LTC3884/LTC3884-1
Dual Output PolyPhase
Step-Down Controller with Sub-Milliohm DCR Sensing
and Digital Power System Management
FEATURES
DESCRIPTION
PMBus/I2C Compliant Serial Interface
– Telemetry Read-Back Includes VIN, IIN, VOUT, IOUT,
Temperature and Faults
– Programmable Voltage, Current Limit, Digital SoftStart/Stop, Sequencing, Margining, OV/UV/OC
n Sub-Milliohm DCR Current Sensing
n Digitally Adjustable Loop Compensation Parameters
n ±0.5% Output Voltage Accuracy Over Temperature
n Integrated Input Current Sense Amplifier
n Internal EEPROM with ECC and Fault Logging
n Integrated N-Channel MOSFET Gate Drivers (LTC3884)
Power Conversion
n Wide V Range: 4.5V to 38V
IN
n V
OUT Range: 0.5V to 3.5V (with Low DCR Setting);
0.5V to 5.5V (without Low DCR Setting)
n Accurate PolyPhase® Current Sharing for Up to 6 Phases
n Available in 48-Lead 7mm × 7mm QFN and
5mm × 6mm GQFN Packages.
n
APPLICATIONS
n
n
The LTC®3884/LTC3884-1 are dual output PolyPhase DC/
DC synchronous step-down switching regulator controllers
with an I2C-based PMBus compliant serial interface. The
controllers employ a constant-frequency current mode
architecture, together with a unique scheme to provide
excellent performance for sub-milliohm DCR applications. The LTC3884/LTC3884-1 are supported by the
LTpowerPlay® software development tool with graphical
user interface (GUI).
Programmable loop compensation allows the controller
to be compensated digitally. Switching frequency, channel
phasing, output voltage, and device address can be programmed both by the digital interface as well as external
configuration resistors. Additionally, parameters can be set
via the digital interface or stored in EEPROM. Both outputs
have independent power good indicators and FAULT function.
The LTC3884 has integrated gate drivers. The LTC3884-1
has three-state PWM pins to drive power blocks or DrMOS
power stages.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6580258, 5408150,
7420359, 8648623, 8786265, 8823352, 7000125. Licensed under U.S. Patent 7000125 and
other related patents worldwide.
Telecom, Datacom, and Storage Systems
Industrial and Point-of-Load Applications
TYPICAL APPLICATION
2mΩ
4.7µF
INTVCC
0.1µF
BOOST1
931Ω
0.22µF
VOUT0
1.8V
30A
4700pF
220pF
LTC3884*
FAULT MANAGEMENT
TO/FROM
OTHER LTC DEVICES
931Ω
ISENSE1+
1µF
VOUT1
1V
30A
2200pF
1µF
10nF
VIN = 12V
VOUT = 1.8V
EXTVCC=0
fSW=350kHz
80
70
4
3
2
60
1
50
0.22µF
ISENSE0–
ISENSE1–
VSENSE1+
VSENSE0+
–
VSENSE0
VSENSE1–
TSNS0
TSNS1
ITH0
ITH1
ITHR0
ITHR1
VDD33 PGND SGND VDD25
5
90
L= 0.33µH
BG1
6
100
DCR = 0.32mΩ
FAULT0
FAULT1
PGOOD0
PGOOD1
SHARE_CLK
ISENSE0+
270µF
×2
330µF
×2
40
POWER LOSS (W)
SDA
SCL
ALERT
RUN0
RUN1
EXTVCC
Efficiency and Power Loss
vs Load Current
VIN
6V TO 15V
0.1µF
SW1
BG0
PMBus
INTERFACE
IIN–
TG1
SW0
L = 0.33µH
10nF
IIN+
BOOST0
DCR = 0.32mΩ
330µF
×2
VIN
TG0
10µF
×2
1Ω
EFFICIENCY (%)
10µF
×2
1µF
EFFICIENCY
POWER LOSS
0
5
10
15
20
LOAD CURRENT (A)
25
30
0
3884 TA01b
220pF
*SOME DETAILS OMITTED FOR CLARITY
3884 TA01a
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1
LTC3884/LTC3884-1
TABLE OF CONTENTS
Features...................................................... 1
Applications................................................. 1
Typical Application ......................................... 1
Description.................................................. 1
Table of Contents........................................... 2
Absolute Maximum Ratings............................... 4
Pin Configuration........................................... 4
Order Information........................................... 5
Electrical Characteristics.................................. 6
Typical Performance Characteristics................... 12
Pin Functions............................................... 17
Block Diagram.............................................. 19
Operation................................................... 20
Overview..................................................................20
Main Control Loop................................................... 21
EEPROM.................................................................. 21
Power-Up and Initialization......................................22
Soft-Start.................................................................23
Time-Based Sequencing..........................................23
Voltage-Based Sequencing......................................23
Shutdown................................................................ 24
Light-Load Current Operation.................................. 24
Switching Frequency and Phase..............................25
PWM Loop Compensation.......................................25
Output Voltage Sensing...........................................25
INTVCC/EXTVCC Power............................................25
Output Current Sensing and Sub Milliohm DCR
Current Sensing.......................................................26
Input Current Sensing.............................................. 27
PolyPhase Load Sharing.......................................... 27
External/Internal Temperature Sense....................... 27
RCONFIG (Resistor Configuration) Pins................... 28
Fault Detection and Handling...................................29
Status Registers and ALERT Masking..................29
Mapping Faults to FAULT Pins............................. 31
Power Good Pins................................................. 31
CRC Protection and ECC...................................... 31
Serial Interface........................................................ 32
Communication Protection.................................. 32
2
Device Addressing................................................... 32
Responses to VOUT, IIN and IOUT Faults.................... 32
Output Overvoltage Fault Response....................33
Output Undervoltage Response...........................33
Peak Output Overcurrent Fault Response............33
Responses to Timing Faults.....................................33
Responses to VIN OV Faults.....................................34
Responses to OT/UT Faults......................................34
Internal Overtemperature Fault Response...........34
External Overtemperature and
Undertemperature Fault Response......................34
Responses to Input Overcurrent and Output
Undercurrent Faults.................................................34
Responses to External Faults...................................34
Fault Logging...........................................................34
Bus Timeout Protection...........................................35
Similarity Between PMBus, SMBus and
I2C 2-Wire Interface.................................................35
PMBus Serial Digital Interface.................................35
PMBus Command Summary............................. 40
PMBus Commands..................................................40
*Data Format...........................................................45
Applications Information................................. 46
Current Limit Programming.....................................46
ISENSE0± and ISENSE1± Pins.......................................46
Inductor DCR Sensing......................................... 47
Inductor Value Calculation.......................................48
Inductor Core Selection...........................................48
Low Value Resistor Current Sensing........................48
Slope Compensation and Inductor Peak Current..... 49
Power MOSFET and Optional Schottky Diode
Selection..................................................................50
Variable Delay Time, Soft-Start and Output
Voltage Ramping.....................................................50
Digital Servo Mode.................................................. 51
Soft Off (Sequenced Off)......................................... 52
INTVCC/EXTVCC Power............................................ 52
Topside MOSFET Driver Supply (CB, DB).................53
Undervoltage Lockout..............................................54
CIN and COUT Selection............................................54
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LTC3884/LTC3884-1
TABLE OF CONTENTS
Fault Indication........................................................55
Open-Drain Pins......................................................55
Phase-Locked Loop and Frequency
Synchronization ......................................................56
Minimum On-Time Considerations..........................56
External Temperature Sense.................................... 57
Input Current Sense Amplifier..................................58
External Resistor Configuration Pins (RCONFIG).....58
Voltage Selection................................................. 59
Frequency Selection............................................ 59
Phase Selection...................................................60
Address Selection Using RCONFIG......................60
Efficiency Considerations........................................ 61
Programmable Loop Compensation........................62
Checking Transient Response..................................63
PolyPhase Configuration.....................................64
Master Slave Operation.......................................64
PC Board Layout Checklist...................................... 67
PC Board Layout Debugging.................................... 67
Design Example.......................................................68
Additional Design Checks........................................69
Connecting the USB to I2C/SMBus/PMBus
Controller to the LTC3884 in System.......................69
LTpowerPlay: An Interactive GUI for
Digital Power........................................................... 70
PMBus Communication and Command
Processing............................................................... 70
PMBus Command Details................................ 73
Addressing and Write Protect..................................73
General Configuration Commands........................... 75
On/Off/Margin......................................................... 76
PWM Configuration................................................. 78
Voltage..................................................................... 81
Input Voltage and Limits...................................... 81
Output Voltage and Limits................................... 82
Output Current and Limits.......................................85
Input Current and Limits ..................................... 87
Temperature.............................................................88
External Temperature Calibration........................88
Timing.....................................................................89
Timing—On Sequence/Ramp..............................89
Timing—Off Sequence/Ramp.............................90
Precondition for Restart...................................... 91
Fault Response........................................................ 91
Fault Responses All Faults................................... 91
Fault Responses Input Voltage............................92
Fault Responses Output Voltage..........................92
Fault Responses Output Current..........................95
Fault Responses IC Temperature.........................96
Fault Responses External Temperature................ 97
Fault Sharing............................................................98
Fault Sharing Propagation...................................98
Fault Sharing Response..................................... 100
Scratchpad............................................................ 100
Identification.......................................................... 101
Fault Warning and Status....................................... 102
Telemetry............................................................... 109
NVM Memory Commands..................................... 113
Store/Restore.................................................... 113
Fault Log Operation........................................... 114
Fault Logging..................................................... 114
Block Memory Write/Read................................ 118
Typical Applications..................................... 119
Package Description.................................... 125
Revision History......................................... 127
Typical Application...................................... 128
Related Parts............................................. 128
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LTC3884/LTC3884-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, IIN+, IIN –............................................... –0.3V to 40V
(VIN – IIN+), (IIN+ – IIN –).............................. –0.3V to 0.3V
BOOST0, BOOST1 (LTC3884)..................... –0.3V to 46V
Switch Transient Voltage (SW0, SW1)
(LTC3884).................................................. –5V to 40V
(BOOST0-SW0), (BOOST1-SW1)
(LTC3884)................................................. –0.3V to 6V
Top Gate Transient Voltage TG0, TG1
(LTC3884).................................................–5V TO 46V
VCC0, VCC1 (LTC3884-1)................................ –0.3V to 6V
Top Gate Transient Voltage PWM0, PWM1
(LTC3884-1).............................................. –0.3V to 6V
ISENSE0+, ISENSE0 –, ISENSE1+, ISENSE1–,
VSENSE0+, VSENSE1+....................................... –0.3V to 6V
VSENSE0 –, VSENSE1–.................................... –0.3V to 0.3V
EXTVCC, INTVCC........................................... –0.3V to 6V
(EXTVCC – VIN).........................................................5.5V
PGOOD0, PGOOD1..................................... –0.3V to 3.6V
RUN0, RUN1, SDA, SCL, ALERT................. –0.3V to 5.5V
ASEL0, ASEL1, VOUT0_CFG0, VOUT1_CFG,
FREQ_CFG, PHASE_CFG..................... –0.3V to 2.75V
FAULT0, FAULT1, SHARE_CLK, WP, SYNC. –0.3V to 3.6V
TSNS0, TSNS1........................................... –0.3V to 3.6V
ITH0, ITH1, ITHR0, ITHR1............................... –0.3V to 3.6V
Operating Junction Temperature Range
(Notes 2, 17, 18)........................................–40°C to 125°C
Storage Temperature Range................. –65°C to 150°C*
*See Derating EEPROM Retention at Temperature in Applications Information section for junction temperatures in excess of 125°C.
PIN CONFIGURATION
LTC3884
LTC3884
TOP VIEW
UK PACKAGE
48-LEAD (7mm × 7mm) PLASTIC QFN
49
49
49
SGND
49
49
38 BG1
37 BOOST1
36 TG1
35 SW1
34 PGOOD1
33 VSENSE1+
32 VSENSE1–
31 ITHR1
30 ITH1
29 VDD33
28 SHARE_CLK
27 WP
26 VDD25
25 PHASE_CFG
RHE PACKAGE
48-LEAD (5mm × 6mm) PLASTIC GQFN
TJMAX = 125°C, θJA = 31°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 49) IS SGND, MUST BE SOLDERED TO PCB
4
PGOOD0 1
VSENSE0+ 2
VSENSE0– 3
ISENSE1+ 4
ISENSE1– 5
ITHR0 6
ITH0 7
ISENSE0+ 8
ISENSE0– 9
TSNS1 10
TSNS0 11
SYNC 12
SCL 13
SDA 14
ALERT 15
FAULT0 16
FAULT1 17
RUN0 18
RUN1 19
ASEL0 20
ASEL1 21
VOUT0_CFG 22
VOUT1_CFG 23
FREQ_CFG 24
49
SGND
36 BOOST1
35 TG1
34 SW1
33 PGOOD1
32 VSENSE1+
31 VSENSE1–
30 ITHR1
29 ITH1
28 VDD33
27 SHARE_CLK
26 WP
25 VDD25
SDA 13
ALERT 14
FAULT0 15
FAULT1 16
RUN0 17
RUN1 18
ASEL0 19
ASEL1 20
VOUT0_CFG 21
VOUT1_CFG 22
FREQ_CFG 23
PHASE_CFG 24
VSENSE0+ 1
VSENSE0– 2
ISENSE1+ 3
ISENSE1– 4
ITHR0 5
ITH0 6
ISENSE0+ 7
ISENSE0– 8
TSNS1 9
TSNS0 10
SYNC 11
SCL 12
48 IIN–
47 IIN+
46 SW0
45 TG0
44 BOOST0
43 BG0
42 PGND
41 EXTVCC
40 VIN
39 INTVCC
48 PGOOD0
47 IIN–
46 IIN+
45 SW0
44 TG0
43 BOOST0
42 BG0
41 PGND
40 EXTVCC
39 VIN
38 INTVCC
37 BG1
TOP VIEW
TJMAX = 125°C, θJA = 31°C/W, θJC = 3.7°C/W
EXPOSED PADS (PIN 49) ARE SGND, MUST BE SOLDERED TO PCB
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LTC3884/LTC3884-1
PIN CONFIGURATION
LTC3884-1
48 IIN–
47 IIN+
46 NC
45 PWM0
44 VCC0
43 NC
42 PGND
41 EXTVCC
40 VIN
39 INTVCC
TOP VIEW
49
49
49
SGND
49
49
38 NC
37 VCC1
36 PWM1
35 NC
34 PGOOD1
33 VSENSE1+
32 VSENSE1–
31 ITHR1
30 ITH1
29 VDD33
28 SHARE_CLK
27 WP
26 VDD25
25 PHASE_CFG
ALERT 15
FAULT0 16
FAULT1 17
RUN0 18
RUN1 19
ASEL0 20
ASEL1 21
VOUT0_CFG 22
VOUT1_CFG 23
FREQ_CFG 24
PGOOD0 1
VSENSE0+ 2
VSENSE0– 3
ISENSE1+ 4
ISENSE1– 5
ITHR0 6
ITH0 7
ISENSE0+ 8
ISENSE0– 9
TSNS1 10
TSNS0 11
SYNC 12
SCL 13
SDA 14
RHE PACKAGE
48-LEAD (5mm × 6mm) PLASTIC GQFN
TJMAX = 125°C, θJA = 31°C/W, θJC = 3.7°C/W
EXPOSED PADS (PIN 49) ARE SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
(http://www.linear.com/product/LTC3884#orderinfo)
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3884EUK#PBF
LTC3884EUK#TRPBF
LTC3884 UK
48-Lead (7mm × 7mm) Plastic QFN
–40°C to 125°C
LTC3884IUK#PBF
LTC3884IUK#TRPBF
LTC3884 UK
48-Lead (7mm × 7mm) Plastic QFN
–40°C to 125°C
LTC3884ERHE#PBF
LTC3884ERHE#TRPBF
LTC3884
48-Lead (5mm × 6mm) Plastic GQFN
–40°C to 125°C
LTC3884IRHE#PBF
LTC3884IRHE#TRPBF
LTC3884
48-Lead (5mm × 6mm) Plastic GQFN
–40°C to 125°C
LTC3884ERHE-1#PBF
LTC3884ERHE-1#TRPBF LTC3884-1
48-Lead (5mm × 6mm) Plastic GQFN
–40°C to 125°C
LTC3884IRHE-1#PBF
LTC3884IRHE-1#TRPBF LTC3884-1
48-Lead (5mm × 6mm) Plastic GQFN
–40°C to 125°C
Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
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5
LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Notes 2, 3). VIN = 12V, EXTVCC = 0V, VRUN0,1 = 3.3V,
fSYNC = 500kHz (externally driven) and all programmable parameters at factory default, unless otherwise specified.
SYMBOL
PARAMETER
CONDITION
VIN
Input Voltage Range
(Note 11)
IQ
Input Voltage Supply Current
VRUN0,1 = 3.3V (Note 16)
VRUN0,1 = 0V (Note 16)
VUVLO
Undervoltage Lockout Threshold
When VIN > 4.3V
VINTVCC Falling
VINTVCC Rising
tINIT
Initialization Time
Time from VIN Applied Until the TON_DELAY
Timer Starts
tOFF(MIN)
Short Cycle Retry Time
MIN
TYP
MAX
UNITS
Input Voltage
l
4.5
38
25
23
V
mA
mA
3.55
3.90
V
V
35
ms
120
ms
Control Loop
Full-Scale Voltage Range
Set Point Accuracy (0.6V ~ 2.5V)
Resolution
LSB Step Size
VOUT_COMMAND = 2.75V,
MFR_PWM_MODE[1] = 1
(Notes 9, 10, 13)
l
l
Full-Scale Voltage Range
Set Point Accuracy (0.6V ~ 5.0V)
Resolution
LSB Step Size
VOUT_COMMAND = 5.5V,
MFR_PWM_MODE[1] = 0
(Notes 9, 10, 13)
l
l
VLINEREG
Line Regulation
6V < VIN < 38V
l
VLOADREG
Load Regulation
∆VITH = 1.35V ~ 0.7V
∆VITH = 1.35V ~ 2V
l
l
IISENSE0,1
Input Pin Bias Current
0V ≤ VPIN ≤ 5.5V
l
VSENSERIN0,1
VSENSE Input Resistance to GND
0V ≤ VPIN ≤ 5.5V
VILIMIT
(Note 15)
VOUTRL
VOUTRH
2.7
–0.5
5.40
–0.5
2.8
0.5
V
%
Bits
mV
5.60
0.5
V
%
Bits
mV
±0.02
%/V
0.01
–0.01
0.1
–0.1
%
%
±1
±3
12
0.688
12
1.375
µA
50
kΩ
12
Steps
VILIM_HIGH
VILIM_LOW
VREV
MFR_PWM_MODE[7],[2]=0, 1, ILIM[3:0]=1100, VOUT ≤ 3.5V
MFR_PWM_MODE[7],[2]=0, 1, ILIM[3:0]=0001, VOUT ≤ 3.5V
MFR_PWM_MODE[7],[2]=0, 1, VOUT ≥ VOV
l
14.5
16.5
9.5
–7.5
18.5
mV
mV
mV
VILIM_HIGH
VILIM_LOW
VREV
MFR_PWM_MODE[7],[2]=1, 1, ILIM[3:0]=1100,VOUT ≤ 3.5V
MFR_PWM_MODE[7],[2]=1, 1, ILIM[3:0]=0001,VOUT ≤ 3.5V
MFR_PWM_MODE[7],[2]=1, 1, VOUT ≥ VOV
l
27.0
29.5
17.0
–15
31.0
mV
mV
mV
VILIM_HIGH
VILIM_LOW
VREV
MFR_PWM_MODE[7],[2]=0, 0, ILIM[3:0]=1100
MFR_PWM_MODE[7],[2]=0, 0, ILIM[3:0]=0001
MFR_PWM_MODE[7],[2]=0, 0, VOUT ≥ VOV
l
35
41.38
25
–18.8
49
mV
mV
mV
VILIM_HIGH
VILIM_LOW
VREV
MFR_PWM_MODE[7],[2]=1, 0, ILIM[3:0]=1100
MFR_PWM_MODE[7],[2]=1, 0, ILIM[3:0]=0001
MFR_PWM_MODE[7],[2]=1, 0, VOUT ≥ VOV
l
67.5
74.5
43.5
–37.5
81.5
mV
mV
mV
gm0,1
Resolution
Error Amplifier gm(MAX)
Error Amplifier gm(MIN)
LSB Step Size
ITH0,1 = 1.35V, MFR_PWM_COMP[7:5] = 0 to 7
RTH0, 1
Resolution
Compensation Resistor RTH(MAX)
Compensation Resistor RTH(MIN)
MFR_PWM_COMP[4:0] = 0 to 31 (See Figure 37)
5
62
0
Bits
kΩ
kΩ
3
5.76
1
0.68
Bits
mmho
mmho
mmho
Gate Drivers (LTC3884)
TG RUP
TG Pull-Up RDS(ON)
TG High
2.6
Ω
TG RDOWN
TG Pull-Down RDS(ON)
TG Low
1.5
Ω
BG RUP
BG Pull-Up RDS(ON)
BG High
2.4
Ω
6
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LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Notes 2, 3). VIN = 12V, EXTVCC = 0V, VRUN0,1 = 3.3V,
fSYNC = 500kHz (externally driven) and all programmable parameters at factory default, unless otherwise specified.
SYMBOL
PARAMETER
CONDITION
BG RDOWN
BG Pull-Down RDS(ON)
BG Low
MIN
TYP
1.1
MAX
UNITS
Ω
TG
tr
tf
TG Transition Time:
Rise Time
Fall Time
(Note 4)
CLOAD = 3300pF
CLOAD = 3300pF
30
30
ns
ns
BG
tr
tf
BG Transition Time:
Rise Time
Fall Time
(Note 4)
CLOAD = 3300pF
CLOAD = 3300pF
30
30
ns
ns
TG/BG, t1D
Top Gate Off to Bottom Gate on
Delay Time
(Note 4) CLOAD = 3300pF at Each Driver
30
ns
BG/TG t2D
Bottom Gate Off to Top Gate on
Delay Time
(Note 4) CLOAD = 3300pF at Each Driver
30
ns
tON(MIN)
Minimum On-Time
60
ns
PWM0/PWM1 Outputs (LTC3884-1)
PWM
PWM Output High Voltage
PWM Output Low Voltage
PWM Output in Hi-Z State
ILOAD = 500µA
ILOAD = –500µA
VCC – 0.2
0.2
5
–5
V
V
µA
OV/UV Output Voltage Supervisor Channel 0/1
9
Bits
VOUSTPSP_RL LSB Step Size
MFR_PWM_MODE[1] = 1 (Note 13)
5.6
mV
VOUSTPSP_RH LSB Step Size
MFR_PWM_MODE[1] = 0 (Note 13)
11.2
mV
N
Resolution
VRANGE_RL
Voltage Monitoring Range
MFR_PWM_MODE[1] = 1
0.5
2.7
V
VRANGE_RH
Voltage Monitoring Range
MFR_PWM_MODE[1] = 0
1
5.6
V
VTHAC0_RL
Threshold Accuracy 1V < VOUT < 2.5V
MFR_PWM_MODE[1] = 1
l
±1.5
%
VTHAC1_RH
Threshold Accuracy 2V < VOUT < 5.5V
MFR_PWM_MODE[1] = 0
l
±1.5
%
tPROPOV
OV Comparator Response Time
VOD = 10% of Threshold
100
µs
tPROPUV
UV Comparator Response Time
VOD = 10% of Threshold
100
µs
VIN Voltage Supervisor
N
Resolution
VINSTP
LSB Step Size
VIN
Full-Scale Voltage
VINTHACCM
Threshold Accuracy 9V < VIN < 38V
Threshold Accuracy 4.5V < VIN ≤ 9V
tPROPVIN
Comparator Response Time
(VIN_ON and VIN_OFF)
9
Bits
76
4.5
VOD = 10% of threshold
mV
38
V
±3
±6.0
%
%
100
µs
Output Voltage Readback
N
Resolution
16
Bits
VOUTSTP
LSB Step Size
244
µV
VF/S
Full-Scale Sense Voltage
VRUNn = 0 (Note 8)
VOUT_TUE
Total Unadjusted Error
VOUT > 0.6V (Note 8)
VOS
Zero-Code Offset Voltage
tCONVERT
Update Rate
8
l
–0.5
V
0.5
%
±500
µV
(Note 6)
90
ms
(Note 5)
10
Bits
VIN Voltage Readback
N
Resolution
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7
LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Notes 2, 3). VIN = 12V, EXTVCC = 0V, VRUN0,1 = 3.3V,
fSYNC = 500kHz (externally driven) and all programmable parameters at factory default, unless otherwise specified.
SYMBOL
PARAMETER
CONDITION
VF/S
Full-Scale Input Voltage
(Note 11)
VINTUE
Total Unadjusted Error
VVIN > 4.5V (Note 8)
MIN
TYP
UNITS
V
0.5
2
l
%
%
(Note 6)
90
ms
Resolution
(Note 5)
10
Bits
VIOUTSTP
LSB Step Size
0V ≤ |VISENSE+ – VISENSE–| < 16mV
16mV ≤ |VISENSE+ – VISENSE–| < 32mV
32mV ≤ |VISENSE+ – VISENSE–| < 64mV
64mV ≤ |VISENSE+ – VISENSE–| < 128mV
15.63
31.25
62.5
125
µV
µV
µV
µV
IF/S
Full-Scale Input Current
(Note 7) DCR or RISENSE = 1mΩ
±128
A
VISENSE+ – VISENSE– > 6mV (Note 8)
tCONVERT
Update Rate
MAX
43
Output Current Readback
N
IOUT_TUE
Total Unadjusted Error
VOS
Zero-Code Offset Voltage
tCONVERT
Update Rate
l
±1.25
%
±50
µV
(Note 6)
90
ms
Resolution
(Note 5)
10
Bits
VIINSTP
LSB Step Size Full-Scale Range = 16mV
LSB Step Size Full-Scale Range = 32mV
LSB Step Size Full-Scale Range = 64mV
15.26
30.52
61
µV
µV
µV
IIN_TUE
Total Unadjusted Error
Gain = 8, 0V ≤ |VIIN+ – VIIN–| ≤ 5mV
Gain = 4, 0V ≤ |VIIN+ – VIIN–| ≤ 20mV
Gain = 2, 0V ≤ |VIIN+ – VIIN–| ≤ 50mV
Gain = 8, 2.5mV ≤ |VIIN+ – VIIN–| VIN = 8V (Note 8)
Gain = 4, 4mV ≤ |VIIN+ – VIIN–| VIN = 8V (Note 8)
Gain = 2, 6mV ≤ |VIIN+ – VIIN–| VIN = 8V (Note 8)
VOS
Zero-Code Offset Voltage
tCONVERT
Update Rate
Input Current Readback
N
±2
±1.3
±1.2
l
l
l
±50
(Note 6)
%
%
%
µV
90
ms
10
Bits
244
µV
Supply Current Readback
N
Resolution
VICHIPSTP
LSB Step Size Full-Scale Range =
256mV
(Note 5)
ICHIPTUE
Total Unadjusted Error
|VIIN+ – VIN| ≤ 150mV (Note 19)
tCONVERT
Update Rate
(Note 6)
±3
l
%
90
ms
0.25
°C
Temperature Readback (T0, T1)
TRES_T
Resolution
T0_TUE
External Temperature Total
Unadjusted Readback Error
TSNS0, TSNS1 ≤ 1.85V (Note 8)
MFR_PWM_MODE_[5] = 0
MFR_PWM_MODE_[5] = 1 (Note 14)
T1_TUE
Internal TSNS TUE
VRUN0,1 = 0.0, fSYNC = 0kHz (Note 8)
±1
°C
tCONVERT
Update Rate
(Note 6)
90
ms
–3
–10
3
10
°C
°C
INTVCC Regulator/EXTVCC
VINTVCC
Internal VCC Voltage No Load
6V ≤ VIN ≤ 38V
VLDO_INT
INTVCC Load Regulation
ICC = 0mA to 20mA, 6V ≤ VIN ≤ 38V
VEXTVCC
EXTVCC Switchover Voltage
VIN ≥ 7V, EXTVCC Rising
VLDO_HYS
EXTVCC Hysteresis
VLDO_EXT
EXTVCC Voltage Drop
8
ICC = 20mA, VEXTVCC = 5.5V
5.25
4.5
5.5
5.75
V
0.5
±2
%
4.7
V
290
mV
50
100
mV
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Notes 2, 3). VIN = 12V, EXTVCC = 0V, VRUN0,1 = 3.3V,
fSYNC = 500kHz (externally driven) and all programmable parameters at factory default, unless otherwise specified.
SYMBOL
PARAMETER
CONDITION
MIN
TYP
MAX
UNITS
VIN_THR
VIN Threshold to Enable EXTVCC
Switchover
VIN Rising
7
V
VIN_THF
VIN Threshold to Disable EXTVCC
Switchover
VIN Falling
6.5
V
VDD33 Regulator
VDD33
Internal VDD33 Voltage
4.5V < VINTVCC or 4.8V < VEXTVCC
ILIM
VDD33 Current Limit
VDD33 = GND, VIN = INTVCC = 4.5V
VDD33_OV
VDD33_UV
3.2
3.3
3.4
V
100
mA
VDD33 Overvoltage Threshold
3.5
V
VDD33 Undervoltage Threshold
3.1
V
VDD25 Regulator
VDD25
Internal VDD25 Voltage
ILIM
VDD25 Current Limit
VDD25 = GND, VIN = INTVCC = 4.5V
2.5
V
80
mA
Oscillator and Phase-Locked Loop
fRANGE
PLL SYNC Range
Syncronized with Falling Edge of SYNC
l
fOSC
Oscillator Frequency Accuracy
Frequency Switch = 250.0 to 1000.0 kHz
l
200
1000
kHz
±7.5
%
VTH(SYNC)
SYNC Input Threshold
VSYNC Falling
VSYNC Rising
1
1.5
VOL(SYNC)
SYNC Low Output Voltage
ILOAD = 3mA
0.2
ILEAK(SYNC)
SYNC Leakage Current in Slave Mode 0V ≤ VPIN ≤ 3.6V
θSYNC-θ0
SYNC to Ch0 Phase Relationship
Based on the Falling Edge of Sync
and Rising Edge of TG0
MFR_PWM_CONFIG[2:0] = 0,2,3
MFR_PWM_CONFIG[2:0] = 5
MFR_PWM_CONFIG[2:0] = 1
MFR_PWM_CONFIG[2:0]= 4,6
0
60
90
120
Deg
Deg
Deg
Deg
θSYNC-θ1
SYNC to Ch1 Phase Relationship
Based on the Falling Edge of Sync
and Rising Edge of TG1
MFR_PWM_CONFIG[2:0] = 3
MFR_PWM_CONFIG[2:0] = 0
MFR_PWM_CONFIG[2:0] = 2,4,5
MFR_PWM_CONFIG[2:0] = 1
MFR_PWM_CONFIG[2:0] = 6
120
180
240
270
300
Deg
Deg
Deg
Deg
Deg
V
V
0.4
±5
V
µA
EEPROM Characteristics
Endurance
(Note 12)
0°C < TJ < 85°C EEPROM Write Operations
l
10,000
Cycles
Retention
(Note 12)
TJ < 125°C
l
10
Years
Mass_Write
Mass Write Operation Time
STORE_USER_ALL, 0°C < TJ < 85°C
During EEPROM Write Operation
l
OV ≤ VPIN ≤ 5.5V
OV ≤ VPIN ≤ 3.6V
440
4100
ms
l
±5
µA
l
±2
µA
1.35
V
Leakage Current SDA, SCL, ALERT, RUN
IOL
Input Leakage Current
Leakage Current FAULTn, PGOODn
IGL
Input Leakage Current
Digital Inputs SCL, SDA, RUNn, GPI0n
VIH
Input High Threshold Voltage
l
l
VIL
Input Low Threshold Voltage
VHYST
Input Hysteresis
CPIN
Input Capacitance
SCL, SDA
0.8
V
0.08
V
10
pF
Digital Input WP
IPUWP
Input Pull-Up Current
WP
10
µA
3884fe
For more information www.linear.com/LTC3884
9
LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C (Notes 2, 3). VIN = 12V, EXTVCC = 0V, VRUN0,1 = 3.3V,
fSYNC = 500kHz (externally driven) and all programmable parameters at factory default, unless otherwise specified.
SYMBOL
PARAMETER
CONDITION
MIN
TYP
MAX
UNITS
Open-Drain Outputs SCL, SDA, FAULTn, ALERT, RUNn, SHARE_CLK, PGOODn
VOL
Output Low Voltage
ISINK = 3mA
0.4
V
Digital Inputs SHARE_CLK, WP
VIH
Input High Threshold Voltage
l
VIL
Input Low Threshold Voltage
l
1.5
0.6
1.8
V
1
V
3
µs
60
µs
10
µs
Digital Filtering of FAULTn
IFLTG
Input Digital Filtering FAULTn
Digital Filtering of PGOODn
IFLTG
Output Digital Filtering PGOODn
Digital Filtering of RUNn
IFLTG
Input Digital Filtering RUN
PMBus Interface Timing Characteristics
fSCL
Serial Bus Operating Frequency
l
10
tBUF
Bus Free Time Between Stop and
Start
l
1.3
µs
tHD(STA)
Hold Time After Repeated Start
Condition After This Period, the First
Clock is Generated
l
0.6
µs
tSU(STA)
Repeated Start Condition Setup Time
l
0.6
tSU(ST0)
Stop Condition Setup Time
l
0.6
tHD(DAT)
Date Hold Time
Receiving Data
Transmitting Data
l
l
0
0.3
Data Setup Time
Receiving Data
l
0.1
tSU(DAT)
tTIMEOUT_SMB Stuck PMBus Timer Non-Block Reads Measured from the Last PMBus Start Event
Stuck PMBus Timer Block Reads
Serial Clock Low Period
l
1.3
tHIGH
Serial Clock High Period
l
0.6
10
10000
kHz
µs
µs
0.9
µs
µs
µs
32
255
tLOW
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3884/LTC3884-1 is tested under pulsed load conditions
such that TJ ≈ TA. The LTC3884E/LTC3884E-1 is guaranteed to meet
performance specifications from 0°C to 85°C. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3884I/LTC3884I-1 is guaranteed over the full –40°C to 125°C operating
junction temperature range. TJ is calculated from the ambient temperature
TA and power dissipation PD according to the following formula:
TJ = TA + (PD • θJA)
The maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board layout,
the rated package thermal impedance and other environmental factors.
400
ms
10000
µs
µs
Note 3: All currents into device pins are positive; all currents out of device pins
are negative. All voltages are referenced to ground unless otherwise specified
Note 4: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels. CLOAD = 3500pF is guaranteed by
design.
Note 5: The data format in PMBus is 5 bits exponent (signed) and 11 bits
mantissa (signed). This limits the output resolution to 10 bits though the
internal ADC is 16 bits and the calculations use 32-bit words.
Note 6: The data conversion is done by default in round robin fashion. All
inputs signals are continuously converted for a typical latency of 90ms.
Setting MFR_ADC_CONTRL value to be 0 to 12, LTC3884 can do fast data
conversion with only 8ms to 10ms. See section PMBus Command for
details.
Note 7: The IOUT_CAL_GAIN = 1.0mΩ and MFR_IOUT_TC = 0.0. Value as
read from READ_IOUT in Amperes.
3884fe
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LTC3884/LTC3884-1
ELECTRICAL CHARACTERISTICS
Note 8: Part tested with PWM disabled. Evaluation in application
demonstrates capability. TUE(%) = ADC Gain Error (%) +100 •
(Zero code Offset + ADC Linearity Error)/Actual Value.
Note 9: All VOUT commands assume the ADC is used to auto zero the
output to achieve the stated accuracy. LTC3884/LTC3884-1 is tested in a
feedback loop that servos VOUT to a specified value.
Note 10: The maximum programmable VOUT voltage is 5.5V when the
output voltage range is High and 2.75V when the output voltage range is
Low.
Note 11: The maximum VIN voltage is 38V.
Note 12: EEPROM endurance and retention are guaranteed by design,
characterization and correlation with statistical process controls. Data
retention is production tested via a high temperature at wafer level. The
minimum retention specification applies for devices whose EEPROM
has been cycled less than the minimum endurance specification. The
RESTORE_USER_ALL command (NVM read) is valid over the entire
operating junction temperature range.
Note 13: MFR_PWM_MODE[1]=1 or 0 sets the output voltage range Low
or High.
Note 14: MFR_PWM_MODE_[5] = 0 or 1 sets the temperature
measurement method through ∆VBE, or through 2VBE.
Note 15: MFR_PWM_MODE[2] = 1 or 0 sets device in low DCR mode or
regular DCR mode respectively. MFR_PWM_MODE[7]=1 or 0 sets device in
high output current range or low current range. See “Output Current Sensing
and sub milliohm DCR Current Sensing” in Operation Section for details.
Only VILIMIT codes 2–8 are supported for DCR sensing.
Note 16: The LTC3884/LTC3884-1 quiescent current (IQ) equals the IQ of
VIN plus the IQ of EXTVCC.
Note 17: The LTC3884/LTC3884-1 includes overtemperature protection
that is intended to protect the device during momentary overload
conditions. Junction temperature will exceed 125°C when overtemperature
protection is active. Continuous operation above the specified maximum
operating junction temperature may impair device reliability.
Note 18: Write operations above TJ = 85°C or below 0°C are possible
although the Electrical Characteristics are not guaranteed and the EEPROM
will be degraded. Read operations performed at temperatures below 125°C
will not degrade the EEPROM. Writing to the EEPROM above 85°C will
result in a degradation of retention characteristics.
Note 19: Properly adjust the input current sensing resistor RVIN to set the
sensing voltage within the maximum voltage of 150mV.
62
56
50
RTH(kΩ)
43
37
31
25
19
12
6
0
0
5
10
15
20
CODE
25
30
35
3884 F01
Figure 1. Programmable RTH
3884fe
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11
LTC3884/LTC3884-1
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VIN = 12V, L = 0.33µH, DCR = 0.32mΩ, EXTVCC = 0V unless otherwise noted.
Efficiency vs Load Current
95
95
89
89
83
83
fSW = 350KHz
77
72
VOUT=1.8V
VOUT=1.5V
VOUT=1.2V
VOUT=1.0V
66
60
EFFICIENCY (%)
EFFICIENCY (%)
Efficiency vs Load Current
0
5
10
15
20
LOAD CURRENT (A)
25
fSW = 500KHz
77
72
VOUT=1.8V
VOUT=1.5V
VOUT=1.2V
VOUT=1.0V
66
60
30
0
5
3884 G01
5
5
4
4
POWERLOSS (W)
POWERLOSS (W)
6
3
VOUT=1.8V
VOUT=1.5V
VOUT=1.2V
VOUT=1.0V
1
0
0
5
10
15
20
LOAD CURRENT (A)
25
30
f SW = 500KHz
3
2
VOUT=1.8V
VOUT=1.5V
VOUT=1.2V
VOUT=1.0V
1
0
0
5
10
15
20
LOAD CURRENT (A)
Load Step
(Forced Continuous Mode)
12
25
30
3884 G04
3884 G03
Load Step
(Discontinuous Mode)
ILOAD
10A/DIV
ILOAD
10A/DIV
IL
10A/DIV
IL
10A/DIV
VOUT
100mV/DIV
AC-COUPLED
VOUT
100mV/DIV
AC-COUPLED
VIN = 12V
50µs/DIV
VOUT = 1.8V
0.3A TO 10A STEP
30
Power Loss vs Output Current
f SW = 350KHz
2
25
3884 G02
Power Loss vs Load Current
6
10
15
20
LOAD CURRENT (A)
3884 G05
VIN = 12V
50µs/DIV
VOUT = 1.8V
0.3A TO 10A STEP
3884 G06
3884fe
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LTC3884/LTC3884-1
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VIN = 12V, L = 0.33µH, DCR = 0.32mΩ, EXTVCC = 0V unless otherwise noted.
Inductor Current at Light Load
Soft-Start Ramp
RUN
2V/DIV
0V
FORCED
CONTINUOUS
MODE
5A/DIV
VOUT
1V/DIV
0V
DISCONTINUOUS
MODE
5A/DIV
VOUT = 1.8V
ILOAD = 1A
1µs/DIV
3884 G07
tRISE = 10ms
tDELAY = 5ms
VOUT = 1.8V
RUN
2V/DIV
0V
RUN
2V/DIV
0V
VOUT
1V/DIV
0V
VOUT
1V/DIV
0V
5ms/DIV
3884 G09
tFALL = 5ms
tDELAY = 10ms
Dynamic Current Sharing During
a Load Transient in a 2-Phase
System
5ms/DIV
3884 G10
Dynamic Current Sharing During
a Load Transient in a 2-Phase
System
10A/DIV
10A/DIV
IL
0A
IL
0A
5µs/DIV
3884 G08
Soft-Off Ramp
Start-Up Into a Prebiased Output
tRISE = 10ms
VOUT = 1.8V
5ms/DIV
3884 G11
5µs/DIV
3884 G12
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13
LTC3884/LTC3884-1
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VIN = 12V, L = 0.33µH, DCR = 0.32mΩ, EXTVCC = 0V unless otherwise noted.
Dynamic Current Sharing During
a Load Transient in a 4-Phase
System
Dynamic Current Sharing During
a Load Transient in a 4-Phase
System
IL
10A/DIV
IL
10A/DIV
0A
0A
3884 G13
5µs/DIV
Phase Current Matching in Two
Phase Systems
Current Limit During an Output
Short Condition
20.2
OC_FAULT LIMIT = 40A,
IL_PEAK = 42A
VOUT
3884 G14
5µs/DIV
18.2
16.2
PHASE CURRENT (A)
GND
IL
10A/DIV
0A
12.1
10.0
8.0
6.0
3.9
3884 G15
5µs/DIV
14.1
CH0
CH1
1.9
–0.1
0
8
16
24
32
OUTPUT CURRENT (A)
40
3884 G16
Current Sense Threshold
vs Duty Cycle
INTVCC Line Regulation
12.0
OVER CURRENT SENSE THRESHOLD (mV)
5.8
5.5
INTVCC (V)
5.2
4.9
4.6
4.3
4.0
14
0
10
20
VIN (V)
30
40
MFM_PWM_MODE[7][2] = 0,1
IOUT_OC_FAULT_LIMIT= 32.5A
11.6
11.2
10.8
10.4
10.0
9.6
9.2
8.8
8.4
8.0
0
3884 G17
20
40
60
DUTY CYCLE (%)
80
100
3884 G18
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LTC3884/LTC3884-1
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VIN = 12V, L = 0.33µH, DCR = 0.32mΩ, EXTVCC = 0V unless otherwise noted.
Quiescent Current
vs Input Voltage
30.0
105
QUIESCENT CURRENT (mA)
102
100
98
27.5
25.0
22.5
20.0
95
17.5
93
15.0
4
13
22
VIN (V)
31
40
10
16
22
VIN (V)
28
34
3884 G19
VREF vs Temperature
40
1.0
RVIN = 2Ω
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
–0.6
–0.8
–1.0
20
3884 G20
1.2220
1.005
1.2218
1.004
VOUT (V)
1.2208
1.2205
1.2203
1.2200
1.010
1.001
1.000
0.999
0.998
1.2198
0.997
1.2195
120
1.015
1.002
1.2210
60
80
100
SUPPLY CURRENT (mA)
VOUT Overvoltage Threshold
vs Temperature (Target 1V)
1.003
1.2213
40
3884 G21
VOUT vs Temperature
1.2215
VREF (V)
4
OV THRESHOLD (V)
SHARE_CLK FREQUENCY (KHz)
107
Supply Current Measurement
Error vs Supply Current
SUPPLY CURRENT MEASUREMENT ERROR (%)
SHARE_CLK Frequency
vs Input Voltage
1.005
1.000
0.995
0.990
0.996
1.2193
1.2190
–55
–10
35
80
TEMPERATURE (°C)
0.995
–55
125
–10
35
80
TEMPERATURE (°C)
125
0.985
–55
–10
35
80
TEMPERATURE (°C)
125
3884 G23
3884 G22
VOUT Overvoltage Threshold
vs Temperature (Target 2V)
3884 G24
VOUT Overvoltage Threshold
vs Temperature (Target 4V)
2.030
4.06
2.020
4.04
SHARE_CLK vs Temperature
107
2.010
2.000
1.990
104
4.02
SHARE_CLK (KHz)
OV THRESHOLD (V)
OV THRESHOLD (V)
106
4.00
3.98
1.980
3.96
1.970
–55
3.94
–55
103
101
100
99
97
96
94
–10
35
80
TEMPERATURE (°C)
125
3884 G25
–10
35
80
TEMPERATURE (°C)
125
3884 G26
93
–55
–10
35
80
TEMPERATURE (°C)
125
3884 G27
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15
LTC3884/LTC3884-1
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VIN = 12V, L = 0.33µH, DCR = 0.32mΩ, EXTVCC = 0V unless otherwise noted.
Underlock Voltage vs Temperature
VOUT Command DNL
4.00
2.00
0.23
RISING
3.90
1.50
0.15
3.80
3.75
3.70
3.65
1.00
0.08
INL (LSB)
3.85
DNL (LSB)
UNDERLOCK VOLTAGE (V)
3.95
0.00
–0.07
0.50
0
–0.15
3.60
FALLING
3.55
3.50
–55
–0.50
–0.22
–10
35
80
TEMPERATURE (°C)
–0.30
0.5
125
1.5
3884 G28
VOUT Error vs VOUT
2.5
3.5
VOUT (V)
4.5
5.5
–1.00
0.50
IOUT Error vs IOUT
0.30
7.14
2
0.00
–0.10
–0.20
–0.30
0.5
16
1.5
2.5
3.5
VOUT (V)
4.5
5.5
3884 G31
IINPUT MEASUREMENT ERROR (mA)
2
0.10
4.29
1.43
–1.43
–4.29
–7.14
–10.00
0.1
8.0
16.0
24.0
IOUT (A)
2.50
3.50
VOUT (V)
4.50
5.50
3884 G30
Input Current Error vs Input Current
10.00
0.20
1.50
3884 G29
0.40
IOUT MEASUREMENT ERROR (mA)
VOUT MEASUREMENT ERROR (mV)
VOUT Command INL
0.30
32.0
40.0
3884 G32
RIINSNS = 5mΩ
1
0
0
–1
–2
–2
–3
0
3
5
8
INPUT CURRENT(A)
10
3884 G33
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LTC3884/LTC3884-1
PIN FUNCTIONS
(UK, RHE)
VSENSE0+/VSENSE1+ (Pin 1/Pin 32, Pin 2/Pin 33): Positive
Output Voltage Sense Inputs.
VSENSE0–/VSENSE1– (Pin 2/Pin 31, Pin 3/Pin 32): Negative
Output Voltage Sense Inputs.
ITH0/ITH1 (Pin 6/Pin 29, Pin 7/Pin 30): Current Control
Threshold and Error Amplifier Compensation Nodes. Each
associated channel’s current comparator tripping threshold
increases with its ITH voltage.
ITHR0/ITHR1 (Pin 5/Pin 30, Pin 6/Pin 31): Loop Compensation Nodes.
ISENSE0+/ISENSE1+ (Pin 7/Pin 3, Pin 8/Pin 4): Current sense
comparator positive inputs, normally connected to DCR
sensing networks or current sensing resistors.
ISENSE0–/ISENSE1– (Pin 8/Pin 4, Pin 9/Pin 5): Current
sense comparator negative inputs, normally connected
to outputs.
SYNC (Pin 11, Pin 12): External Clock Synchronization
Input and Open-Drain Output Pin. If an external clock is
present at this pin, the switching frequency will be synchronized to the external clock. If clock master mode is
enabled, this pin will pull low at the switching frequency
with a 500ns pulse to ground. A resistor pull-up to 3.3V
is required in the application if the LTC3884 is the master.
SCL (Pin 12, Pin 13): Serial Bus Clock Input. Open-drain
output can hold the output low if clock stretching is enabled.
A pull-up resistor to 3.3V is required in the application.
SDA (Pin 13, Pin 14): Serial Bus Data Input and Output.
A pull-up resistor to 3.3V is required in the application.
ALERT (Pin 14, Pin 15): Open-Drain Digital Output. Connect the SMBALERT signal to this pin. A pull-up resistor
to 3.3V is required in the application.
FAULT0/FAULT1 (Pin 15/Pin 16, Pin 16/Pin 17): Digital
Programmable FAULT Inputs and Outputs. Open-drain output. A pull-up resistor to 3.3V is required in the application.
RUN0/RUN1 (Pin 17/Pin 18, Pin 18/Pin 19): Enable Run
Input and Output. Logic high on these pins enables the
controller. An open-drain output holds the pin low until
the LTC3884 is out of reset. This pin should be driven by
an open-drain digital output. A pull-up resistor to 3.3V is
required in the application.
ASEL0/ASEL1 (Pin 19/Pin 20, Pin 20/Pin 21): Serial Bus
Address Select Inputs. Connect optional ±1% resistor
dividers between VDD25 and SGND to these pins to select
the serial bus interface address. Refer to the Applications
Information section for more details. Minimize capacitance
when the pin is open to assure accurate detection of the
pin state.
VOUT0_CFG/VOUT1_CFG (Pin 21/Pin 22, Pin 22/Pin 23):
Output Voltage Select Pins. Connect optional ±1% resistor
divider between VDD25 VOUT_CFG and SGND in order to
select output voltage for each channel. If the pin is left
open, the IC will use the value programmed in EEPROM.
Refer to the Applications Information section for more
details. Minimize capacitance when the pin is open to
assure accurate detection of the pin state.
FREQ_CFG (Pin 23, Pin 24): Frequency Select Pin. Connect optional ±1% resistor divider between VDD25 and
FREQ_CFG SGND in order to select PWM switching frequency. Refer to the Applications Information section for
more details. Minimize capacitance when the pin is open
to assure accurate detection of the pin state.
PHASE_CFG (Pin 24, Pin 25): Phase Select Pin. Connect
±1% resistor divider between VDD25 PHASE_CFG SGND
to this pin to configure the phase of each PWM channel
relative to SYNC. If the pin is left open, the IC will use the
value programmed in the NVM. Refer to the Applications
Information section for more details. Minimize capacitance
when the pin is open to assure accurate detection of the
pin state.
VDD25 (Pin 25, Pin 26): Internally Generated 2.5V Power
Supply Output Pin. Bypass this pin to SGND with a low
ESR 1μF capacitor. Do not load this pin with external current except for the ±1% resistor dividers required for the
configuration pins.
WP (Pin 26, Pin 27): Write Protect Pin Active High. An
internal 10μA current source pulls the pin to VDD33. If WP
is high, the PMBus writes are restricted.
SHARE_CLK (Pin 27, Pin 28): Share Clock, Bidirectional
Open-Drain Clock Sharing Pin. Nominally 100kHz. Used to
synchronize the timing between multiple LTC3884s. Tie all
SHARE_CLK pins together. All LTC3884s will synchronize
to the fastest clock. A pull-up resistor to 3.3V is required.
3884fe
For more information www.linear.com/LTC3884
17
LTC3884/LTC3884-1
PIN FUNCTIONS
(UK, RHE)
VDD33 (Pin 28, Pin 29): Internally Generated 3.3V Power
Supply Output Pin. Bypass this pin to SGND with a low
ESR 1μF capacitor. Do not load this pin with external current except for the pull-up resistors required for FAULTn,
SCLK, SYNC and possibly RUNn, SDA and SCL, PGOODn.
INTVCC (Pin 38, Pin 39): Internal Regulator 5.5V Output.
The control circuits are powered from this voltage. Decouple this pin to PGND with a minimum of 4.7μF low ESR
tantalum or ceramic capacitor. This regulator is mainly
designed for internal circuits, not to be used as supply
for the other ICs.
EXTVCC (Pin 40, Pin 41): External Power Input to an
Internal Switch Connected to INTVCC. This switch closes
and supplies the IC power, bypassing the internal regulator
whenever EXTVCC is higher than 4.7V and VIN is higher
than 7V. EXTVCC also powers up VDD33 when EXTVCC is
higher than 4.7V and INTVCC is lower than 3.8V. Do not
exceed 6V on this pin. Decouple this pin to PGND with a
minimum of 4.7μF low ESR tantalum or ceramic capacitor.
If the EXTVCC pin is not used to power INTVCC, the EXTVCC
pin must be tied GND. The EXTVCC pin may be connected
to a higher voltage than the VIN pin.
VIN (Pin 39, Pin 40): Main Input Supply. Decouple this
pin to PGND with a capacitor (1µF to 10µF). For applications where the main input power is 6V or below, tie the
VIN and INTVCC pins together. If the input current sense
amplifier is not used, this pin must be shorted to the IIN+
and IIN– pins.
BG0/BG1 (LTC3884) (Pin 42/Pin 37, Pin 43/Pin 38):
Bottom Gate Driver Outputs. These pins drive the gates
of the bottom N-channel MOSFETs between PGND and
INTVCC.
BOOST0/BOOST1 (LTC3884) (Pin 43/Pin 36, Pin 44/Pin 37):
Boosted Floating Driver Supplies. The (+) terminal of the
booststrap capacitors connect to these pins. These pins
swing from a diode voltage drop below INTVCC up to
VIN + INTVCC.
SW0/SW1 (LTC3884) (Pin 45/Pin 34, Pin 46/Pin 35):
Switch Node Connections to Inductors. Voltage swings
at the pins are from a diode (internal body diode) voltage
drop below ground to VIN.
TSNS0/TSNS1 (Pin 10/Pin 9, Pin 11/Pin 10): External
Diode Temperature Sense. Connect to the anode of a diode
connected PNP transistor and star-connect the cathode
to GND (Pin 49) in order to sense remote temperature. A
bypass capacitor between the anode and cathode must
be located in close proximity to the transistor. If external
temperature sense elements are not installed, short pin
to ground and set the UT_FAULT_LIMIT to –275°C and
the UT_FAULT_RESPONSE to ignore.
IIN+ (Pin 46, Pin 47): Positive Current Sense Comparator
Input. If the input current sense amplifier is not used, this
pin must be shorted to the IIN– and VIN pins.
IIN– (Pin 47, Pin 48): Negative Current Sense Comparator
Input. If the input current sense amplifier is not used, this
pin must be shorted to the IIN+ and VIN pins.
PGOOD0/PGOOD1 (Pin 48/Pin 33, Pin 1/ Pin 34): Power
Good Indicator Outputs. Open-drain logic output that is
pulled to ground when the output exceeds the UV and
OV regulation window. The output is deglitched by an
internal 60µs filter. A pull-up resistor to 3.3V is required
in the application.
PGND (Pin 41/Pin 42): Power Ground.
VCC0/VCC1 (LTC3884-1) (Pin 44/Pin 37): Supply to PWM.
Connected to INTVCC or VDD33. Bypass to PGND with a
1µF capacitor.
PWM0/PWM1 (LTC3884-1) (Pin 45/Pin 36): PWM Outputs.
These are the three-state control outputs with a voltage
swing of GND to VCC.
SGND (Exposed Pad Pin 49): Internal Signal Ground.
All small-signal and compensation components should
connect to this ground, which in turn connects to PGND
at single point.
TG0/TG1 (LTC3884) (Pin 44/Pin 35, Pin 45/Pin 36): Top
Gate Driver Outputs. These are the outputs of the floating
drivers with a voltage swing equal to INTVCC superimposed
on the switch node voltages.
18
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
BLOCK DIAGRAM
(UK PACKAGE, LTC3884)
VIN
RVIN
39
41R
VIN ON/OFF
+
–
R
CIN
46
+
A=N
–
RIINSNS
IIN–
47
EXTVCC
OV
PGOOD0
PGOOD0 48
35R
R
VSUPPLY
IIN+
UV
EXTVCC
40
5.5VREG
9-BIT VIN
DAC
INTVCC
INTVCC
38
VDD33
3.3V
SUBREG
S
R Q
PWM_CLOCK
ICMP
–
+
5k
+
–
DB
BOOST0
43
FCNT
REV
TG0
44
PREBIAS
ON
UV
UVLO
SS
VOUT0
COUT
BG0
M2
42
RUN
PGND
CVCC
41
OV
1
5k
M1
CB
SW0
45
SWITCH
LOGIC
AND
ANTISHOOTTHROUGH
REV
ILIM RANGE SELECT
HI: 1:1
LO: 1:1.8
VDD33
28
ISENSE0+
7
ISENSE0–
SLOPE
COMPENSATION
GM
INTVCC
UVLO
ITH0
CCTP
CTH
ACTIVE
CLAMP
6
ITHR0
ILIM DAC
(3 BITS)
16-BIT
ADC
RTH
5
EA
+ –
VSTBY
2µA
OV
UV
+ –
+
–
32µA
+
–
–
+
+
–
–
+
+
10:1 –
MUX +
–
+
–
+
–
+
–+
–
8
11R
7R
IVIN_SNS1
–
AD
+
ISENSE1+
ISENSE1–
VSENSE1+
VSENSE1–
PWM0
ICHIP
7R
11R
+ –
2
VSENSE0–
VSENSE0+
1
TSNS0
10
TMUX
10R
REF
SGND
SGND
4R
1.22V
12-BIT
SET POINT
DAC
11 SYNC
PHASE DET
9-BIT
OV
DAC
9-BIT
UV
DAC
VCO
PHASE SELECTOR
VDD33
PWM
CLOCK
CLOCK DIVIDER
VDD25
SCL 12
SDA 13
ALERT 14
PMBus
INTERFACE
(400kHz
COMPATIBLE)
WP 26
FAULT0 15
RUN0 17
SHARE_CLK 27
VDD33
COMPARE
MAIN
CONTROL
2.5V
SUBREG
SLAVE
MISO
CLK MOSI
MASTER
VDD33
SINC3
UVLO
25 VDD25
OSC
(32MHz)
19 ASEL0
20 ASEL1
CHANNEL
TIMING
MANAGEMENT
CONFIG
DETECT
PROGRAM
ROM
RAM
EEPROM
21 VOUT0_CFG
23 FREQ_CFG
24 PHASE_CFG
3884 F02
Figure 2. Block Diagram, One of Two Channels (Channel 0 Shown)
3884fe
For more information www.linear.com/LTC3884
19
LTC3884/LTC3884-1
OPERATION
OVERVIEW
n
The LTC3884-1 has all the features that LTC3884 has,
except the LTC3884 includes MOSFET gate drivers while
the LTC3884-1 does not. LTC3884 is used in applications
where the gate driver is required while the LTC3884-1
is used in applications where the gate driver is external,
for example a DrMOS power stage. In the remainder of
this document, all the descriptions, features, operation
and applications of LTC3884 apply to LTC3884-1, unless
otherwise specified.
n
The LTC3884 is a dual channel/dual phase, constantfrequency, analog current mode controller for DC/DC stepdown applications with a digital interface. The LTC3884
digital interface is compatible with PMBus which supports
bus speeds of up to 400kHz. A Typical Application circuit
is shown on the first page of this data sheet.
n
LTC3884 is very similar to LTC3880, but has numerous
new features as shown in bold:
Programmable Output Voltage
Programmable Input Voltage On and Off Threshold
Voltage
n
Programmable Current Limit
n
Programmable Switching Frequency
n
Programmable OV and UV Threshold voltage
n
Programmable ON and Off Delay Times
n
Programmable Output Rise/Fall Times
Phase-Locked Loop for Synchronous PolyPhase
Operation (2, 3, 4 or 6 Phases).
n
Integrated Gate Drivers (LTC3884)
n
Nonvolatile Configuration Memory with ECC
n
n
Major features include:
Optional External Configuration Resistors for Key
Operating Parameters
Optional Timebase Interconnect for Synchronization
Between Multiple Controllers
n
Sub-Milliohm DCR Sensing
n
WP Pin to Protect Internal Configuration
n
Dedicated Power Good Indicators
n
Stand Alone Operation After User Factory Configuration
n
Direct Input and Chip Current Sensing
n
PMBus, Version 1.2, 400kHz Compliant Interface
n
Programmable Loop Compensation Parameters
n
TINIT Start-Up Time: 35ms
The PMBus interface provides access to important power
management data during system operation including:
n
n
n
PWM Synchronization Circuit, (See Frequency and
Phasing Section for Details)
MFR_ADC_CONTROL for Fast ADC Sampling of One
Parameter (as Fast as 8ms) (See PMBus Command
for Details)
Fully Differential Output Sensing for Both Channels;
VOUT0/1 Both Programmable Up to 5.5V
n
Power-Up and Program EEPROM with EXTVCC
n
Input Voltage Up to 38V
n
Dual Diode Temperature Sensing
n
n
n
n
External System Temperature via Optional Diode Sense
Elements
n
Average Output Current
n
Average Output Voltage
n
Average Input Voltage
n
Average Input Current
n
Average Chip Input Current from VIN
n
SYNC Contention Circuit (Refer to Frequency and
Phase Section for Details)
Internal Controller Temperature
Configurable, Latched and Unlatched Individual Fault
and Warning Status
Individual channels are accessed through the PMBus using
the PAGE command, i.e., PAGE 0 or 1.
Fault Logging
20
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
OPERATION
Fault reporting and shutdown behavior are fully configurable. Two individual FAULT0, FAULT1 outputs are
provided, both of which can be masked independently.
Three dedicated pins for ALERT, PGOOD0/1 functions are
provided. The shutdown operation also allows all faults
to be individually masked and can be operated in either
unlatched (hiccup) or latched modes.
Individual status commands enable fault reporting over
the serial bus to identify the specific fault event. Fault or
warning detection includes the following:
n Output Undervoltage/Overvoltage
n Input Undervoltage/Overvoltage
n Input and Output Overcurrent
n Internal Overtemperature
n External Overtemperature
n
Communication, Memory or Logic (CML) Fault
MAIN CONTROL LOOP
The LTC3884 is a constant-frequency, current mode stepdown controller containing two channels operating with
user-defined relative phasing. During normal operation the
top MOSFET is turned on when the clock for that channel
sets the RS latch, and turned off when the main current
comparator, ICMP, resets the RS latch. The peak inductor
current at which ICMP resets the RS latch is controlled by
the voltage on the ITH pin which is the output of each error amplifier, EA. The EA negative terminal is equal to the
differential voltage between VSENSE+ and VSENSE– divided
by 5.5 (or 2.75 if MFR_PWM_MODE[1] = 1). The positive
terminal of the EA is connected to the output of a 12-bit
DAC with values ranging from 0V to 1.024V. The output
voltage, through feedback of the EA, will be regulated to
5.5 times the DAC output (or 2.75 times). The DAC value
is calculated by the part to synthesize the user's desired
output voltage. The output voltage is programmed by the
user either with the resistor configuration pins detailed
in Table 3 or by the PMBus VOUT command (either from
EEPROM or by PMBus command). Refer to the PMBus
command section of the data sheet or the PMBus specification for more details. The PMBus VOUT_COMMAND can
be executed at any time while the device is running. This
command will typically have a latency less than 10ms. The
user is encouraged to refer to the PMBus Power System
Management Protocol Specification to understand how to
program the LTC3884.
http://www.pmbus.org/specs.html
Continuing the basic operation description, the currentmode controller will turn off the top gate when the peak
current is reached. If the load current increases, sense
voltage will slightly droop with respect to the DAC reference.
This causes the ITH voltage to increase until the average
inductor current matches the new load current. After the
top MOSFET has turned off, the bottom MOSFET is turned
on. In continuous conduction mode, the bottom MOSFET
stays on until the end of the switching cycle.
EEPROM
The LTC3884 contains internal EEPROM (nonvolatile
memory) with Error Correction Coding (ECC) to store user
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 above TJ =
85°C are possible although the Electrical Characteristics
are not guaranteed and the EEPROM will be degraded.
Read operations performed at temperatures between
–40°C and 125°C will not degrade the EEPROM. Writing
to the EEPROM above 85°C will result in a degradation of
retention characteristics. The fault logging function, which
is useful in debugging system problems that may occur
at high temperatures, only writes to fault log EEPROM
locations. If occasional writes to these registers occur
above 85°C, the slight degradation in the data retention
characteristics of the fault log will not take away from the
usefulness of the function.
It is recommended that the EEPROM not be written
when the die temperature is greater than 85°C. If the die
temperature exceeds 130°C, the LTC3884 will disable all
EEPROM write operations. All EEPROM write operations
will be re-enabled when the die temperature drops below
125°C. (The controller will also disable all the switching
when the die temperature exceeds the internal overtemperature fault limit 160°C with a 10°C hysteresis)
3884fe
For more information www.linear.com/LTC3884
21
LTC3884/LTC3884-1
OPERATION
The degradation in EEPROM retention for temperatures
>125°C can be approximated by calculating the dimensionless acceleration factor using the following equation:
AF = e
POWER-UP AND INITIALIZATION
⎡⎛ Ea ⎞ ⎛
⎞⎤
1
1
–
⎢⎜⎝ ⎟⎠ •⎜
⎟⎠ ⎥
+273
+273
T
T
k
⎝ USE
STRESS
⎦
⎣
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
TUSE = 125°C,
([(1.4/8.617 • 10–5) • (1/398 – 1/403)] )
AF = e
= 16.6
The equivalent operating time at 125°C = 16.6 hours.
Thus the overall retention of the EEPROM was degraded by
16.6 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 integrity of the entire onboard EEPROM is checked with
a CRC calculation each time its data is to be read, such as
after a power-on reset or execution of a RESTORE_USER_
ALL command. If a CRC error occurs, the CML bit is set in
the STATUS_BYTE and STATUS_WORD commands, the
EEPROM CRC Error bit in the STATUS_MFR_SPECIFIC
command is set, and the ALERT and RUN pins pulled
low (PWM channels off). At that point the device will only
respond at special address 0x7C, which is activated only
after an invalid CRC has been detected. The chip will also
respond at the global addresses 0x5A and 0x5B, but use
of these addresses when attempting to recover from a
CRC issue is not recommended. All power supply rails
associated with either PWM channel of a device reporting
an invalid CRC should remain disabled until the issue is
resolved. See the application Information section or contact the factory for details on efficient in-system EEPROM
22
programming, including bulk EEPROM Programming,
which the LTC3884 also supports.
The LTC3884 is designed to provide standalone supply
sequencing and controlled turn-on and turn-off operation.
It operates from a single input supply (4.5V to 38V) while
three on-chip linear regulators generate internal 2.5V, 3.3V
and 5.5V. If VIN does not exceed 6V, and the EXTVCC pin
is not driven by an external supply, the INTVCC and VIN
pins must be tied together. The controller configuration is
initialized by an internal threshold based UVLO where VIN
must be approximately 4V and the 5.5V, 3.3V and 2.5V
linear regulators must be within approximately 20% of
the regulated values. In addition to power supply,a PMBus
RESTORE_USER_ALL or MFR_RESET command can
initialize the part too.
The EXTVCC pin is driven by an external regulator to improve
efficiency of the circuit and minimize power loss on the
LTC3884 when VIN is high. The EXTVCC pin must exceed
approximately 4.7V, and VIN must exceed approximately
7V before the INTVCC LDO operates from the EXTVCC pin.
To minimize application power, the EXTVCC pin can be
supplied by a switching regulator.
During initialization, the external configuration resistors
are identified and/or contents of the NVM are read into the
controller’s commands and the BGn, TGn pins are held low
for LTC3884. The RUNn and FAULTn and PGOODn are held
low for the LTC3884, or PWM pins are in three-state for the
LTC3884-1. The LTC3884 will use the contents of Table 3
to Table 6 to determine the resistor defined parameters.
See the Resistor Configuration section for more details.
The resistor configuration pins only control some of the
preset values of the controller. The remaining values are
programmed in NVM either at the factory or by the user.
If the configuration resistors are not inserted or if the ignore
RCONFIG bit is asserted (bit 6 of the MFR_CONFIG_ALL
configuration command), the LTC3884 will use only the
contents of NVM to determine the DC/DC characteristics. The
ASEL0/1 value read at power-up or reset is always respected
unless the pin is open. The ASEL0/1 will set the MSB and
the LSB from the detected threshold. See the Applications
Information section for more details.
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
OPERATION
After the part has initialized, an additional comparator monitors VIN. The VIN_ON threshold must be exceeded before
the output power sequencing can begin. After VIN is initially
applied, the part will typically require 35ms to initialize and
begin the TON_DELAY timer. The readback of voltages and
currents may require an additional 0ms to 90ms.
SOFT-START
The method of start-up sequencing described below is time
based. The part must enter the run state prior to soft-start.
The run pins are released by the LTC3884 after the part is
initialized and VIN is greater than the VIN_ON threshold. If
multiple LTC3884s are used in an application, they all hold
their respective run pins low until all devices are initialized
and VIN exceeds the VIN_ON threshold for every device.
The SHARE_CLK pin assures all the devices connected to
the signal use the same time base. The SHARE_CLK pin is
held low until the part has been initialized after VIN is applied. The LTC3884 can be set to turn-off (or remain off)
if SHARE_CLK is low (set bit 2 of MFR_CHAN_CONFIG to
1). This allows the user to assure synchronization across
numerous ADI ICs even if the RUN pins cannot be connected together due to board constraints. In general, if the
user cares about synchronization between chips it is best
not only to connect all the respective RUN pins together
but also to connect all the respective SHARE_CLK pins
together and pull up to VDD33 with a 10k resistor. This assures all chips begin sequencing at the same time and use
the same time base.
After the RUN pins release and prior to entering a constant
output voltage regulation state, the LTC3884 performs a
monotonic initial ramp or “soft-start”. Soft-start is performed
by actively regulating the load voltage while digitally ramping
the target voltage from 0V to the commanded voltage setpoint. Once the LTC3884 is commanded to turn on (after
power up and initialization), the controller waits for the
user specified turn-on delay (TON_DELAY) prior to initiating this output voltage ramp. The rise time of the voltage
ramp can be programmed using the TON_RISE command
to minimize inrush currents associated with the start-up
voltage ramp. The soft-start feature is disabled by setting
the value of TON_RISE to any value less than 0.25ms. The
LTC3884 PWM always uses discontinuous mode during the
TON_RISE operation. In discontinuous mode, the bottom
gate is turned off as soon as reverse current is detected in
the inductor. This will allow the regulator to start up into
a pre-biased load. When the TON_MAX_FAULT_LIMIT is
reached, the part transitions to continuous mode, if so
programmed. If TON_MAX_FAULT_LIMIT is set to zero,
there is no time limit and the part transitions to the desired
conduction mode after TON_RISE completes and VOUT has
exceeded the VOUT_UV_FAULT_LIMIT and IOUT_OC is
not present. However setting TON_MAX_FAULT_LIMIT to
a value of 0 is not recommended.
TIME-BASED SEQUENCING
The default mode for sequencing the outputs on and off is
time based. Each output is enabled after waiting TON_DELAY
amount of time following either a RUN pin going high,
a PMBus command to turn on or the VIN rising above a
preprogrammed voltage. Off sequencing is handled in a
similar way. To assure proper sequencing, make sure all
ICs connect the SHARE_CLK pin together and RUN pins
together. If the RUN pins cannot be connected together
for some reasons, set bit 2 of MFR_CHAN_ CONFIG to 1.
This bit requires the SHARE_CLK pin to be clocking before
the power supply output can start. When the RUN pin is
pulled low, the LTC3884 will hold the pin low for the MFR_
RESTART_DELAY. The minimum MFR_RESTART_ DELAY
is TOFF_DELAY + TOFF_FALL + 136ms. This delay assures
proper sequencing of all rails. The LTC3884 calculates this
delay internally and will not process a shorter delay. However,
a longer commanded MFR_RESTART_DELAY will be used
by the part. The maximum allowed value is 65.52 seconds.
VOLTAGE-BASED SEQUENCING
The sequence can also be voltage based. As shown in
Figure 3, The PGOODn pin is asserted when the UV threshold
is exceeded for each output. It is possible to feed the PGOOD
pin from one LTC3884 into the RUN pin of the next LTC3884
in the sequence, especially across multiple LTC3884s. The
PGOODn has a 60μs filter. If the VOUT voltage bounces around
the UV threshold for a long period of time it is possible for
the PGOODn output to toggle more than once. To minimize
this problem, set the TON_RISE time under 100ms.
3884fe
For more information www.linear.com/LTC3884
23
LTC3884/LTC3884-1
OPERATION
If a fault in the string of rails is detected, only the faulted
rail and downstream rails will fault off. The rails in the
string of devices in front of the faulted rail will remain on
unless commanded off.
Voltage-Based Sequencing by Cascading PGs Into RUN Pins
START
RUN 0
PGOOD0
LTC3884
RUN 1
PGOOD1
RUN 0
PGOOD0
LTC3884
RUN 1
PGOOD1
LIGHT-LOAD CURRENT OPERATION
3884 F03
TO NEXT CHANNEL
IN THE SEQUENCE
Figure 3. Event (Voltage) Based Sequencing
SHUTDOWN
The LTC3884 supports two shutdown modes. The first
mode is closed-loop shutdown response, with user defined turn-off delay (TOFF_DELAY) and ramp down rate
(TOFF_FALL). The controller will maintain the mode of
operation for TOFF_FALL. The second mode is 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, instead of TOFF_FALL.
The shutdown occurs in response to a fault condition or
loss of SHARE_CLK (if bit 2 of MFR_CHAN_ CONFIG is set
to a 1) or VIN falling below the VIN_OFF threshold or FAULT
pulled low externally (if the MFR_FAULT_ RESPONSE is
set to inhibit). Under these conditions the power stage
is disabled in order to stop the transfer of energy to the
load as quickly as possible. The shutdown state can be
entered from the soft-start or active regulation states or
through user intervention.
There are two ways to respond to faults; which are retry mode
and latched off mode. In retry mode, the controller responds
to a fault by shutting down and entering the inactive state
for a programmable delay time (MFR_RETRY_DELAY). This
delay minimizes the duty cycle associated with autonomous
retries if the fault that causes the shutdown disappears once
24
the output is disabled. 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 multiple outputs are
controlled by the same FAULTn pin, the decay time of the
faulted output determines the retry delay. 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. Alternatively,
latched off mode means the controller remains latched-off
following a fault and clearing requires user intervention such
as toggling RUNn or commanding the part OFF then ON.
The LTC3884 has two modes of operation: high efficiency
discontinuous conduction mode or forced continuous
conduction mode. Mode selection is done using the
MFR_PWM _MODE command (discontinuous conduction is always the start-up mode, forced continuous is the
default running mode).
If a controller is enabled for discontinuous operation, the
inductor current is not allowed to reverse. The reverse current
comparator’s output, IREV, turns off the bottom gate of the
external MOSFET just before the inductor current reaches
zero, preventing it from reversing and going negative.
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 ITH pin. In this mode, the efficiency at
light loads is lower than in discontinuous mode operation.
However, continuous mode exhibits lower output ripple
and less interference with audio circuitry, but may result in
reverse inductor current, which can cause the input supply
to boost. The VIN_OV_FAULT_LIMIT can detect this and
turn off the offending channel. However, this fault is based
on an ADC read and can take up to tCONVERT to detect. If
there is a concern about the input supply boosting, keep
the part in discontinuous conduction mode.
If the part is set to discontinuous mode operation, as the
inductor average current increases, the controller will
automatically modify the operation from discontinuous
mode to continuous mode.
3884fe
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LTC3884/LTC3884-1
OPERATION
SWITCHING FREQUENCY AND PHASE
The switching frequency of the PWM can be established
with an internal oscillator or an external time base. The
internal phase-locked loop (PLL) synchronizes PWM
control to this timing reference with proper phase relation,
whether the clock is provided internally or externally. The
device can also be configured to provide the master clock
to other ICs through PMBus command, NVM setting, or
external configuration resistors as outlined in Table 4.
As clock master, the LTC3884 will drive its open-drain SYNC
pin at the selected rate with a pulse width of 500ns. An external
pull-up resistor between SYNC and VDD33 is required in this
case. Only one device connected to SYNC should be designated
to drive the pin. But if multiple LTC3884s programmed as
clock masters are wired to the same SYNC line with a pullup resistor, just one of the devices is automatically elected to
provide clocking, and the others disable their SYNC outputs.
The LTC3884 will automatically revert to an external SYNC
input, disabling its own SYNC, as long as the external
SYNC frequency is greater than 80% of the programmed
SYNC frequency. The external SYNC input shall have a
duty cycle between 20% and 80%.
Whether configured to drive SYNC or not, the LTC3884
can continue PWM operation using its own internal
oscillator if an external clock signal is subsequently lost.
The device can also be programmed to always require
an external oscillator for PWM operation by setting bit
4 of MFR_CONFIG_ALL. The status of the SYNC driver
circuit is indicated by bit 10 of MFR_PADS.
The MFR_PWM_CONFIG command can be used to
configure the phase of each channel. Desired phase
can also be set from EEPROM or external configuration
resistors as outlined in Table 5. Designated phase is
the relationship between the falling edge of SYNC and
the internal clock edge that sets the PWM latch to turn
on the top power switch. Additional small propagation
delays to the PWM control pins will also apply. Both
channels must be off before the FREQUENCY_SWITCH
and MFR_PWM_CONFIG commands can be written to
the LTC3884.
The phase relationships and frequency are independent
of each other, providing numerous application options.
Multiple LTC3884 ICs can be synchronized to realize
a PolyPhase array. In this case the phases should be
separated by 360/n degrees, where n is the number of
phases driving the output voltage rail.
PWM LOOP COMPENSATION
The internal PWM loop compensation resistors RITHn
of the LTC3884 can be adjusted using bit[4:0] of the
MFR_PWM_COMP command.
The transconductance of the LTC3884 PWM error amplifier
can be adjusted using bit[7:5] of the MFR_PWM_COMP
command. These two loop compensation parameters
can be programmed when device is in operation. Refer
to the Programmable Loop Compensation subsection in
the Applications Information section for further details.
OUTPUT VOLTAGE SENSING
Both channels in LTC3884 have differential amplifiers,
which allow the remote sensing of the load voltage between VSENSEn+ and VSENSEn– pins. The telemetry ADC is
also fully differential and makes measurements between
VSENSEn+ and VSENSEn– pins respectively. The maximum
allowed sense voltages for both channels is 5.5V.
INTVCC/EXTVCC POWER
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTVCC pin.
When the EXTVCC pin is shorted to GND or tied to a voltage
less than 4.7V, an internal 5.5V linear regulator supplies
INTVCC power from VIN. If EXTVCC is taken above approximately 4.7V and VIN is higher than 7.0V, the 5.5V regulator
is turned off and an internal switch is turned on, connecting
EXTVCC to INTVCC. Using the EXTVCC allows the INTVCC
power to be derived from a high efficiency external source
such as a switching regulator output.
EXTVCC can provide power to the internal 3.3V linear
regulator even when VIN is not present, which allows the
LTC3884 to be initialized and programmed even without
main power being applied.
3884fe
For more information www.linear.com/LTC3884
25
LTC3884/LTC3884-1
OPERATION
10k
4.99k
10k
10k
LTC3884 + POWER STAGE
ITH0
ITH1
ITHR0
ISENSE0+
ITHR1
ISENSE0–
FAULT0
VSENSE0+
RUN0
VSENSE0–
RUN1
ALERT
FAULT1
SYNC (ENABLED)
ISENSE1+
SHARE_CLK
ISENSE1–
VDD33
VSENSE1+
VSENSE1–
SGND
PGND
10k
RUN
ALERT
FAULT
SYNC
SHARE_CLK
1µF
NOTE: SOME CONNECTORS
AND COMPONENTS OMITTED
FOR CLARITY
BOTH CHIPS HAVE THE INTERNAL
FREQUENCY COMMAND SET TO THE
SAME DESIRED PWM FREQUENCY
1µF
1/2 LTC3884 + POWER STAGE
ITH0
VDD33
L/DCR
R
C
L/DCR
R
C
L/DCR
R
ISENSE0+
ISENSE0–
VSENSE0+
VSENSE0–
RUN0
ALERT
FAULT0
SYNC (DISABLED)
SHARE_CLK
SGND
GND
C
LOAD
3884 F04
Figure 4. Load Sharing Connections for 3-Phase Operation
Each top MOSFET driver is biased from the floating bootstrap
capacitor, CB, which normally recharges during each off cycle
through an external diode when the bottom MOSFET turns
on. If the input voltage VIN decreases to a voltage close to
VOUT, the loop may enter dropout and attempt to turn on
the top MOSFET continuously. The dropout detector detects
this and forces the top MOSFET off for about one-twelfth
of the clock period plus 100ns every three cycles to allow
CB to recharge. However, it is recommended that a load
be present or the IC operates at low frequency during the
drop-out transition to ensure CB is recharged.
OUTPUT CURRENT SENSING AND SUB MILLIOHM
DCR CURRENT SENSING
For DCR current sense applications, a resistor in series with
a capacitor is placed across the inductor. In this configuration, the resistor is tied to the FET side of the inductor
while the capacitor is tied to the load side of the inductor
as shown in Figure 4. If the RC values are chosen such that
the RC time constant matches the inductor time constant
(L/DCR, where DCR is the inductor series resistance), the
resultant voltage appearing across the capacitor equals the
voltage across the inductor series resistance (VDCR) and
26
thus represents the current flowing through the inductor.
In addition to this regular current sensing, the LTC3884
employs a unique architecture to enhance the signal-tonoise ratio by 14dB, enabling it to operate with a small sense
signal (as low as 2mV) via a sub-milliohm value of inductor
DCR (such as 0.2mΩ) to improve the power efficiency for
the heavy load applications while VOUT ≤ 3.5V. As shown
in Figure 4, externally the new architecture only requires
reducing R by 4/5, i.e., RLOWDCR = 1/5Rnomdcr. Better
signal-to-noise ratio helps to reduce jitter at the output
with as low as 2mV sensing signal. Low DCR improves
power efficiency in heavy system loads. So the new DCR
sensing scheme provides a perfect solution for larger
power, and noise sensitive systems. In the meantime, the
current limit threshold is still a function of the inductor
peak current and its DCR value, and can be accurately set
with the MFR_PWM_MODE[2], MFR_PWM_MODE[7].
See Figure 26.
The RC calculations are based on the room temperature
DCR of the inductor. The RC time constant should remain
constant as a function of temperature. This assures the
transient response of the circuit is the same regardless
of the temperature. The DCR of the inductor has a large
For more information www.linear.com/LTC3884
3884fe
LTC3884/LTC3884-1
OPERATION
temperature coefficient, approximately 3900ppm/°C. The
temperature coefficient of the inductor must be written to
the MFR_IOUT_CAL_GAIN_TC register. The external temperature is sensed near the inductor and used to modify
the internal current limit circuit to maintain an essentially
constant current limit with temperature. In this application,
the ISENSEn+ pin is connected to the FET side of the DCR
sensing filter capacitor while the ISENSEn– pin is placed on
the load side of the capacitor. The current sensed from the
input is then given by the expression VDCR/DCR. VDCR is
digitized by the LTC3884’s telemetry ADC with an input
range of ±128mV, a noise floor of 7μVRMS, and a peak-peak
noise of approximately 46.5μV. The LTC3884 computes
the inductor current using the DCR value stored in the
IOUT_CAL_GAIN command and the temperature coefficient
stored in command MFR_IOUT_CAL_GAIN_TC. The resulting current value is returned by the READ_IOUT command.
PolyPhase LOAD SHARING
INPUT CURRENT SENSING
External temperature can best be measured using a remote,
diode-connected PNP transistor such as the MMBT3906.
The emitter should be connected to a TSNS pin while the
base and collector terminals of the PNP transistor should
be returned directly to the LTC3884 SGND pin. Two different currents are applied to the diode (nominally 2μA
and 32μA) and the temperature is calculated from a ∆VBE
measurement made with the internal 16-bit monitor ADC
(see Figure 5).
To sense the total input current consumed by the LTC3884
and the power stage, a resistor is placed between the supply voltage and the drain of the top N-channel MOSFET.
The IIN+ and IIN– pins are connected to the sense resistor.
The filtered voltage is amplified by the internal high side
current sense amplifier and digitized by the LTC3884’s
telemetry ADC. The input current sense amplifier has
three gain settings of 2x, 4x, and 8x set by the bit[6:5] of
the MFR_PWM_CONFIG command. The maximum input
sense voltage for the three gain settings is 50mV, 20mV,
and 5mV respectively. The LTC3884 computes the input
current using the R value stored in the IIN_CAL_GAIN
command. The resulting measured power stage current
is returned by the READ_IIN command.
The LTC3884 uses the RVIN resistor to measure the VIN
pin supply current being consumed by the LTC3884. This
value is returned by the MFR_READ_ICHIP command. The
chip current is calculated by using the R value stored in the
MFR_RVIN command. Refer to the subsection titled Input
Current Sense Amplifier in the Applications Information
section for further details.
Multiple LTC3884s can be arrayed in order to provide a
balanced load-share solution by bussing the necessary
pins. Figure 4 illustrates the shared connections required
for load sharing.
If an external oscillator is not provided, the SYNC pin should
only be enabled on one of the LTC3884s. The other(s)
should be programmed to disable SYNC using bit 4 of
MFR_CONFIG_ALL. If an external oscillator is present, the
chip with the SYNC pin enabled will detect the presence
of the external clock and disable its output.
Multiple chips need to tie all the VSENSE+ pins together, and
all the VSENSE– pins together, and ITHR and ITH together
as well.
EXTERNAL/INTERNAL TEMPERATURE SENSE
TSNS
LTC3884
SGND
SGND
10nF
MMBT3906
3884 F05
Figure 5. Temperature Sense Circuit
The LTC3884 also supports direct VBE based external
temperature measurements. In this case the diode or diode network is trimmed to a specific voltage at a specific
current and temperature. In general this method does not
yield as accurate result as the single PNP transistor ∆VBE
method, but may function better in a noisy application.
Refer to MFR_PWM_MODE in the PMBus Command Details section for additional information on programming
the LTC3884 for these two external temperature sense
3884fe
For more information www.linear.com/LTC3884
27
LTC3884/LTC3884-1
OPERATION
configurations. The calculated temperature is returned by
the PMBus READ_TEMPERATURE_1 command. Refer to
the Applications Information section for details on proper
layout of external temperature sense elements and PMBus
commands that can be used to improve the accuracy of
calculated temperatures. The READ_TEMPERATURE_2
command returns the internal junction temperature of the
LTC3884 using an on-chip diode with a ∆VBE measurement and calculation.
The slope of the external temperature sensor can be
modified with the temperature slope coefficient stored in
MFR_TEMP_1_GAIN. Typical PNPs require temperature
slope adjustments slightly less than 1. The MMBT3906 has
a recommended value in this command of approximately
MFR_TEMP_1_GAIN = 0.991 based on the ideality factor
of 1.01. Simply invert the ideality factor to calculate the
MFR_TEMP_1_GAIN. Different manufacturers and different lots may have different ideality factors. Consult with the
manufacturer to set this value. The offset of the external
temperature sense can be adjusted by MFR_TEMP_1_OFFSET. A value of 0 in this register sets the temperature offset
to –273.15°C.
If the PNP cannot be placed in direct contact with the
inductor, the slope or offset can be increased to account
for temperature mismatches. If the user is adjusting the
slope, the intercept point is at absolute zero, –273.15°C, so
small adjustments in slope can change the apparent measured temperature significantly. Another way to artificially
increase the slope of the temperature term is to increase
the MFR_IOUT_CAL_GAIN_TC term. This will modify the
temperature slope with respect to room temperature.
RCONFIG (RESISTOR CONFIGURATION) PINS
There are six input pins utilizing 1% resistor dividers
between VDD25 and SGND to select key operating parameters. The pins are ASEL0, ASEL1, FREQ_CFG, VOUT0_CFG,
VOUT1_CFG, PHASE_CFG. If pins are floated, the value
stored in the corresponding NVM command is used. If
bit 6 of the MFR_CONFIG_ALL configuration command
is asserted in NVM, the resistor inputs are ignored upon
power-up except for ASEL0 and ASEL1 which are always
respected. The resistor configuration pins are only measured
28
during a power-up reset or after a MFR_RESET or after a
RESTORE_USER_ALL command is executed.
The VOUTn_CFG pin settings are described in Table 3. These
pins select the output voltages for the LTC3884’s analog
PWM controllers. If the pin is open, the VOUT_COMMAND
command is loaded from NVM to determine the output
voltage. The default setting is to have the switcher off
unless the voltage configuration pins are installed.
The following parameters are set as a percentage of the
output voltage if the RCONFIG pins are used to determine
the output voltage:
n
n
n
n
n
n
n
VOUT_OV_FAULT_LIMIT..................................... +10%
VOUT_OV_WARN_LIMIT................................... +7.5%
VOUT_MAX....................................................... +7.5%
VOUT_MARGIN_HIGH..........................................+5%
VOUT_MARGIN_LOW...........................................–5%
VOUT_UV_WARN_LIMIT...................................–6.5%
VOUT_UV_FAULT_LIMIT.......................................–7%
The FREQ_CFG pin settings are described in Table 4. This
pin selects the switching frequency. The phase relationships
between the two channels and SYNC pin are determined by
the PHASE_CFG pin described in Table 5. To synchronize
to an external clock, the part should be put into external
clock mode (SYNC output disabled but frequency set to
the nominal value). If no external clock is supplied, the part
will clock at the programmed frequency. If the application
is multiphase and the SYNC signal between chips is lost,
the parts will not operate at the designed phase even if
they are programmed and trimmed to the same frequency.
This may increase the ripple voltage on the output, possibly produce undesirable operation. If the external SYNC
signal is being generated internally and external SYNC is
not selected, bit 10 of MFR_PADS will be asserted. If no
frequency is selected and the external SYNC frequency is
not present, a PLL_FAULT will occur. If the user does not
wish to see the ALERT from a PLL_FAULT even if there is
not a valid synchronization signal at power-up, the ALERT
mask for PLL_FAULT must be written. See the description
on SMBALERT_MASK for more details. If the SYNC pin is
connected between multiple ICs only one of the ICs should
have the SYNC pin enabled, and all other ICs should be
configured to have the SYNC pin disabled.
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
OPERATION
The ASEL0,1 pin settings are described in Table 6. ASEL1
selects the top 3 bits of the slave address for the LTC3884.
ASEL0 selects the bottom 4 bits of the slave address for
the LTC3884. If ASEL1 is floating, the 3 most significant
bits are retrieved from the NVM MFR_ADDRESS command. If ASEL0 is floating, the 4 LSB bits stored in NVM
MFR_ADDRESS command are used to determine the 4 LSB
bits of the slave address. For more detail, refer to Table 6.
Note: Per the PMBus specification, pin programmed
parameters can be overridden by commands from the
digital interface with the exception of ASEL which is
always honored. Do not set any part address to 0x5A or
0x5B because these are global addresses and all parts
will respond to them.
FAULT DETECTION AND HANDLING
A variety of fault and warning reporting and handling
mechanisms are available. Fault and warning detection
capabilities include:
n
Input OV FAULT Protection and UV Warning
n
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 and Warn Protection
n
CML Fault (Communication, Memory or Logic)
n
External Fault Detection via the Bidirectional FAULTn
Pins.
In addition, the LTC3884 can map any combination of
fault indicators to their respective FAULTn pin using the
propagate FAULTn response commands, MFR_FAULT_
PROPAGATE. Typical usage of a FAULTn 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 FAULTn pins
can be used as inputs to detect external faults downstream
of the controller that require an immediate response.
Any fault or warning event will always cause the ALERT
pin to assert low unless the fault or warning is masked by
the SMBALERT_MASK. The pin will remain asserted low
until the CLEAR_FAULTS command is issued, the fault bit
is written to a 1 or bias power is cycled or a MFR_RESET
command is issued, or the RUN pins are toggled OFF/ON
or the part is commanded OFF/ON via PMBus or an ARA
command operation is performed. The MFR_FAULT_
PROPAGATE command determines if the FAULT pins are
pulled low when a fault is detected.
Output and input fault event handling is controlled by the
corresponding fault response byte as specified in Tables 7
to 12. 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 conditions
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,
assuming the fault condition itself is not immediately
destructive. The MFR_RETRY_DELAY must be greater
than 120ms. It can not exceed 83.88 seconds.
Status Registers and ALERT Masking
Figure 6 summarizes the internal LTC3884 status registers accessible by PMBus command. These contain
indication of various faults, warnings and other important
operating conditions. As shown, the STATUS_BYTE and
STATUS_WORD commands also summarize contents of
other status registers. Refer to PMBus Command Details
for specific information.
NONE OF THE ABOVE in STATUS_BYTE indicates that
one or more of the bits in the most-significant nibble of
STATUS_WORD are also set.
In general, any asserted bit in a STATUS_x register also
pulls the ALERT pin low. Once set, ALERT will remain low
until one of the following occurs.
n
A CLEAR_FAULTS or MFR_RESET Command Is Issued
n
The Related Status Bit Is Written to a One
n
The Faulted Channel Is Properly Commanded Off and
Back On
3884fe
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29
LTC3884/LTC3884-1
OPERATION
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)
(PAGED)
STATUS_CML
7
6
5
4
3
2
1
0
Chip Not Driving ALERT Low
Chip Not Busy
Internal Calculations Not Pending
Output Not In Transition
EEPROM Initialized
(reads 0)
SHARE_CLK_LOW
WP Pin High
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
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
EEPROM ECC Status
Reserved
Reserved
Reserved
Reserved
DESCRIPTION
General Fault or Warning Event
General Non-Maskable Event
Dynamic
Status Derived from Other Bits
7
6
5
4
3
2
1
0
Internal Temperature Fault
Internal Temperature Warning
EEPROM CRC Error
Internal PLL Unlocked
Fault Log Present
VDD33 UV or OV Fault
VOUT Short Cycled
FAULT Pulled Low By External Device
(PAGED)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
VDD33 OV Fault
VDD33 UV Fault
(reads 0)
(reads 0)
Invalid ADC Result(s)
SYNC Clocked by External Source
Channel 1 is POWER_GOOD
Channel 0 is POWER_GOOD
LTC3884 Forcing RUN1 Low
LTC3884 Forcing RUN0 Low
RUN1 Pin State
RUN0 Pin State
LTC3884 Forcing FAULT1 Low
LTC3884 Forcing FAULT0 Low
FAULT1 Pin State
FAULT0 Pin State
MFR_PADS
MFR_INFO
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
VIN_OV Fault
(reads 0)
VIN_UV Warning
(reads 0)
Unit Off for Insuffcient VIN
(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
3884 F06
MASKABLE GENERATES ALERT BIT CLEARABLE
Yes
No
No
No
Yes
Yes
No
Not Directly
Yes
Yes
No
No
Figure 6. LTC3884 Status Register Summary
30
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
OPERATION
n
n
The LTC3884 Successfully Transmits Its Address During
a PMBus ARA
Bias Power Is Cycled
With some exceptions, the SMBALERT_MASK command
can be used to prevent the LTC3884 from asserting
ALERT for bits in these registers on a bit-by-bit basis.
These mask settings are promoted to STATUS_WORD
and STATUS_BYTE in the same fashion as the status bits
themselves. For example, if ALERT is masked for all bits
in Channel 0 STATUS_VOUT, then ALERT is effectively
masked for the VOUT bit in STATUS_WORD for PAGE 0.
The BUSY bit in STATUS_BYTE also asserts ALERT low
and cannot be masked. This bit can be set as a result of
various internal interactions with PMBus communication.
This fault occurs when a command is received that cannot
be safely executed with one or both channels enabled. As
discussed in Application Information, BUSY faults can
be avoided by polling MFR_COMMON before executing
some commands.
If masked faults occur immediately after power up, ALERT
may still be pulled low because there has not been time
to retrieve all of the programmed masking information
from EEPROM.
Status information contained in MFR_COMMON and
MFR_PADS can be used to further debug or clarify the
contents of STATUS_BYTE or STATUS_WORD as shown,
but the contents of these registers do not affect the state
of the ALERT pin and may not directly influence bits in
STATUS_BYTE or STATUS_WORD.
Mapping Faults to FAULT Pins
Channel-to-channel fault (including channels from multiple
LTC3884s) dependencies can be created by connecting
FAULTn pins together. In the event of an internal fault, one
or more of the channels is configured to pull the bussed
FAULTn pins low. The other channels are then configured
to shut down when the FAULTn pins are pulled low. For
autonomous group retry, the faulted channel is configured to let go of the FAULTn 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 FAULTn 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 or, set bit 0 of
MFR_CONFIG_ALL to a 1.
The status of all faults and warnings is summarized in the
STATUS_WORD and STATUS_BYTE commands.
Additional fault detection and handling capabilities are:
Power Good Pins
The PGOODn pins of the LTC3884 are connected to the
open drains of internal MOSFETs. The MOSFETs turn on
and pull the PGOODn pins low when the channel output
voltage is not within the channel’s UV and OV voltage thresholds. During TON_DELAY and TON_RISE sequencing, the
PGOODn pin is held low. The PGOODn pin is also pulled
low when the respective RUNn pin is low. The PGOODn
pin response is deglitched by an internal 60μs digital filter.
The PGOODn pin and PGOOD status may be different at
times due to communication latency of up to 10µs.
CRC Protection and ECC
The LTC3884 contains internal EEPROM with error correction coding (ECC) to store user configuration settings and
fault login formation. EEPROM endurance and retention for
user space and fault log pages are specified in the Absolute
Maximum Ratings and Electrical Characteristics tables.
The integrity of the NVM memory is checked after a power
on reset. A CRC error will prevent the controller from leaving the inactive state. If a CRC error occurs, the CML bit is
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. NVM
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 LTC3884 manufacturing section of the NVM is mirrored. If both copies are corrupted, 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
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LTC3884/LTC3884-1
OPERATION
occurred. The user is cautioned to disable both output
power supply rails associated with this specific part.
There are no provisions for field repair of NVM faults in
the manufacturing section.
SERIAL INTERFACE
The LTC3884 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
NVM or an external resistor divider. In addition the LTC3884
always responds to the global broadcast address of 0x5A
(7 bit) or 0x5B (7 bit).
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) write block. 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 LTC3884.
Communication Protection
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
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.
or both of these global addresses. Reading from global
addresses is strongly discouraged.
Device addressing provides the standard means of the
PMBus master communicating with a single instance of
an LTC3884. 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.
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.
Reading from rail addresses is also strongly discouraged.
All four means of PMBus addressing require the user to
employ disciplined planning to avoid addressing conflicts.
Communication to LTC3884 devices at global and rail addresses should be limited to command write operations.
RESPONSES TO VOUT, IIN and IOUT FAULTS
VOUT OV and UV conditions are monitored by comparators.
The OV and UV limits are set in three ways.
n
DEVICE ADDRESSING
n
The LTC3884 offers five different types of addressing over
the PMBus interface, specifically: 1) global, 2) device, 3)
rail addressing and 4) alert response address (ARA).
n
Global addressing provides a means of the PMBus master
to address all LTC3884 devices on the bus. The LTC3884
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 LTC3884 devices
on the bus. Other ADI device types may respond at one
32
As a Percentage of the VOUT if Using the Resistor
Configuration Pins
In NVM if Either Programmed at the Factory or Through
the GUI
By PMBus Command
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 time latency
of up to tCONVERT. The IOUT calculation accounts for the
DCR or sense resistor and their temperature coefficient.
The input current is equal to the voltage measured across
the RIINSNS resistor divided by the resistors value as set
with the MFR_RVIN command. If this calculated input
current exceeds the IN_OC_WARN_LIMIT the ALERT pin
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is pulled low and the IIN_OC_WARN bit is asserted in the
STATUS_INPUT command.
The digital processor within the LTC3884 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_ DELAY 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. However,
the reverse output current is monitored while device is in
OV fault. When it reaches the limit, both top and bottom
MOSFETs are turned off. The top and bottom MOSFETs will
keep their state until the overvoltage condition is cleared
regardless of the PMBus VOUT_OV_FAULT_RESPONSE
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_RESPONSE
command, the user can select any of the following behaviors:
n
OV Pull-Down Only (OV Cannot Be Ignored)
n
Shut Down (Stop Switching) Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY
Either the Latch Off or Retry fault responses can be deglitched in increments of (0-7) • 10μs. See Table 7.
Output Undervoltage Response
The response to an undervoltage comparator output can
be the following:
Peak Output Overcurrent Fault Response
Due to the current mode control algorithm, peak output
current across the inductor is always limited on a cycle-bycycle basis. The value of the peak current limit is specified
in sense voltage in the EC table. The current limit circuit
operates by limiting the ITH maximum voltage. If DCR sensing is used, the ITH maximum voltage has a temperature
dependency directly proportional to the TC of the DCR
of the inductor. The LTC3884 automatically monitors the
external temperature sensors and modifies the maximum
allowed ITH to compensate for this term.
The overcurrent fault processing circuitry can execute the
following behaviors:
n
Current Limit Indefinitely
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY.
The overcurrent responses can be deglitched in increments
of (0-7) • 16ms. See Table 9
RESPONSES TO TIMING FAULTS
TON_MAX_FAULT_LIMIT is the time allowed for VOUT to
rise and settle at start-up. The TON_MAX_FAULT_LIMIT
condition is predicated upon detection of the VOUT_UV_
FAULT_LIMIT as the output is undergoing a SOFT_START
sequence. The TON_MAX_ FAULT_LIMIT time is started
after TON_DELAY has been reached and a SOFT_START
sequence is started. The resolution of the TON_MAX_
FAULT_LIMIT is 10μs. If the VOUT_UV_FAULT _LIMIT
is not reached within the TON_MAX_FAULT_LIMIT time,
the response of this fault is determined by the value of
the TON_MAX_FAULT_RESPONSE command value. This
response may be one of the following:
Ignore
n
n
Ignore
Shut Down Immediately—Latch Off
n
n
Shut Down (Stop Switching) Immediately—Latch Off
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY.
n
n
The UV responses can be deglitched. See Table 8.
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY.
This fault response is not deglitched. A value of 0 in
TON_MAX_FAULT_LIMIT means the fault is ignored. The
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LTC3884/LTC3884-1
OPERATION
TON_MAX_FAULT_LIMIT should be set longer than the
TON_RISE time. It is recommended TON_MAX_FAULT_
LIMIT 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 11.
RESPONSES TO VIN OV FAULTS
VIN overvoltage is measured with the ADC. The response
is naturally deglitched by the 90ms typical response time
of the ADC. The fault responses are:
n
Ignore
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY. See Table 9.
RESPONSES TO INPUT OVERCURRENT AND OUTPUT
UNDERCURRENT FAULTS
Input overcurrent and output undercurrent are measured
with the ADC. The fault responses are:
n
Ignore
n
Ignore
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Latch Off
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY. See Table 11.
n
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY
See Table 11.
RESPONSES TO OT/UT FAULTS
Internal Overtemperature Fault Response
An internal temperature sensor protects against NVM
damage. Above 85°C, no writes to NVM are recommended.
Above 130°C,the internal overtemperature warn threshold
is exceeded and the part disables the NVM and does not reenable until the temperature has dropped to 125°C. When
the die temperature exceed 160°C the internal 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 10.
External Overtemperature and Undertemperature
Fault Response
Two external temperature sensors can be used to sense
the temperature of critical circuit elements like inductors
and power MOSFETs. The OT_FAULT_ RESPONSE and
UT_FAULT_ RESPOSE commands are used to determine
the appropriate response to an overtemperature and under
temperature condition, respectively. If no external sense
elements are used (not recommended) set the UT_FAULT_
RESPONSE to ignore and set the UT_FAULT_LIMIT to
–275°C. The fault responses are:
34
RESPONSES TO EXTERNAL FAULTS
When either FAULTn pin is pulled low, the OTHER bit is
set in the STATUS_WORD command, the appropriate bit
is set in the STATUS_MFR_SPECIFIC 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 FAULTn pin going low by
modifying the MFR_FAULT_RESPONSE command. To
avoid the ALERT pin asserting low when FAULT is pulled
low, assert bit 1 of MFR_CHAN_CONFIG, or mask the
ALERT using the SMBALERT_MASK command.
FAULT LOGGING
The LTC3884 has fault logging capability. Data is logged
into memory in the order shown in Table 13. The data is
stored in a continuously updated buffer in RAM. When a
fault event occurs, the fault log buffer is copied from the
RAM buffer into NVM. 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. The fault log data remains in NVM until a
MFR_FAULT _LOG_CLEAR command is issued. Issuing
this command re-enables the fault log feature. Before
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re-enabling fault log, be sure no faults are present and a
CLEAR_FAULTS command has been issued.
When the LTC3884 powers-up or exits its reset state, it
checks the NVM for a valid fault log. If a valid fault log
exists in NVM, 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 LTC3884 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. A
FAULTn being externally pulled low will not trigger a fault
logging event.
BUS TIMEOUT PROTECTION
The LTC3884 implements a timeout feature to avoid persistent faults on 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 35ms or the LTC3884 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 LTC3884 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. The timeout
period defaults to 32ms.
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 LTC3884 supports the
full PMBus frequency range from 10kHz to 400kHz.
SIMILARITY BETWEEN PMBus, SMBus AND I2C
2-WIRE INTERFACE
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
timeouts to prevent persistent 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/PMBus reads. If a general purpose
I2C controller is used, check that repeat start is supported.
The LTC3884 supports the maximum SMBus clock speed
of 100kHz and is compatible with the higher speed PMBus specification (between 100kHz and 400kHz) if MFR_
COMMON polling or clock stretching is enabled. For robust
communication and operation refer to the Note section in
the PMBus command summary. Clock stretching is enabled
by asserting bit 1 of MFR_CONFIG_ALL.
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 SERIAL DIGITAL INTERFACE
The LTC3884 communicates with a host (master) using the
standard PMBus serial bus interface. The Timing Diagram,
Figure 7, 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. The LTC3884
is a slave device. The master can communicate with the
LTC3884 using the following formats:
n
Master Transmitter, Slave Receiver
n
Master Receiver, Slave Transmitter
The following PMBus protocols are supported:
n
Write Byte, Write Word, Send Byte
n
Read Byte, Read Word, Block Read, Block Write
n
Alert Response Address
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35
LTC3884/LTC3884-1
OPERATION
Figures 8-25 illustrate the aforementioned PMBus protocols. All transactions support PEC and GCP (group
command protocol). The Block Read supports 255 bytes
of returned data. For this reason, the PMBus timeout may
be extended when reading the fault log.
the slave receiver) the master transmitter becomes a
master receiver and the slave receiver becomes a slave
transmitter.
n
Figure 8 is a key to the protocol diagrams in this section.
PEC is optional.
A value shown below a field in the following figures is
mandatory value for that field.
Refer to Figure 8 for a legend.
The data formats implemented by PMBus are:
n
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.
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.
Master transmitter transmits to slave receiver. The
transfer direction in this case is not changed.
Master reads slave immediately after the first byte. At
the moment of the first acknowledgment (provided by
SDA
tf
tr
tLOW
tSU(DAT)
tHD(SDA)
tf
tSP
tr
tBUF
SCL
tHD(STA)
tHD(DAT)
tHIGH
START
CONDITION
tSU(STA)
tSU(STO)
3884 F07
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Figure 7. Timing Diagram
Table 1. Abbreviations of Supported Data Formats
PMBus
TERMINOLOGY
SPECIFICATION
ADI
REFERENCE TERMINOLOGY DEFINITION
L11
Linear
Part II ¶7.1
Linear_5s_1s
L16
Linear VOUT_MODE
Part II ¶8.2
Linear_16u
CF
DIRECT
Part II ¶7.2
Varies
Reg
register bits
Part II ¶10.3
Reg
ASC
text characters
Part II ¶22.2.1
ASCII
36
Floating point 16-bit data: value = Y • 2N,
where N = b[15:1] and Y = b[10:0], both
two’s compliment binary integers.
EXAMPLE
b[15:0] = 0x9807 = 10011_000_0000_0111
value = 7 • 2–13 = 854E-6
Floating point 16-bit data: value = Y • 2–12, b[15:0] = 0x4C00 = 0100_1100_0000_0000
where Y = b[15:0], an unsigned integer.
value = 19456 • 2–12 = 4.75
16-bit data with a custom format
defined in the detailed PMBus command
description.
Often an unsigned or two’s compliment
integer.
Per-bit meaning defined in detailed PMBus PMBus STATUS_BYTE command.
command description.
ISO/IEC 8859-1 [A05]
LTC (0x4C5443)
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OPERATION
S
START CONDITION
Sr
REPEATED START CONDITION
Rd
READ (BIT VALUE OF 1)
Wr
WRITE (BIT VALUE OF 0)
A
ACKNOWLEDGE (THIS BIT POSITION MAY BE 0
FOR AN ACK OR 1 FOR A NACK)
P
STOP CONDITION
PEC PACKET ERROR CODE
MASTER TO SLAVE
SLAVE TO MASTER
...
CONTINUATION OF PROTOCOL
3884 F08
Figure 8. PMBus Packet Protocol Diagram Element Key
1
7
S
1
1
SLAVE ADDRESS Rd/Wr A
1
P
3884 F09
Figure 9. Quick Command Protocol
1
7
S
1
1
SLAVE ADDRESS Wr A COMMAND CODE A
1
1
8
P
3884 F10
Figure 10. Send Byte Protocol
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
PEC
A
1
P
3884 F11
Figure 11. 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
3884 F12
Figure 12. 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
3884 F13
Figure 13. Write Byte Protocol with PEC
1
S
7
1
1
8
1
SLAVE ADDRESS Wr A COMMAND CODE A
8
1
8
1
DATA BYTE LOW
A
DATA BYTE HIGH
A
1
P
3884 F14
Figure 14. 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
3884 F15
Figure 15. Write Word Protocol with PEC
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LTC3884/LTC3884-1
OPERATION
1
7
S
1
1
8
1
1
1
7
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
8
1
1
DATA BYTE
A
P
3884 F16
Figure 16. Read Byte Protocol
1
S
7
1
1
8
1
1
7
1
8
1
DATA BYTE
A
1
SLAVE ADDRESS Wr A COMMAND CODE A Sr SLAVE ADDRESS Rd A
PEC
1
1
A
P
3884 F17
Figure 17. 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
1
1
DATA BYTE HIGH A
8
P
3884 F18
Figure 18. 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
3884 F19
Figure 19. Read Word Protocol with PEC
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
BYTE COUNT = N A
8
1
8
1 …
8
1
DATA BYTE 1
A
DATA BYTE 2
A …
DATA BYTE N
A
…
1
P
3884 F22
Figure 20. 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
BYTE COUNT = N A
8
1
8
1 …
8
1
8
1
1
DATA BYTE 1
A
DATA BYTE 2
A …
DATA BYTE N
A
PEC
A
P
…
3884 F21
Figure 21. Block Read Protocol with PEC
38
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OPERATION
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
8
A …
1
Sr SLAVE ADDRESS Rd A
8
1
DATA BYTE 1
A
…
1
A …
DATA BYTE M
8
1
BYTE COUNT = N A
8
1
1
DATA BYTE 1
A
…
8
1 …
8
1
1
DATA BYTE 2
A …
DATA BYTE N
A
P
3884 F22
Figure 22. 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
8
A …
1
Sr SLAVE ADDRESS Rd A
8
1
DATA BYTE 1
A
…
1
DATA BYTE M
8
A …
1
BYTE COUNT = N A
8
1
1
DATA BYTE 1
A
…
8
1 …
8
1
8
1
1
DATA BYTE 2
A …
DATA BYTE N
A
PEC
A
P
3884 F23
Figure 23. Block Write – Block Read Process Call with PEC
1
7
1
1
8
1
1
S ALERT RESPONSE Rd A DEVICE ADDRESS A
ADDRESS
P
3884 F24
Figure 24. Alert Response Address Protocol
1
7
1
1
8
1
S ALERT RESPONSE Rd A DEVICE ADDRESS A
ADDRESS
8
1
1
PEC
A
P
3884 F25
Figure 25. Alert Response Address Protocol with PEC
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39
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
PMBus COMMANDS
The following tables list supported PMBus commands and
manufacturer specific commands. A complete description
of these commands can be found in the “PMBus Power
System Mgt Protocol Specification – Part II – Revision
1.2”. Users are encouraged to reference this specification.
Exceptions or manufacturer specific implementations are
listed below in Table 2. Floating point values listed in the
“DEFAULT VALUE” column are either Linear 16-bit Signed
(PMBus Section 8.3.1) or Linear_5s_11s (PMBus Section 7.1) format, whichever is appropriate for the command.
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 im-
plicitly 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 subsection titled PMBus Communication and
Command Processing in the Applications Information
section for further details.
Table 2. Summary (Note: The Data Format abbreviations are detailed at the end of this table.)
COMMAND NAME
CMD
CODE DESCRIPTION
TYPE
DATA
PAGED FORMAT UNITS
PAGE
0x00 Provides integration with multi-page PMBus
devices.
R/W Byte
N
Reg
OPERATION
0x01 Operating mode control. On/off, margin high
and margin low.
R/W Byte
Y
Reg
ON_OFF_CONFIG
0x02 RUN pin and PMBus bus on/off command
configuration.
R/W Byte
Y
Reg
CLEAR_FAULTS
0x03 Clear any fault bits that have been set.
Send Byte
N
PAGE_PLUS_WRITE
0x05 Write a command directly to a specified page.
W Block
N
PAGE_PLUS_READ
0x06 Read a command directly from a specified page. Block R/W
N
WRITE_PROTECT
0x10 Level of protection provided by the device
against accidental changes.
R/W Byte
N
STORE_USER_ALL
0x15 Store user operating memory to EEPROM.
Send Byte
N
RESTORE_USER_ALL
0x16 Restore user operating memory from EEPROM.
Send Byte
N
CAPABILITY
0x19 Summary of PMBus optional communication
protocols supported by this device.
R Byte
N
Reg
SMBALERT_MASK
0x1B Mask ALERT activity
Block R/W
Y
Reg
VOUT_MODE
0x20
VOUT_COMMAND
Output voltage format and exponent (2–12).
NVM
DEFAULT
VALUE PAGE
0x00
73
Y
0x80
77
Y
0x1E
77
NA
102
69
73
Reg
Y
Y
0x00
74
NA
113
NA
113
0xB0
101
see CMD
103
2–12
83
R Byte
Y
Reg
0x21 Nominal output voltage set point.
R/W Word
Y
L16
V
Y
1.0
0x1000
84
VOUT_MAX
0x24 Upper limit on the commanded output voltage
including VOUT_MARGIN_HI.
R/W Word
Y
L16
V
Y
2.75
0x2C00
83
VOUT_MARGIN_HIGH
0x25 Margin high output voltage set point. Must be
greater than VOUT_COMMAND.
R/W Word
Y
L16
V
Y
1.05
0x10CD
84
VOUT_MARGIN_LOW
0x26 Margin low output voltage set point. Must be
less than VOUT_COMMAND.
R/W Word
Y
L16
V
Y
0.95
0x0F33
84
40
0x14
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
COMMAND NAME
CMD
CODE DESCRIPTION
VOUT_TRANSITION_
RATE
0X27 Rate the output changes when VOUT
commanded to a new value.
R/W Word
Y
L11
V/ms
Y
0.25
0xAA00
90
FREQUENCY_SWITCH
0x33 Switching frequency of the controller.
R/W Word
N
L11
kHz
Y
425k
0xFB52
81
VIN_ON
0x35 Input voltage at which the unit should start
power conversion.
R/W Word
N
L11
V
Y
6.5
0xCB40
82
VIN_OFF
0x36 Input voltage at which the unit should stop
power conversion.
R/W Word
N
L11
V
Y
6.0
0xCB00
82
IOUT_CAL_GAIN
0x38 The ratio of the voltage at the current sense
pins to the sensed current. For devices using a
fixed current sense resistor, it is the resistance
value in mΩ.
R/W Word
Y
L11
mΩ
Y
0.32
0xAA8F
85
VOUT_OV_FAULT_LIMIT
0x40 Output overvoltage fault limit.
R/W Word
Y
L16
V
Y
1.1
0x119A
83
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
92
VOUT_OV_WARN_LIMIT
0x42 Output overvoltage warning limit.
R/W Word
Y
L16
V
Y
1.075
0x1133
83
VOUT_UV_WARN_LIMIT
0x43 Output undervoltage warning limit.
R/W Word
Y
L16
V
Y
0.925
0x0ECD
84
VOUT_UV_FAULT_LIMIT
0x44 Output undervoltage fault limit.
R/W Word
Y
L16
V
Y
0.9
0x0E66
84
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
93
IOUT_OC_FAULT_LIMIT
0x46 Output overcurrent fault limit.
R/W Word
Y
L11
Y
45.0
0xE2D0
86
IOUT_OC_FAULT_
RESPONSE
0x47 Action to be taken by the device when an output
overcurrent fault is detected.
R/W Byte
Y
Reg
Y
0x00
95
IOUT_OC_WARN_LIMIT
0x4A Output overcurrent warning limit.
R/W Word
Y
L11
A
Y
35.0
0xE230
87
OT_FAULT_LIMIT
0x4F External overtemperature fault limit.
R/W Word
Y
L11
C
Y
100.0
0xEB20
88
OT_FAULT_RESPONSE
0x50 Action to be taken by the device when an
external overtemperature fault is detected,
R/W Byte
Y
Reg
Y
0xB8
97
OT_WARN_LIMIT
0x51 External overtemperature warning limit.
R/W Word
Y
L11
C
Y
85.0
0xEAA8
88
UT_FAULT_LIMIT
0x53 External undertemperature fault limit.
R/W Word
Y
L11
C
Y
–40.0
0xE580
89
UT_FAULT_RESPONSE
0x54 Action to be taken by the device when an
external undertemperature fault is detected.
R/W Byte
Y
Reg
Y
0xB8
97
VIN_OV_FAULT_LIMIT
0x55 Input supply overvoltage fault limit.
R/W Word
N
L11
Y
15.5
0xD3E0
81
VIN_OV_FAULT_
RESPONSE
0x56 Action to be taken by the device when an input
overvoltage fault is detected.
R/W Byte
Y
Reg
Y
0x80
92
VIN_UV_WARN_LIMIT
0x58 Input supply undervoltage warning limit.
R/W Word
N
L11
V
Y
6.3
0xCB26
82
IIN_OC_WARN_LIMIT
0x5D Input supply overcurrent warning limit.
R/W Word
N
L11
A
Y
10.0
0xD280
87
TON_DELAY
0x60 Time from RUN and/or Operation on to output
rail turn-on.
R/W Word
Y
L11
ms
Y
0.0
0x8000
89
TYPE
DATA
PAGED FORMAT UNITS
A
V
NVM
DEFAULT
VALUE PAGE
3884fe
For more information www.linear.com/LTC3884
41
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
COMMAND NAME
CMD
CODE DESCRIPTION
TYPE
DATA
PAGED FORMAT UNITS
NVM
DEFAULT
VALUE PAGE
TON_RISE
0x61 Time from when the output starts to rise
until the output voltage reaches the VOUT
commanded value.
R/W Word
Y
L11
ms
Y
8.0
0xD200
89
TON_MAX_FAULT_LIMIT
0x62 Maximum time from the start of TON_RISE for
VOUT to cross the VOUT_UV_FAULT_LIMIT.
R/W Word
Y
L11
ms
Y
10.00
0xD280
90
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
95
TOFF_DELAY
0x64 Time from RUN and/or Operation off to the start R/W Word
of TOFF_FALL ramp.
Y
L11
ms
Y
0.0
0x8000
90
TOFF_FALL
0x65 Time from when the output starts to fall until
the output reaches zero volts.
R/W Word
Y
L11
ms
Y
8.00
0xD200
90
TOFF_MAX_WARN_
LIMIT
0x66 Maximum allowed time, after TOFF_FALL
completed, for the unit to decay below 12.5%.
R/W Word
Y
L11
ms
Y
150.0
0xF258
91
STATUS_BYTE
0x78 One byte summary of the unit’s fault condition.
R/W Byte
Y
Reg
NA
104
STATUS_WORD
0x79 Two byte summary of the unit’s fault condition.
R/W Word
Y
Reg
NA
104
STATUS_VOUT
0x7A Output voltage fault and warning status.
R/W Byte
Y
Reg
NA
105
STATUS_IOUT
0x7B Output current fault and warning status.
R/W Byte
Y
Reg
NA
105
STATUS_INPUT
0x7C Input supply fault and warning status.
R/W Byte
N
Reg
NA
106
STATUS_TEMPERATURE
0x7D External temperature fault and warning status
for READ_TEMERATURE_1.
R/W Byte
Y
Reg
NA
106
STATUS_CML
0x7E Communication and memory fault and warning
status.
R/W Byte
N
Reg
NA
107
STATUS_MFR_SPECIFIC
0x80 Manufacturer specific fault and state
information.
R/W Byte
Y
Reg
NA
107
READ_VIN
0x88 Measured input supply voltage.
R Word
N
L11
V
NA
110
READ_IIN
0x89 Measured input supply current.
R Word
N
L11
A
NA
110
READ_VOUT
0x8B Measured output voltage.
R Word
Y
L16
V
NA
110
READ_IOUT
0x8C Measured output current.
R Word
Y
L11
A
NA
110
READ_TEMPERATURE_1
0x8D External temperature sensor temperature. This
is the value used for all temperature related
processing, including IOUT_CAL_GAIN.
R Word
Y
L11
C
NA
110
READ_TEMPERATURE_2
0x8E Internal die junction temperature. Does not
affect any other commands.
R Word
N
L11
C
NA
110
READ_FREQUENCY
0x95 Measured PWM switching frequency.
R Word
Y
L11
Hz
NA
110
READ_POUT
0x96 Measured output power
R Word
Y
L11
W
N/A
110
READ_PIN
0x97 Calculated input power
R Word
Y
L11
W
N/A
111
PMBus_REVISION
0x98 PMBus revision supported by this device.
Current revision is 1.2.
R Byte
N
Reg
0x22
101
MFR_ID
0x99 The manufacturer ID of the LTC3884 in ASCII.
R String
N
ASC
LTC
101
MFR_MODEL
0x9A Manufacturer part number in ASCII.
R String
N
ASC
MFR_VOUT_MAX
0xA5 Maximum allowed output voltage including
VOUT_OV_FAULT_LIMIT.
R Word
Y
L16
MFR_PIN_ACCURACY
0xAC Returns the accuracy of the READ_PIN command
R Byte
N
USER_DATA_00
0xB0 OEM RESERVED. Typically used for part
serialization.
R/W Word
N
42
Reg
LTC3884
101
V
5.7
0x5B33
85
%
5.0%
111
NA
101
Y
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
COMMAND NAME
CMD
CODE DESCRIPTION
USER_DATA_01
0xB1 Manufacturer reserved for LTpowerPlay.
R/W Word
Y
Reg
Y
NA
101
USER_DATA_02
0xB2 OEM RESERVED. Typically used for part
serialization.
R/W Word
N
Reg
Y
NA
101
USER_DATA_03
0xB3 An NVM word available for the user.
R/W Word
Y
Reg
Y
0x0000
101
USER_DATA_04
0xB4 An NVM word available for the user.
R/W Word
N
Reg
Y
0x0000
101
MFR_INFO
0xB6 Manufacturing specific information.
R Word
N
Reg
MFR_EE_UNLOCK
0xBD Contact factory.
118
MFR_EE_ERASE
0xBE Contact factory.
118
TYPE
DATA
PAGED FORMAT UNITS
NVM
DEFAULT
VALUE PAGE
109
118
MFR_EE_DATA
0xBF Contact factory.
MFR_CHAN_CONFIG
0xD0 Configuration bits that are channel specific.
R/W Byte
Y
Reg
Y
0x1D
75
MFR_CONFIG_ALL
0xD1 General configuration bits.
R/W Byte
N
Reg
Y
0x21
76
MFR_FAULT_
PROPAGATE
0xD2 Configuration that determines which faults are
propagated to the FAULT pin.
R/W Word
Y
Reg
Y
0x6993
98
MFR_PWM_COMP
0xD3 PWM loop compensation configuration
R/W Byte
Y
Reg
Y
0xAE
79
MFR_PWM_MODE
0xD4 Configuration for the PWM engine.
R/W Byte
Y
Reg
Y
0xC7
78
MFR_FAULT_RESPONSE
0xD5 Action to be taken by the device when the
FAULT pin is externally asserted low.
R/W Byte
Y
Reg
Y
0xC0
100
MFR_OT_FAULT_
RESPONSE
0xD6 Action to be taken by the device when an
internal overtemperature fault is detected.
R Byte
N
Reg
0xC0
96
MFR_IOUT_PEAK
0xD7 Report the maximum measured value of READ_
IOUT since last MFR_CLEAR_PEAKS.
R Word
Y
L11
NA
111
MFR_ADC_CONTROL
0xD8 ADC telemetry parameter selected for repeated
fast ADC read back
R/W Byte
N
Reg
0x00
112
MFR_RETRY_DELAY
0xDB Retry interval during FAULT retry mode.
R/W Word
Y
L11
ms
Y
350.0
0xFABC
91
MFR_RESTART_DELAY
0xDC Minimum time the RUN pin is held low by the
LTC3884.
R/W Word
Y
L11
ms
Y
500.0
0xFBE8
91
MFR_VOUT_PEAK
0xDD Maximum measured value of READ_VOUT
since last MFR_CLEAR_PEAKS.
R Word
Y
L16
V
NA
111
MFR_VIN_PEAK
0xDE Maximum measured value of READ_VIN since
last MFR_CLEAR_PEAKS.
R Word
N
L11
V
NA
111
MFR_TEMPERATURE_1_
PEAK
0xDF Maximum measured value of external
Temperature (READ_TEMPERATURE_1) since
last MFR_CLEAR_PEAKS.
R Word
Y
L11
C
NA
111
MFR_READ_IIN_PEAK
0xE1 Maximum measured value of READ_IIN
command since last MFR_CLEAR_PEAKS
R Word
N
L11
A
NA
111
MFR_CLEAR_PEAKS
0xE3 Clears all peak values.
Send Byte
N
NA
103
MFR_READ_ICHIP
0xE4 Measured supply current of the LTC3884
R Word
N
L11
NA
111
MFR_PADS
0xE5 Digital status of the I/O pads.
R Word
N
Reg
NA
108
Sets the 7-bit I2C address byte.
MFR_ADDRESS
0xE6
R/W Byte
N
Reg
MFR_SPECIAL_ID
0xE7 Manufacturer code representing the LTC3884
and revision
R Word
N
Reg
MFR_IIN_CAL_GAIN
0xE8 The resistance value of the input current sense
element in mΩ.
R/W Word
N
L11
A
A
Y
mΩ
Y
0x4F
75
0x4C0X
101
5.0
0xCA80
87
3884fe
For more information www.linear.com/LTC3884
43
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
COMMAND NAME
CMD
CODE DESCRIPTION
MFR_FAULT_LOG_
STORE
0xEA Command a transfer of the fault log from RAM
to EEPROM.
Send Byte
N
NA
115
MFR_FAULT_LOG_
CLEAR
0xEC Initialize the EEPROM block reserved for fault
logging.
Send Byte
N
NA
118
MFR_FAULT_LOG
0xEE Fault log data bytes.
R Block
N
Reg
NA
115
MFR_COMMON
0xEF Manufacturer status bits that are common
across multiple ADI chips.
R Byte
N
Reg
NA
108
MFR_COMPARE_USER_
ALL
0xF0 Compares current command contents with
NVM.
Send Byte
N
NA
113
MFR_TEMPERATURE_2_
PEAK
0xF4 Peak internal die temperature since last MFR_
CLEAR_PEAKS.
R Word
N
L11
NA
112
MFR_PWM_CONFIG
0xF5 Set numerous parameters for the DC/DC
controller including phasing.
R/W Byte
N
Reg
Y
0x10
80
MFR_IOUT_CAL_GAIN_
TC
0xF6 Temperature coefficient of the current sensing
element.
R/W Word
Y
CF
ppm/
˚C
Y
3900
0x0F3C
85
MFR_RVIN
0xF7 The resistance value of the VIN pin filter element R/W Word
in mΩ.
N
L11
mΩ
Y
1000
0x03E8
82
MFR_TEMP_1_GAIN
0xF8 Sets the slope of the external temperature
sensor.
R/W Word
Y
CF
Y
1.0
0x4000
88
MFR_TEMP_1_OFFSET
0xF9 Sets the offset of the external temperature
sensor with respect to –273.1°C
R/W Word
Y
L11
Y
0.0
0x8000
88
MFR_RAIL_ADDRESS
0xFA Common address for PolyPhase outputs to
adjust common parameters.
R/W Byte
Y
Reg
Y
0x80
75
MFR_REAL_TIME
0xFB 48-bit share-clock counter value.
R Block
N
CF
NA
xx
MFR_RESET
0xFD Commanded reset without requiring a power
down.
Send Byte
N
NA
77
TYPE
Note 1: Commands indicated with Y in the NVM column indicate that these
commands are stored and restored using the STORE_USER_ALL and
RESTORE_USER_ALL commands, respectively.
Note 2: Commands with a default value of NA indicate “not applicable”.
Commands with a default value of FS indicate “factory set on a per part
basis”.
Note 3: The LTC3884 contains additional commands not listed in this
table. Reading these commands is harmless to the operation of the IC;
however, the contents and meaning of these commands can change
without notice.
44
DATA
PAGED FORMAT UNITS
NVM
Y
C
C
DEFAULT
VALUE PAGE
Note 4: Some of the unpublished commands are read-only and will
generate a CML bit 6 fault if written.
Note 5: Writing to commands not published in this table is not permitted.
Note 6: The user should not assume compatibility of commands
between different parts based upon command names. Always refer to
the manufacturer’s data sheet for each part for a complete definition of a
command’s function.
ADI strives to keep command functionality compatible between all ADI
devices. Differences may occur to address specific product requirements.
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
PMBus COMMAND SUMMARY
*DATA FORMAT
L11
Linear_5s_11s
PMBus data field b[15:0]
Value = Y • 2N
where N = b[15:11] is a 5-bit two’s complement integer and Y = b[10:0] is an 11-bit
two’s complement integer
Example:
For b[15:0] = 0x9807 = ‘b10011_000_0000_0111
Value = 7 • 2–13 = 854 • 10–6
From “PMBus Spec Part II: Paragraph 7.1”
L16
Linear_16u
PMBus data field b[15:0]
Value = Y • 2N
where Y = b[15:0] is an unsigned integer and N = Vout_mode_parameter is a 5-bit two’s
complement exponent that is hardwired to –12 decimal
Example:
For b[15:0] = 0x9800 = ‘b1001_1000_0000_0000
Value = 19456 • 2–12 = 4.75
From “PMBus Spec Part II: Paragraph 8.2”
Reg
Register
PMBus data field b[15:0] or b[7:0].
Bit field meaning is defined in detailed PMBus Command Description.
I16
Integer Word
PMBus data field b[15:0]
Value = Y
where Y = b[15:0] is a 16 bit unsigned integer
Example:
For b[15:0] = 0x9807 = ‘b1001_1000_0000_0111
Value = 38919 (decimal)
CF
ASC
Custom Format
Value is defined in detailed PMBus Command Description.
This is often an unsigned or two’s complement integer scaled by an MFR specific
constant.
ASCII Format
A variable length string of text characters conforming to ISO/IEC 8859-1 standard.
3884fe
For more information www.linear.com/LTC3884
45
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
CURRENT LIMIT PROGRAMMING
The cycle-by-cycle current limit threshold voltage, VILIMIT,
across the ISENSEn+ and ISENSEn– pins is proportional to
VITH. The VITH limit can be programmed from 1.45V to 2.2V
using the PMBUS command IOUT_OC_FAULT_LIMIT.
See Figure 26. The LTC3884 has four ranges of current limit programming. Properly setting the value of
MFR_PWM_MODE[2] and MFR_PWM_MODE[7], and
IOUT_OC_FAULT_LIMIT, see the section of the PMBus
commands, the device can regulate output voltage with the
peak current under the value of IOUT_OC_FAULT_LIMIT
in normal operation. In case of output current exceeding
46
that current limit, an OC fault will be issued. Each range in
Figure 26 affects the loop gain, and subsequently affects
the loop stability, so setting range of current limiting is
a part of loop design.
100
80
RC =
60
VILIMIT (mV)
The Typical Application on the back page is a common
LTC3884 application circuit. The LTC3884 is mainly
designed for low DCR application via PMBus command
MFR_PWM_MODE[2] = 1 applicable when 0 ≤ VOUT ≤
3.5V, but it can be also configured to be regular DCR or
regular resistor sensing by setting MFR_PWM_MODE[2]
= 0 for 0≤ VOUT ≤ 5.5V. The choice among them is largely
a design trade-off between cost, power consumption and
accuracy. DCR sensing is becoming popular because it
saves expensive current sensing resistors and is more
power efficient, especially in high current applications.
Low DCR provides the most power efficient solution, and
best signal-to-noise ratio of the input sensing voltage.
The accuracy of the current reading and current limit
are typically limited by the accuracy of the DCR resistor
(accounted for in the IOUT_CAL_GAIN parameter of the
LTC3884). Thus current sensing resistors provide the
most accurate current sensing and limiting for the application. Other external component selection is driven
by the load requirement, and begins with the selection of
RSENSE (if RSENSE is used) and inductor value. Next, the
power MOSFETs are selected. Then the input and output
capacitors are selected. To have a stable loop performance
and reliability, the loop compensation parameters such
as GM of error amplifier programmed by MFR_PWM_
COMP[7:5] and RTH by MFR_PWM_ COMP[4:0] together
with current limit value and Voltage range set by bit 1 of
MFR_ PWM_MODE have to be properly selected. All other
programmable parameters do not affect the loop gain, allowing parameters to be modified without impacting the
transient response to load changes.
L
DCR
MFR_PWM_MODE[2]=0
MFR_PWM_MODE[7]=1
MFR_PWM_MODE[2]=0
MFR_PWM_MODE[7]=0
40
20
0
RC =
–20
–40
MFR_PWM_MODE[2]=1
MFR_PWM_MODE[7]=1
MFR_PWM_MODE[2]=1
MFR_PWM_MODE[7]=0
L
5 • DCR
3994 F26
0
0.5
1
1.5
VITH (V)
2
2.5
3
Figure 26. VITH vs VILIMIT
The LTC3884 will account for the DCR of the inductor if
the device is configured for DCR sensing and automatically updates the current limit as the inductor temperature
changes. The temperature coefficient of the DCR is stored
in the MFR_IOUT_TC register. The setting MFR_PWM_
MODE[2] = 1, MFR_PWM_MODE[7] = 0 allows for the use
of very low DCR inductors or sense resistors. In this mode,
the peak output current is up to 16.5mV/DCR and represents
the application the LTC3884 is mainly designed for. Keep
in mind this operation is on a cycle-by-cycle basis and is
only a function of the peak inductor current. The average
inductor current is monitored by the ADC converter and
can provide a warning if too much average output current
is detected. The overcurrent fault is detected when the ITH
voltage hits the maximum value. The digital processor
within the LTC3884 provides the ability to either ignore
the fault, shut down and latch off or shut down and retry
indefinitely (hiccup). Refer to the overcurrent portion of
the Operation section for more details.
ISENSE0± AND ISENSE1± PINS
The ISENSE+ and ISENSE– pins are the inputs to the current
comparator and the A/D. The common mode input voltage range of the current comparators is 0V to 5.5V and
0V to 3.5V in low DCR mode. Both the SENSE pins are
high impedance inputs with small input currents typically
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less than 1µA. The high impedance inputs to the current
comparators enable accurate DCR sensing. Do not float
these pins during normal operation.
Filter components connected to the ISENSE± traces should
be placed close to the IC. The positive and negative traces
should be routed differentially and Kelvin connected to the
current sense element; see Figure 27. A non-Kelvin connection or improper placement can add parasitic inductance
and capacitance to the current sense element, degrading the
signal at the sense terminals and making the programmed
current limit perform poorly. In a PolyPhase system, poor
placement of the sensing element will result in sub-optimal
current sharing between power stages. If DCR sensing is
used (Figure 28a), sense resistor R1 should be placed close
to the inductor to prevent noise from coupling into sensitive
small-signal nodes. The capacitor C1 should be placed close
to the IC pins. Any impedance difference between the ISENSE+
and ISENSE– signal paths can result in loss of accuracy in the
current reading of the ADC. The current reading accuracy
can be improved by matching the impedance of the two
signal paths. To accomplish this add a series resistor R3
between VOUT and ISENSE– equal to R1. A capacitor of 1µF
or greater should be placed in parallel with this resistor.
TO SENSE FILTER,
NEXT TO THE CONTROLLER
where:
VSENSE(MAX): Maximum sense voltage across the inductor DCR for a given ITH voltage
IMAX: Maximum load current
∆IL: Inductor ripple current
DCR: Inductor resistance
The RC sense filter time constant must be set by the following equations:
RC =
RC =
L
5 • DCR
L
DCR
at MFR_PWM_MODE[2] = 1 for low DCR
at MFR_PWM_MODE[2] = 0 for normal DCR
During normal DCR sensing, the voltage ripple across C1 is
equal to the voltage ripple across the inductor DCR. During
low DCR sensing, the voltage ripple across C1 is equal to
the 5x the voltage ripple across the inductor DCR.
VIN
INTVCC
VIN
BOOST
INDUCTOR
TG
INDUCTOR OR RSENSE
R1
ISENSE+
3884 F27
C2
>1µF
C1*
R3
ISENSE–
OPTIONAL
Figure 27. Sense Lines Placement with Inductor DCR
3884 F28a
Figure 28a. Inductor DCR Current Sense Circuit (LTC3884)
Inductor DCR Sensing
The DCR is the DC winding resistance of the inductor's
copper, which is often less than 1mΩ for high current
inductors. In high current and low output voltage applications, a conduction loss of a high DCR or a sense resistor
will cause a significant reduction in power efficiency. For a
specific output requirement, choose the inductor with the
DCR that satisfies the maximum desirable sense voltage,
and uses the relationship of the sense pin filters to output
inductor characteristics as depicted in the following:
VSENSE(MAX)
DCR =
ΔI
IMAX + L
2
VOUT
BG
GND
COUT
DCR
L
SW
LTC3884
VIN
INTVCC
VIN
SENSE RESISTOR
PLUS PARASITIC
INDUCTANCE
BOOST
TG
RS
SW
ESL
VOUT
LTC3884
BG
GND
ISENSE+
ISENSE–
RF
C F*
CF • 2RF ≤ ESL/RS
POLE-ZERO
CANCELLATION
3884 F28b
RF
*FILTER COMPONENTS
PLACED NEAR SENSE PINS
Figure 28b. Resistor Current Sense Circuit (LTC3884)
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To ensure the load current will be delivered over the full
operating temperature range, the temperature coefficient
of DCR resistance, approximately 3900ppm/°C, should
be taken into consideration.
Typically, C is selected in the range of 0.047µF to 0.47µF.
This forces R1 to around 2kΩ @ MFR_PWM_MODE[2]=0,
400Ω @ MFR_PWM_MODE[2]=1 reducing error that might
have been caused by the ISENSE pins’ ±1µA current (R3
and C2 are for reducing sensing error caused by input
current through R1).
There will be some power loss in R that relates to the
duty cycle, and will be the most in continuous mode at
the maximum input voltage:
PLOSS (R) =
( VIN(MAX) – VOUT ) • VOUT
R
Ensure that R1 has a power rating higher than this value.
However, DCR sensing eliminates the conduction loss of
sense resistor; it will provide better efficiency at heavy loads.
To maintain a good signal-to-noise ratio for low current
sense signals, it is best to enable the LOW DCR sensing
network (MFR_PWM_MODE[2] = 1, RC = L/(5 • DCR)).
For a DCR sensing application, the ripple voltage will be
determined by the equation:
ΔVSENSE =
VOUT VIN – VOUT
•
VIN RC • fOSC
Low DCR sensing can be used at ∆VSENSE signals as low
as 2mV.
INDUCTOR VALUE CALCULATION
Given the desired input and output voltages, the inductor
value and operating frequency, fOSC, directly determine
the inductor peak-to-peak ripple current:
IRIPPLE =
VOUT ( VIN – VOUT )
VIN • fOSC •L
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors, and output voltage
ripple. Thus, at a given frequency, the highest efficiency
48
operation is obtained with a small ripple current, which
requires a large inductor.
A reasonable starting point is to choose a ripple current
that is about 40% of IOUT(MAX). Note that the largest ripple
current occurs at the highest input voltage. To guarantee
that the ripple current does not exceed a specified maximum, the inductor should be chosen according to:
L≥
VOUT ( VIN – VOUT )
VIN • fOSC •IRIPPLE
INDUCTOR CORE SELECTION
Once the inductor value is determined, the type of inductor must be selected. Core loss is independent of core
size for a fixed inductor value, but it is very dependent on
inductance. As the inductance increases, core losses go
down. Unfortunately, increased inductance requires more
turns of wire and therefore copper losses increase. Ferrite
designs have very low core loss and are preferred at high
switching frequencies, so design goals can concentrate
on copper loss and preventing saturation. Ferrite core
materials saturate hard, which means that the inductance collapses abruptly when the peak design current is
exceeded. This results in an abrupt increase in inductor
ripple current and consequent output voltage ripple. Do
not allow the core to saturate!
LOW VALUE RESISTOR CURRENT SENSING
A typical sensing circuit using a discrete resistor is shown
in Figure 28b. RSENSE is chosen based on the required
output current.
The current comparator has a maximum threshold
VSENSE(MAX) determined by the ILIMIT setting. The input
common mode range of the current comparator is 0V to
5.5V. The current comparator threshold sets the peak of
the inductor current, yielding a maximum average output
current IMAX equal to the peak value less half the peakto-peak ripple current ∆IL. To calculate the sense resistor
value, use the equation:
RSENSE =
VSENSE(MAX)
ΔI
IMAX + L
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Due to possible PCB noise in the current sensing loop, the
AC current sensing ripple of ∆VSENSE = ∆IL • RSENSE also
needs to be checked in the design to get a good signal-tonoise ratio. In general, for a reasonably good PCB layout,
a 15mV minimum ∆VSENSE voltage is recommended as a
conservative number to start with for RSENSE applications.
For previous generation current mode controllers, the
maximum sense voltage was high enough (e.g., 75mV for
the LTC1628/LTC3728 family) that the voltage drop across
the parasitic inductance of the sense resistor represented
a relatively small error. In the newer and higher current
density solutions, the value of the sense resistor can be
less than 1mΩ and the peak sense voltage can be less than
20mV. Also, inductor ripple currents greater than 50%
with operation up to 750kHz are becoming more common.
Under these conditions, the voltage drop across the sense
resistor’s parasitic inductance is no longer negligible. A
typical sensing circuit using a discrete resistor is shown in
Figure 28b. In previous generations of controllers, a small
RC filter placed near the IC was commonly used to reduce
the effects of the capacitive and inductive noise coupled
in the sense traces on the PCB. A typical filter consists of
two series 100Ω resistors connected to a parallel 1000pF
capacitor, resulting in a time constant of 200ns.
This same RC filter, with minor modifications, can be used
to extract the resistive component of the current sense
signal in the presence of parasitic inductance. For example,
Figure 29a illustrates the voltage waveform across a 2mΩ
resistor with a PCB footprint of 2010. The waveform is
the superposition of a purely resistive component and a
purely inductive component. It was measured using two
scope probes and waveform math to obtain a differential
measurement. Based on additional measurements of the
inductor ripple current and the on-time, tON, and off-time,
tOFF, of the top switch, the value of the parasitic inductance
was determined to be 0.5nH using the equation:
ESL =
VESL(STEP) tON • tOFF
•
ΔIL
tON + tOFF
(1)
If the RC time constant is chosen to be close to the parasitic inductance divided by the sense resistor (L/R), the
resultant waveform looks resistive, as shown in Figure 29b.
For applications using low maximum sense voltages,
check the sense resistor manufacturer’s data sheet for
information about parasitic inductance. In the absence of
data, measure the voltage drop directly across the sense
resistor to extract the magnitude of the ESL step and use
Equation 1 to determine the ESL. However, do not overfilter
the signal. Keep the RC time constant less than or equal to
the inductor time constant to maintain a sufficient ripple
voltage on VRSENSE for optimal operation of the current
loop controller.
VSENSE
20mV/DIV
VESL(STEP)
500ns/DIV
3884 F29a
Figure 29a. Voltage Measured Directly Across RSENSE
VSENSE
20mV/DIV
500ns/DIV
3884 F29b
Figure 29b. Voltage Measured After the RSENSE Filter
SLOPE COMPENSATION AND INDUCTOR PEAK
CURRENT
Slope compensation provides stability in constantfrequency current-mode architectures by preventing
sub-harmonic oscillations at high duty cycles. This is accomplished internally by adding a compensation ramp to
the inductor current signal. The LTC3884 uses a patented
current limit technique that counteracts the compensating
ramp. This allows the maximum inductor peak current to
remain unaffected throughout all duty cycles.
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POWER MOSFET AND OPTIONAL SCHOTTKY DIODE
SELECTION
Two external power MOSFETs must be selected for each
controller in the LTC3884: one N-channel MOSFET for the
top (main) switch, and one N-channel MOSFET for the bottom (synchronous) switch. The peak-to-peak drive levels
are set by the INTVCC voltage. This voltage is typically 5.5V.
Consequently, logic-level threshold MOSFETs must be used
in most applications. The only exception is if low input voltage is expected (VIN < 5V); then, sub-logic level threshold
MOSFETs (VGS(TH) < 3V) should be used. Pay close attention to the BVDSS specification for the MOSFETs as well;
most of the logic-level MOSFETs are limited to 30V or less.
Selection criteria for the power MOSFETs include the onresistance, RDS(ON), Miller capacitance, CMILLER, input
voltage and maximum output current. Miller capacitance,
CMILLER, can be approximated from the gate charge curve
usually provided on the MOSFET manufacturers’ data
sheet. CMILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
flat divided by the specified change in VDS. This result is
then multiplied by the ratio of the application applied VDS
to the gate charge curve specified VDS. When the IC is
operating in continuous mode the duty cycles for the top
and bottom MOSFETs are given by:
Main Switch Duty Cycle =
VOUT
VIN
Synchronous Switch Duty Cycle =
VIN – VOUT
VIN
The MOSFET power dissipations at maximum output
current are given by:
V
2
PMAIN = OUT (IMAX ) (1+ δ ) •RDS(ON) +
VIN
⎞
( VIN )2 ⎛⎜⎝ IMAX
)•
⎟ (R ) (C
2 ⎠ DR MILLER
⎡
1 ⎤
1
+
⎢
⎥ • fOSC
⎢⎣ VINTVCC – VTH(MIN) VTH(MIN) ⎥⎦
V –V
2
PSYNC = IN OUT (IMAX ) • (1+ δ ) •RDS(ON)
VIN
50
where δ is the temperature dependency of RDS(ON) and
RDR (approximately 2Ω) is the effective driver resistance
at the MOSFET’s Miller threshold voltage. VTH(MIN) is
the typical MOSFET minimum threshold voltage. Both
MOSFETs have I2R losses while the topside N-channel
equation includes an additional term for transition losses,
which are highest at high input voltages. For VIN < 20V
the high current efficiency generally improves with larger
MOSFETs, while for VIN > 20V the transition losses rapidly
increase to the point that the use of a higher RDS(ON) device
with lower CMILLER actually provides higher efficiency. The
synchronous MOSFET losses are greatest at high input
voltage when the top switch duty factor is low or during
a short-circuit when the synchronous switch is on close
to 100% of the period.
The term (1 + d) is generally given for a MOSFET in the
form of a normalized RDS(ON) vs Temperature curve, but
δ = 0.005/°C can be used as an approximation for low
voltage MOSFETs.
The optional Schottky diodes conduct during the dead
time between the conduction of the two power MOSFETs.
These prevent the body diodes of the bottom MOSFETs
from turning on, storing charge during the dead time and
requiring a reverse recovery period that could cost as much
as 3% in efficiency at high VIN. A 1A to 3A Schottky is
generally a good compromise for both regions of operation due to the relatively small average current. Larger
diodes result in additional transition losses due to their
larger junction capacitance.
VARIABLE DELAY TIME, SOFT-START AND OUTPUT
VOLTAGE RAMPING
The LTC3884 must enter the run state prior to soft-start.
The RUNn pin is released after the part initializes and VIN
is greater than the VIN_ON threshold. If multiple LTC3884s
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 VIN 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.
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After the RUNn pin releases, the controller waits for the
user-specified turn-on delay (TON_DELAY) prior to initiating an output voltage ramp. Multiple LTC3884s and
other ADI 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 Analog Devices ICs
are configured to allow the fastest SHARE_CLK signal to
control the timing of all devices). The SHARE_CLK signal
can be ±10% in frequency, thus the actual time delays will
have proportional variance.
Soft-start is performed by actively regulating the load voltage while digitally ramping the target voltage from 0.0V
to the commanded voltage set point. The rise time of the
voltage ramp can be programmed using the TON_RISE
command to minimize inrush currents associated with the
start-up voltage ramp. The soft-start feature is disabled
by setting TON_RISE to any value less than 0.250ms.
The LTC3884 will perform the necessary math internally
to assure the voltage ramp is controlled to the desired
slope. However, the voltage slope cannot be any faster
than the fundamental limits of the power stage. The shorter
TON_RISE time is set, the larger the discrete steps in the
TON_RISE ramp will appear. The number of steps in the
ramp is equal to TON_RISE/0.1ms.
The LTC3884 PWM will always use discontinuous mode
during the TON_RISE operation. In discontinuous mode,
the bottom gate is turned off for LTC3884 or PWM is in
three-state for LTC3884-1 as soon as reverse current is
detected in the inductor. This will allow the regulator to
start up into a pre-biased load.
There is no traditional tracking feature in the LTC3884.
However, two outputs can be given the same TON_RISE
and TON_DELAY times to effectively ramp up at the same
time. If the RUN pin is released at the same time and both
LTC3884s use the same time base, the outputs will track
very closely. If the circuit is in a PolyPhase configuration,
all timing parameters must be the same.
The method of start-up sequencing described above is time
based. For concatenated events it is possible to control
the RUNn pins based on the PGOODn pin of a different
controller. There is 60µs filtering to the PGOODn inside
the device. If unwanted transitions still occur on PGOODn,
place a capacitor to ground on the PGOODn pin to filter the
waveform. The RC time-constant of the filter should be set
sufficiently fast to assure no appreciable delay is incurred.
A value of 300μs to 500μs will provide some additional
filtering without significantly delaying the trigger event.
DIGITAL SERVO MODE
For maximum accuracy in the regulated output voltage,
enable the digital servo loop by asserting bit 6 of the
MFR_PWM_MODE command. In digital servo mode, the
LTC3884 will adjust the regulated output voltage based
on the ADC voltage reading. Every 90ms the digital servo
loop will step the LSB of the DAC (nominally 1.375mV or
0.688mV depending on the voltage range bit) until the
output is at the correct ADC reading. At power-up this mode
engages after TON_MAX_FAULT_LIMIT unless the limit is
set to 0 (infinite). If the TON_MAX_FAULT_LIMIT is set to
0 (infinite), the servo begins after TON_RISE is complete
and VOUT has exceeded the VOUT_UV_FAULT_LIMIT.
This same point in time is when the output changes from
discontinuous to the programmed mode as indicated in
MFR_PWM_MODE bit 0. Refer to Figure 30 for details on
the VOUT waveform under time-based sequencing. If the
TON_MAX_FAULT_LIMIT is set to a value greater than 0
and the TON_MAX_FAULT_RESPONSE is set to ignore
0x00, the servo begins:
1. After the TON_RISE sequence is complete
2. After the TON_MAX_FAULT_LIMIT time is reached; and
3. After the VOUT_UV_FAULT_LIMIT has been exceed or
the IOUT_OC_FAULT_LIMIT is no longer active.
If the TON_MAX_FAULT_LIMIT is set to a value greater
than 0 and the TON_MAX_FAULT_RESPONSE is not set
to ignore 0X00, the servo begins:
1. After the TON_RISE sequence is complete;
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2. After the TON_MAX_FAULT_LIMIT time has expired
and both VOUT_UV_FAULT and IOUT_OC_FAULT 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.
VOUT will decay at the natural rate determined by the load
impedance. If the controller is in discontinuous mode, the
controller will not pull negative current and the output
will be pulled low by the load, not the power stage. The
maximum fall time is limited to 1.3 seconds. The shorter
TOFF_FALL time is set, the larger the discrete steps in the
TOFF_FALL ramp will appear. The number of steps in the
ramp is equal to TOFF_FALL/0.1ms.
DIGITAL SERVO
MODE ENABLED FINAL OUTPUT
VOLTAGE REACHED
TON_MAX_FAULT_LIMIT
VOUT
DAC VOLTAGE
ERROR (NOT
TO SCALE)
VOUT
TIME DELAY OF
200-400ms
TOFF_DELAY
TON_DELAY
TON_RISE
TIME
3884 F30
Figure 30. Timing Controlled VOUT Rise
SOFT OFF (SEQUENCED OFF)
In addition to a controlled start-up, the LTC3884 also supports controlled turn-off. The TOFF_DELAY and TOFF_FALL
functions are shown in Figure 31. TOFF_FALL is processed
when the RUN pin goes low or if the part is commanded
off. If the part faults off or FAULTn is pulled low externally
and the part is programmed to respond to this, the output
will three-state rather than exhibiting a controlled ramp.
The output will decay as a function of the load. The output
voltage will operate as shown in Figure 31 so long as the
part is in forced continuous mode and the TOFF_FALL
time is sufficiently slow that the power stage can achieve
the desired slope. The TOFF_FALL 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_FALL 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_FALL, the controller will cease to sink current and
52
TOFF_FALL
TIME
3884 F31
Figure 31. TOFF_DELAY and TOFF_FALL
INTVCC/EXTVCC POWER
Power for the top and bottom MOSFET drivers and most
other internal circuitry are derived from the INTVCC pin.
When the EXTVCC pin is shorted to GND or tied to a voltage less than 4.7V, or VIN is lower than 7V, an internal
5.5V linear regulator supplies INTVCC power from VIN. If
EXTVCC is taken above 4.7V and VIN is higher than 7V,
the 5.5V regulator is turned off and an internal switch is
turned on connecting EXTVCC to INTVCC. EXTVCC can be
applied before VIN. The regulator can supply a peak current
of 100mA. Both INTVCC and EXTVCC need to be bypassed
to ground with a minimum of 1μF ceramic capacitor or
low ESR electrolytic capacitor. No matter what type of bulk
capacitor is used, an additional 0.1μF ceramic capacitor
placed directly adjacent to the INTVCC and GND pins is
highly recommended. Good bypassing is needed to supply the high transient currents required by the MOSFET
gate drivers.
High input voltage application in which large MOSFETs
are being driven at high frequencies may cause the
maximum junction temperature rating for the LTC3884
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to be exceeded. The INTVCC current, of which a large
percentage is due to the gate charge current, is supplied
from either the VIN or EXTVCC pin. If the LTC3884 internal
regulator is powered from the VIN pin, the power through
the IC is equal to VIN • IINTVCC. The gate charge current
is dependent on operating frequency as discussed in the
Efficiency Considerations section. The junction temperature
can be estimated by using the equations in Note 2 of the
Electrical Characteristics. For example, at 70°C ambient,
the LTC3884 INTVCC current is limited to less than 44mA
from a 40V supply:
TJ = 70°C + 44mA • 40V • 31°C/W = 125°C
To prevent the maximum junction temperature from being
exceeded, the LTC3884 internal LDO can be powered from
the EXTVCC pin, providing significant system efficiency
improvement and thermal gains. If the EXTVCC pin is not
used to power INTVCC, the EXTVCC pin must be tied to
GND; do not float this pin. The VIN current resulting from
the gate driver and control circuitry will be reduced to a
minimum by supplying the INTVCC current from the EXTVCC:
⎛ VEXTVCC ⎞ ⎛
⎞
1
⎜⎝ V
⎟⎠ ⎜⎝ Efficiency ⎟⎠
IN
Tying the EXTVCC pin to a 5.5V supply reduces the junction temperature in the previous example from 125°C to:
TJ = 70°C + 42mA • 5.5V • 31°C/W + 2mA • 40V • 31°C/W
= 80°C
Do not tie INTVCC on the LTC3884 to an external supply
because INTVCC will attempt to pull the external supply
high and hit current limit, significantly increasing the die
temperature.
For applications where VIN is less than 6V, tie the VIN and
INTVCC pins together to the supply voltage through a 1Ω
or 2.2Ω resistor as shown in Figure 32. To minimize the
voltage drop caused by the gate charge current a low ESR
capacitor must be connected to the VIN/INTVCC pins. This
configuration will override the INTVCC linear regulator and
will prevent INTVCC from dropping too low. Make sure the
INTVCC voltage exceeds the RDS(ON) test voltage for the
MOSFETs, which is typically 4.5V for logic level devices.
The UVLO on INTVCC is set to approximately 4V.
VIN
RVIN
1Ω
LTC3884
INTVCC
CINTVCC
4.7µF
PGND
+
5V
CIN
3884 F32
Figure 32. Setup for a 5V Input
VIN
1Ω TO 5Ω
BOOST
TG
VIN
CB
0.1µF
DB
LTC3884
SW
INTVCC
BG
CINTVCC
4.7µF
PGND
3884 F33
Figure 33. Boost Circuit to Minimize PWM Jitter
TOPSIDE MOSFET DRIVER SUPPLY (CB, DB)
External bootstrap capacitors, CB, connected to the BOOSTn
pin supplies the gate drive voltages for the topside MOSFETs. Capacitor CB in the Block Diagram is charged through
external diode DB from INTVCC when the SWn pin is low.
When one of the topside MOSFETs is to be turned on, the
driver places the CB voltage across the gate source of the
desired MOSFET. This enhances the MOSFET and turns on
the topside switch. The switch node voltage, SWn, rises to
VIN and the BOOSTn pin follows. With the topside MOSFET
on, the boost voltage is above the input supply: VBOOST =
VIN + VINTVCC. The value of the boost capacitor, CB, needs
to be 100 times that of the total input capacitance of the
topside MOSFET(s). The reverse breakdown of the external
Schottky diode must be greater than VIN(MAX).
PWM jitter has been observed in some designs operating
at higher VIN/VOUT ratios. This jitter does not substantially
affect the circuit accuracy. Referring to Figure 33, PWM
jitter can be removed by inserting a series resistor with a
value of 1Ω to 5Ω between the cathode of the diode and
the BOOSTn pin. A resistor case size of 0603 or larger is
recommended to reduce ESL and achieve the best results.
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UNDERVOLTAGE LOCKOUT
The LTC3884 is initialized by an internal threshold-based
UVLO where VIN must be approximately 4V and INTVCC,
VDD33, and VDD25 must be within approximately 20% of
their regulated values. In addition, VDD33 must be within
approximately 7% of the targeted value before the RUN
pin is released. After the part has initialized, an additional
comparator monitors VIN. The VIN_ON threshold must be
exceeded before the power sequencing can begin. When
VIN drops below the VIN_OFF threshold, the SHARE_CLK
pin will be pulled low and VIN 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. If FAULTB is held low when VIN is
applied, ALERT will be asserted low even if the part is
programmed to not assert ALERT when FAULTB is held
low. If I2C communication occurs before the LTC3884 is
out of reset and only a portion of the command is seen by
the part, this can be interpreted as a CML fault. If a CML
fault is detected, ALERT is asserted low.
It is possible to program the contents of the NVM in the
application if the VDD33 supply is externally driven directly
to VDD33 or through EXTVCC. This will activate the digital
portion of the LTC3884 without engaging the high voltage sections. PMBus communications are valid in this
supply configuration. If VIN has not been applied to the
LTC3884, bit 3 (NVM Not Initialized) in MFR_COMMON
will be asserted low. If this condition is detected, the part
will only respond to addresses 5A and 5B. To initialize
the part issue the following set of commands: global address 0x5B command 0xBD data 0x2B followed by global
address 5B 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 VIN is applied a MFR_RESET command must be issued to allow the
PWM to be enabled and valid ADC conversions to be read.
CIN AND COUT SELECTION
In continuous mode, the source current of the top MOSFET
is a square wave of duty cycle (VOUT)/(VIN). To prevent
large voltage transients, a low ESR capacitor sized for the
54
maximum RMS current of one channel must be used. The
maximum RMS capacitor current is given by:
CIN Required IRMS ≈
1/2
IMAX
⎡⎣( VOUT ) ( VIN – VOUT ) ⎤⎦
VIN
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT/2. This simple worst-case condition is commonly used for design because even significant deviations
do not offer much relief. Note that capacitor manufacturers’
ripple current ratings are often based on only 2000 hours
of life. This makes it advisable to further derate the capacitor, or to choose a capacitor rated at a higher temperature
than required. Several capacitors may be paralleled to meet
size or height requirements in the design. Due to the high
operating frequency of the LTC3884, ceramic capacitors
can also be used for CIN. Always consult the manufacturer
if there is any question.
The benefit of using a LTC3884 in 2-phase operation can
be calculated by using the equation above for the higher
power controller and then calculating the loss that would
have resulted if both controller channels switched on at
the same time. The total RMS power loss is lower when
both controllers are operating due to the reduced overlap
of current pulses required through the input capacitor’s
ESR. This is why the input capacitor’s requirement calculated above for the worst-case controller is adequate
for the dual controller design. Also, the input protection
fuse resistance, battery resistance, and PC board trace
resistance losses are also reduced due to the reduced
peak currents in a 2-phase system. The overall benefit of
a multiphase design will only be fully realized when the
source impedance of the power supply/battery is included
in the efficiency testing. The sources of the top MOSFETs
should be placed within 1cm of each other and share a
common CIN(s). Separating the sources and CIN may produce undesirable voltage and current resonances at VIN.
A small (0.1μF to 1μF) bypass capacitor between the chip
VIN pin and ground, placed close to the LTC3884, is also
suggested. A 2.2Ω to 10Ω resistor placed between CIN
(C1) and the VIN pin provides further isolation between
the two LTC3884s.
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The selection of COUT is driven by the effective series
resistance (ESR). Typically, once the ESR requirement
is satisfied, the capacitance is adequate for filtering. The
output ripple (∆VOUT) is approximated by:
OPEN-DRAIN PINS
The LTC3884 has the following open-drain pins:
3.3V Pins
1. FAULT
⎛
⎞
1
ΔVOUT ≈IRIPPLE ⎜ ESR +
8 • f •COUT ⎟⎠
⎝
2. SYNC
where f is the operating frequency, COUT is the output
capacitance and IRIPPLE is the ripple current in the inductor. The output ripple is highest at maximum input voltage
since IRIPPLE increases with input voltage.
3. SHARE_CLK
4. PGOODn
5V Pins (5V pins operate correctly when pulled to 3.3V.)
1. RUNn
FAULT INDICATION
2. ALERT
The LTC3884 FAULT pins are configurable to indicate a
variety of faults including OV, UV, OC, OT, timing faults,
and peak over current faults. In addition, the FAULT pins
can be pulled low by external sources indicating a fault in
some other portion of the system. The fault response is
configurable and allows the following options:
3. SCL
n
Ignore
n
Shut Down Immediately—Latch Off
n
Shut Down Immediately—Retry Indefinitely at the Time
Interval Specified in MFR_RETRY_DELAY
Refer to the PMBus section of the data sheet and the
PMBus specification for more details.
The OV response is automatic. If an OV condition is detected, TGn goes low and BGn is asserted.
Fault logging is available on the LTC3884. 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 LTC3884 internal temperature is in excess of 85°C,
writes into the NVM (other than fault logging) are 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 temperature drops below 120°C.
4. SDA
All the above pins have on-chip pull-down transistors that
can sink 3mA at 0.4V. The low threshold on the pins is
0.8V; thus, there is 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 is:
RPULLUP =
tRISE
= 1k
3 •100pF
The closest 1% resistor value is 1k. 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 a one time constant. The
SYNC pin has an on-chip pull-down transistor with the
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LTC3884/LTC3884-1
APPLICATIONS INFORMATION
output held low for nominally 500ns. 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.
The SHARE_CLK pull-up resistor has a similar equation
with a period of 10µs and a pull-down time of 1μs. The
RC time constant should be approximately 3μs or faster.
PHASE-LOCKED LOOP AND FREQUENCY
SYNCHRONIZATION
The LTC3884 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 the PWM
controller 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 that 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
200kHz and 1MHz. Nominal parts will have a range beyond
this; however, operation to a wider frequency range is not
guaranteed.
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
56
fault can be cleared by writing a 1 to the bit. If the user
does not wish to see the ALERT pin assert if a PLL_FAULT
occurs, the SMBALERT_MASK command can be used to
prevent the alert.
If the SYNC signal is not clocking in the application, the
nominal programmed frequency will control the internal
PWM circuitry. However, if multiple parts share the SYNC
pins and the signal is not clocking, the parts will not be
synchronized and excess voltage ripple on the output may
be present. Bit 10 of MFR_PADS will be asserted low if
this condition exists.
If the TG/BG (LTC3884) or PWM (LTC3884-1) appear 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 versus the intended signal.
Review routing of digital control signals and minimize
crosstalk to the SYNC signal to avoid this problem. Multiple
LTC3884s are required to share one SYNC pin in PolyPhase
configurations. For other configurations, connecting the
SYNC pins to form a single SYNC signal is optional. If the
SYNC pin is shared between LTC3884s, only one LTC3884
can be programmed with a frequency output. All the other
LTC3884s should be programmed to disable the SYNC
output. However their frequency should be programmed
to the nominal desired value.
MINIMUM ON-TIME CONSIDERATIONS
Minimum on-time, tON(MIN), is the smallest time duration
that the LTC3884 is capable of turning on the top MOSFET.
It is determined by internal timing delays and the gate
charge required to turn off the top MOSFET. Low duty
cycle applications may approach this minimum limit and
care should be taken to ensure that:
tON(MIN) <
VOUT
VIN • 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.
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The minimum on-time for the LTC3884 is approximately
60ns. Reasonably good PCB layout, minimum 30% inductor current ripple and at least 2mV for LOW DCR structure
or 10mV to 15mV for regular DCR ripple on the current
sense signal are required to avoid increasing the minimum
on-time. The minimum on-time can be affected by PCB
switching noise in the voltage and current loop. As the peak
current sense voltage decreases, the minimum on-time
gradually increases to 90ns. This is of particular concern
in forced continuous applications with low ripple current
at light loads. If the duty cycle drops below the minimum
on-time limit in this situation, a significant amount of cycle
skipping can occur with correspondingly larger current
and voltage ripple.
EXTERNAL TEMPERATURE SENSE
The LTC3884 is capable of measuring the power stage
temperature of each channel. Multiple methods using
silicon junction type remote sensors are supported. The
voltage produced by the remote sense circuit is digitized
by the internal ADC, and the computed temperature value
is returned by the paged READ_TEMPERATURE_1 telemetry command.
The most accurate external temperature measurement
can be made using a diode-connected PNP transistor
such as the MMBT3906 as shown in Figure 34 with bit 5
of MFR_PWM_MODE should be set to 0 ∆VBE when using
this sensor configuration. The transistor should be placed
in contact with or immediately adjacent to the power stage
inductor. Its emitter should be connected to the TSNSn pin
while the base and collector terminals of the PNP transistor
should be returned to the LTC3884 GND paddle using a
Kevin connection. For best noise immunity, the connections should be routed differentially and a 10nF capacitor
should be placed in parallel with the diode-connected PNP.
Parasitic PCB trace inductance between the capacitor and
transistor should be minimized. Avoid placing PCB vias
between the transistor and capacitor.
The LTC3884 also supports direct junction voltage measurements when bit 5 of MFR_PWM_MODE_LTC3884 is
set to 1. The factory defaults support a resistor trimmed
TSNS
LTC3884
10nF
GND
MMBT3906
GND
3884 F34
Figure 34. External ∆VBE Temperature Sense
495µA
TSNS
LTC3884
GND
GND
1nF
1.35V AT 25°C
3884 F35
Figure 35. 2D+R Temperature Sense
dual diode network as shown in Figure 35. This second
measurement method is not generally as accurate as the
first, but it supports legacy power blocks or may prove
necessary if high noise environments prevent use of the
∆VBE approach with its lower signal levels.
For either method, the slope of the external temperature
sensor can be modified with the coefficient stored in
MFR_TEMP_1_GAIN. With the ∆VBE approach, typical
PNPs require temperature slope adjustments slightly
less than 1. The MMBT3906 has a recommended value
in this command of approximately MFR_TEMP_1_GAIN
= 0.991 based on the ideality factor of 1.01. Simply invert
the ideality factor to calculate the MFR_TEMP_1_GAIN.
Different manufacturers and different lots may have different ideality factors. Consult with the manufacturer to
set this value. Bench characterization over temperature is
recommended when adjusting MFR_TEMP_1_GAIN for
the direct p-n junction measurement.
The offset of the external temperature sense can be adjusted
by MFR_TEMP_1_OFFSET.
If an external temperature sense element is not used, the
TSNSn pin must be shorted to GND. The UT_FAULT_LIMIT
must be set to –275°C, and the UT_FAULT_RESPONSE
must be set to ignore. The user also needs to set the
IOUT_CAL_GAIN_TC to a value of 0.
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To ensure proper use of these temperature adjustment
parameters, refer to the specific formulas given for the
two methods by the MFR_PWM_MODE command in the
later section covering PMBus command details.
INPUT CURRENT SENSE AMPLIFIER
The LTC3884 input current sense amplifier can sense the
supply current into the VIN pin using an external resistor as well as the power stage current using an external
sense resistor shown in Figure 36. Unless care is taken to
mitigate the frequency noise caused by the discontinuous
input current, significant input current measurement error
may occur. The noise will be the greatest in high current
applications and at large step-down ratios. Careful layout
and filtering at the VIN pin is recommended to minimize
measurement error. The VIN pin should be filtered with
a resistor and a ceramic capacitor. The filter should be
located as close to the VIN pin as possible. The supply
side of the VIN pin filter should be Kelvin connected to the
supply side of the RIINSNS resistor. A 2Ω resistor should
be sufficient for most applications. The resistor will cause
an IR voltage drop from the supply to the VIN pin due to
the current flowing into the VIN pin. To compensate for
this voltage drop, the MFR_RVIN command value should
be set to the nominal resistor value. The LTC3884 will
multiply the MFR_READ_ICHIP measurement value by the
user defined MFR_RVIN value and add this voltage to the
measured voltage at the VIN pin. Therefore
READ_VIN = VVIN_PIN + (MFR_READ_ICHIP • MFR_RVIN)
Therefore the READ_VIN command will return the value
of the voltage at the supply side of the VIN pin filter. If no
VIN filter element is used, set MFR_RVIN = 0.
The capacitor from the drain of M1 to ground should be
a low ESR ceramic capacitor. It should be placed as close
as possible to the drain of M1 to supply high frequency
58
transient input current. This will help prevent noise from
the top gate MOSFET from feeding into the input current
sense amplifier inputs and supply.
If the input current sense amplifier is not used, short the
VIN, IIN+, and IIN– pins together.
RIINSNS
VIN
10µF
LTC3884
TG
M1
IIN-
2Ω
10µF
IIN+
SW
VIN
BG
M2
3884 F36
Figure 36. Low Noise Input Current Sense Circuit
EXTERNAL RESISTOR CONFIGURATION PINS
(RCONFIG)
The LTC3884 is factory programmed to use the external
resistor configuration. This allows output voltage, PWM
frequency, PWM phasing, and the PMBus address to be
set by the user without programming the part through the
PMBus interface or purchasing custom programmed parts.
To use resistor programming, the RCONFIG pins require
a resistor divider between VDD25 and GND. The RCONFIG
pins are only interrogated at initial power up and during a
reset, so modifying their values on the fly while the part
is powered will have no effect. However, this does mean
that RCONFIG pins on the same IC can be shared with a
single resistor divider if they require identical programming. Resistors with a tolerance of 1% or better must be
used to assure proper operation. In the following tables,
RTOP is connected between VDD25 and the RCONFIG pin
while RBOT is connected between the pin and GND. Noisy
clock signals should not be routed near these pins.
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Voltage Selection
Frequency Selection
When an output voltage is set using the VOUT_CFGn pins
(by Table 3) the following parameters are set as a percentage of the output voltage:
The PWM switching frequency is set according to Table 4.
The SYNC pins must be shared in PolyPhase configurations where multiple LTC3884s or multiple LTC3884s and
LTC3874s are used to produce the output. If the configuration is not PolyPhase the SYNC pins do not have to be
shared. If the SYNC pins are shared between LTC3884s
only one SYNC pin should be enabled; all other SYNC pins
should be disabled. A pull-up resistor to VDD33 is required
on the SYNC pin.
n
n
n
n
n
n
n
VOUT_OV_FAULT_LIMIT.................................... +10%
VOUT_OV_WARN_LIMIT................................... +7.5%
VOUT_MAX....................................................... +7.5%
VOUT_MARGIN_HIGH..........................................+5%
VOUT_MARGIN_LOW...........................................–5%
VOUT_UV_WARN_LIMIT.................................. –6.5%
VOUT_UV_FAULT_LIMIT...................................... –7%
If VOUT is 2.5V or lower, low range is used. When VOUT is
set using the VOUT_CFGn pins, the part will turn on the
rail modifying the OPERATION command, if required, to
respond to PMBus commands.
Table 3. VOUT_CFGn Resistor Programming
RTOP (kΩ)
RBOTTOM (kΩ)
VOUT (V)
ON/OFF
0 or Open
Open
NVM
NVM
10
23.2
5.000
ON
10
15.8
3.300
ON
16.2
20.5
2.500
ON
16.2
17.4
1.800
ON
20
17.8
1.500
ON
20
15
1.350
ON
20
12.7
1.250
ON
20
11
1.200
ON
24.9
11.3
1.150
ON
24.9
9.09
1.100
ON
24.9
7.32
1.050
ON
24.9
5.76
0.900
ON
24.9
4.32
0.750
ON
30.1
3.57
0.650
ON
30.1
1.96
0.600
ON
Open
0
NVM
OFF
Table 4. FREQ_CFG Resistor Programming
RTOP (kΩ)
RBOTTOM (kΩ)
FREQUENCY (kHz)
0 or Open
Open
NVM
10
23.2
NVM
10
15.8
NVM
16.2
20.5
NVM
16.2
17.4
NVM
20
17.8
NVM
20
15
NVM
20
12.7
NVM
20
11
1000
24.9
11.3
750
24.9
9.09
650
24.9
7.32
575
24.9
5.76
500
24.9
4.32
425
30.1
3.57
350
30.1
1.96
250
Open
0
External Clock
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Phase Selection
Address Selection Using RCONFIG
The phase of the channels with respect to the falling edge
of SYNC is set using the values in Table 5.
The LTC3884 address is selected based on the programming
of the two configuration pins ASEL0 and ASEL1 according to
Table 6. ASEL0 programs the bottom four bits of the device
address for the LTC3884, and ASEL1 programs the three
most significant bits. Either portion of the address can also
be retrieved from the MFR_ADDRESS value in EEPROM. If
both pins are left open, the full 7-bit MFR_ADDRESS value
stored in EEPROM is used to determine the device address.
The LTC3884 always responds to 7-bit global addresses
0x5A and 0x5B. MFR_ADDRESS should not be set to either
of these values because these are global addresses and all
parts will respond to them.
Table 5. PHASE_CFG Resistor Programming
RTOP
SYNC TO CH0 SYNC TO CH1
(DEGREES)
(DEGREES)
SYNC
ENABLE
(kΩ)
RBOTTOM
(kΩ)
0 or Open
Open
NVM
NVM
NVM
10
23.2
NVM
NVM
NVM
10
15.8
NVM
NVM
NVM
16.2
20.5
120
300
16.2
17.4
60
240
20
17.8
120
240
20
15
0
120
20
12.7
0
240
20
11
90
270
24.9
11.3
0
180
24.9
9.09
120
300
24.9
7.32
60
240
24.9
5.76
120
240
24.9
4.32
0
120
30.1
3.57
0
240
30.1
1.96
90
270
Open
0
0
180
DISABLE
ENABLE
For example in a 4-phase configuration clocked at 500kHz,
all of the LTC3884s must be set to the desired frequency
and phase and only one LTC3884 should be set to the
desired frequency with the SYNC pin enabled. All phasing
is with respect to the falling edge of SYNC.
For LTC3884 Chip 1, set the frequency to 500kHz with 90°
and 270° phase shift with the SYNC pin enabled:
Frequency RTOP = 24.9kΩ and RBOT = 5.76kΩ
Phase RTOP = 30.1kΩ and RBOT = 1.96kΩ
Table 6. ASELn Resistor Programming
RTOP (kΩ)
0 or Open
10
10
16.2
16.2
20
20
20
20
24.9
24.9
24.9
24.9
24.9
30.1
30.1
Open
RBOTTOM (kΩ)
Open
23.2
15.8
20.5
17.4
17.8
15
12.7
11
11.3
9.09
7.32
5.76
4.32
3.57
1.96
0
ASEL1
DEVICE ADDRESS
BITS[6:4]
BINARY
HEX
EEPROM
111
110
101
100
011
010
001
000
7
6
5
4
3
2
1
0
ASEL0
DEVICE ADDRESS
BITS[3:0]
BINARY
HEX
EEPROM
1111
F
1110
E
1101
D
1100
C
1011
B
1010
A
1001
9
1000
8
0111
7
0110
6
0101
5
0100
4
0011
3
0010
2
0001
1
0000
0
For LTC3884 Chip 2, set the frequency to 500kHz with
0°and 180° phase shift and the SYNC pin disabled:
Frequency 24.9kΩ and RBOT = 5.76kΩ
Phase RTOP = 24.9kΩ and RBOT = 11.3kΩ
60
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Table 6A1. MFR_ADDRESS Command Examples
Expressing Both 7- or 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
Global4
0x5B 0xB6
0
1
0
1
1
0
1
1
0
Default
0x4F 0x9E
0
1
0
0
1
1
1
1
0
0
1
0
1
1
0
1
0
0
Example 1
0x60 0xC0
0
1
1
0
0
0
0
0
0
Example 2
0x61 0xC2
0
1
1
0
0
0
0
1
0
1
0
0
0
0
0
0
0
0
Disabled2,3,5
Note 1: This table can be applied to the MFR_CHANNEL_ADDRESS,
and MFR_RAIL_ADDRESS commands as well as 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),
or 0x5A or 0x5B(7 bit) to the MFR_ADDRESS, MFR_CHANNEL_
ADDRESS or the MFR_RAIL_ADDRESS commands.
Note 5: To disable the address enter 0x80 in the MFR_ADDRESS
command. The 0x80 is greater than the 7-bit address field, disabling
the address.
EFFICIENCY CONSIDERATIONS
The percent efficiency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efficiency and which change would
produce the most improvement. Percent efficiency can be
expressed as: %Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percentage of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC3884 circuits: 1) IC VIN current, 2) INTVCC
regulator current, 3) I2R losses, 4) Topside MOSFET
transition losses.
1. The VIN current is the DC supply current given in the
Electrical Characteristics table, which excludes MOSFET
driver and control currents. VIN current typically results
in a small (<0.1%) loss.
2. INTVCC current is the sum of the MOSFET driver and
control currents (LTC3884). The MOSFET driver current
results from switching the gate capacitance of the power
MOSFETs. Each time a MOSFET gate is switched from
low to high to low again, a packet of charge dQ moves
from INTVCC to ground. The resulting dQ/dt is a current out of INTVCC that is typically much larger than the
control circuit current. In continuous mode, IGATECHG =
f(QT + QB), where QT and QB are the gate charges of the
topside and bottom side MOSFETs. For the LTC3884-1,
the gate driver is inside the DrMOS, which is powered
by some other supply. Similar power loss occurs with
that supply.
3. I2R losses are predicted from the DC resistances of
the fuse (if used), MOSFET, inductor, and current sense
resistor. In continuous mode, the average output current
flows through the inductor and RSENSE, but is “chopped”
between the topside MOSFET and the synchronous
MOSFET. If the two MOSFETs have approximately the
same RDS(ON), then the resistance of one MOSFET can
simply be summed with the resistances of the inductor
and RSENSE to obtain I2R losses. For example, if each
RDS(ON) = 10mΩ, RL = 10mΩ, RSENSE = 5mΩ, then the
total resistance is 25mΩ. This results in losses ranging
from 2% to 8% as the output current increases from
3A to 15A for a 5V output, or a 3% to 12% loss for a
3.3V output. Efficiency varies as the inverse square of
VOUT for the same external components and output
power level. The combined effects of increasingly lower
output voltages and higher currents required by high
performance digital systems is not doubling but quadrupling the importance of loss terms in the switching
regulator system!
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61
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
4. Transition losses apply only to the topside MOSFET(s),
and become significant only when operating at high
input voltages (typically 15V or greater). Transition
losses can be estimated from:
gm
Transition Loss = (1.7) • VIN2 • IO(MAX) • CRSS • f
RTH
Other “hidden” losses such as copper trace and internal
battery resistances can account for an additional 5% to
10% efficiency degradation in portable systems. It is very
important to include these “system” level losses during
the design phase. The internal battery and fuse resistance
losses can be minimized by making sure that CIN has adequate charge storage and very low ESR at the switching
frequency. A 25W supply will typically require a minimum
of 20μF to 40μF of capacitance having a maximum of
20mΩ to 50mΩ of ESR. The LTC3884 2-phase architecture
typically halves this input capacitance requirement over
competing solutions. Other losses including Schottky conduction losses during dead time and inductor core losses
generally account for less than 2% total additional loss.
ITHR
ITH
CTH
CTHP
+
VREF
–
FB
3884 F37
Figure 37. Programmable Loop Compensation
TYPE II COMPENSATION
GAIN
INCREASE gm
FREQUENCY
PROGRAMMABLE LOOP COMPENSATION
The LTC3884 offers programmable loop compensation
to optimize the transient response without any hardware
change. The error amplifier gain gm varies from 1.0mmho
to 5.73mmho, and the compensation resistor RTH varies
from 0kΩ to 62kΩ inside the controller. Two compensation
capacitors, CTH and CTHP, are required in the design and
the typical ratio between CTH and CTHP is 10.
3884 F38
Figure 38. Error Amp gm Adjust
TYPE II COMPENSATION
GAIN
By adjusting the gm and RTH only, the LTC3884 can provide
a flexible type II compensation network to optimize the
loop over a wide range of output capacitors. Adjusting
the gm will change the gain of the compensation over the
whole frequency range without moving the pole and zero
location, as shown in Figure 38.
Adjusting the RTH will change the pole and zero location,
as shown in Figure 39. It is recommended that the user
determines the appropriate value for the gm and RTH using
the LTPowerCAD tool.
62
INCREASE RTH
FREQUENCY
3884 F39
Figure 39. RTH Adjust
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LTC3884/LTC3884-1
APPLICATIONS INFORMATION
CHECKING TRANSIENT RESPONSE
The regulator loop response can be checked by looking at
the load current transient response. Switching regulators
take several cycles to respond to a step in DC (resistive)
load current. When a load step occurs, VOUT shifts by an
amount equal to ∆ILOAD (ESR), where ESR is the effective
series resistance of COUT. ∆ILOAD also begins to charge or
discharge COUT generating the feedback error signal that
forces the regulator to adapt to the current change and
return VOUT to its steady-state value. During this recovery
time VOUT can be monitored for excessive overshoot or
ringing, which would indicate a stability problem. The
availability of the ITH pin not only allows optimization of
control loop behavior but also provides a DC-coupled and
AC-filtered closed-loop response test point. The DC step,
rise time and settling at this test point truly reflects the
closed-loop response. Assuming a predominantly second
order system, phase margin and/or damping factor can be
estimated using the percentage of overshoot seen at this
pin. The bandwidth can also be estimated by examining
the rise time at the pin. The ITHR external capacitor shown
in the Typical Application circuit will provide an adequate
starting point for most applications. The programmable
parameters that affect loop gain are the voltage range,
bit[1] of the MFR_PWM_MODE command, the current
range, bit[2] and bit[7] of the MFR_PWM_MODE command, the gm of the PWM channel amplifier bits [7:5] of
MFR_PWM_COMP, and the internal RTH compensation
resistor, bits[4:0] of MFR_PWM_COMP. Be sure to establish these settings prior to compensation calculation.
The ITH series internal RTH external CTH filter sets the
dominant pole-zero loop compensation. The internal RTH
value can be modified (from 0Ω to 62kΩ) using bits[4:0]
of the MFR_PWM_ COMP command. Adjust the value
of RTH to optimize transient response once the final PCB
layout is done and the particular CTH filter capacitor and
output capacitor type and value have been determined. The
output capacitors need to be selected because the various
types and values determine the loop gain and phase. An
output current pulse of 20% to 80% of full-load current
having a rise time of 1μs to 10μs will produce output voltage and ITH pin waveforms that will give a sense of the
overall loop stability without breaking the feedback loop.
Placing a power MOSFET with a resistor to ground directly
across the output capacitor and driving the gate with an
appropriate signal generator is a practical way to produce
to a load step. The MOSFET + RSERIES will produce output
currents approximately equal to VOUT/RSERIES. RSERIES
values from 0.1Ω to 2Ω are valid depending on the current
limit settings and the programmed output voltage. The
initial output voltage step resulting from the step change
in output current may not be within the bandwidth of the
feedback loop, so this signal cannot be used to determine
phase margin. This is why it is better to look at the ITH pin
signal which is in the feedback loop and is the filtered and
compensated control loop response. The gain of the loop
will be increased by increasing RTH and the bandwidth
of the loop will be increased by decreasing CTH. If RTH is
increased by the same factor that CTH is decreased, the
zero frequency will be kept the same, thereby keeping the
phase shift the same in the most critical frequency range of
the feedback loop. The gain of the loop will be proportional
to the transconductance of the error amplifier which is
set using bits[7:5] of the MFR_PWM_COMP command.
The output voltage settling behavior is related to the
stability of the closed-loop system and will demonstrate
the actual overall supply performance. A second, more
severe transient is caused by switching in loads with large
(>1μF) supply bypass capacitors. The discharged bypass
capacitors are effectively put in parallel with COUT, causing
a rapid drop in VOUT. No regulator can alter its delivery of
current quickly enough to prevent this sudden step change
in output voltage if the load switch resistance is low and
it is driven quickly. If the ratio of CLOAD to COUT is greater
than 1:50, the switch rise time should be controlled so that
the load rise time is limited to approximately 25 • CLOAD.
Thus a 10μF capacitor would require a 250μs rise time,
limiting the charging current to about 200mA.
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63
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
PolyPhase Configuration
Master Slave Operation
When configuring a PolyPhase rail with multiple LTC3884s,
the user must share the SYNC, ITH, ITHR, SHARE_CLK,
FAULT, and ALERT pins of these parts. Be sure to use pullup resistors on FAULT, SHARE_CLK and ALERT. One of
the part’s SYNC pins must be set to the desired switching
frequency, and all other FREQUENCY_SWITCH commands
must be set to External Clock. If an external oscillator is
provided, set the FREQUENCY_SWITCH command to
External Clock for all parts. The relative phasing of all
the channels should be spaced equally. The MFR_RAIL_
ADDRESS of all the devices should be set to the same value.
LTC3884 (as Master) can work with LTC3874 (as slave) very
efficiently to deliver very large output currents. LTC3874 is
a very small simple device, which has two current loops,
but no PMBus, and no voltage loops.
When connecting a PolyPhase rail with LTC3884s, connect
the VIN pins of the LTC3884s directly back to the supply
voltage through the VIN pin filter networks.
64
Both LTC3884 and LTC3874 devices are mainly designed
for low DCR applications, and with the same relationship
between VITH vs VISENSE (see Figure 40).
Figure 40 is the schematic of a 3+1 application using a
LTC3884 and a LTC3874. LTC3884 channel 0 provides
VOUT0 of 1.5V and 30A output current, and channel 1
together with channel 0 and channel 1 in the LTC3874
to provide VOUT1 of 1.0V, with 90A output current. Both
chips are programmed to be LOW DCR configuration, and
channel1 of LTC3884 and channel 0/1 of the LTC3874 are
programmed to have the same current limit. Connecting
ITH1 of LTC3884 with ITH0 and ITH1 of LTC3874 together
forms three current loops. The voltage loop inside the
LTC3884 regulates ITH1, which then regulates all three
current loops with the same gain and current limit, and
ultimately delivers the same amount of current per phase.
Programming the phase of each channel properly, these
three channels form a perfect PolyPhase configuration.
3884fe
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VOUT0
For more information www.linear.com/LTC3884
MMBT3906-AL3-R
330µF
6.3V
x2
931Ω
1%
VDD33
Q3
BSC010NE2LSI
Q1
BSC050NE2LS
BG0
SW0
RUN1
10nF
RUN0
10k
ISENSE1–
VSENSE1+
VSENSE1–
TSNS1
ITH1
ISENSE1+
EXTVCC
ASEL1
FREQ_CFG
PHASE_CFG
ASEL0
VOUT1_CFG
VOUT0_CFG
BG1
SW1
BOOST1
TG1
IIN+ IIN–
LTC3884
VIN
2.2µF
VDD25
1µF
ITHR1
ITHR0
VDD33 PGND SGND VDD25
ITH0
ISENSE0–
VSENSE0+
VSENSE0–
TSNS0
ISENSE0+
RUN0
RUN1
WP
SHARE_CLK
1500pF
VDD33
150pF
220nF
SHARE_CLK
10k
FAULT1
SDA SDA
SCL
SCL
ALERT
ALERT
FAULT
FAULT0
10k
10k
10k
10k
10k
10k
SYNC
INTVCC
BOOST0
TG0
D2
SYNC
10k PGOOD0
PGOOD0
PGOOD1 PGOOD1
4.99k
0.1µF
4.7µF
D1
1500pF
ITH1
17.8k
VDD25
20k
0.1µF
2mΩ
47pF
220nF
4.32k
10nF
Q4
BSC010NE2LSI
Q2
BSC050NE2LS
24.9k
10µF
x2
715Ω
1%
744301025
DCR=0.32 mΩ
L2
0.25µH
270µF
16V
x2
1Ω
1%
330µF
6.3V
x2
330µF
6.3V
x2
L3
0.25µH
100µF
6.3V
x2
100µF 744301025
6.3V DCR=0.32 mΩ
x2
VOUT1 1.0V / 90A
VIN
7V to 14V
715Ω
1%
Q7
BSC010NE2LSI
Q6
BSC050NE2LS
10µF
x2
D3
SYNC
FAULT
RUN1
220nF
0.1µF
4.7µF
SYNC
RUN0
RUN1
FAULT0
FAULT1
ITH0
ITH1
ISENSE0–
TG1
PGOOD1
0.1µF
D4
10µF
x2
100K
220nF
Q9
BSC010NE2LSI
Q8
BSC050NE2LS
D1, D2, D3, D4: CMDSH3-TR
MODE0
MODE1
GND
FREQ
ILIM
PHASMD
EXTVCC
ISENSE1–
ISENSE1+
BG1
SW1
BOOST1
INTVCC
LTC3874
ISENSE0+
BG0
SW0
BOOST0
TG0
VIN
INTVCC1
10K
20K
INTVCC1
715Ω
1%
744301025
DCR = 0.32mΩ
L4
0.25µH
100µF
6.3V
x2
Figure 40. Master/Slave 3 +1 High Efficiency, Low DCR Sense, 425kHz, Dual-Output, 1.5V/30A and 1.0V/90A Buck Converter (LTC3884/LTC3874)
100µF
6.3V
x2
1.5V / 30A
L1
0.33µH
744301033
DCR=0.32 mΩ
10µF
x2
2mΩ
C3
1µF
3884 TA05
330µF
6.3V
x2
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
3884fe
65
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
RIINSNS
VIN
IIN–
TSNS
IIN+
Q1
LTC3884
RVIN
C1
TG
ISENSE–
SW
VIN
CVIN
L
ISENSE+
SYNC
CB
BOOST
RUN
VSENSE+
VSENSE–
M1
BG
RSENSE
VOUT
M2
D1
1µF
CERAMIC
ITHR
ITH
INTVCC
+
VDD25
PGND/SGND
+
CINTVCC
CIN
COUT
+
VDD33
3884 F40a
Figure 41a. Recommended Printed Circuit Layout Diagram, Single Phase Shown
SW1
L1
D1
RSENSE1
VOUT1
COUT1
RL1
VIN
RIN
CIN
SW0
BOLD LINES INDICATE
HIGH SWITCHING
CURRENT. KEEP LINES
TO A MINIMUM LENGTH.
D0
L0
RSENSE0
VOUT0
COUT0
RL0
3884 F40b
Figure 41b. Branch Current Waveforms
66
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LTC3884/LTC3884-1
APPLICATIONS INFORMATION
PC BOARD LAYOUT CHECKLIST
PC BOARD LAYOUT DEBUGGING
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the IC. These items are also illustrated graphically in the
layout diagram of Figure 41a. Figure 41b illustrates the
current waveforms present in the various branches of a
synchronous regulator operating in continuous mode.
Check the following in your layout:
It is helpful to use a DC-50MHz current probe to monitor
the current in the inductor while testing the circuit. Monitor
the output switching node (SWn pin) to synchronize the
oscilloscope to the internal oscillator and probe the actual
output voltage as well. Check for proper performance
over the operating voltage and current range expected
in the application. The frequency of operation should be
maintained over the input voltage range down to dropout
and until the output load drops below the low current
operation threshold.
1. Is the top N-channel MOSFET, M1, located within 1cm
of CIN?
2. Are signal ground and power ground kept separate? The
ground return of CINTVCC must return to the combined
COUT (–) terminals.
3. The ITH trace should be as short as possible.
4. The loop formed by the top N-channel MOSFET,
Schottky diode and the CIN capacitor should have
short leads and PC trace lengths.
5. The output capacitor (–) terminals should be connected
as close as possible to the (–) terminals of the input
capacitor by placing the capacitors next to each other
and away from the Schottky loop described in item 4.
6. Are the ISENSE+ and ISENSE– leads routed together
with minimum PC trace spacing? The filter capacitor
between ISENSE+ and ISENSE– should be as close as
possible to the IC. Ensure accurate current sensing with
Kelvin connections at the sense resistor or inductor,
whichever is used for current sensing.
7. Is the INTVCC decoupling capacitor connected close
to the IC, between the INTVCC and the power ground
pins? This capacitor carries the MOSFET driver current
peaks. An additional 1µF ceramic capacitor placed
immediately next to the INTVCC and GND pins can
help improve noise performance substantially.
8. Keep the switching nodes (SWn), top gate nodes
(TGn), and boost nodes (BOOSTn) away from sensitive
small-signal nodes, especially from the voltage and
current sensing feedback pins. All of these nodes
have very large and fast moving signals and therefore
should be kept on the “output side” of the LTC3884
and occupy minimum PC trace area. If DCR sensing
is used, place the top resistor (Figure 25a, R1) close
to the switching node.
The duty cycle percentage should be maintained from cycle
to cycle in a well-designed, low noise PCB implementation.
Variation in the duty cycle at a subharmonic rate can suggest noise pickup at the current or voltage sensing inputs
or inadequate loop compensation. Overcompensation of
the loop can be used to tame a poor PC layout if regulator
bandwidth optimization is not required.
Reduce VIN from its nominal level to verify operation
of the regulator in dropout. Check the operation of the
undervoltage lockout circuit by further lowering VIN while
monitoring the outputs to verify operation.
Investigate whether any problems exist only at higher output currents or only at higher input voltages. If problems
coincide with high input voltages and low output currents,
look for capacitive coupling between the BOOSTn, SWn,
TGn, and possibly BGn connections and the sensitive voltage and current pins. The capacitor placed across the current sensing pins needs to be placed immediately adjacent
to the pins of the IC. This capacitor helps to minimize the
effects of differential noise injection due to high frequency
capacitive coupling. If problems are encountered with
high current output loading at lower input voltages, look
for inductive coupling between CIN, Schottky and the top
MOSFET components to the sensitive current and voltage
sensing traces. In addition, investigate common ground
path voltage pickup between these components and the
GND pin of the IC.
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67
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
DESIGN EXAMPLE
As a design example for a 2-channel medium current
regulator, assume VIN = 12V nominal, VIN = 20V maximum,
VOUT0 = 3.3V, VOUT1 = 1.5V, IMAX0,1 = 30A and f = 500kHz.
The regulated output is established by the VOUT_
COMMAND stored in NVM or placing the following resistor divider between VDD25 the RCONFIG pin and SGND:
1. VOUT0_CFG, RTOP = 10k, RBOTTOM = 15.8k
2. VOUT1_CFG, RTOP = 20k, RBOTTOM = 17.8k
The frequency and phase are set by NVM or by setting
the resistor divider between VDD25 FREQ_CFG and SGND
and VDD25 PHASE_CFG and SGND.
Frequency RTOP = 24.9kΩ and RBOTTOM = 5.76kΩ
Phase RTOP = open and RBOTTOM = 0Ω
The address is set to XF where X is the MSB stored in NVM.
The following parameters are set as a percentage of the
output voltage if the resistor configuration pins are used
to determined output voltage:
n
n
n
n
n
n
n
VOUT_OV_FAULT_LIMIT..................................... +10%
VOUT_OV_WARN_LIMIT................................... +7.5%
VOUT_MAX....................................................... +7.5%
VOUT_MARGIN_HIGH..........................................+5%
VOUT_MARGIN_LOW...........................................–5%
VOUT_UV_WARN_LIMIT...................................–6.5%
VOUT_UV_FAULT_LIMIT.......................................–7%
All other user defined parameters must be programmed
into the NVM. The GUI can be utilized to quickly set up
the part with the desired operating parameters.
The inductance values are based on a 28% maximum
ripple current assumption (8.4A). The highest value of
ripple current occurs at the maximum input voltage:
Channel 0 will have 8.1A (27%) ripple, and channel 1 will
have 8.4A (28%) ripple. The peak inductor current will be
the maximum DC value plus one-half the ripple current or
34A for channel 0 and 34.2A for channel 1. The minimum
on time occurs on channel 1 at the maximum VIN, and
should not be less than 60ns:
tON(MIN) =
VOUT
VIN(MAX) • f
=
1.5V
= 150ns
20V • 500kHz
The next design focuses on only Channel1.
The Würth 744301033 0.33μH (0.32mΩ DCR TYP at 25°C)
is used for channel 1. So IOUT_CAL_GAIN = 0.32mΩ.
Based on the output current and inductor value, it is considered to be a perfect example of low DCR application. Set:
MFR_PWM_MODE[2] = 1
then choose C = 220nF, R1 = L/(DCR • C • 5) = 937Ω
Choose R1 = 931Ω.
The maximum power loss in R1 is related to the duty
cycle, and will occur in continuous mode at the maximum
input voltage:
PLOSSR1 =
( VIN(MAX) – VOUT ) • VOUT
R1
(20 −1.5) •1.5 = 29.8mW
=
931
The current limit will be set 20% higher than the peak
value to assure variation in components and noise in the
system do not limit the average current.
VILIMIT = IPEAK • RDCR(MAX) = (1 + 20%) • 34.2A • 0.32mΩ
= 13.1mV
⎤
VOUT ⎡
V
L=
⎢1– OUT ⎥
f • ΔIL(MAX) ⎢⎣ VIN(MAX) ⎥⎦
Channel 0 will require 0.68μH and channel 1 will require
0.33μH. respectively. At the nominal input the ripple will be:
68
⎤
VOUT ⎡
V
⎢1– OUT ⎥
f •L ⎢⎣ VIN(NOM) ⎥⎦
ΔIL(NOM) =
Based on Figure 26, set MFR_PWM_MODE[2], [7] = 1,0
and IOUT_CAL_GAIN = 0.32mΩ in GUI, and enter the
value with IOUT_OC_FAULT_LIMIT = 41.04A, the LTC3884
will automatically set the current limit to 40.64A, based
on the IOUT_FAULT_LIMIT table, (see PMBus command
for details).
3884fe
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LTC3884/LTC3884-1
APPLICATIONS INFORMATION
The power dissipation on the topside MOSFET can be easily estimated. Choose a INFINEON BSC050NE2LS topside
MOSFET. RDS(ON) = 7.1mΩ, CMILLER = 35pF. At maximum
input voltage with T estimated = 75°C and a bottom side
MOSFET a INFINEON BSC010NE2LSI, RDS(ON) = 1.1mΩ:
PMAIN =
1.5V
2
• ( 30A ) • ⎡⎣1+ ( 0.005) ( 75°C – 25°C) ⎤⎦
20V
2
•0.0071Ω + ( 20V ) ( 30A / 2) ( 2Ω )
1 ⎞
1
⎛
+
⎜⎝
⎟ ( 35pF ) ( 500kHz ) = 751mW
5.5 – 2.8 2.8 ⎠
The loss in the bottom side MOSFET is:
PSYNC =
20V – 1.5V
2
• (30A ) •
20V
⎡⎣1+ (0.005) (75°Cº −25°C)⎤⎦ • 0.001Ω
=11.04W
Both MOSFETS have I2R losses while the PMAIN equation
includes an additional term for transition losses, which
are highest at high input voltages. CIN is chosen for an
RMS current rating of:
CIN Required IRMS = 34.2/12 • (3.3 • (12– 3.3))1/2 = 15A
COUT is chosen with an ESR of 0.006Ω for low output
ripple. The output ripple in continuous mode will be highest
at the maximum input voltage. The output voltage ripple
due to ESR is:
VORIPPLE = RESR • (ΔIL) = 0.006Ω • 8.1 ≈ 48.6mV
ADDITIONAL DESIGN CHECKS
Tie FAULT0 and FAULT1 together and pull up to VDD33 with
a 10k resistor. Tie RUN0 and RUN1 together and pull up
to VDD33 with a 10k resistor.
If there are other ADI PSM parts, connect the RUN pins
between chips and connect the FAULT pins between chips.
Be sure all PMBus pins have resistor pull-up to VDD33
and connect these inputs across all ADI PSM parts in the
application.
Tie SHARE_CLK high with a 4.99k resistor to VDD33 and
share between all ADI PSM parts in the application. Be sure a
unique address for each chip can be decoded with the ASEL0
and ASEL1 pins. Refer to Table 6. For maximum flexibility,
allow board space for RTOP and RBOTTOM for any parameter
that is set with resistors such as ASEL0 and ASEL1.
CONNECTING THE USB TO I2C/SMBus/PMBus
CONTROLLER TO THE LTC3884 IN SYSTEM
The ADI USB-to-I2C/SMBus/PMBus adapter (DC1613A or
equivalent) can be interfaced to the LTC3884 on the user’s
board for programming, telemetry and system debug.
The adapter, when used in conjunction with LTpowerPlay,
provides a powerful way to debug an entire power system. Faults are quickly diagnosed using telemetry, fault
status commands and the fault log. The final configuration can be quickly developed and stored to the LTC3884
EEPROM. Figure 42 illustrates the application schematic
for powering, programming and communication with one
or more LTC3884s via the ADI I2C/SMBus/PMBus adapter
regardless of whether or not system power is present. If
system power is not present the dongle will power the
LTC3884 through the VDD33 supply pin. To initialize the
part when VIN 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
LTC3884 can now communicate with, and the project file
can be updated. To write the updated project file to the
NVM issue a STORE_USER _ALL command. When VIN is
applied, a MFR_RESET must be issued to allow the PWM
to be enabled and valid ADCs to be read.
Because of the adapter’s limited current sourcing capability,
only the LTC3884s, their associated pull-up resistors and
the I2C pull-up resistors should be powered from the ORed
3.3V supply. In addition any device sharing the I2C bus
connections with the LTC3884 should 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. If VIN is applied, the DC1613A
will not supply the power to the LTC3884s on the board. It
is recommended the RUNn pins be held low or no voltage
configuration resistors inserted to avoid providing power
to the load until the part is fully configured.
3884fe
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69
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
VIN
LTC
CONTROLLER
HEADER
ISOLATED
3.3V
SDA
100k
100k
VIN
VDD33
TP0101K
SCL
1µF
10k
VDD25
1µF
LTC3884
SDA
10k
SCL
WP
PGND/SGND
TO LTC DC1613
USB TO I2C/SMBus/PMBus
CONTROLLER
VIN
TP0101K
VDD33
1µF
VDD25
1µF
LTC3884
SDA
VGS MAX ON THE TP0101K IS 8V IF VIN > 16V
CHANGE THE RESISTOR DIVIDER ON THE PFET GATE
SCL
WP
PGND/SGND
3884 F41
Figure 42. Controller Connection
The LTC3884 is fully isolated from the host PC’s ground by
the DC1613A.The 3.3V from the adapter and the LTC3884
VDD33 pin must be driven to each LTC3884 with a separate
PFET. If both VIN and EXTVCC are not applied, the VDD33
pins can be in parallel because the on-chip LDO is off. The
controller 3.3V current limit is 100mA but typical VDD33
currents are under 15mA. The VDD33 does back drive the
INTVCC/EXTVCC pin. Normally this is not an issue if VIN
is open.
during board bring-up to program or tweak the power
system or to diagnose power issues when bring up rails.
LTpowerPlay utilizes Analog Devices’s USB-to-I2C/SMBus/
PMBus adapter to communication with one of the many
potential targets including the DC2165A demo board, the
DC2298A socketed programming board, 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.
LTpowerPlay: AN INTERACTIVE GUI FOR DIGITAL
POWER
A great deal of context sensitive help is available with
LTpower Play along with several tutorial demos. Complete
information is available at:
LTpowerPlay (Figure 43) is a powerful Windows-based
development environment that supports Analog Devices digital power system management ICs including
the LTC3884. The software supports a variety of different tasks. LTpowerPlay can be used to evaluate Analog
Devices ICs by connecting to a demo board or the user
application. LTpowerPlay can also be used in an offline
mode (with no hardware present) 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
70
http://www.linear.com/ltpowerplay
PMBus COMMUNICATION AND COMMAND
PROCESSING
The LTC3884 has a one deep buffer to hold the last data
written for each supported command prior to processing
as shown in Figure 44, 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
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
Figure 43. LTpowerPlay Screen Shot
CMD
PMBus
WRITE
WRITE COMMAND
DATA BUFFER
DECODER
CMDS
DATA
MUX
CALCULATIONS
PENDING
S
R
PAGE
•
•
•
VOUT_COMMAND
0x00
0x21
•
•
•
MFR_RESET
INTERNAL
PROCESSOR
FETCH,
CONVERT
DATA
AND
EXECUTE
0xFD
x1
3884 F43
Figure 44. Write Command Data Processing
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
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71
LTC3884/LTC3884-1
APPLICATIONS INFORMATION
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 45 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 v1.1, 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.
// wait until chip is not busy
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 45. Example of a Command Write of VOUT_COMMAND
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
(‘chip not busy’). When the part is busy specifically because it is in a transitional VOUT state (margining hi/lo,
72
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_COMMAND register is provided in Figure 45.
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 to create a SAFE_WRITE_BYTE() and SAFE_WRITE_
WORD() subroutine. The above polling mechanism allows
your 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 v1.1,
Part II, Section 10.8.7 is required to communicate The
LTC3884 is not recommended in applications with bus
speeds in excess of 400kHz.
3884fe
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
ADDRESSING AND WRITE PROTECT
CMD
CODE
0x00
0x05
0x06
COMMAND NAME
PAGE
PAGE_PLUS_WRITE
PAGE_PLUS_READ
DESCRIPTION
Provides integration with multi-page PMBus devices.
Write a supported command directly to a PWM channel.
Read a supported command directly from a PWM
channel.
0x10 Level of protection provided by the device against
accidental changes.
0xE6 Sets the 7-bit I2C address byte.
0xFA Common address for PolyPhase outputs to adjust
common parameters.
WRITE_PROTECT
MFR_ADDRESS
MFR_RAIL_ADDRESS
DATA
DEFAULT
TYPE
PAGED FORMAT UNITS NVM VALUE
R/W Byte
N
Reg
0x00
W Block
N
Block
N
R/W
R/W Byte
N
Reg
Y
0x00
R/W Byte
R/W Byte
N
Y
Reg
Reg
Y
Y
0x4F
0x80
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 commands 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 LTC3884
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 46.
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
A
UPPER DATA
BYTE
A
PEC BYTE
A
1
8
1
A
COMMAND
CODE
A
…
1
P
3884 F45
Figure 46. Example of PAGE_PLUS_WRITE
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 .
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73
LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 the Process Call protocol. An example of the PAGE_PLUS_READ command with PEC is shown
in Figure 47.
1
7
S
SLAVE
ADDRESS
1
7
Sr
SLAVE
ADDRESS
1
R
1
1
W
PAGE_PLUS
A
A
COMMAND CODE
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
3884 F46
Figure 47. Example of PAGE_PLUS_READ
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 LTC3884 will NACK the entire PAGE_PLUS packet and issue a CML
fault for Invalid/Unsupported Data.
WRITE_PROTECT
The WRITE_PROTECT command is used to control writing to the LTC3884 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.
BYTE MEANING
0x80 Disable all writes except to the WRITE_PROTECT, PAGE, MFR_
EE_UNLOCK, and STORE_USER_ALL commands.
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 commands.
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 commands.
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.
If WP pin is high, PAGE, OPERATION, MFR_CLEAR_PEAKS, MFR_EE_UNLOCK, WRITE_PROTECT and CLEAR_FAULTS
commands are supported. Individual fault bits can be cleared by writing a 1 to the respective bits in the STATUS
commands.
74
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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, the ASEL0 and ASEL1 pins are still used to determine the LSB
and MSB, respectively, of the channel address. If the ASEL0 and ASEL1 pins are both open, the LTC3884 will use the
address value stored in NVM. If the ASEL0 pin is open, the LTC3884 will use the lower 4 bits of the MFR_ADDRESS
value stored in NVM to construct the effective address of the part. If the ASEL1 pin is open, the LTC3884 will use the
upper 4 bits of the MFR_ADDRESS value stored in NVM to construct the effective address of the part.
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 LTC3884 will detect bus contention and may 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 COMMANDS
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
0x1D
MFR_CONFIG_ALL
0xD1
General configuration bits.
R/W Byte
N
Reg
Y
0x21
MFR_CHAN_CONFIG
General purpose configuration command common to multiple ADI 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
Enable Short Cycle recognition if this bit is set to a 1.
2
SHARE_CLOCK control. If SHARE_CLOCK is held low, the output is disabled.
1
No FAULT ALERT, ALERT is not pulled low if FAULT is pulled low externally. Assert this bit if either POWER_GOOD or VOUT_UVUF are
propagated on FAULT.
0
Disables the VOUT decay value requirement for MFR_RETRY_TIME and tOFF(MIN) 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.
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75
LTC3884/LTC3884-1
PMBus COMMAND DETAILS
A shortCycle event occurs whenever the PWM channel is commanded back ON, or reactivated, after the part has been
commanded OFF and is processing either the TOFF_DELAY or the TOFF_FALL states. The PWM channel can be turned
ON and OFF through either the RUN pin and or the PMBus OPERATION command.
If the PWM channel is reactivated during the TOFF_DELAY, the part will perform the following:
1. Immediately tri-state the PWM channel output;
2. Start the retry delay timer as specified by the tOFF(MIN).
3. After the tOFF(MIN) value has expired, the PWM channel will proceed to the TON_DELAY state and the STATUS_
MFR_SPECIFIC bit #1 will assert.
If the PWM channel is reactivated during the TOFF_FALL, the part will perform the following:
1. Stop ramping down the PWM channel output;
2. Immediately tri-state the PWM channel output;
3. Start the retry delay timer as specified by the tOFF(MIN).
4. After the tOFF(MIN) value has expired, the PWM channel will proceed to the TON_DELAY state and the STATUS_
MFR_SPEFIFIC bit #1 will assert.
If the SHORT Cycle event occurs and the ShortCycle MFR_CHAN_CONFIG bit is not set, the PWM channel state machine
will complete its TOFF_DELAY and TOFF_FALL operations as previously commanded by the user.
MFR_CONFIG_ALL
General purpose configuration command common to multiple ADI products.
BIT
MEANING
7
Enable Fault Logging.
6
Ignore Resistor Configuration Pins.
5
Mask PMBus, PartII, Section 10.9.1 Violations.
4
Disable SYNC output.
3
Enable 255ms PMBus timeout.
2
PMBus command writes require a valid Packet Error Checking, PEC, byte to be accepted.*
1
Enable the use of PMBus clock stretching.
0
Execute CLEAR_FAULTS on rising edge of either RUN pin.
*PMBus command writes that have a valid PEC byte are always processed. PMBus command
writes that have an invalid PEC byte are not processed and set a CML status fault.
This command has one data byte.
ON/OFF/MARGIN
COMMAND NAME
CMD
CODE
DESCRIPTION
ON_OFF_CONFIG
0x02
OPERATION
0x01
MFR_RESET
0xFD
76
TYPE
PAGED
RUN pin and PMBus bus on/off command configuration.
R/W Byte
Y
Operating mode control. On/off, margin high and margin
low.
R/W Byte
Y
Commanded reset without requiring a power-down.
Send Byte
N
DATA
FORMAT UNITS
NVM
DEFAULT
VALUE
Reg
Y
0x1E
Reg
Y
0x80
NA
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PMBus COMMAND DETAILS
ON_OFF_CONFIG
The ON_OFF_CONFIG command specifies the combination of RUNn pin input state and PMBus commands needed to
turn the PWM channel on and off.
Supported Values:
VALUE
MEANING
0x1F
OPERATION value and RUNn pin must both command the device to start/run. Device executes immediate off when commanded off.
0x1E
OPERATION value and RUNn pin must both command the device to start/run. Device uses TOFF_ command values when commanded off.
0x17
RUNn pin control with immediate off when commanded off. OPERATION on/off control ignored.
0x16
RUNn pin control using TOFF_ command values when commanded off. OPERATION on/off control ignored.
Programming an unsupported ON_OFF_CONFIG value will generate a CML fault and the command will be ignored.
This command has one data byte.
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 RESET
or POWER_ON 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. If VIN is applied to a part with factory default programming and the VOUT_CONFIG resistor
configuration pins are not installed, the outputs will be commanded off.
The part defaults to the Sequence Off state.
This command has one data byte.
Supported Values:
VALUE
MEANING
0xA8
Margin high.
0x98
Margin low.
0x80
On (VOUT back to nominal even if bit 3 of ON_OFF_CONFIG is not set).
0x40*
Soft off (with sequencing).
0x00*
Immediate off (no sequencing).
*Device does not respond to these commands if bit 3 of ON_OFF_CONFIG is not set.
Programming an unsupported OPERATION value will generate a CML fault and the command will be ignored.
This command has one data byte.
MFR_RESET
This command provides a means to reset the LTC3884 from the serial bus. This forces the LTC3884 to turn off both
PWM channels, load the operating memory from internal EEPROM, clear all faults and then perform a soft-start of
both PWM channels, if enabled.
This write-only command has no data bytes.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
PWM CONFIGURATION
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
DEFAULT
FORMAT UNITS NVM VALUE
MFR_PWM_COMP
0xD3
PWM loop compensation configuration
R/W Byte
Y
Reg
Y
0xAE
MFR_PWM_MODE
0xD4
Configuration for the PWM engine.
R/W Byte
Y
Reg
Y
0xC7
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
425
0xFB52
kHz
MFR_PWM_MODE
The MFR_PWM_MODE command sets important PWM controls for each channel.
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
7
0b
1b
6
5
MEANING
Use High Range of ILIMIT
Low Current Range
High Current Range
Enable Servo Mode
External temperature sense:
0: ΔVBE measurement.
[4:3]
2
1
1b
0b
Bit[0]
0b
1b
1: Direct voltage measurement.
Reserved
Enable ultra-low DCR current sense
VOUT Range
The maximum output voltage is 2.75V
The maximum output voltage is 5.5V
Mode
Discontinuous
Forced Continuous
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. This bit value should not be changed when the
channel output is active. Writing this bit when the channel is active will generate a CML fault.
Bit [6] The LTC3884 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).
When Bit[5] is cleared, the LTC3884 computes temperature in °C from ∆VBE measured by the ADC at the TSNSn pin as
T = (G • ΔVBE • q/(K • ln(16))) – 273.15 + O
When Bit[5] is set, the LTC3884 computes temperature in °C from TSNSn voltage measured by the ADC as
T = (G • (1.35 – VTSNSn + O)/4.3e-3) + 25
78
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
For both equations,
G = MFR_TEMP_1_GAIN • 2–14, and
O = MFR_TEMP_1_OFFSET
Bit[2] determines if the part uses sub-milliohm DCR for sensing the output current. This is a very critical selection
in terms of overcurrent limit. It is highly recommend that Bit[2] should not be changed when device is in operation.
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 should not be changed when the channel output is active. Writing
this bit when the channel is active will generate a CML fault.
Bit[0] determines if the PWM mode of operation is discontinuous (pulse-skipping mode), or forced continuous conduction mode. Whenever the channel is ramping on, the PWM mode will be discontinuous, regardless of the value of
this bit. This command has one data byte.
MFR_PWM_COMP
The MFR_PWM_COMP command sets the gm of the PWM channel error amplifiers and the value of the internal RITHn
compensation resistors. This command affects the loop gain of the PWM output which may require modifications to
the external compensation network.
BIT
MEANING
BIT [7:5]
Error Amplifier GM Adjust (mS)
000b
1.00
001b
1.68
010b
2.35
011b
3.02
100b
3.69
101b
4.36
110b
5.04
111b
5.73
BIT [4:0]
RITH (kΩ)
00000b
0
00001b
0.25
00010b
0.5
00011b
0.75
00100b
1
00101b
1.25
00110b
1.5
00111b
1.75
01000b
2
01001b
2.5
01010b
3
01011b
3.5
01100b
4
01101b
4.5
01110b
5
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
01111b
5.5
10000b
6
10001b
7
10010b
8
10011b
9
10100b
11
10101b
13
10110b
15
10111b
17
11000b
20
11001b
24
11010b
28
11011b
32
11100b
38
11101b
46
11110b
54
11111b
62
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
channels must be commanded off. If either channel is in the RUN state and this command is written, the command
will be NACK’d and a BUSY fault will be asserted.
BIT
MEANING
7
Reserved
[6:5]
00b
01b
10b
11b
Input current sense gain.
2x gain. 0mV to 50mV range.
4x gain. 0mV to 20mV range.
8x gain. 0mV to 5mV range.
Reserved
4
Share Clock Enable : If this bit is 1, the
SHARE_CLK pin will not be released until
VIN > VIN_ON. The SHARE_CLK pin will be
pulled low when VIN < VIN_OFF. If this bit is 0, the
SHARE_CLK pin will not be pulled low when VIN <
VIN_OFF except for the initial application of VIN.
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
80
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
FREQUENCY_SWITCH
The FREQUENCY_SWITCH command sets the switching frequency, in kHz, of the LTC3884.
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. The RUN pin must be low or both channels must be
commanded off. If the part is in the RUN state and this command is written, the command will be NACK'd 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 and Limits
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
DEFAULT
VALUE
VIN_OV_FAULT_LIMIT
0x55
Input supply overvoltage fault limit.
R/W
Word
N
L11
V
Y
15.5
0xD3E0
VIN_UV_WARN_LIMIT
0x58
Input supply undervoltage warning limit.
R/W
Word
N
L11
V
Y
6.3
0xCB26
VIN_ON
0x35
Input voltage at which the unit should start
power conversion.
R/W
Word
N
L11
V
Y
6.5
0xCB40
VIN_OFF
0x36
Input voltage at which the unit should stop
power conversion.
R/W
Word
N
L11
V
Y
6.0
0xCB00
MFR_RVIN
0xF7
The resistance value of the VIN pin filter
element in milliohms
R/W
Word
N
L11
mΩ
Y
1000
0x03E8
VIN_OV_FAULT_LIMIT
The VIN_OV_FAULT_LIMIT command sets the value of the input voltage measured by the ADC, in volts, that causes
an input overvoltage fault.
This command has two data bytes in Linear_5s_11s format.
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81
LTC3884/LTC3884-1
PMBus COMMAND DETAILS
VIN_UV_WARN_LIMIT
The VIN_UV_WARN_LIMIT command sets the value of input voltage measured by the ADC that causes an input undervoltage warning. This warning is disabled until the input exceeds the input startup threshold value set by the VIN_ON
command and the unit has been enabled. If the VIN Voltage drops below the VIN_OV_WARN_LIMIT the device:
• Sets the INPUT Bit Is the STATUS_WORD
• Sets the VIN Undervoltage Warning Bit in the STATUS_INPUT Command
• Notifies the Host by Asserting ALERT, unless Masked
VIN_ON
The VIN_ON command sets the input voltage, in Volts, at which the unit starts power conversion.
This command has two data bytes and is formatted in Linear_5s_11s format.
VIN_OFF
The VIN_OFF command sets the input voltage, in Volts, at which the unit stops power conversion.
This command has two data bytes and is formatted in Linear_5s_11s format.
MFR_RVIN
The MFR_RVIN command is used to set the resistance value of the VIN pin filter element in milliohms. (See also
READ_VIN). Set MFR_RVIN equal to 0 if no filter element is used.
This command has two data bytes and is formatted in Linear_5s_11s format.
Output Voltage and Limits
COMMAND NAME
VOUT_MODE
VOUT_MAX
VOUT_OV_FAULT_ LIMIT
CMD CODE DESCRIPTION
0x20
Output voltage format and exponent
(2–12).
0x24
Upper limit on the output voltage
the unit can command regardless of
any other commands.
0x40
Output overvoltage fault limit.
VOUT_OV_WARN_ LIMIT
0x42
Output overvoltage warning limit.
VOUT_MARGIN_HIGH
0x25
VOUT_COMMAND
0x21
Margin high output voltage set
point. Must be greater than VOUT_
COMMAND.
Nominal output voltage set point.
VOUT_MARGIN_LOW
0x26
VOUT_UV_WARN_ LIMIT
0x43
Margin low output voltage set
point. Must be less than VOUT_
COMMAND.
Output undervoltage warning limit.
VOUT_UV_FAULT_ LIMIT
0x44
Output undervoltage fault limit.
MFR_VOUT_MAX
0xA5
Maximum allowed output voltage.
82
TYPE
R Byte
PAGED
Y
DATA
FORMAT
Reg
UNITS
NVM
R/W
Word
Y
L16
V
Y
R/W
Word
R/W
Word
R/W
Word
Y
L16
V
Y
Y
L16
V
Y
Y
L16
V
Y
R/W
Word
R/W
Word
Y
L16
V
Y
Y
L16
V
Y
R/W
Word
R/W
Word
R Word
Y
L16
V
Y
Y
L16
V
Y
Y
L16
V
DEFAULT
VALUE
2–12
0x14
2.75
0x2C00
1.1
0x119A
1.075
0x1133
1.05
0x10CD
1.0
0x1000
0.95
0x0F33
0.925
0x0ECD
0.9
0x0E66
5.7
0x5B33
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 5.8V.
The maximum output voltage the LTC3884 can produce is 5.5V including VOUT_MARGIN_HIGH. However, the
VOUT_OV_FAULT_LIMIT can be commanded as high as 5.7V.
This command has two data bytes and is formatted in Linear_16u format.
VOUT_OV_FAULT_LIMIT
The VOUT_OV_FAULT_LIMIT command sets the value of the output voltage measured by the OV supervisor comparator at the sense pins, in volts, which causes an output overvoltage fault.
If the VOUT_OV_FAULT_LIMIT is modified and the part is in the RUN state, 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 honored 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 or 0x00, the FAULT pin will not assert if VOUT_OV_FAULT
is propagated. The LTC3884 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 by the ADC at the sense pins,
in volts, which causes an output voltage high warning. The MFR_VOUT_PEAK value can 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 tCONVERT.
This command has two data bytes and is formatted in Linear_16u format.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 should be greater than VOUT_COMMAND. The
maximum guaranteed value on VOUT_MARGIN_HIGH is 5.5V.
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 5.5V.
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_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 by the ADC 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 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 by the UV supervisor comparator 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.
84
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 is 5.5V. If
the output voltage is set to low range (Bit 1 of MFR_PWM_MODE set to a 1) the MFR_VOUT_MAX is 2.75V. Entering
a VOUT_COMMAND value greater than this will result in a CML fault and the output voltage setting will be clamped
to the maximum level. This will also result in Bit 3 VOUT_MAX_Warning in the STATUS_VOUT command being set.
This read only command has 2 data bytes and is formatted in Linear_16u format.
OUTPUT CURRENT AND LIMITS
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
DEFAULT
VALUE
mΩ
Y
0.32
0xAA8F
Y
3900
0x0F3C
IOUT_CAL_GAIN
0x38
The ratio of the voltage at the current R/W Word
sense pins to the sensed current. For
devices using a fixed current sense
resistor, it is the resistance value in
mΩ.
Y
L11
MFR_IOUT_CAL_GAIN_TC
0xF6
Temperature coefficient of the current R/W Word
sensing element.
Y
CF
IOUT_OC_FAULT_LIMIT
0x46
Output overcurrent fault limit.
R/W Word
Y
L11
A
Y
45.0
0xE2D0
IOUT_OC_WARN_LIMIT
0x4A
Output overcurrent warning limit.
R/W Word
Y
L11
A
Y
34.0
0xE230
IOUT_CAL_GAIN
The IOUT_CAL_GAIN command is used to set the resistance value of the current sense resistor in milliohms. (see
also MFR_IOUT_CAL_GAIN_TC).
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
sense resistor or 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,
MFR_IOUT_PEAK, IOUT_OC_FAULT_LIMIT and IOUT_OC_WARN_LIMIT.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 following table lists the
progammable peak output current limit value in mV between ISENSE+ and ISENSE–. The actual value of current limit is
(ISENSE+ – ISENSE–)/IOUT_CAL_GAIN in Amperes.
CODE
0000
0001
0010
0011
0100
0101
MFR_PWM_MODE[2]=1 (Sub-milli Ω DCR)
L
RC =
5 • DCR
MFR_PWM_MODE[7]=0
MFR_PWM_MODE[7]=1
High Current Range (mV)
Low Current Range (mV)
15.45
8.59
16.59
9.22
17.73
9.85
18.86
10.48
20.42
11.34
21.14
11.74
0110
22.27
12.37
0111
23.41
13.01
1000
24.55
13.64
1001
25.68
14.27
1010
26.82
14.90
1011
27.95
15.53
1100
29.50
16.50
1101
30.23
16.79
1110
31.36
17.42
1111
32.50
18.06
Note: Only VILIMIT codes 2–8 are supported for DCR sensing.
MFR_PWM_MODE[2]=0 (Normal Value of DCR)
L
RC =
DCR
MFR_PWM_MODE[7]=1
MFR_PWM_MODE[7]=0
High Current Range (mV)
Low Current Range (mV)
38.64
21.46
41.48
23.04
44.32
24.62
47.16
26.20
51.04
28.36
52.84
29.36
55.68
58.52
61.36
64.20
67.05
69.89
74.50
75.57
78.41
81.25
30.93
32.51
34.09
35.67
37.25
38.83
41.38
41.98
43.56
45.14
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:
Peak Current Limit = IOUT_CAL_GAIN • (1 + MFR_IOUT_CAL_GAIN_TC • (READ_TEMPERTURE_1-27.0)).
The LTC3884 automatically convert currents to the appropriate internal bit value.
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.
If the IOUT_OC_FAULT_LIMIT is exceeded, the device:
• Sets the IOUT bit in the STATUS word
• Sets the IOUT Overcurrent fault bit in the STATUS_IOUT
• Notifies the host by asserting ALERT, unless masked
This command has two data bytes and is formatted in Linear_5s_11s format.
86
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
IOUT_OC_WARN_LIMIT
This command sets the value of the output current measured by the ADC 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
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
Input Current and Limits
COMMAND NAME
MFR_IIN_CAL_GAIN
CMD
CODE DESCRIPTION
0xE8 The resistance value of the input current sense
element in mΩ.
TYPE
R/W Word
DATA
FORMAT
L11
UNITS
mΩ
NVM
Y
DEFAULT
VALUE
5.000
0xCA80
MFR_IIN_CAL_GAIN
The MFR_IIN_CAL_GAIN command is used to set the resistance value of the input current sense resistor in milliohms.
(see also READ_IIN).
This command has two data bytes and is formatted in Linear_5s_11s format.
COMMAND NAME
IIN_OC_WARN_LIMIT
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
R/W Word
N
L11
A
Y
CMD CODE DESCRIPTION
0x5D
Input overcurrent warning
limit.
DEFAULT
VALUE
10.0
0xD280
IIN_OC_WARN_LIMIT
The IIN_OC_WARN_LIMIT command sets the value of the input current measured by the ADC, 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
• Sets the IIN Overcurrent Warning bit[1] in the STATUS_INPUT command, and
• Notifies the host by asserting ALERT pin
This command has two data bytes and is formatted in Linear_5s_11s format.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
TEMPERATURE
External 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 external temperature
sensor.
R/W Word
Y
CF
MFR_TEMP_1_OFFSET
0xF9
Sets the offset of the external temperature
sensor.
R/W Word
Y
L11
C
Y
1.0
0x4000
Y
0.0
0x8000
MFR_TEMP_1_GAIN
The MFR_TEMP_1_GAIN command will modify the slope of the external 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 16-bit 2’s complement integer. The effective gain 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 external 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 Linear_5s_11s format.
External Temperature Limits
COMMAND NAME
CMD CODE DESCRIPTION
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
DEFAULT
VALUE
OT_FAULT_LIMIT
0x4F
External overtemperature fault limit.
R/W Word
Y
L11
C
Y
100.0
0xEB20
OT_WARN_LIMIT
0x51
External overtemperature warning
limit.
R/W Word
Y
L11
C
Y
85.0
0xEAA8
UT_FAULT_LIMIT
0x53
External undertemperature fault limit.
R/W Word
Y
L11
C
Y
–40.0
0xE580
OT_FAULT_LIMIT
The OT_FAULT_LIMIT command sets the value of the external sense temperature measured by the ADC, 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 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 external sense temperature measured by the ADC, in degrees
Celsius, which causes an overtemperature warning. The READ_TEMPERATURE_1 value will be used to determine if
this limit has been exceeded.
88
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PMBus COMMAND DETAILS
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 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 external sense temperature measured by the ADC, in degrees Celsius,
which causes an undertemperature fault. The READ_TEMPERATURE_1 value will be used to determine if this limit has been
exceeded.
Note: If the temp sensors are not installed, the UT_FAULT_LIMIT can be set to –275°C and UT_FAULT_LIMIT response
set to ignore to avoid ALERT being asserted.
This command has two data bytes and is formatted in Linear_5s_11s format.
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.
TYPE
PAGED
R/W Word
Y
DATA
FORMAT
L11
UNITS
ms
NVM
Y
DEFAULT
VALUE
0.0
0x8000
8.0
0xD200
R/W Word
Y
L11
ms
Y
R/W Word
Y
L11
ms
Y
10.0
0xD280
R/W Word
Y
L11
V/ms
Y
0.25
0xAA00
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. The resulting turn-on delay will have a typical delay of
270µs for TON_DELAY = 0 and an uncertainty of ±50µs for all values of TON_DELAY.
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 LTC3884 digital slope will be bypassed and the output voltage
transition will only be controlled by the analog performance of the PWM switcher. The number of steps in TON_RISE
is equal to TON_RISE (in ms)/0.1ms with an uncertainty of ±0.1ms.
This command has two data bytes and is formatted in Linear_5s_11s format.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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. The commanded
rate of change does not apply when the unit is commanded on or off. The maximum allowed slope is 4V/ms.
This command has two data bytes and is formatted in Linear_5s_11s format.
Timing—Off Sequence/Ramp
COMMAND NAME
TOFF_DELAY
TOFF_FALL
TOFF_MAX_WARN_LIMIT
CMD CODE DESCRIPTION
TYPE
0x64
Time from RUN and/or Operation off to
R/W Word
the start of TOFF_FALL ramp.
Time from when the output starts to fall R/W Word
0x65
until the output reaches zero volts.
Maximum allowed time, after TOFF_FALL R/W Word
0x66
completed, for the unit to decay below
12.5%.
PAGED
Y
DATA
FORMAT
L11
UNITS
ms
NVM
Y
Y
L11
ms
Y
Y
L11
ms
Y
DEFAULT
VALUE
0.0
0x8000
8.0
0xD200
150
0xF258
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. The resulting turn off delay will have a typical delay of
270µs for TOFF_DELAY = 0 and an uncertainty of ±50µs for all values of TOFF_DELAY. TOFF_DELAY is not applied
when a fault event occurs
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 PWM output will be
set to high impedance 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 number of steps in TOFF_FALL is equal to TOFF_FALL (in ms)/0.1ms with an uncertainty
of ±0.1ms.
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.
90
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
TOFF_MAX_WARN_LIMIT
The TOFF_MAX_WARN_LIMIT command sets the value, in milliseconds, on how long the output voltage exceeds
12.5% of the programmed voltage before 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.
A data value of 0ms means that there is no limit and that the output voltage exceeds 12.5% of the programmed 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
CMD CODE DESCRIPTION
MFR_RESTART_ DELAY
0xDC
Minimum time the RUN pin is held
low by the LTC3884.
TYPE
PAGED
DATA
FORMAT
UNITS
NVM
R/W Word
Y
L11
ms
Y
DEFAULT
VALUE
500
0xFBE8
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 0 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
PAGED
DATA
FORMAT
UNITS
NVM
R/W Word
Y
L11
ms
Y
DEFAULT
VALUE
350
0xFABC
MFR_RETRY_DELAY
This command sets the time in milliseconds between retries 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.
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Fault Responses Input Voltage
COMMAND NAME
VIN_OV_FAULT_RESPONSE
CMD CODE DESCRIPTION
0x56
Action to be taken by the device when an
input supply overvoltage fault is detected.
TYPE
R/W Byte
DATA
PAGED FORMAT
Y
UNITS
Reg
NVM
DEFAULT
VALUE
Y
0x80
VIN_OV_FAULT_RESPONSE
The VIN_OV_FAULT_RESPONSE command instructs the device on what action to take in response to an input overvoltage fault. The data byte is in the format given in Table 11.
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
• Sets the VIN 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 7.
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 values recognized for this command are:
0x00–Part performs OV pull down only, or OV_PULLDOWN.
0x80–The device shuts down (disables the output) and the unit does not attempt to retry. (PMBus, Part II, Section 10.7).
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0xB8–The device shuts down (disables the output) and device attempts to 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 RESET through the command or removal of VIN.
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 RESET through the command or
removal of VIN. 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.
Table 7. VOUT_OV_FAULT_RESPONSE Data Byte Contents
BITS
7:6
DESCRIPTION
Response
VALUE
00
For all values of bits [7:6], the LTC3884:
• 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 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
5:3
• Bias power is removed and reapplied to the LTC3884.
Retry Setting
2:0
Delay Time
10
11
MEANING
Part performs OV pull down only or OV_PULLDOWN
(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
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 RUN 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.
000-111 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 8.
The device also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• Sets the VOUT bit in the STATUS_WORD
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• 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.
Table 8. 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 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
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.
000
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 RUN 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.
For all values of bits [7:6], the LTC3884:
• 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 RESTORE_USER_ALL command.
• The device receives a MFR_RESET command.
• The device supply power is cycled.
5:3
2:0
94
Retry Setting
Delay Time
000-111 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.
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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 11.
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.
Note: The PWM channel remains in discontinues mode until the TON_MAX_FAULT_LIMIT has been exceeded.
This command has one data byte.
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 9.
The device also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• 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.
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Table 9. IOUT_OC_FAULT_RESPONSE Data Byte Contents
BITS
7:6
DESCRIPTION
VALUE
Response
00
The LTC3884 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 constantcurrent or brick-wall limiting).
01
Not supported.
10
The LTC3884 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 LTC3884 shuts down immediately and responds as
programmed by the Retry Setting in bits [5:3].
000
The unit does not attempt to restart. The output remains
disabled until the fault is cleared by cycling the RUN pin or
removing bias power.
111
The device attempts to restart 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. Note: The retry interval
is set by the MFR_RETRY_DELAY command.
For all values of bits [7:6], the LTC3884:
• 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 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
• The device receives a RESTORE_USER_ALL command.
MEANING
• The device receives a MFR_RESET command.
• The device supply power is cycled.
5:3
2:0
Retry Setting
Delay Time
000-111 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 response.
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
DATA
FORMAT
R Byte
N
Reg
UNITS
NVM
DEFAULT
VALUE
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 10.
The LTC3884 also:
• Sets the NONE_OF_THE_ABOVE bit in the STATUS_BYTE
• 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.
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Table 10. Data Byte Contents MFR_OT_FAULT_RESPONSE
BITS
7:6
DESCRIPTION
VALUE
MEANING
Response
00
Not supported. Writing this value will generate a CML fault.
For all values of bits [7:6], the LTC3884:
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 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
• Bias power is removed and reapplied to the LTC3884.
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 External 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 an
external overtemperature fault is detected,
R/W Byte
Y
Reg
Y
0xB8
UT_FAULT_ RESPONSE
0x54
Action to be taken by the device when an
external undertemperature fault is detected.
R/W Byte
Y
Reg
Y
0xB8
OT_FAULT_RESPONSE
The OT_FAULT_RESPONSE command instructs the device on what action to take in response to an external overtemperature fault on the external temp sensors. The data byte is in the format given in Table 11.
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 command has one data byte.
UT_FAULT_RESPONSE
The UT_FAULT_RESPONSE command instructs the device on what action to take in response to an external undertemperature fault on the external temp sensors. The data byte is in the format given in Table 11.
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
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This condition is detected by the ADC so the response time may be up to tCONVERT.
This command has one data byte.
Table 11. Data Byte Contents: TON_MAX_FAULT_RESPONSE, VIN_OV_FAULT_RESPONSE,
OT_FAULT_RESPONSE, UT_FAULT_RESPONSE
BITS
7:6
DESCRIPTION
VALUE
MEANING
Response
00
The PMBus device continues operation without interruption.
For all values of bits [7:6], the LTC3884:
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
Not supported. Writing this value will generate a CML fault.
000
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 RUN 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
• 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 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
• The device receives a RESTORE_USER_ALL command.
• The device receives a MFR_RESET command.
• The device supply power is cycled.
5:3
2:0
Retry Setting
Delay Time
FAULT SHARING
Fault Sharing Propagation
COMMAND NAME
MFR_FAULT_
PROPAGATE
CMD CODE
0xD2
DESCRIPTION
Configuration that determines which faults
are propagated to the FAULT pins.
TYPE
PAGED
DATA
FORMAT
R/W Word
Y
Reg
UNITS
NVM
DEFAULT
VALUE
Y
0x6993
MFR_FAULT_PROPAGATE
The MFR_FAULT_PROPAGATE command enables the faults that can cause the FAULTn pin to assert low. The command is formatted as shown in Table 12. Faults can only be propagated to the FAULTn pin if they are programmed to
respond to faults.
This command has two data bytes.
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Table 12: FAULTn Propagate Fault Configuration
The FAULT0 and FAULT1 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)
B[15]
SYMBOL
VOUT disabled while not decayed.
B[14]
Mfr_fault_propagate_short_CMD_cycle
OPERATION
This is used in a PolyPhase configuration when bit 0 of the MFR_CHAN_CONFIG_LTC3884 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 FAULT pin is asserted during this condition
if bit 15 is asserted.
0: No action
Mfr_fault_propagate_ton_max_fault
1: Asserts low if commanded off then on before the output has sequenced off. Re-asserts high
tOFF(MIN) after sequence off.
0: No action if a TON_MAX_FAULT fault is asserted
b[13]
1: Associated output will be asserted low if a TON_MAX_FAULT fault is asserted
FAULT0 is associated with page 0 TON_MAX_FAULT faults
FAULT1 is associated with page 1 TON_MAX_FAULT faults
b[12]
b[11]
Reserved
Mfr_fault0_propagate_int_ot,
b[10]
b[9]
b[8]
Mfr_fault1_propagate_int_ot
Reserved
Reserved
Mfr_fault0_propagate_ut,
0: No action if the UT_FAULT_LIMIT fault is asserted
Mfr_fault1_propagate_ut
1: Associated output will be asserted low if the UT_FAULT_LIMIT fault is asserted
0: No action if the MFR_OT_FAULT_LIMIT fault is asserted
1: Associated output will be asserted low if the MFR_OT_FAULT_LIMIT fault is asserted
FAULT0 is associated with page 0 UT faults
b[7]
Mfr_fault0_propagate_ot,
FAULT1 is associated with page 1 UT faults
0: No action if the OT_FAULT_LIMIT fault is asserted
Mfr_fault1_propagate_ot
1: Associated output will be asserted low if the OT_FAULT_LIMIT fault is asserted
FAULT0 is associated with page 0 OT faults
FAULT1 is associated with page 1 OT faults
b[6]
b[5]
b[4]
Reserved
Reserved
Mfr_fault0_propagate_input_ov,
b[3]
b[2]
Mfr_fault1_propagate_input_ov
Reserved
Mfr_fault0_propagate_iout_oc,
0: No action if the IOUT_OC_FAULT_LIMIT fault is asserted
Mfr_fault1_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
FAULT0 is associated with page 0 OC faults
b[1]
Mfr_fault0_propagate_vout_uv,
FAULT1 is associated with page 1 OC faults
0: No action if the VOUT_UV_FAULT_LIMIT fault is asserted
Mfr_fault1_propagate_vout_uv
1: Associated output will be asserted low if the VOUT_UV_FAULT_LIMIT fault is asserted
FAULT0 is associated with page 0 UV faults
b[0]
Mfr_fault0_propagate_vout_ov,
FAULT1 is associated with page 1 UV faults
0: No action if the VOUT_OV_FAULT_LIMIT fault is asserted
Mfr_fault1_propagate_vout_ov
1: Associated output will be asserted low if the VOUT_OV_FAULT_LIMIT fault is asserted
FAULT0 is associated with page 0 OV faults
FAULT1 is associated with page 1 OV faults
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PMBus COMMAND DETAILS
Fault Sharing Response
COMMAND NAME
CMD CODE DESCRIPTION
MFR_FAULT_RESPONSE
0xD5
Action to be taken by the device when the
FAULT pin is asserted low.
TYPE
R/W Byte
PAGED
Y
DATA
FORMAT
Reg
UNITS
NVM
Y
DEFAULT
VALUE
0xC0
MFR_FAULT_RESPONSE
The MFR_FAULT_RESPONSE command instructs the device on what action to take in response to the FAULTn pin
being pulled low by an external source.
Supported Values:
VALUE
MEANING
0xC0
FAULT_INHIBIT The LTC3884 will three-state the output in response to the FAULT pin pulled low.
0x00
FAULT_IGNORE The LTC3884 continues operation without interruption.
The device also:
• Sets the MFR Bit in the STATUS_WORD.
• Sets Bit 0 in the STATUS_MFR_SPECIFIC Command to Indicate FAULTn Is Being Pulled Low
• Notifies the Host by Asserting ALERT, Unless Masked
This command has one data byte.
SCRATCHPAD
COMMAND NAME
USER_DATA_00
USER_DATA_01
USER_DATA_02
USER_DATA_03
USER_DATA_04
100
CMD CODE DESCRIPTION
0xB0
OEM reserved. Typically used for part
serialization.
0xB1
Manufacturer reserved for LTpowerPlay.
0xB2
OEM reserved. Typically used for part
serialization.
0xB3
A NVM word available for the user.
0xB4
A NVM word available for the user.
TYPE
R/W Word
PAGED
N
DATA
FORMAT
Reg
NVM
Y
DEFAULT
VALUE
NA
R/W Word
R/W Word
Y
N
Reg
Reg
Y
Y
NA
NA
R/W Word
R/W Word
Y
N
Reg
Reg
Y
Y
0x0000
0x0000
UNITS
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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_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 LTC3884 in ASCII.
0x9A
Manufacturer part number in ASCII.
0xE7
Manufacturer code representing the LTC3884.
TYPE
R Byte
PAGED
N
DATA
FORMAT
Reg
R Byte
N
Reg
0xB0
R String
R String
R Word
N
N
N
ASC
ASC
Reg
LTC
LTC3884
0x4C0X
UNITS
NVM
FS
DEFAULT
VALUE
0x22
PMBus_REVISION
The PMBUS_REVISION command indicates the revision of the PMBus to which the device is compliant. The LTC3884
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 LTC3884 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 LTC3884 using ASCII characters.
This read-only command is in block format.
MFR_MODEL
The MFR_MODEL command indicates the manufacturer’s part number of the LTC3884 using ASCII characters.
This read-only command is in block format.
MFR_SPECIAL_ID
The 16-bit word representing the part name and revision. 0x4C denotes the part is an LTC3884, XX is adjustable by
the manufacturer.
This read-only command has two data bytes.
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101
LTC3884/LTC3884-1
PMBus COMMAND DETAILS
FAULT WARNING AND STATUS
COMMAND NAME
CLEAR_FAULTS
SMBALERT_MASK
CMD CODE DESCRIPTION
0x03
Clear any fault bits that have been set.
0x1B
Mask activity.
MFR_CLEAR_PEAKS
STATUS_BYTE
0xE3
0x78
STATUS_WORD
0x79
STATUS_VOUT
0x7A
STATUS_IOUT
0x7B
STATUS_INPUT
STATUS_ TEMPERATURE
0x7C
0x7D
STATUS_CML
0x7E
STATUS_MFR_ SPECIFIC
0x80
MFR_INFO
MFR_PADS
MFR_COMMON
0xB6
0xE5
0xEF
TYPE
Send Byte
Block R/W
Y
Y
Reg
DEFAULT
VALUE
NA
See CMD
Details
NA
NA
Y
Reg
NA
Y
Reg
NA
Y
Reg
NA
N
Y
Reg
Reg
NA
NA
N
Reg
NA
Y
Reg
NA
N
N
N
Reg
Reg
Reg
NA
NA
NA
PAGED
N
Y
Clears all peak values.
Send Byte
One byte summary of the unit’s fault
R/W Byte
condition.
Two byte summary of the unit’s fault
R/W Word
condition.
Output voltage fault and warning
R/W Byte
status.
Output current fault and warning
R/W Byte
status.
Input supply fault and warning status. R/W Byte
External temperature fault and warning R/W Byte
status for READ_TEMERATURE_1.
Communication and memory fault and R/W Byte
warning status.
Manufacturer specific fault and state
R/W Byte
information.
Manufacturing specific information.
R Word
Digital status of the I/O pads.
R Word
Manufacturer status bits that are
R Byte
common across multiple ADI chips.
FORMAT
Reg
UNITS
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.
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 command is issued.
• Bias power is removed and reapplied to the integrated circuit
102
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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 45 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 46 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_LTC3884.
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.
SMBALERT_MASK Default Setting: (Refer Also to Figure 2)
STATUS RESISTER
ALERT Mask Value MASKED BITS
STATUS_VOUT
STATUS_IOUT
0x00
0x00
None
None
1
7
S
SLAVE
ADDRESS
1
1
W
A SMBALERT_MASK A
COMMAND CODE
8
1
8
1
STATUS_x
A
COMMAND CODE
8
1
MASK BYTE
A
1
P
3884 F47
Figure 48. Example of Writing SMBALERT_MASK
1
7
S
SLAVE
ADDRESS
1
1
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
3884 F48
Figure 49. Example of Reading SMBALERT_MASK
STATUS_TEMPERATURE
STATUS_CML
STATUS_INPUT
STATUS_MFR_SPECIFIC
0x00
0x00
0x00
0x11
None
None
None
Bit 4 (internal PLL unlocked), bit 0 (FAULT pulled low by external device)
MFR_CLEAR_PEAKS
The MFR_CLEAR_PEAKS command clears the MFR_*_PEAK data values. A MFR_RESET command will also clear the
MFR_*_PEAK data values.
This write-only command has no data bytes.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
STATUS_BYTE
The STATUS_BYTE command returns one byte of information with a summary of the most critical faults. This is the
lower byte of the status word.
STATUS_BYTE Message Contents:
BIT
7*
6
STATUS BIT NAME
BUSY
OFF
5
4
3
2
1
0
VOUT_OV
IOUT_OC
VIN_UV
TEMPERATURE
CML
NONE OF THE ABOVE
MEANING
A fault was declared because the LTC3884 was unable to respond.
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.
An output overcurrent fault has occurred.
Not supported (LTC3884 returns 0).
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.
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
MEANING
15
VOUT
An output voltage fault or warning has occurred.
14
IOUT
An output current fault or warning has occurred.
13
INPUT
An input voltage fault or warning has occurred.
12
MFR_SPECIFIC
A fault or warning specific to the LTC3884 has occurred.
11
POWER_GOOD#
The POWER_GOOD state is false if this bit is set.
10
FANS
Not supported (LTC3884 returns 0).
9
OTHER
Not supported (LTC3884 returns 0).
8*
UNKNOWN
Not supported (LTC3884 returns 0).
*ALERT can be asserted if either of these bits is set. It may be cleared by writing a 1 to its bit position in the STATUS_BYTE, in lieu of a CLEAR_FAULTS
command.
If any of the bits in the upper byte are set, NONE_OF_THE_ABOVE is asserted.
This command has two data bytes.
104
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PMBus COMMAND DETAILS
STATUS_VOUT
The STATUS_VOUT command returns one byte of VOUT status information.
STATUS_VOUT Message Contents:
BIT
7
6
5
4
3
2
1
0
MEANING
VOUT overvoltage fault.
VOUT overvoltage warning.
VOUT undervoltage warning.
VOUT undervoltage fault.
VOUT max warning.
TON max fault.
TOFF max fault.
Not supported (LTC3884 returns 0).
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.
Any supported fault bit in this command will initiate an ALERT event.
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 (LTC3884 returns 0).
5
IOUT overcurrent warning.
4:0
Not supported (LTC3884 returns 0).
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.
Any supported fault bit in this command will initiate an ALERT event. This command has one data byte.
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105
LTC3884/LTC3884-1
PMBus COMMAND DETAILS
STATUS_INPUT
The STATUS_INPUT command returns one byte of VIN (VINSNS) status information.
STATUS_INPUT Message Contents:
BIT
7
6
5
4
3
2
1
0
MEANING
VIN overvoltage fault.
Not supported (LTC3884 returns 0).
VIN undervoltage warning.
Not supported (LTC3884 returns 0).
Unit off for insufficient VIN.
Not supported (LTC3884 returns 0).
IIN overcurrent warning.
Not supported (LTC3884 returns 0).
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.
Any supported fault bit in this command will initiate an ALERT event. Bit 3 of this command is not latched and will not
generate an ALERT even if it is set. This command has one data byte.
STATUS_TEMPERATURE
The STATUS_TEMPERATURE commands returns one byte with status information on temperature. This is a paged
command and is related to the respective READ_TEMPERATURE_1 value.
STATUS_TEMPERATURE Message Contents:
BIT
MEANING
7
External overtemperature fault.
6
External overtemperature warning.
5
Not supported (LTC3884 returns 0).
4
External undertemperature fault.
3:0
Not supported (LTC3884 returns 0).
.
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.
This command has one data byte.
106
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PMBus COMMAND DETAILS
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 (LTC3884 returns 0).
1
Other communication fault.
0
Other memory or logic fault.
If either bit 3 or bit 4 of this command is set, a serious and significant internal error has been detected. Continued
operation of the part is not recommended if these bits are continuously 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.
Any supported fault bit in this command will initiate an ALERT event.
This command has one data byte.
STATUS_MFR_SPECIFIC
The STATUS_MFR_SPECIFIC commands returns one byte with the manufacturer specific status information.
The format for this byte is:
BIT
MEANING
7
Internal Temperature Fault Limit Exceeded.
6
Internal Temperature Warn Limit Exceeded.
5
Factory Trim Area NVM CRC Fault.
4
PLL is Unlocked
3
Fault Log Present
2
VDD33 UV or OV Fault
1
ShortCycle Event Detected
0
FAULT Pin Asserted Low by External Device
If any of these bits are set, the MFR bit in the STATUS_WORD will be set, and ALERT may be asserted.
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. However, 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.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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. May Occur Briefly on Current Measurement Channels During Normal Operation
SYNC clocked by external device (when LTC3884 configured to drive SYNC pin)
Channel 1 Power Good
Channel 0 Power Good
LTC3884 Driving RUN1 Low
LTC3884 Driving RUN0 Low
RUN1 Pin State
RUN0 Pin State
LTC3884 Driving FAULT1 Low
LTC3884 Driving FAULT0 Low
FAULT1 Pin State
FAULT0 Pin State
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 ADI digital power and telemetry products.
BIT
MEANING
7
Chip Not Driving ALERT Low
6
LTC3884 Not Busy
5
Calculations Not Pending
4
LTC3884 Outputs Not in Transition
3
NVM Initialized
2
Reserved
1
SHARE_CLK Timeout
0
WP Pin Status
This read-only command has one data byte.
108
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PMBus COMMAND DETAILS
MFR_INFO
The MFR_INFO command contains additional status bits that are LTC3884-specific and may be common to multiple
ADI PSM products.
MFR_INFO Data Contents:
BIT
15:5
4
MEANING
Reserved.
EEPROM ECC status.
0: Corrections made in the EEPROM user space.
1: No corrections made in the EEPROM user space.
3:0
Reserved
EEPROM ECC status is updated after each RESTORE_USER_ALL or RESET command, a power-on reset or an EEPROM
bulk read operation. This read-only command has two data bytes.
TELEMETRY
COMMAND NAME
READ_VIN
READ_IIN
READ_VOUT
READ_IOUT
READ_TEMPERATURE_1
CMD
CODE
0x88
0x89
0x8B
0x8C
0x8D
READ_TEMPERATURE_2
0x8E
READ_FREQUENCY
READ_POUT
READ_PIN
MFR_PIN_ACCURACY
MFR_IOUT_PEAK
0x95
0x96
0x97
0xAC
0xD7
MFR_VOUT_PEAK
0xDD
MFR_VIN_PEAK
0xDE
MFR_TEMPERATURE_1_PEAK
0xDF
MFR_READ_IIN_PEAK
0xE1
MFR_READ_ICHIP
MFR_TEMPERATURE_2_PEAK
0xE4
0xF4
MFR_ADC_CONTROL
0xD8
DESCRIPTION
TYPE
PAGED FORMAT UNITS
Measured input supply voltage.
R Word
N
L11
V
Measured input supply current.
R Word
N
L11
A
Measured output voltage.
R Word
Y
L16
V
Measured output current.
R Word
Y
L11
A
External diode junction temperature. This
R Word
Y
L11
C
is the value used for all temperature related
processing, including IOUT_CAL_GAIN.
Internal junction temperature. Does not affect
R Word
N
L11
C
any other commands.
Measured PWM switching frequency.
R Word
Y
L11
Hz
Calculated output power.
R Word
Y
L11
W
Calculated input power.
R Word
N
L11
W
Returns the accuracy of the READ_PIN command R Byte
N
%
Report the maximum measured value of
R Word
Y
L11
A
READ_IOUT since last MFR_CLEAR_PEAKS.
Maximum measured value of READ_VOUT
R Word
Y
L16
V
since last MFR_CLEAR_PEAKS.
Maximum measured value of READ_VIN since
R Word
N
L11
V
last MFR_CLEAR_PEAKS.
Maximum measured value of external
R Word
Y
L11
C
Temperature (READ_TEMPERATURE_1) since
last MFR_CLEAR_PEAKS.
Maximum measured value of READ_IIN
R Word
N
L11
A
command since last MFR_CLEAR_PEAKS.
Measured current used by the LTC3884.
R Word
N
L11
A
R Word
N
L11
C
Peak internal die temperature since last
MFR_CLEAR_PEAKS.
ADC telemetry parameter selected for repeated R/W Byte
N
N
Reg
fast ADC read back.
NVM
DEFAULT
VALUE
NA
NA
NA
NA
NA
NA
NA
NA
NA
5.0%
NA
NA
NA
NA
NA
NA
NA
NA
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
READ_VIN
The READ_VIN command returns the measured VIN pin voltage, in volts added to READ_ICHIP • MFR_RVIN. This
compensates for the IR voltage drop across the VIN filter element due to the supply current of the LTC3884.
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 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, as measured across the input current sense resistor
(see also MFR_IIN_CAL_GAIN).
This read-only command has two 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 LTC3884’s die 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_FREQUENCY
The READ_FREQUENCY command is a reading of the PWM switching frequency in kHz.
This read-only command has 2 data bytes and is formatted in Linear_5s_11s format.
READ_POUT
The READ_POUT command is a reading of the DC/DC converter output power in Watts. POUT is calculated based on
the most recent correlated output voltage and current reading.
This read-only command has 2 data bytes and is formatted in Linear_5s_11s format.
110
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
READ_PIN
The READ_PIN command is a reading of the DC/DC converter input power in Watts. PIN is calculated based on the
most recent input voltage and current reading.
This read-only command has 2 data bytes and is formatted in Linear_5s_11s format.
MFR_PIN_ACCURACY
The MFR_PIN_ACCURACY command returns the accuracy, in percent, of the value returned by the READ_PIN command.
There is one data byte. The value is 0.1% per bit which gives a range of ±0.0% to ±25.5%.
This read-only command has one data byte and is formatted as an unsigned integer.
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_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.
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_READ_IIN_PEAK
The MFR_READ_IIN_PEAK command reports the highest current, in Amperes, reported by the READ_IIN measurement.
This command is cleared using the MFR_CLEAR_PEAKS command.
This command has two data bytes and is formatted in Linear_5s_11s format.
MFR_READ_ICHIP
The MFR_READ_ICHIP command returns the measured input current, in Amperes, used by the LTC3884.
This command has two data bytes and is formatted in Linear_5s_11s format.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
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_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 tCONVERT.
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 2 ADC conversions or approximately 16ms (external temperature conversions
may have a latency of up to 3 ADC conversion or approximately 24ms). 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 (less then 1 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.
COMMANDED VALUE
0x0F
0x0E
0x0D
0x0C
0x0B
0x0A
0x09
0x08
0x07
0x06
0x05
0x04
0x03
0x02
0x01
0x00
TELEMETRY COMMAND NAME
READ_TEMPERATURE_1
READ_IOUT
READ_VOUT
READ_TEMPERATURE_1
READ_IOUT
READ_VOUT
READ_TEMPERATURE_2
READ_IIN
MFR_READ_ICHIP
READ_VIN
DESCRIPTION
Reserved
Reserved
Reserved
Channel 1 external temperature
Reserved
Channel 1 measured output current
Channel 1 measured output voltage
Channel 0 external temperature
Reserved
Channel 0 measured output current
Channel 0 measured output voltage
Internal junction temperature
Measured input supply current
Measured supply current of the LTC3884
Measured input supply voltage
Standard ADC Round Robin Telemetry
If a reserved command value is entered, the telemetry will default to Internal IC Temperature and issue a CML fault. CML
faults will continue to be issued by the LTC3884 until a valid command value is entered. The accuracy of the measured
input supply voltage is only guaranteed if the MFR_ADC_CONTROL command is set to standard round robin telemetry.
This write-only command has 1 data byte and is formatted in register format.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
NVM MEMORY COMMANDS
Store/Restore
COMMAND NAME
STORE_USER_ALL
CMD
CODE
0x15
RESTORE_USER_ALL
0x16
MFR_COMPARE_USER_ALL
0xF0
DESCRIPTION
TYPE
Store user operating memory to
Send Byte
EEPROM.
Restore user operating memory from Send Byte
EEPROM.
Compares current command contents Send Byte
with NVM.
PAGED
N
FORMAT
UNITS
NVM
DEFAULT
VALUE
NA
N
NA
N
NA
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.
Executing this command if the die temperature exceeds 85°C or is below 0°C is not recommended and the data retention of 10 years cannot be guaranteed. 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 LTC3884 and programming of the NVM can be initiated when EXTVCC or VDD33 is available
and VIN is not applied. To enable the part in this state, using global address 0x5B write MFR_EE_UNLOCK to 0x2B
followed by 0xC4. The LTC3884 will now communicate normally, and the project file can be updated. To write the
updated project file to the NVM issue a STORE_USER_ALL command. When VIN is applied, a MFR_RESET 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 instructs the LTC3884 to copy the contents of the non-volatile User memory to
the matching locations in the Operating Memory. The values in the Operating Memory are overwritten by the value
retrieved from the User commands. The LTC3884 ensures both channels are off, loads the operating memory from
the internal EEPROM, clears all faults, reads the resistor configuration pins, and then performs a soft-start of both
PWM channels if applicable.
STORE_USER_ALL, MFR_COMPARE_USER_ALL and RESTORE_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.
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.
This write-only command has no data bytes.
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
Fault Log Operation
A conceptual diagram of the fault log is shown in Figure 50. The fault log provides telemetry recording capability to
the LTC3884. During normal operation, the contents of the status registers, the output voltage readings, temperature
readings as well as peak values of these quantities are stored in a continuously updated buffer in RAM. You can think
of the operation as being similar to a strip chart recorder. When a fault occurs, the contents are written into EEPROM
for nonvolatile storage. The EEPROM fault log is then locked. The part can be powered down with the fault log available
for reading at a later time. As a consequence of adding ECC, the area in the EEPROM available for fault log is reduced.
When reading the fault log from RAM, all 6 events of cyclical data remain. However, when the fault log is read from
EEPROM (after a reset), the last 2 events are lost. The read length of 147 bytes remains the same, but the fifth and
sixth events are a repeat of the fourth event.
RAM
EEPROM
8
ADC READINGS
CONTINUOUSLY
FILL BUFFER
TIME OF FAULT
TRANSFER TO
EEPROM AND
LOCK
•
•
•
•
•
•
AFTER FAULT
READ FROM
EEPROM AND
LOCK BUFFER
3884 F49
Figure 50. Fault Log Conceptual Diagram
Fault Logging
COMMAND NAME
MFR_FAULT_LOG
MFR_FAULT_LOG_ STORE
MFR_FAULT_LOG_CLEAR
114
CMD CODE DESCRIPTION
0xEE
Fault log data bytes.
0xEA
Command a transfer of the fault log from RAM
to EEPROM.
0xEC
Initialize the EEPROM block reserved for fault
logging.
DATA
TYPE
PAGED FORMAT UNITS
R Block
N
CF
Send Byte
N
Send Byte
N
NVM
Y
DEFAULT
VALUE
NA
NA
NA
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PMBus COMMAND DETAILS
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 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 13. 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_FAULT_LOG will 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.
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 NVM just as if a fault event
occurred. This command will set bit 3 of the STATUS_MFR_SPECIFIC fault if bit 7 “Enable Fault Logging” 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.
This write-only command has no data bytes.
Table 13. 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
Fault Source
MFR_REAL_TIME
[7:0]
[7:0]
[15:8]
[7:0]
[7:0]
[7:0]
[15:8]
[23:16]
[31:24]
[39:32]
[47:40]
ASC
Reg
Reg
Reg
0
1
2
3
4
5
6
7
8
9
10
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.
Refer to Table 13a.
48 bit share-clock counter value when fault occurred (200µs resolution).
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
MFR_VOUT_PEAK (PAGE 0)
[15:8]
L16
11
MFR_VOUT_PEAK (PAGE 1)
[7:0]
[15:8]
L16
12
13
MFR_IOUT_PEAK (PAGE 0)
[7:0]
[15:8]
L11
14
15
MFR_IOUT_PEAK (PAGE 1)
[7:0]
[15:8]
L11
16
17
MFR_VIN_PEAK
READ_TEMPERATURE1 (PAGE 0)
READ_TEMPERATURE1 (PAGE 1)
READ_TEMPERATURE2
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
L11
L11
L11
L11
18
19
20
21
22
23
24
25
26
CYCLICAL DATA
EVENT n
READ_VOUT (PAGE 1)
READ_IOUT (PAGE 0)
READ_IOUT (PAGE 1)
READ_VIN
READ_IIN
STATUS_VOUT (PAGE 0)
STATUS_VOUT (PAGE 1)
STATUS_WORD (PAGE 0)
STATUS_WORD (PAGE 1)
STATUS_MFR_SPECIFIC (PAGE 0)
STATUS_MFR_SPECIFIC (PAGE 1)
116
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
Peak READ_VOUT on Channel 1 since last power-on or CLEAR_PEAKS
command.
Peak READ_IOUT on Channel 0 since last power-on or CLEAR_PEAKS
command.
Peak READ_IOUT on Channel 1 since last power-on or CLEAR_PEAKS
command.
Peak READ_VIN since last power-on or CLEAR_PEAKS command.
External temperature sensor 0 during last event.
External temperature sensor 1 during last event.
LTC3884 die temperature sensor during last event.
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)
Peak READ_VOUT on Channel 0 since last power-on or CLEAR_PEAKS
command.
LIN 16
LIN 16
LIN 16
LIN 16
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
BYTE
BYTE
WORD
WORD
WORD
WORD
BYTE
BYTE
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
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LTC3884/LTC3884-1
PMBus COMMAND DETAILS
EVENT n-1
(data measured before fault was detected)
READ_VOUT (PAGE 0)
[15:8]
[7:0]
READ_VOUT (PAGE 1)
[15:8]
[7:0]
READ_IOUT (PAGE 0)
[15:8]
[7:0]
READ_IOUT (PAGE 1)
[15:8]
[7:0]
READ_VIN
[15:8]
[7:0]
READ_IIN
[15:8]
[7:0]
STATUS_VOUT (PAGE 0)
STATUS_VOUT (PAGE 1)
STATUS_WORD (PAGE 0)
[15:8]
[7:0]
STATUS_WORD (PAGE 1)
[15:8]
[7:0]
STATUS_MFR_SPECIFIC (PAGE 0)
STATUS_MFR_SPECIFIC (PAGE 1)
EVENT n-5
(Oldest Recorded Data)
READ_VOUT (PAGE 0)
READ_VOUT (PAGE 1)
READ_IOUT (PAGE 0)
READ_IOUT (PAGE 1)
READ_VIN
READ_IIN
STATUS_VOUT (PAGE 0)
STATUS_VOUT (PAGE 1)
STATUS_WORD (PAGE 0)
STATUS_WORD (PAGE 1)
STATUS_MFR_SPECIFIC (PAGE 0)
STATUS_MFR_SPECIFIC (PAGE 1)
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
[15:8]
[7:0]
LIN 16
LIN 16
LIN 16
LIN 16
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
BYTE
BYTE
WORD
WORD
WORD
WORD
BYTE
BYTE
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
LIN 16
LIN 16
LIN 16
LIN 16
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
LIN 11
BYTE
BYTE
WORD
WORD
WORD
WORD
BYTE
BYTE
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
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PMBus COMMAND DETAILS
Table 13a: 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
TEMP_OT_FAULT Channel 0
0x06
TEMP_UT_FAULT Channel 0
0x07
VIN_OV_FAULT
0x0A
MFR_TEMPERATURE_2_OT_FAULT
0x10
TON_MAX_FAULT Channel 1
0x11
VOUT_OV_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
PAGED FORMAT UNITS
NVM
DEFAULT
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_DATA.
R/W Byte
N
Reg
NA
MFR_EE_DATA
0xBF
Data transferred to and from EEPROM using
sequential PMBus word reads or writes. Supports bulk
programming.
R/W
Word
N
Reg
NA
All the NVM commands are disabled if the die temperature exceeds 130°C. NVM commands are re-enabled when the
die temperature drops below 125°C.
MFR_EE_xxxx
The MFR_EE_xxxx commands facilitate bulk programming of the LTC3884 internal EEPROM. Contact the factory for
details.
118
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VOUT0
1.5V/30A
100µF
x2
6.3V
For more information www.linear.com/LTC3884
931Ω
1%
10nF
VDD33
Q3
BSC010NE2LSI
Q1
BSC050NE2LS
BG1
SW1
BOOST1
TG1
IIN–
ITH1
ITH0
ITHR0
VDD33
2.2µF
PGND GND VDD25
1µF
VDD25
ITHR1
ISENSE1–
VSENSE1+
VSENSE1–
TSNS1
ISENSE1+
EXTVCC
PHASE_CFG
ASEL1
FREQ_CFG
ASEL0
VOUT1_CFG
VOUT0_CFG
IIN+
ISENSE0–
VSENSE0+
VSENSE0–
TSNS0
ISENSE0+
RUN0
RUN1
WP
SHARE_CLK
FAULT1
FAULT0
ALERT
SCL
SDA
PGOOD1
SYNC
PGOOD0
BG0
SW0
LTC3884
INTVCC VIN
BOOST0
TG0
VDD33
D2
1500pF
220nF
10k
10k
10k
10k
10k
10k
10k
10k
10k
10k
4.99k
0.1µF
150pF
4.7µF
0.1µF
24.9k
1500pF
220nF
10nF
Q4
BSC010NE2LSI
Q2
BSC050NE2LS
5.76k
150pF
17.8k
20k
VDD25
D1
10µF
x2
3884 TA02
330µF
x2
6.3V
VIN
6V to 14V
D1, D2: CMDSH3-TR
MMBT3906-AL3-R
715Ω
1%
270µF
16V
x2
1Ω
1%
744301025
DCR=0.32 mΩ
L2
0.25µH
Low DCR Sensing, 425kHz, High Efficiency, Dual-Output 1.5V/30A and 1.0V/30A, Buck Converter
MMBT3906-AL3-R
330µF
x2
6.3V
744301033
DCR=0.32 mΩ
L1
0.33µH
10µF
x2
2mΩ
1µF
VOUT1
100µF 1.0V/30A
x2
6.3V
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
3884fe
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120
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330µF
x2
6.3V
MMBT3906-AL3-R
100µF
x2
6.3V
744301025
DCR = 0.32mΩ
L1
0.25µH
10nF
VDD33
715Ω
1%
100pF
Q3
BSC010NE2LSI
Q1
BSC050NE2LS
10µF
x2
SCL
ALERT
10k
10k
10k
4.7nF
220nF
INTVCC
ALERT
FAULT0
FAULT1
SCL
SDA
SYNC
PGOOD0
PGOOD1
BG0
SW0
BOOST0
TG0
D2
BG1
SW1
BOOST1
IIN–
TG1
330µF
6.3V
x2
VDD33
VDD33
2.2µF
1µF
10nF
10nF
MMBT3906-AL3-R
MMBT3906-AL3-R
VDD33_1
VDD33
VSENSE0–
TSNS0
ITH0
ITHR0
IIN+
BG1
SW1
BOOST1
IIN–
TG1
VDD25_1
PGND SGND VDD25
1µF
VSENSE1–
TSNS1
ITH1
ITHR1
VSENSE1+
ISENSE1–
ISENSE1+
EXTVCC
FREQ_CFG
PHASE_CFG
ASEL1
ASEL0
LTC3884 VOUT0_CFG
VOUT1_CFG
VIN
2.2µF
4 Phase, 500kHz, High Efficiency, Single-Output, 1.0V/120A Buck Converter
VDD25
PGND SGND VDD25
VSENSE1–
TSNS1
ITH1
ITHR1
100µF
x2
6.3V
VSENSE0–
TSNS0
ITH0
ITHR0
100µF
x2
6.3V
VSENSE0+
ISENSE0–
VSENSE1+
SHARE_CLK
RUN0
RUN1
ALERT
FAULT0
FAULT1
SCL
SDA
SYNC
PGOOD0
PGOOD1
BG0
SW0
BOOST0
TG0
VSENSE0+
220nF
RUN
SHARECLK
FAULT
ALERT
SCL
SDA
PGOOD
SYNC
0.1µF
ISENSE0+
330µF
6.3V
x2
715Ω
1%
Q8
BSC010NE2LSI
Q7
BSC050NE2LS
INTVCC
ISENSE1–
VOUT
1.0V/120A
744301025
DCR = 0.32mΩ
L3
0.25µH
D4
ISENSE1+
715Ω
1%
744301025
DCR = 0.32mΩ
L2
0.25µH
4.7µF
ISENSE0+
220nF
4.32k
24.9k
VDD25
Q4
BSC010NE2LSI
Q2
BSC050NE2LS
10µF
x2
ISENSE0–
5.76k
24.9k
0.1µF
D1
270µF
16V
x2
1Ω
1%
WP
EXTVCC
PHASE_CFG
FREQ_CFG
ASEL1
ASEL0
VOUT0_CFG
VOUT1_CFG
IIN+
LTC3884
VIN
10µF
x2
C3
1µF
WP
SHARE_CLK
RUN0
RUN
RUN1
10k SHARECLK
FAULT
SDA
10k
10k
PGOOD
10k
4.99k SYNC
0.1µF
4.7µF
2mΩ
VDD25_1
5.76k
24.9k
10nF
270µF
16V
x2
1Ω
1%
715Ω
1%
330µF
6.3V
x2
744301025
DCR = 0.32mΩ
L4
0.25µH
C3
1µF
MMBT3906-AL3-R
220nF
5.76k
24.9k
Q10
BSC010NE2LSI
Q9
BSC050NE2LS
D1, D2, D3, D4: CMDSH3-TR
11k
20k
0.1µF
D3
10µF
x2
2mΩ
3889 F40
100µF
x2
6.3V
VIN
6V TO 14V
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
3884fe
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
1µF
2mΩ
10µF
x2
4.7µF
INTVCC
L1
0.68µH
Q1
BSC032NE2LS
SER2009-681ML
DCR=0.63 mΩ
VIN
4.99k
10k
BG0
LTC3884
SYNC
PGOOD0
10k
VOUT0_CFG
VOUT1_CFG
ASEL1
ALERT
10k
FAULT0
FAULT1
10k
SHARE_CLK
10k
RUN0
RUN1
WP
10k
100µF
6.3V
x2
10nF
MMBT3906-AL3-R
150pF
1500pF
16.2k
10k
24.9k
20.5k
15.8k
5.76k
4.52k
1%
ASEL0
FREQ_CFG
PHASE_CFG
EXTVCC
+
220nF
SER2010-901ML
DCR=0.9 mΩ
VDD25
SCL
10k
330µF
6.3V
x2
Q4
BSC010NE2LSI
BG1
L2
0.9µH
Q2
BSC024NE2LS
SW1
SDA
10k
VDD33
0.1µF
PGOOD1
10k
976Ω
1%
270µF
16V
x2
2mΩ
BOOST1
SW0
Q3
BSC010NE2LSI
VIN
7V to 14V
IIN–
TG1
BOOST0
10k
VOUT0
2.5V/25A
IIN+
TG0
0.1µF
10µF
x2
D1
D2
1Ω
1%
ISENSE0
ISENSE1+
ISENSE0–
VSENSE0+
VSENSE0–
TSNS0
ITH0
ITHR0
ISENSE1–
VSENSE1+
VSENSE1–
TSNS1
ITH1
ITHR1
VDD33 PGND SGND VDD25
VDD33
2.2µF
220nF
100µF
6.3V
x2
150pF 10nF
1500pF
MMBT3906-AL3-R
VDD25
1µF
330µF
6.3V
x2
VOUT1
3.3V/25A
3884 TA06
D1, D2: CMDSH3-TR
High Efficiency, 425kHz, Dual-Output, 2.5V/25A and 3.3V/25A Buck Converter
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121
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
C3
1µF
2mΩ
10µF
x2
4.7µF
D1
D2
INTVCC
L1
1µH
Q1
BSC024NE2LS
VIN
IIN+
TG1
BOOST0
SER2011-102ML
DCR=1.2 mΩ
4.99k
10k
3.74k
1%
VDD33
BG0
10k
10k
10k
SCL
VOUT1_CFG
ALERT
FAULT0
FREQ_CFG
ASEL1
FAULT1
PHASE_CFG
RUN0
RUN1
WP
100µF
6.3V
x2
MMBT3906-AL3-R
10nF
150pF
3.3nF
SER2011-102ML
DCR=1.2 mΩ
10k
23.2k
30.1k
24.9k
3.74k
1%
1.96k
5.76k
ASEL0
EXTVCC
+
ISENSE0
ISENSE1+
ISENSE0–
VSENSE0+
VSENSE0–
TSNS0
ITH0
ITHR0
ISENSE1–
VSENSE1+
VSENSE1–
TSNS1
ITH1
220nF
330µF
6.3V
x2
L2
1µH
VDD25
VOUT0_CFG
SHARE_CLK
10k
Q2
BSC024NE2LS
Q4
BSC010NE2LSI
BG1
LTC3884
SYNC
PGOOD0
SDA
10k
0.1µF
SW1
PGOOD1
10k
2mΩ
BOOST1
SW0
Q3
BSC010NE2LSI
VIN
10V to 14V
270µF
16V
x2
IIN–
TG0
0.1µF
10µF
x2
1Ω
1%
VDD33
PGND SGND
VDD33
2.2µF
VDD25
ITHR1
VDD25
220nF
VOUT
5.0V/60A
100µF
6.3V
x2
330µF
6.3V
x2
10nF
MMBT3906-AL3-R
1µF
D1, D2: CMDSH3-TR
3884 TA08
Low DCR Sensing, 250kHz, Single-Output, 5V/60A Buck Converter
122
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100µF
6.3V
x2
C_N
C_P
330µF
6.3V
x2
150pF
For more information www.linear.com/LTC3884
LTC3884
BG1
SW1
BOOST1
TG1
IIN–
VSENSE1–
ISENSE1–
VSENSE1+
ISENSE1+
ASEL1
ASEL0
EXTVCC
PHASE_CFG
FREQ_CFG
VOUT0_CFG
VOUT1_CFG
IIN+
VDD33
2.2µF
1µF
VDD25
TSNS1
ITH1
ITHR0
ITHR1
VDD33 PGND SGND VDD25
VSENSE0–
TSNS0
ITH0
ISENSE0–
VSENSE0+
ISENSE0+
RUN0
RUN1
WP
FAULT0
FAULT1
SHARE_CLK
ALERT
SCL
PGOOD0
PGOOD1
SDA
SYNC
BG0
SW0
VIN
47nF
4.32k
24.9k
VDD25
0.1µF
INTVCC
330µF
6.3V
x2
5.76k
24.9k
10µF
x4
100µF
6.3V
x2
GND
GND
GND
VGATE
GND
PWML
PWMH
VIN1
VIN2
C_N
C_P
TEMP_N
TEMP_P
VOUT2
VOUT1
VRA001-4C3G
High Efficiency, 425kHz, Single-Output 1.0V/80A Buck Converter with Power Blocks
3.3nF
47nF
10k
10k
10k
10k
10k
10k
10k
INTVCC
TG0
BOOST0
INTVCC
0.1µF
GND
GND
VDD33
INTVCC
4.99k
VGATE
GND
TEMP_P
4.7µF
GND
PWML
VOUT2
TEMP_N
PWMH
VIN1
VIN2
VOUT1
VRA001-4C3G
10µF
x4
2mΩ
3884 TA09
VOUT
1.0V/80A
1µF
VIN
7V to 13V
270µF
16V
x2
1Ω
1%
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
3884fe
123
LTC3884/LTC3884-1
TYPICAL APPLICATIONS
0.47µF
1mΩ
665Ω
1Ω
VIN
7V TO 14V
VIN IIN+
10nF
PWM0
ISENSE0+
5k
5k
5k
5k
TSNS1
5k
SDA
PWM1
SCL
ITH0
SHARE_CLK
ALERT
ITH1
TOUT/FLT
0.47µF
6.8nF
VOUT 0_CFG
FAULT0
VOUT 1_CFG
24.9k
24.9k
ASEL0
EXTVCC
PGOOD1
PHASE_CFG
VIN
22µF
×4
24.9k
1µF
ASEL1
PGOOD0
VDR
5V
7.32k
5.76k
EN
PWM
VOS
VDRV
TOUT/FLT
5.76k
LGND
47pF
LOWDCR
PWM0
ISENSE0+
VDRV
ISENSE1+
VCC1
ISENSE1–
ITH1
EXTVCC
220nF
VDR
5V
FREQ
COUT4
470µF
×2
2.5V
0Ω
VOS
TOUT/FLT
0.215µH, L3
COUT5
100µF
×3
6.3V
+
COUT6
470µF
×2
2.5V
PGND
VCC
LGND
4.7µF
PWM1
VCC0
+
330pF
BOOT
PHASE
VIN
TDA21470
SW
MODE1
ITH0
ITH
1µF
22µF
×4
MODE0
FAULT1
VDD33_1
VIN1
EN
PWM
FAULT0
COUT3
100µF
×3
6.3V
4.7µF
4.7µF
ISENSE0–
0.215µH, L2
PGND
VCC
0.47µF
VIN
INTVCC
PHASM0
RUN0
LTC3874-1
ILIM
RUN1
0Ω
PHASE
TDA21470
SW
4.7µF
GND
SYNC
330pF
BOOT
VIN1
FREQ_CFG
SYNC
0.1µF
VOUT
1.05V
120A
665Ω
330pF
2Ω
VIN
7V TO 14V
+
COUT2
470µF
×2
2.5V
PGND
LGND
4.7µF
ITH
ITHR0
VCC1
RUN1
5k
VDRV
VCC
VDD25
RUN0
5k
VOS
COUT1
100µF
×3
6.3V
4.7µF
ITHR1
FAULT1
5k
EN
PWM
0.215µH, L1
LTC3884-1
VCC0
4.7µF
VDR
5V
220nF
ISENSE1+
VDD33
VDD33
220nF
ISENSE0–
ISENSE1–
WP
TSNS0
BOOT
PHASE
VIN
TDA21470
SW
22µF
×4
IIN– INTVCC
VSENSE0+
VSENSE1+
VSENSE0–
VSENSE1–
VOUT
10nF
VIN1
4.7µF
2.2µF
0Ω
VIN1
330pF
4.7µF
665Ω
220nF
100k
0.47µF
0Ω
GND
VIN1
22µF
×4
PINS NOT USED IN CIRCUITS TDA21470: REFIN , GATEL, IOUT, OCSET
COUT1, 3, 5, 7: MURATA GRM32ER60J107ME20L (100µF, 6.3V, X5R, 1210)
COUT2, 4, 6, 8: PANASONIC ETPF470M5H (470µF, 2.5V)
L1, L2, L3, L4: EATON FP1007R3-R22-R (0.215µH, DCR = 0.29mΩ)
VDR FROM EXTERNAL 5V POWER SUPPLY
VDR
5V
BOOT
PHASE
VIN
TDA21470
SW
EN
PWM
VOS
VDRV
TOUT/FLT
VCC
4.7µF
0.215µH, L4
COUT7
100µF
×3
6.3V
+
COUT8
470µF
×2
2.5V
PGND
LGND
3884 TA10
330pF
4.7µF
665Ω
Low DCR Sensing, 500kHz 4-Phase 1.05 Step-Down Converter
124
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTC3884#packaging for the most recent package drawings.
UK Package
48-Lead Plastic QFN (7mm × 7mm)
(Reference LTC DWG # 05-08-1704 Rev C)
0.70 ±0.05
5.15 ±0.05
5.50 REF
6.10 ±0.05 7.50 ±0.05
(4 SIDES)
5.15 ±0.05
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
7.00 ±0.10
(4 SIDES)
0.75 ±0.05
R = 0.10
TYP
R = 0.115
TYP
47 48
0.40 ±0.10
PIN 1 TOP MARK
(SEE NOTE 6)
1
2
PIN 1
CHAMFER
C = 0.35
5.50 REF
(4-SIDES)
5.15 ±0.10
5.15 ±0.10
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WKKD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
(UK48) QFN 0406 REV C
0.25 ±0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
3884fe
For more information www.linear.com/LTC3884
125
LTC3884/LTC3884-1
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTC3884#packaging for the most recent package drawings.
RHE Package
48-Lead Plastic GQFN (5mm × 6mm)
(Reference LTC DWG # 05-08-1527 Rev B)
0.60
0.55
3.60 ±0.05
2.60
±0.10
0.20 ±0.05
0.80
1.90
±0.10
0.40 BSC
0.85 × 1.10
(×4)
0.25
PACKAGE
OUTLINE
5.20 ±0.05
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
1.00 REF
5.00 ±0.10
PIN 1 NOTCH
0.35 × 45°
CHAMFER
0.80 REF
39
48
38
PIN 1
TOP MARK
(SEE NOTE 6)
1
0.55
REF
1.10 × 0.85
(×4)
0.25 REF
1.90
±0.10
6.00 ±0.10
0.25
REF
2.60
±0.10
0.40
BSC
0.85
±0.10
0.20
±0.05
0.80 REF
14
24
(RHE48) GQFN 0617 REV B
24
1.00 REF
0.65 ±0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
126
15
1.10 ±0.10
0.40 ±0.10
BOTTOM VIEW—EXPOSED PAD
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.25mm ON ANY SIDE
5. EXPOSED PAD SHALL BE Pd Ni Au PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3884fe
For more information www.linear.com/LTC3884
LTC3884/LTC3884-1
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
11/15
Added Note 19.
10
B
2/16
Corrected top mark.
4
Modified IIN– switch circuitry.
17
C
5/17
Added ECC.
All
D
9/17
Added LTC3884-1 part numbers and RHE package option.
Changed operation default value.
E
11/17
38, 73
1, 4, 5, 7, 11,
17, 18, 20, 22,
51, 56, 61,
124, 126
Added conditions and change limits for PWM.
7
Temp dotted tSU(DAT).
10
Changed package type description from QFN to GQFN.
1, 5
3884fe
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license
is granted
by implication
or otherwise under any patent or patent rights of Analog Devices.
For more
information
www.linear.com/LTC3884
127
LTC3884/LTC3884-1
TYPICAL APPLICATION
2mΩ
10µF
x2
Q1
BSC050NE2LS
L1
0.25µH
4.7µF
INTVCC
IIN+ IIN–
TG0
0.1µF
TG1
BOOST0
744301025
DCR=0.32mΩ
Q3
BSC010NE2LSI
4.99k
10k
10k
715Ω
1%
10k
VDD33
10k
10k
SW1
BG0
BG1
LTC3884
Q4
BSC010NE2LSI
L2
0.25µH
744301025
DCR=0.32mΩ
100µF
6.3V
x2
10nF
VOUT0_CFG
SCL
VOUT1_CFG
ALERT
FREQ_CFG
PHASE_CFG
20k
24.9k
24.9k
715Ω
1%
11k
4.32k
5.76k
EXTVCC
ASEL0
ASEL1
ISENSE0+
ISENSE1+
ISENSE1–
ISENSE0–
VSENSE0+
VSENSE1+
–
VSENSE0
VSENSE1–
TSNS0
TSNS1
ITH0
ITH1
ITHR0
ITHR1
VDD33
PGND SGND VDD25
220nF
100µF
6.3V
x2
330µF
6.3V
x2
VOUT
1.2V/60A
10nF
MMBT3906-AL3-R
VDD33
3.3nF
VDD25
PGOOD0
PGOOD1
SDA
RUN0
RUN1
WP
220nF
150pF
BOOST1
SW0
FAULT0
FAULT1
SHARE_CLK
10k
MMBT3906-AL3-R
270µF
16V
x2
Q2
BSC050NE2LS
0.1µF
VIN
6V TO 14V
SYNC
10k
330µF
6.3V
x2
VIN
1Ω
1%
10µF
x2
D1
D2
C3
1µF
VDD25
2.2µF
1µF
D1, D2: CMDSH3-TR
3884 TA11
Low DCR Sensing, 425kHz, Single-Output, 1.2V/60A Buck Converter
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6A Monolithic Synchronous DC/DC Step-Down Converter
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Licensed under U.S. Patent 7000125 and other related patents worldwide.
128
3884fe
LT 1117 REV E • PRINTED IN USA
For more information www.linear.com/LTC3884
www.linear.com/LTC3884
ANALOG DEVICES, INC. 2017