.
STATUS_BYTE Message Contents:
BIT
STATUS BIT NAME
MEANING
7
BUSY
6
OFF
A fault was declared because the LTM4676A was unable to respond.
5
VOUT_OV
4
IOUT_OC
An output overcurrent fault has occurred.
3
VIN_UV
Not supported (LTM4676A returns 0).
2
TEMPERATURE
1
CML
0
NONE OF THE ABOVE
This bit is set if the channel is not providing power to its output, regardless of the reason, including simply not
being enabled.
An output overvoltage fault has occurred.
A temperature fault or warning has occurred.
A communications, memory or logic fault has occurred.
A fault Not listed in bits[7:1] has occurred.
This command has one data byte
Any supported fault bit in this command will initiate an ALERT event.
STATUS_WORD
The STATUS_WORD command returns a two-byte summary of the channel’s fault condition. The low byte of the
STATUS_WORD is the same as the STATUS_BYTE command.
STATUS_WORD High Byte Message Contents:
BIT
STATUS BIT NAME
15
VOUT
An output voltage fault or warning has occurred.
MEANING
14
IOUT
An output current fault or warning has occurred.
13
INPUT
An SVIN input voltage fault or warning has occurred.
12
MFR_SPECIFIC
A fault or warning specific to the LTM4676A has occurred.
11
POWER_GOOD#
The POWER_GOOD state is false if this bit is set.
10
FANS
Not supported (LTM4676A returns 0).
9
OTHER
Not supported (LTM4676A returns 0).
8
UNKNOWN
Not supported (LTM4676A returns 0).
Any supported fault bit in this command will initiate an ALERT event.
This command has two data bytes.
4676af
For more information www.linear.com/LTM4676A
113
LTM4676A
Appendix C: PMBus Command Details
STATUS_VOUT
The STATUS_VOUT command returns one byte of VOUT status information.
STATUS_VOUT Message Contents:
BIT
MEANING
7
VOUT overvoltage fault.
6
VOUT overvoltage warning.
5
VOUT undervoltage warning.
4
VOUT undervoltage fault.
3
VOUT_MAX warning.
2
TON_MAX fault.
1
TOFF_MAX warning.
0
Not supported by the LTM4676A (returns 0).
ALERT can be asserted if any of bits[7:1] are set. These may be cleared by writing a 1 to their bit position in STATUS_VOUT, in lieu of a CLEAR_FAULTS
command.
This command has one data byte.
STATUS_IOUT
The STATUS_IOUT command returns one byte of IOUT status information.
STATUS_IOUT Message Contents:
BIT
MEANING
7
IOUT overcurrent fault.
6
Not supported (LTM4676A returns 0).
5
IOUT overcurrent warning.
4:0
Not supported (LTM4676A returns 0).
ALERT can be asserted if any supported bits are set. Any supported bit may be cleared by writing a 1 to that bit position in STATUS_IOUT, in lieu of a
CLEAR_FAULTS command.
This command has one data byte.
STATUS_INPUT
The STATUS_INPUT command returns one byte of VIN (SVIN) status information.
STATUS_INPUT Message Contents:
BIT
MEANING
7
SVIN overvoltage fault.
6
Not supported (LTM4676A returns 0).
5
SVIN undervoltage warning.
4
Not supported (LTM4676A returns 0).
3
Unit off for insufficient SVIN voltage.
2
Not supported (LTM4676A returns 0).
1
Input over current warning.
0
Not supported (LTM4676A returns 0)
ALERT can be asserted if bit 7 is set. Bit 7 may be cleared by writing it to a 1, in lieu of a CLEAR_FAULTS command.
This command has one data byte.
114
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
STATUS_TEMPERATURE
The STATUS_TEMPERATURE command returns one byte of sensed power stage temperature status information.
STATUS_TEMPERATURE Message Contents:
BIT
MEANING
7
External overtemperature fault.
6
External overtemperature warning.
5
Not supported (LTM4676A returns 0).
4
External undertemperature fault.
3:0
Not supported (LTM4676A returns 0).
ALERT can be asserted if any supported bits are set. Any supported bit may be cleared by writing a 1 to that bit position in STATUS_TEMPERATURE, in
lieu of a CLEAR_FAULTS command.
This command has one data byte.
STATUS_CML
The STATUS_CML command returns one byte of status information on received commands, internal memory and logic.
STATUS_CML Message Contents:
BIT
MEANING
7
Invalid or unsupported command received.
6
Invalid or unsupported data received.
5
Packet error check failed.
4
Memory fault detected.
3
Processor fault detected.
2
Reserved (LTM4676A returns 0).
1
Other communication fault.
0
Other memory or logic fault.
ALERT can be asserted if any supported bits are set. Any supported bit may be cleared by writing a 1 to that bit position in STATUS_CML, in lieu of a
CLEAR_FAULTS command.
This command has one data byte.
STATUS_MFR_SPECIFIC
The STATUS_MFR_SPECIFIC commands returns one byte with the manufacturer specific status information.
Each channel has a copy of the same information. Only bit 0 is page specific.
The format for this byte is:
BIT
MEANING
7
Internal Temperature Fault Limit Exceeded.
6
Internal Temperature Warn Limit Exceeded.
5
NVM CRC Fault.
4
PLL is Unlocked
3
Fault Log Present
2
VDD33 UV or OV Fault
0
GPIO Pin Asserted Low by External Device (paged)
4676af
For more information www.linear.com/LTM4676A
115
LTM4676A
Appendix C: PMBus Command Details
If any of these bits are set, the MFR bit in the STATUS_WORD will be set.
The user is permitted to write a 1 to any bit in this command to clear a specific fault. This permits the user to clear
status by means other than using the CLEAR_FAULTS command. Exception: The fault log present bit can only be
cleared by issuing the MFR_FAULT_LOG_CLEAR command.
Any supported fault bit in this command will initiate an ALERT event.
This command has one data byte.
MFR_PADS
This command provides the user a means of directly reading the digital status of the I/O pins of the device. The bit
assignments of this command are as follows:
BIT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ASSIGNED DIGITAL PIN
VDD33 OV Fault
VDD33 UV Fault
Reserved
Reserved
ADC Values Invalid, Occurs During Start-Up
SYNC Output Disabled Due to External Clock
PowerGood1
PowerGood0
Device Driving RUN1 Low
Device Driving RUN0 Low
RUN1
RUN0
Device Driving GPIO1 Low
Device Driving GPIO0 Low
GPIO1
GPIO0
A 1 indicates the condition is true.
This read-only command has two data bytes.
MFR_COMMON
The MFR_COMMON command contains bits that are common to all LTC digital power and telemetry products.
BIT
MEANING
7
MODULE NOT DRIVING ALERT LOW
6
MODULE NOT BUSY
5
CALCULATIONS NOT PENDING
4
OUTPUT NOT IN TRANSITION
3
NVM Initialized
2
Reserved
1
SHARE_CLK Timeout
0
WP Pin Status
This read-only command has one data byte.
116
For more information www.linear.com/LTM4676A
4676af
LTM4676A
Appendix C: PMBus Command Details
STATUS_WORD
STATUS_VOUT*
7
6
5
4
3
2
1
0
VOUT_OV Fault
VOUT_OV Warning
VOUT_UV Warning
VOUT_UV Fault
VOUT_MAX Warning
TON_MAX Fault
TOFF_MAX Warning
(reads 0)
15
14
13
12
11
10
9
8
VOUT
IOUT
INPUT
MFR_SPECIFIC
POWER_GOOD#
(reads 0)
(reads 0)
(reads 0)
7
6
5
4
3
2
1
0
BUSY
OFF
VOUT_OV
IOUT_OC
(reads 0)
TEMPERATURE
CML
NONE OF THE ABOVE
STATUS_BYTE
(PAGED)
STATUS_IOUT
7
6
5
4
3
2
1
0
IOUT_OC Fault
(reads 0)
IOUT_OC Warning
(reads 0)
(reads 0)
(reads 0)
(reads 0)
(reads 0)
MFR_COMMON
7
6
5
4
3
2
1
0
STATUS_TEMPERATURE
OT Fault
OT Warning
(reads 0)
UT Fault
(reads 0)
(reads 0)
(reads 0)
(reads 0)
Module Not Driving ALERT Low
Module Not Busy
Internal Calculations Not Pending
Output Not In Transition
EEPROM Initialized
(reads 0)
SHARE_CLK_LOW
WP Pin High
STATUS_CML
Invalid/Unsupported Command
Invalid/Unsupported Data
Packet Error Check Failed
Memory Fault Detected
Processor Fault Detected
(reads 0)
Other Communication Fault
Other Memory or Logic Fault
DESCRIPTION
General Fault or Warning Event
Dynamic
Status Derived from Other Bits
MASKABLE GENERATES ALERT BIT CLEARABLE
Yes
No
No
7
6
5
4
3
2
1
0
Internal Temperature Fault
Internal Temperature Warning
EEPROM CRC Error
Internal PLL Unlocked
Fault Log Present
(reads 0)
VOUT Short Cycled
GPIO Pulled Low By External Device
(PAGED)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
VDD33 0V
VDD33 UV
(reads 0)
(reads 0)
Invalid ADC Result(s)
SYNC Output Disabled Externally
Channel 1 is POWER_GOOD
Channel 0 is POWER_GOOD
LTM4676A Forcing RUN1 Low
LTM4676A Forcing RUN0 Low
RUN1 Pin State
RUN0 Pin State
LTM4676A Forcing GPIO1 Low
LTM4676A Forcing GPIO0 Low
GPIO1 Pin State
GPIO0 Pin State
MFR_PADS
(PAGED)
7
6
5
4
3
2
1
0
VIN_OV Fault SVIN
(reads 0)
VIN_UV Warning SVIN
(reads 0)
Unit Off for Insuffcient SVIN Voltage
(reads 0)
IIN_OC Warning
(reads 0)
STATUS_MFR_SPECIFIC
(PAGED)
(PAGED)
7
6
5
4
3
2
1
0
STATUS_INPUT
7
6
5
4
3
2
1
0
Yes
No
Not Directly
Yes
No
No
4676A SR01
Figure 61. Summary of the Status Registers
4676af
For more information www.linear.com/LTM4676A
117
LTM4676A
Appendix C: PMBus Command Details
Telemetry
COMMAND NAME
CMD
CODE DESCRIPTION
READ_VIN
0x88
Measured input supply (SVIN) voltage.
R Word
READ_VOUT
0x8B
Measured output voltage.
READ_IIN
0x89
Calculated input supply current.
MFR_READ_IIN
0xED
READ_IOUT
READ_TEMPERATURE_1
READ_TEMPERATURE_2
READ_DUTY_CYCLE
TYPE
PAGED FORMAT UNITS NVM
DEFAULT
VALUE
N
L11
V
NA
R Word
Y
L16
V
NA
R Word
N
L11
A
NA
Calculated input current per channel.
R Word
Y
L11
A
NA
0x8C
Measured output current.
R Word
Y
L11
A
NA
0x8D
Power stage temperature sensor. This is the value
R Word
used for all temperature related processing, including
IOUT_CAL_GAIN.
Y
L11
C
NA
0x8E
Control IC die temperature. Does not affect any other
registers.
R Word
N
L11
C
NA
0x94
Duty cycle of the top gate control signal.
R Word
Y
L11
%
NA
READ_POUT
0x96
Calculated output power.
R Word
Y
L11
W
NA
MFR_VOUT_PEAK
0xDD
Maximum measured value of READ_VOUT since last
MFR_CLEAR_PEAKS.
R Word
Y
L16
V
NA
MFR_VIN_PEAK
0xDE
Maximum measured value of READ_VIN since last
MFR_CLEAR_PEAKS.
R Word
N
L11
V
NA
MFR_TEMPERATURE_1_PEAK
0xDF
Maximum measured value of power stage
temperature (READ_TEMPERATURE_1) since last
MFR_CLEAR_PEAKS.
R Word
Y
L11
C
NA
MFR_TEMPERATURE_2_PEAK
0xF4
Maximum measured value of control IC die
temperature (READ_TEMPERATURE_2) since last
MFR_CLEAR_PEAKS.
R Word
N
L11
C
NA
MFR_IOUT_PEAK
0xD7
Report the maximum measured value of READ_IOUT R Word
since last MFR_CLEAR_PEAKS.
Y
L11
A
NA
MFR_ADC_CONTROL
0xD8
ADC telemetry parameter selected for repeated fast
ADC read back.
R/W
Byte
N
Reg
0x00
MFR_ADC_TELEMETRY_
STATUS
0xDA
ADC telemetry status indicating which parameter is
most recently converted when the short round robin
ADC loop is enabled
R/W
Byte
N
Reg
NA
READ_VIN
The READ_VIN command returns the measured SVIN input voltage, in volts.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
READ_VOUT
The READ_VOUT command returns the measured output voltage in the same format as set by the VOUT_MODE
command.
This read-only command has two data bytes and is formatted in Linear_16u format.
READ_IIN
The READ_IIN command returns the input current in Amperes. Note: Input current is calculated from READ_IOUT
current and the READ_DUTY_CYCLE value from both outputs plus the MFR_IIN_OFFSET. For accurate values at low
currents the part must be in continuous conduction mode. The greatest source of error if DCR sensing is used, is the
accuracy of the inductor parasitic DC resistance (DCR) at room temperature IOUT_CAL_GAIN.
READ_IIN = MFR_READ_IIN_PAGE0 + MFR_READ_IIN_PAGE1
118
For more information www.linear.com/LTM4676A
4676af
LTM4676A
Appendix C: PMBus Command Details
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
MFR_READ_IIN
The MFR_READ_IIN command is a paged reading of the input current that applies the paged MFR_IIN_OFFSET
parameter. This calculation is similar to READ_IIN except the paged values are used.
MFR_READ_IIN = MFR_IIN_OFFSET + (IOUT • DUTY_CYCLE)
This command has 2 data bytes and is formatted in Linear_5s_11s format.
READ_IOUT
The READ_IOUT command returns the average output current in amperes. The IOUT value is a function of:
a) the differential voltage measured across the ISENSE pins
b) the IOUT_CAL_GAIN value
c) the MFR_IOUT_CAL_GAIN_TC value, and
d) READ_TEMPERATURE_1 value
e) The MFR_TEMP_1_GAIN and the MFR_TEMP_1_OFFSET
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
READ_TEMPERATURE_1
The READ_TEMPERATURE_1 command returns the temperature, in degrees Celsius, of the external sense element.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
READ_TEMPERATURE_2
The READ_TEMPERATURE_2 command returns the temperature, in degrees Celsius, of the internal sense element.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
READ_DUTY_CYCLE
The READ_DUTY_CYCLE command returns the duty cycle of controller, in percent.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
READ_POUT
The READ_POUT command is a paged reading of the DC/DC converter output power in Watts. The POUT is calculated
based on the most recent correlated output voltage and current readings.
This command has 2 data bytes and is formatted in Linear_5s_11s format.
MFR_VOUT_PEAK
The MFR_VOUT_PEAK command reports the highest voltage, in volts, reported by the READ_VOUT measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This read-only command has two data bytes and is formatted in Linear_16u format.
4676af
For more information www.linear.com/LTM4676A
119
LTM4676A
Appendix C: PMBus Command Details
MFR_VIN_PEAK
The MFR_VIN_PEAK command reports the highest voltage, in volts, reported by the READ_VIN measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
MFR_TEMPERATURE_1_PEAK
The MFR_TEMPERATURE_1_PEAK command reports the highest temperature, in degrees Celsius, reported by the
READ_TEMPERATURE_1 measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
MFR_TEMPERATURE_2_PEAK
The MFR_TEMPERATURE_2_PEAK command reports the highest temperature, in degrees Celsius, reported by the
READ_TEMPERATURE_2 measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
MFR_IOUT_PEAK
The MFR_IOUT_PEAK command reports the highest current, in amperes, reported by the READ_IOUT measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This read-only command has two data bytes and is formatted in Linear_5s_11s format.
MFR_ADC_CONTROL
The MFR_ADC_CONTROL command determines the ADC read back selection. A default value of 0 in the command runs
the standard telemetry loop with all parameters updated in a round robin fashion with a typical latency of 100ms. The
user can command a non-zero value to monitored a single parameter with an approximate update rate of 8ms. This
command has a latency of up to two ADC conversions or approximately 16ms (power stage temperature conversions
may have a latency of up to three ADC conversion or approximately 24ms). Selecting a value of 0x0D will enable a
short round robin loop. This commanded value runs a short telemetry loop only selecting VOUT0, IOUT0, VOUT1 and
IOUT1 in a round robin manner. The round robin typical latency is 27ms. It is recommended the part remain in standard
telemetry mode except for special cases where fast ADC updates of a single parameter is required. The part should be
commanded to monitor the desired parameter for a limited period of time (say, less than a second) then set the command back to standard round robin mode. If this command is set to any value except standard round robin telemetry
(0) all warnings and faults associated with telemetry other than the selected parameter are effectively disabled and
voltage servoing is disabled. When round robin is reasserted, all warnings and faults and servo mode are re-enabled.
120
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
COMMANDED VALUE
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
0x0D
0x0E-0xFF
TELEMETRY SELECTED
Standard ADC Round Robin Telemetry
SVIN
Reserved
Reserved
Internal IC Temperature
Channel 0 VOUT
Channel 0 IOUT
Reserved
Channel 0 Power Stage-Sensed Temperature
Channel 1 VOUT
Channel 1 IOUT
Reserved
Channel 1 Power Stage or TSNS1a-Sensed Temperature
ADC Short Round Robin
Reserved
If a reserved command value is entered, the part will default to Internal IC Temperature and issue a CML[6] fault.
CML[6] faults will continue to be issued by the LTM4676A until a valid command value is entered.
This read/write command has 1 data byte and is formatted in register format.
MFR_ADC_TELEMETRY_STATUS
The MFR_ADC_TELEMETRY_STATUS command provides the user the means to determine the most recent ADC
conversion when the MFR_ADC_CONTROL short round robin loop is enabled using command 0xD8 value 0x0D. The
bit assignments of this command are as follows:
BIT
7
6
5
4
3
2
1
0
TELEMETRY DATA AVAILABLE
Reserved returns 0
Reserved returns 0
Reserved returns 0
Reserved returns 0
Channel 1 IOUT readback (IOUT1)
Channel 1 VOUT readback (VOUT1)
Channel 0 IOUT readback (IOUT0)
Channel 0 VOUT readback (VOUT0)
Write to MFR_ADC_TELEMETRY_STATUS with data bits set to 1 clear the respective bits.
This read/write command has 1 data byte and is formatted in register format.
NVM (EEPROM) Memory Commands
Store/Restore
COMMAND NAME
STORE_USER_ALL
RESTORE_USER_ALL
CMD
CODE
0x15
0x16
MFR_COMPARE_USER_ALL
0xF0
DESCRIPTION
Store user operating memory to EEPROM.
Restore user operating memory from EEPROM.
Identical to MFR_RESET.
Compares current command contents with NVM.
TYPE
PAGED FORMAT UNITS NVM
Send Byte
N
Send Byte
N
Send Byte
N
DEFAULT
VALUE
NA
NA
NA
4676af
For more information www.linear.com/LTM4676A
121
LTM4676A
Appendix C: PMBus Command Details
STORE_USER_ALL
The STORE_USER_ALL command instructs the PMBus device to copy the non-volatile user contents of the Operating
Memory to the matching locations in the non-volatile User NVM memory (EEPROM).
The 10 year data retention can only be guaranteed when STORE_USER_ALL is executed at 0°C ≤ TJ ≤ 85°C. Executing
this command at junction temperatures above 85°C or below 0°C is not recommended because data retention cannot
be guaranteed for that condition. If the die temperature exceeds 130°C, the STORE_USER_ALL command is disabled.
The command is re-enabled when the IC temperature drops below 125°C.
Communication with the LTM4676A and programming of the EEPROM can be initiated when VDD33 is available and
SVIN is not applied. To enable the part in this state, using global address 0x5B write 0x2B followed by 0xC4. The part
can now be communicated with, and the project file updated. To write the updated project file to the EEPROM issue a
STORE_USER_ALL command. When SVIN is applied, a MFR_RESET or RESTORE_USER_ALL must be issued to allow
the PWM to be enabled and valid ADCs to be read.
This write-only command has no data bytes.
RESTORE_USER_ALL
The RESTORE_USER_ALL command provides an alternate means by which the user can perform a MFR_RESET of
the LTM4676A.
This write-only command has no data bytes.
MFR_COMPARE_USER_ALL
The MFR_COMPARE_USER_ALL command instructs the PMBus device to compare current command contents with
what is stored in non-volatile memory. If the compare operation detects differences, a CML bit 0 fault will be generated.
MFR_COMPARE_USER_ALL commands are disabled if the die exceeds 130°C and are not re-enabled until the die
temperature drops below 125°C.
This write-only command has no data bytes.
Fault Logging
COMMAND NAME
CMD
CODE
MFR_FAULT_LOG
0xEE
Fault log data bytes. This sequentially retrieved data is
used to assemble a complete fault log.
MFR_FAULT_LOG_ STORE
0xEA
Command a transfer of the fault log from RAM to
EEPROM.
MFR_FAULT_LOG_CLEAR
0xEC
DESCRIPTION
TYPE
DATA
PAGED FORMAT UNITS
CF
NVM
DEFAULT
VALUE
Y
NA
R Block
N
Send Byte
N
NA
Initialize the EEPROM block reserved for fault logging. Send Byte
N
NA
MFR_FAULT_LOG
The MFR_FAULT_LOG command allows the user to read the contents of the FAULT_LOG after the first fault occurrence
since the last MFR_FAULT_LOG_CLEAR command was last written. The contents of this command are stored in non-volatile
memory, and are cleared by the MFR_FAULT_LOG_CLEAR command. The length and content of this command are listed
in Table 30. If the user accesses the MFR_FAULT_LOG command and no fault log is present, the command will return a
data length of 0. If a fault log is present, the MFR_FAUTL_LOG will always return a block of data 147 bytes long. If a fault
occurs within the first second of applying power, some of the earlier pages in the fault log may not contain valid data.
122
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
NOTE: The approximate transfer time for this command is 3.4ms using a 400kHz clock.
This read-only command is in block format.
MFR_FAULT_LOG_STORE
The MFR_FAULT_LOG_STORE command forces the fault log operation to be written to EEPROM just as if a fault
event occurred. This command will generate a MFR_SPECIFIC fault if the “Enable Fault Logging” bit is set in the MFR_
CONFIG_ALL command.
If the die temperature exceeds 130°C, the MFR_FAULT_LOG_STORE command is disabled until the IC temperature
drops below 125°C.
Up-Time Counter is in the Fault Log header. The counter is the time since the last module reset (MFR_RESET,
RESTORE_USER_ALL, or SVIN - power cycle) in 200µs increments. This is a 48-bit binary counter.
This write-only command has no data bytes.
Table 30. Fault Logging. This table outlines the format of the block data from a read block data of the MFR_FAULT_LOG command.
Data Format Definitions
DATA
Block Length
LIN 11 = PMBus = Rev 1.2, Part 2, section 7.1
LIN 16 = PMBus Rev 1.2, Part 2, section 8. Mantissa portion only
BYTE = 8 bits interpreted per definition of this command
BITS
DATA
FORMAT
BYTE
BYTE NUM BLOCK READ COMMAND
147
The MFR_FAULT_LOG command is a fixed length of 147 bytes
The block length will be zero if a data log event has not been captured
HEADER INFORMATION
Fault Log Preface
[7:0]
ASC
[7:0]
[15:8]
Reg
[7:0]
Fault Source
MFR_REAL_TIME
[7:0]
Reg
[7:0]
Reg
Refer to Table 31.
5
48 bit share-clock counter value when fault occurred (200µs resolution).
[23:16]
7
[31:24]
8
[39:32]
9
10
L16
[15:8]
[15:8]
[7:0]
11
Peak READ_VOUT on Channel 0 since last power-on or CLEAR_PEAKS
command.
12
L16
[7:0]
MFR_IOUT_PEAK (PAGE 0)
4
6
[7:0]
MFR_VOUT_PEAK (PAGE 1)
2
[15:8]
[15:8]
Returns LTxx beginning at byte 0 if a partial or complete fault log exists.
Word xx is a factory identifier that may vary part to part.
3
[47:40]
MFR_VOUT_PEAK (PAGE 0)
0
1
13
Peak READ_VOUT on Channel 1 since last power-on or CLEAR_PEAKS
command.
14
L11
15
Peak READ_IOUT on Channel 0 since last power-on or CLEAR_PEAKS
command.
16
4676af
For more information www.linear.com/LTM4676A
123
LTM4676A
Appendix C: PMBus Command Details
Table 30. Fault Logging. This table outlines the format of the block data from a read block data of the MFR_FAULT_LOG command.
MFR_IOUT_PEAK (PAGE 1)
[15:8]
MFR_VIN_PEAK
[15:8]
L11
[7:0]
L11
[7:0]
READ_TEMPERATURE1 (PAGE 0)
[15:8]
[15:8]
L11
[15:8]
19
Peak READ_VIN since last power-on or CLEAR_PEAKS command.
21
Channel 0 power stage during last event.
22
L11
[7:0]
READ_TEMPERATURE2
18
Peak READ_IOUT on Channel 1 since last power-on or CLEAR_PEAKS
command.
20
[7:0]
READ_TEMPERATURE1 (PAGE 1)
17
L11
[7:0]
24
Channel 1 power stage or TSNS1a-sensed temperature 1 during last
event.
25
Internal temperature sensor during last event.
23
26
CYCLICAL DATA
EVENT n
Event “n” represents one complete cycle of ADC reads through the MUX
at time of fault. Example: If the fault occurs when the ADC is processing
step 15, it will continue to take readings through step 25 and then store
the header and all 6 event pages to EEPROM
(Data at Which Fault Occurred; Most Recent Data)
READ_VOUT (PAGE 0)
[15:8]
LIN 16
27
[7:0]
LIN 16
28
READ_VOUT (PAGE 1)
[15:8]
LIN 16
29
[7:0]
LIN 16
30
[15:8]
LIN 11
31
[7:0]
LIN 11
32
[15:8]
LIN 11
33
[7:0]
LIN 11
34
READ_VIN
[15:8]
LIN 11
35
[7:0]
LIN 11
36
READ_IIN
[15:8]
LIN 11
37
[7:0]
READ_IOUT (PAGE 0)
READ_IOUT (PAGE 1)
LIN 11
38
STATUS_VOUT (PAGE 0)
BYTE
39
STATUS_VOUT (PAGE 1)
BYTE
40
STATUS_WORD (PAGE 0)
STATUS_WORD (PAGE 1)
[15:8]
WORD
41
[7:0]
WORD
42
[15:8]
WORD
43
[7:0]
WORD
44
STATUS_MFR_SPECIFIC (PAGE 0)
BYTE
45
STATUS_MFR_SPECIFIC (PAGE 1)
BYTE
46
[15:8]
LIN 16
47
[7:0]
LIN 16
48
[15:8]
LIN 16
49
[7:0]
LIN 16
50
[15:8]
LIN 11
51
[7:0]
LIN 11
52
EVENT n-1
(data measured before fault was detected)
READ_VOUT (PAGE 0)
READ_VOUT (PAGE 1)
READ_IOUT (PAGE 0)
124
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Appendix C: PMBus Command Details
Table 30. Fault Logging. This table outlines the format of the block data from a read block data of the MFR_FAULT_LOG command.
READ_IOUT (PAGE 1)
[15:8]
LIN 11
53
[7:0]
LIN 11
54
READ_VIN
[15:8]
LIN 11
55
[7:0]
LIN 11
56
[15:8]
LIN 11
57
[7:0]
LIN 11
58
STATUS_VOUT (PAGE 0)
BYTE
59
STATUS_VOUT (PAGE 1)
BYTE
60
WORD
61
READ_IIN
STATUS_WORD (PAGE 0)
[15:8]
[7:0]
WORD
62
STATUS_WORD (PAGE 1)
[15:8]
WORD
63
[7:0]
WORD
64
STATUS_MFR_SPECIFIC (PAGE 0)
BYTE
65
STATUS_MFR_SPECIFIC (PAGE 1)
BYTE
66
[15:8]
LIN 16
127
[7:0]
LIN 16
128
READ_VOUT (PAGE 1)
[15:8]
LIN 16
129
[7:0]
LIN 16
130
READ_IOUT (PAGE 0)
[15:8]
LIN 11
131
[7:0]
LIN 11
132
READ_IOUT (PAGE 1)
[15:8]
LIN 11
133
[7:0]
LIN 11
134
[15:8]
LIN 11
135
[7:0]
LIN 11
136
[15:8]
LIN 11
137
[7:0]
LIN 11
138
BYTE
139
*
*
*
EVENT n-5
(Oldest Recorded Data)
READ_VOUT (PAGE 0)
READ_VIN
READ_IIN
STATUS_VOUT (PAGE 0)
STATUS_VOUT (PAGE 1)
BYTE
140
STATUS_WORD (PAGE 0)
[15:8]
WORD
141
[7:0]
WORD
142
STATUS_WORD (PAGE 1)
[15:8]
WORD
143
[7:0]
WORD
144
STATUS_MFR_SPECIFIC (PAGE 0)
BYTE
145
STATUS_MFR_SPECIFIC (PAGE 1)
BYTE
146
4676af
For more information www.linear.com/LTM4676A
125
LTM4676A
Appendix C: PMBus Command Details
Table 31. Explanation of Position_Fault Values
POSITION_FAULT VALUE
SOURCE OF FAULT LOG
0xFF
MFR_FAULT_LOG_STORE
0x00
TON_MAX_FAULT Channel 0
0x01
VOUT_OV_FAULT Channel 0
0x02
VOUT_UV_FAULT Channel 0
0x03
IOUT_OC_FAULT Channel 0
0x05
OT_FAULT Channel 0
0x06
UT_FAULT Channel 0
0x07
VIN_OV_FAULT Channel 0
0x0A
MFR_OT_FAULT Channel 0
0x10
TON_MAX_FAULT Channel 1
0x11
VOUT_OV_FAULT Channel 1
0x12
VOUT_UV_FAULT Channel 1
0x13
IOUT_OC_FAULT Channel 1
0x15
OT_FAULT Channel 1
0x16
UT_FAULT Channel 1
0x17
VIN_OV_FAULT Channel 1
0x1A
MFR_OT_FAULT Channel 1
MFR_FAULT_LOG_CLEAR
The MFR_FAULT_LOG_CLEAR command will erase the fault log file stored values. It will also clear bit 3 in the
STATUS_MFR_SPECIFIC command. After a clear is issued, the status can take up to 8ms to clear.
This write-only command is send bytes.
Block Memory Write/Read
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
DATA
DEFAULT
PAGED FORMAT UNITS NVM VALUE
MFR_EE_UNLOCK
0xBD
Unlock user EEPROM for access by MFR_EE_ERASE and
MFR_EE_DATA commands.
R/W Byte
N
Reg
NA
MFR_EE_ERASE
0xBE
Initialize user EEPROM for bulk programming by MFR_EE_ R/W Byte
DATA.
N
Reg
NA
MFR_EE_DATA
0xBF
Data transferred to and from EEPROM using sequential
PMBus word reads or writes. Supports bulk programming.
N
Reg
NA
R/W
Word
All the (EEPROM) commands are disabled if the die temperature exceeds 130°C. (EEPROM) commands are re-enabled
when the die temperature drops below 125°C.
MFR_EE_xxxx
MFR_EE_XXXX commands are used to facilitate bulk programming of the internal EEPROM. Contact the factory for
more details.
126
4676af
For more information www.linear.com/LTM4676A
LTM4676A
Package Description
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
Table 32. LTM4676A BGA Pinout
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
ISNS0b–
ISNS0a–
F1
ISNS0b+
F2
ISNS0a+
A1
VOUT0
B1
VOUT0
C1
VOUT0
D1
VOUT0
E1
A2
VOUT0
B2
VOUT0
C2
VOUT0
D2
VOUT0
E2
A3
VOUT0
B3
VOUT0
C3
VOUT0
D3
VOUT0
E3
GND
F3
GND
A4
GND
B4
GND
C4
GND
D4
GND
E4
GPIO0
F4
GPIO1
A5
SNUB0
B5
GND
C5
TSNS0b
D5
TSNS0a
E5
ALERT
F5
RUN0
A6
GND
B6
GND
C6
GND
D6
SDA
E6
SCL
F6
RUN1
A7
GND
B7
GND
C7
GND
D7
GND
E7
SYNC
F7
SGND
A8
GND
B8
GND
C8
GND
D8
COMP0b
E8
COMP0a
F8
SGND
+
–
A9
GND
B9
GND
C9
GND
D9
VOSNS0
E9
VOSNS0
F9
INTVCC
A10
GND
B10
SW0
C10
DNC
D10
VORB0+
E10
VORB0–
F10
GND
A11
VIN0
B11
VIN0
C11
VIN0
D11
VIN0
E11
DNC
F11
SVIN
A12
VIN0
B12
VIN0
C12
VIN0
D12
VIN0
E12
VIN0
F12
SVIN
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
PIN ID
FUNCTION
G1
ISNS1b–
H1
ISNS1b+
J1
VOUT1
K1
VOUT1
L1
VOUT1
M1
VOUT1
G2
ISNS1a
–
H2
ISNS1a
+
J2
VOUT1
K2
VOUT1
L2
VOUT1
M2
VOUT1
G3
GND
H3
GND
J3
VOUT1
K3
VOUT1
L3
VOUT1
M3
VOUT1
G4
ASEL
H4
FSWPHCFG
J4
GND
K4
GND
L4
GND
M4
GND
G5
VOUT0CFG
H5
VTRIM0CFG
J5
TSNS1a
K5
TSNS1b
L5
GND
M5
SNUB1
G6
VOUT1CFG
H6
VTRIM1CFG
J6
VDD25
K6
WP
L6
GND
M6
GND
G7
SGND
H7
SHARE_CLK
J7
VDD33
K7
GND
L7
GND
M7
GND
G8
SGND
H8
COMP1a
J8
COMP1b
K8
GND
L8
GND
M8
GND
G9
INTVCC
H9
VOSNS1
J9
VORB1
K9
GND
L9
GND
M9
GND
G10
GND
H10
GND
J10
GND
K10
DNC
L10
SW1
M10
GND
G11
GND
H11
DNC
J11
VIN1
K11
VIN1
L11
VIN1
M11
VIN1
G12
GND
H12
VIN1
J12
VIN1
K12
VIN1
L12
VIN1
M12
VIN1
4676af
For more information www.linear.com/LTM4676A
127
LTM4676A
Package Description
TOP VIEW
1
2
3
4
5
6
7
8
9
10
11
12
SNUB0
A
VOUT0
GND
GND
SW0
GND
DNC
VIN0
B
GND
TSNS0b
C
VOUT0
TSNS0a
SDA
GND
+
COMP0b VOSNS0
VORB0+
SYNC
–
COMP0a VOSNS0
VORB0–
VIN0
D
ISNS0b–
ISNS0a–
GPIO0
ALERT
SCL
ISNS0b+
ISNS0a+
GPIO1
RUN0
RUN1
ISNS1b–
ISNS1a–
ISNS1b+
ISNS1a+
DNC
E
SVIN
SVIN
F
GND
ASEL
SGND
VOUT0CFG VOUT1CFG
INTVCC
G
FSWPHCFG VTRIM0CFG VTRIM1CFG SHARE_CLK COMP1a
VOSNS1
GND
DNC
H
TSNS1a
VDD25
TSNS1b
WP
VDD33
COMP1b
VORB1
J
VOUT1
DNC
VIN1
K
GND
GND
SW1
L
VOUT1
SNUB1
GND
GND
VIN1
M
Package Photograph
128
4676af
For more information www.linear.com/LTM4676A
aaa Z
0.630 ±0.025 Ø 144x
3.1750
3.1750
SUGGESTED PCB LAYOUT
TOP VIEW
1.9050
PACKAGE TOP VIEW
E
0.6350
0.0000
0.6350
4
1.9050
PIN “A1”
CORNER
6.9850
5.7150
4.4450
4.4450
5.7150
6.9850
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of itsinformation
circuits as described
herein will not infringe on existing patent rights.
For more
www.linear.com/LTM4676A
6.9850
5.7150
4.4450
3.1750
1.9050
0.6350
0.0000
0.6350
1.9050
3.1750
4.4450
5.7150
6.9850
Y
X
D
// bbb Z
DETAIL B
H2
MOLD
CAP
ccc Z
SYMBOL
A
A1
A2
b
b1
D
E
e
F
G
H1
H2
aaa
bbb
ccc
ddd
eee
H1
SUBSTRATE
A1
NOM
5.01
0.60
4.41
0.75
0.63
16.00
16.00
1.27
13.97
13.97
0.41
4.00
A
MAX
5.21
0.70
4.51
0.90
0.66
Z
NOTES
DETAIL B
PACKAGE SIDE VIEW
A2
0.46
4.05
0.15
0.10
0.20
0.30
0.15
TOTAL NUMBER OF BALLS: 144
0.36
3.95
MIN
4.81
0.50
4.31
0.60
0.60
b1
DIMENSIONS
ddd M Z X Y
eee M Z
DETAIL A
Øb (144 PLACES)
aaa Z
Z
(Reference LTC DWG # 05-08-1920 Rev B)
BGA Package
144-Lead (16mm × 16mm × 5.01mm)
e
11
b
10
9
7
G
6
5
e
PACKAGE BOTTOM VIEW
8
4
3
2
1
DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
BALL DESIGNATION PER JESD MS-028 AND JEP95
7
TRAY PIN 1
BEVEL
!
PACKAGE IN TRAY LOADING ORIENTATION
LTMXXXXXX
µModule
M
L
K
J
H
G
F
E
D
C
B
A
3
SEE NOTES
PIN 1
7
SEE NOTES
BGA 144 0213 REV B
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY
6. SOLDER BALL COMPOSITION IS 96.5% Sn/3.0% Ag/0.5% Cu
5. PRIMARY DATUM -Z- IS SEATING PLANE
4
3
2. ALL DIMENSIONS ARE IN MILLIMETERS
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
COMPONENT
PIN “A1”
F
b
12
DETAIL A
LTM4676A
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
4676af
129
LTM4676A
Typical Application
CINH
22µF
×3
VIN0
VIN1
SVIN
VOUT0
TSNS0a
TSNS0b
ISNS0a+
ISNS0b+
ISNS0a–
ISNS0b–
VORB0+
VOSNS0+
VOSNS0–
–
V
VDD33
10k
×9
SCL
SDA
ALERT
RUN0
RUN1
GPIO0
GPIO1
SYNC
SHARE_CLK
WP
SMBus INTERFACE WITH
PMBus COMMAND SET
ON/OFF CONTROL, FAULT
MANAGEMENT, POWER
SEQUENCING
PWM CLOCK SYNCH.
TIME BASE SYNCH.
• SLAVE ADDRESS = 1001111_R/W (0X4F)
• SWITCHING FREQUENCY: 350kHz
• NO GUI CONFIGURATION AND
NO PART SPECIFIC PROGRAMMING REQUIRED
IN MULTI-MODULE SYSTEMS, CONFIGURING
RAIL_ADDRESS IS RECOMMENDED
LTM4676A
22.6k
1%
±50ppm/°C
COUT0
100µF
×7
VOUT0, 1.0V
ADJUSTABLE
UP TO 13A
LOAD0
ORB0
VORB1
VOUT1
TSNS1a
TSNS1b
ISNS1a+
ISNS1b+
ISNS1a–
ISNS1b–
VOSNS1
SGND
GND
CINL
220µF
INTVCC
VDD25
SW0
SW1
SNUB0
SNUB1
+
COMP0a
COMP0b
COMP1a
COMP1b
ASEL
FSWPHCFG
VOUT0CFG
VTRIM0CFG
VOUT1CFG
VTRIM1CFG
VIN
5.75V TO 17V
COUT1
100µF
×7
VOUT1, 1.8V
ADJUSTABLE
UP TO 13A
LOAD1
4676A F62
6.34k
1%
±50ppm/°C
Figure 62. 13A, 1V and 13A, 1.8V Output DC/DC µModule Regulator with Serial Interface
Design Resources
SUBJECT
µModule Design and Manufacturing Resources
µModule Regulator Products Search
DESCRIPTION
Design:
Manufacturing:
• Selector Guides
• Quick Start Guide
• Demo Boards and Gerber Files
• PCB Design, Assembly and Manufacturing Guidelines
• Free Simulation Tools
• Package and Board Level Reliability
1. Sort table of products by parameters and download the result as a spread sheet.
2. Search using the Quick Power Search parametric table.
Quick videos detailing how to bench test electrical and thermal performance of µModule products.
TechClip Videos
Digital Power System Management
Linear Technology’s family of digital power supply management ICs are highly integrated solutions that
offer essential functions, including power supply monitoring, supervision, margining and sequencing,
and feature EEPROM for storing user configurations and fault logging.
Related Parts
PART NUMBER
LTM4620A
LTM4630
LTM4641
DESCRIPTION
Dual 13A or Single 26A Step-Down µModule Regulator
Dual 18A or Single 36A Step-Down µModule Regulator
10A µModule Regulator with Advanced Input and Load
Protection
LTC3880/LTC3883 Dual and Single Output DC/DC Controllers with Power
System Management
LTC2977/LTC2974 8- and 4-Channel PMBus Power System Managers
COMMENTS
4.5V ≤ VIN ≤ 16V, 0.6V ≤ VOUT ≤ 5.3V, 15mm × 15mm × 4.41mm LGA
4.5V ≤ VIN ≤ 15V, 0.6V ≤ VOUT ≤ 1.8V, 16mm × 16mm × 4.41mm LGA
4.5V ≤ VIN ≤ 38V, 0.6V ≤ VOUT ≤ 6V, 15mm × 15mm × 5.01mm BGA
Licensed under U.S. Patent 7000125 and other related patents worldwide.
TUE is total unadjusted error.
130
0.5% TUE 16-Bit ADC, Voltage/Current/Temperature Monitoring and
Supervision
0.25% TUE 16-Bit ADC, Voltage/Temperature Monitoring and Supervision
4676af
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA
For 95035-7417
more information www.linear.com/LTM4676A
●
●
(408) 432-1900 FAX: (408) 434-0507
www.linear.com/LTM4676A
LT 0515 • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2015