TI1 LM25066IAPSQE/NOPB Intel node manager compliant system power management and protection ic Datasheet

LM25066I, LM25066IA
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Intel Node Manager Compliant System Power Management and Protection IC with PMBus
Check for Samples: LM25066I, LM25066IA
FEATURES
DESCRIPTION
•
While the LM25066I/A is functionally similar to the
LM25066/A, the LM25066I/A is fully compliant to Intel
Node Manager 2.0, 2.5 and adds the READ_EIN
energy accumulator feature. The LM25066I/A
combines a high-performance hot-swap controller
with a PMBus 1.2™ compliant SMBus/I2C interface to
accurately measure, control and protect the electrical
operating conditions of critical systems. The
LM25066I/A continuously supplies real-time power,
voltage, current, temperature, and fault data to the
system management host via the SMBus interface.
1
2
•
•
•
•
•
•
•
•
•
•
•
Fully Node Manager 2.0 and 2.5 Compliant with
I2C/SMBus interface and PMBus™ compliant
command structure
Input voltage range: 2.9V to 17V
Programmable 25mV or 46mV current limit
threshold
Read_EIN accurately measures true input
power via simultaneous sampling
Configurable circuit breaker protection for
hard shorts
Configurable under- and over-voltage lockouts
with hysteresis
Real time monitoring of VIN, VOUT, IIN, PIN, VAUX
with 12-bit resolution and 1 kHz sampling rate
Current measurement accuracy: ±1%
(LM25066IA) and Power measurement
accuracy: ±2.0% (LM25066IA) over temperature
Averaging of VIN, IIN, PIN, and VOUT over
programmable interval ranging from 0.001 to 4
seconds
Programmable WARN and FAULT thresholds
with SMBA notification
Blackbox capture of telemetry measurements
and device status triggered by WARN or
FAULT condition
24-lead WQFN package
The LM25066I/A control block includes a unique hotswap architecture that provides current and power
limiting to protect sensitive circuitry even during the
most stressful conditions. A fast-acting circuit breaker
prevents damage in the event of a short circuit on the
output. The input under-voltage, over-voltage
hysteresis, insertion delay time and fault detection
time are all configurable. A temperature monitoring
block on the LM25066I/A interfaces with a low-cost
external
diode
for
continuous
temperature
assessment of the external MOSFET or other thermal
sensitive components. The POWER GOOD output
provides a fast alert when the input and/or output
voltages are outside their programmed range.
Accurate power readings are accomplished by using
the
READ_EIN
command.
A
black
box
(Telemetry/Fault Snapshot) function captures and
stores telemetry data and device status in the event
of a warning or a fault.
APPLICATIONS
•
•
•
Server backplane systems
Basestation power distribution systems
Solid state circuit breaker (eFuse)
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2012–2013, Texas Instruments Incorporated
LM25066I, LM25066IA
SNVS824C – JUNE 2012 – REVISED MARCH 2013
www.ti.com
Typical Application Schematic
Q2
VIN
CIN
VOUT
RS
Q1
DZ
R1
VIN
CLOAD
GATE
SENSE
OUT
R4
DIODE
UVLO/EN
UVLO/EN
R2
FB
VDD
R5
OVLO
R3
RPG
VDD
ADR2
N/C
ADR1
N/C
ADR0
PGD
LM25066I/A
VAUX
RETRY
SMBA
SMBus
Interface
Auxillary ADC Input
(0V - 1.16V)
CB
SDA
CL
SCL
VDD
VREF
CVDD
GND
TIMER
CVREF
PWR
RPWR
CT
GATE
SENSE
VIN
UVLO/EN
OVLO
GND
SDA
Connection Diagram
OUT
SCL
SMBA
PGD
Exposed
Pad
VREF
FB
CB
CL
RETRY
VDD
VAUX
ADR0
TIMER
ADR1
DIODE
ADR2
24
PWR
5x4 mm WQFN 24L
1
Solder exposed pad to ground.
Top View
WQFN-24
2
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Pin Descriptions
Pin
No.
Name
Description
Applications Information
Pad
Exposed
Pad
Exposed pad of WQFN
package
No internal electrical connection. Solder to the ground plane to reduce thermal resistance.
1
ADR2
SMBUS address line 2
3 - state address line. Should be connected to GND, VDD, or left floating.
2
ADR1
SMBUS address line 1
3 - state address line. Should be connected to GND, VDD, or left floating.
3
ADR0
SMBUS address line 0
3 - state address line. Should be connected to GND, VDD, or left floating.
4
VDD
Internal sub-regulator
output
Internally sub-regulated 4.5V bias supply. Connect a 1 µF capacitor on this pin to ground
for bypassing.
5
CL
Current limit range
Connect this pin to GND to set the nominal over-current threshold at 25mV. Connecting
CL to VDD will set the over-current threshold to be 46mV.
6
CB
Circuit breaker range
This pin sets the circuit breaker protection point in relation to the over-current trip point.
When connected to GND, this pin will set the circuit breaker point to be 1.8 times the
over-current threshold. Connecting this pin to VDD sets the circuit breaker trip point to be
3.6 times the over-current threshold.
7
FB
Power Good feedback
An external resistor divider from OUT sets the output voltage at which the PGD pin
switches. The threshold at the pin is 1.167V. An internal 24 µA current source provides
hysteresis.
8
RETRY
Fault retry input
This pin configures the power up fault retry behavior. When this pin is grounded, the
device will continually try to engage power during a fault. If the pin is connected to VDD,
the device will latch off during a fault.
9
TIMER
Timing capacitor
An external capacitor connected to this pin sets the insertion time delay, fault timeout
period and restart timing.
10
PWR
Power limit set
11
PGD
Power Good indicator
12
OUT
Output feedback
Connect to the output rail (external MOSFET source). Internally used to determine the
MOSFET VDS voltage for power limiting, and to monitor the output voltage.
Connect to the external MOSFET's gate.
An external resistor connected to this pin, in conjunction with the current sense resistor
(RS), sets the maximum power dissipation allowed in the external series pass MOSFET.
An open drain output. This output is high when the voltage at the FB pin is above 1.167V
and the input supply is within its under-voltage and over-voltage thresholds. Connect via a
pullup resistor to the output rail (external MOSFET source) or any other voltage to be
monitored.
13
GATE
Gate drive output
14
SENSE
Current sense input
The voltage across the current sense resistor (RS) is measured from VIN to this pin. If the
voltage across RS reaches over-current threshold, the load current is limited and the fault
timer activates.
15
VIN
Positive supply input
A small ceramic bypass capacitor close to this pin is recommended to suppress transients
which occur when the load current is switched off.
16
UVLO/EN
Under-voltage lockout
An external resistor divider from the system input voltage sets the under-voltage turn-on
threshold. An internal 23 µA current source provides hysteresis. The enable threshold at
the pin is 1.16V. This pin can also be used for remote shutdown control.
17
OVLO
Over-voltage lockout
An external resistor divider from the system input voltage sets the over-voltage turn-off
threshold. An internal 23 µA current source provides hysteresis. The disable threshold at
the pin is 1.16V.
18
GND
Circuit ground
19
SDA
SMBus data pin
Data pin for SMBus.
Clock pin for SMBus.
20
SCL
SMBus clock
21
SMBA
SMBus alert line
22
VREF
Internal Reference
23
DIODE
External diode
24
VAUX
Auxiliary voltage input
Alert pin for SMBus, active low.
Internally generated precision 2.73V reference used for analog to digital conversion.
Connect a 1 µF capacitor on this pin to ground for bypassing.
Connect this to a diode-configured NPN transistor for temperature monitoring.
Auxiliary pin allows voltage telemetry from an external source. Full scale input of 1.16V.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
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Absolute Maximum Ratings (1)
VIN, SENSE to GND
(2)
-0.3V to 24V
GATE, FB, UVLO/EN, OVLO, PGD to GND
(2)
-0.3V to 20V
Out to GND
-1 to 20V
SCL, SDA, SMBA, CL, CB, ADR0, ADR1, ADR2, VDD, VAUX, DIODE, RETRY to GND
-0.3V to 6V
VIN to SENSE
-0.3V to +0.3V
ESD Rating, Human Body Model (3)
2kV
Storage Temperature
-65°C to +150°C
Junction Temperature
+150°C
(1)
(2)
(3)
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional.
The GATE pin voltage is typically 7.5V above VIN when the LM25066I/A is enabled. Therefore, the Absolute Maximum Rating of 24V for
VIN and SENSE apply only when the LM25066I/A is disabled or for a momentary surge to that voltage since the Absolute Maximum
Rating for the GATE pin is 20V.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Operating Ratings
VIN, SENSE, OUT voltage
2.9V to 17V
VDD
2.9V to 5.5V
−40°C to +125°C
Junction Temperature
Electrical Characteristics
Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
Input (VIN Pin)
IIN-EN
Input Current, enabled
UVLO = 2V and OVLO = 0.7V
5.8
8
mA
POR
Power On Reset threshold at VIN
VIN increasing
2.6
2.8
V
POREN Hysteresis
VIN decreasing
150
PORHYS
mV
VDD Regulator (VDD pin)
VDD
VDDILIM
IVDD = 5mA, VIN = 12V
4.3
4.5
4.7
IVDD = 5mA, VIN = 4.5V
3.5
3.9
4.3
25
45
1.147
1.16
1.173
V
18
23
28
µA
VDD Current Limit
V
V
mA
UVLO/EN, OVLO Pins
UVLOTH
UVLO threshold
VUVLO Falling
UVLOHYS
UVLO hysteresis current
UVLO = 1V
UVLODEL
UVLO delay
Delay to GATE high
8
Delay to GATE low
20
UVLOBIAS
µs
UVLO bias current
UVLO = 3V
OVLOTH
OVLO threshold
VOVLO rising
1.141
1.16
1.185
V
OVLOHYS
OVLO hysteresis current
OVLO = 1V
-28
-23
-18
µA
OVLODEL
OVLO delay
Delay to GATE high
19
Delay to GATE low
9
OVLOBIAS
OVLO bias current
1
OVLO = 1V
µA
µs
1
µA
60
mV
1
µA
Power Good (PGD pin)
(1)
4
PGDVOL
Output low voltage
ISINK = 2 mA
PGDIOH
Off leakage current
VPGD = 17V
PGDDELAY
Power Good Delay
VFB to VPG
25
115
ns
Current out of a pin is indicated as a negative value.
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Electrical Characteristics (continued)
Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
1.141
1.167
1.19
V
-31
-24
-18
µA
1
µA
15
mV
FB Pin
FBTH
FB Threshold
FBHYS
FB Hysteresis Current
FBLEAK
Off Leakage Current
VFB rising
VFB = 1V
Power Limit (PWR Pin)
PWRLIM
IPWR
RSAT(PWR)
Power limit sense voltage (VIN-SENSE)
SENSE-OUT = 12V, RPWR = 25 kΩ
9
12.5
PWR pin current
VPWR = 2.5V
-10
µA
PWR pin impedance when disabled
UVLO = 0.7V
180
Ω
Gate Control (GATE Pin)
IGATE
VGATE
Source current
Normal operation
-28
-22
-16
µA
Fault Sink current
UVLO = 1V
1.5
POR Circuit Breaker sink current
VIN - SENSE = 150 mV or VIN < RPOR,
VGATE = 5V
105
2
2.5
mA
190
275
mA
Gate output voltage in normal operation
GATE voltage with respect to ground
17
18.8
20.3
V
OUT bias current, enabled
OUT = VIN, normal operation
16
µA
Disabled, OUT = 0V, SENSE = VIN
-12
µA
OUT Pin
IOUT-EN
IOUT-DIS
OUT bias current, disabled
(2)
Current Limit
VCL
tCL
ISENSE
Threshold voltage
CL = GND
22.5
25
27.5
CL = GND, TJ = 10°C to 85°C
23
25
27
CL = VDD
41
46
52
mV
Response time
VIN-SENSE stepped from 0 mV to 80 mV
1.2
µs
SENSE input current
Enabled, SENSE = OUT
33
µA
Disabled, OUT = 0V
46
Enabled, OUT = 0V
45
Circuit Breaker
VCB
VCB
tCB
Threshold voltage x 1.8
VIN - SENSE, CL = GND, CB = GND
35
45
55
CB:CL Ratio
CB = GND
1.6
1.8
2
mV
Threshold voltage x 3.6
VIN - SENSE, CL = GND, CB = VDD
70
90
110
CB:CL Ratio
CB = VDD
3.1
3.6
4
Response time
VIN - SENSE stepped from 0 mV to 150
mV, time to GATE low, no load
0.6
1.2
µs
1.54
1.7
1.85
V
0.85
1.0
1.07
V
mV
Timer (TIMER pin)
VTMRH
Upper threshold
VTMRL
Lower threshold
ITIMER
(2)
Restart cycles
Insertion time current
End of 8th cycle
0.3
V
Re-enable threshold
0.3
V
-8
-5.5
-3
µA
Sink current, end of insertion time
TIMER pin = 2V
1.4
1.9
2.4
mA
Fault detection current
-120
-90
-60
µA
Fault sink current
2.8
DCFAULT
Fault Restart Duty Cycle
0.67
%
tFAULT_DELAY
Fault to GATE low delay
17
µs
TIMER pin reaches the upper threshold
µA
OUT bias current (disabled) due to leakage current through an internal 0.9 MΩ resistance from SENSE to VOUT.
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Electrical Characteristics (continued)
Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
2.703
2.73
2.757
V
Internal Reference
VREF
Reference Voltage
ADC and MUX
Resolution
12
Bits
Integral Non-Linearity
ADC only
+/-1
LSB
tAQUIRE
Acquisition + Conversion Time
Any channel
100
µs
tRR
INL
6
Acquisition Round Robin Time
Cycle all channels
1
ms
IINFSR
Current input full scale range
CL = GND
30.2
mV
CL = VDD
60.4
mV
IINLSB
Current input LSB
CL = GND
7.32
µV
CL = VDD
14.64
µV
VAUXFSR
VAUX input full scale range
1.16
V
VAUXLSB
VAUX input LSB
283.2
µV
VINFSR
Input voltage full scale range
18.7
V
VINLSB
Input voltage LSB
4.54
mV
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Electrical Characteristics (continued)
Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and
Symbol
Parameter
Conditions
Min
Typ
Max
Unit
+1
%
Telemetry Accuracy LM25066IA
IINACC
VACC
PINACC
Input Current Accuracy
VAUX, VIN, VOUT Accuracy
Input Power Accuracy
VIN – SENSE = 25mV, CL = GND
TJ = 10°C to 85°C
-1
VIN – SENSE = 25mV, CL = GND
-1.2
+1
VIN – SENSE = 50mV, CL = VDD
-1.8
+1.8
VIN- SENSE= 5mV, CL= GND
TJ = 10°C to 85°C
-5
+5
VIN, VOUT = 12V
VAUX = 1V
TJ = 10°C to 85°C
-1
+1
VIN, VOUT = 12V
VAUX = 1V
-1
+1.2
VIN = 12V, VIN – SENSE = 25mV,
CL = GND
-2.0
+2.0
%
VIN – SENSE = 25mV, CL = GND
-2.7
+2.4
%
VIN – SENSE = 25mV, CL = GND
TJ = 10°C to 85°C
-2.4
+2.4
VIN, VOUT = 12V
VAUX = 1V
-1.6
+1.4
VIN, VOUT = 12V
VAUX = 1V
TJ = 10°C to 85°C
-1.4
+1.4
VIN = 12V, VIN – SENSE = 25mV,
CL = GND
-3.0
+3.0
%
10
°C
%
Telemetry Accuracy LM25066I
IINACC
VACC
PINACC
Input Current Accuracy
VAUX, VIN, VOUT Accuracy
Input Power Accuracy
%
Remote Diode Temperature Sensor
TACC
Temperature Accuracy Using Local
Diode
TA = 10°C to 85°C
2
Remote Diode Resolution
IDIODE
9
External Diode Current Source
High level
250
Low level
9.4
Diode Current Ratio
bits
300
µA
µA
26
PMBus Pin Thresholds (SMBA, SDA, SCL)
VIL
Data, Clock Input Low Voltage
VIH
Data, Clock Input High Voltage
VOL
Data Output Low Voltage
IPULLUP = 4mA
ILEAK
Input Leakage Current
SDA, SMBA, SCL = 5V
Pin Capacitance
SDA, SCL
CL
0.8
V
2.1
5.5
V
0
0.4
V
1
µA
5
pF
Configuration Pin Thresholds (CB, CL, RETRY)
VIH
ILEAK
Thermal
(3)
Threshold Voltage
3
Input Leakage Current
V
CL, CB, RETRY = 5V
1
mA
(3)
θJA
Junction to Ambient
42.3
°C/W
θJC
Junction to Case
9.5
°C/W
Junction-to-ambient thermal resistance is highly application and board layout dependent. Specified thermal resistance values for the
package specified is based on a 4-layer, 4"x3", 2/1/1/2 oz. Cu board as per JEDEC standards is used.
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Typical Performance Characteristics
Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12V. All graphs show junction temperature.
VIN Pin Current
5.5
SENSE Pin Current (Enabled)
VIN = 17V
5.0
VIN = 12V
4.5
4.0
VIN = 3V
3.5
3.0
-40 -20
0
20 40 60 80 100 120 140
54
SENSE PIN CURRENT (ENABLED) ( A)
VIN INPUT CURRENT (mA)
6.0
50
VIN = 17V
46
VIN = 12V
42
38
VIN = 2.9V
34
30
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 1.
Figure 2.
50
VIN = 17V
48
46
44
VIN = 12V
42
40
38
VIN = 2.9V
36
34
-40 -20
OUT Pin Current (Enabled)
OUTPUT PIN CURRENT (ENABLED) ( A)
SENSE PIN CURRENT (DISABLED) ( A)
SENSE Pin Current (Disabled)
52
28
24
VIN = 17V
20
16
VIN = 12V
12
8
VIN = 2.9V
4
0 20 40 60 80 100 120
TEMPERATURE (°C)
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 3.
Figure 4.
GATE Pin Voltage
20
VIN = 17V
-4
VIN = 17V
-6
-8
VIN = 12V
-10
-12
-14
18
GATE PIN VOLTAGE (V)
OUTPUT PIN CURRNET (DISABLED) ( A)
OUT Pin Current (Disabled)
-2
VIN = 12V
16
VIN = 9V
14
VIN = 5V
12
10
8
-16
VIN = 2.9V
VIN = 2.9V
-18
6
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 5.
8
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Figure 6.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12V. All graphs show junction temperature.
GATE Pin Source Current
Power Limit Threshold
24
POWER LIMIT THRESHOLD (mV)
GATE PIN SOURCE CURRENT ( A)
23
22
21
20
VIN = 5V TO 17V
19
18
17
VIN = 2.9V
16
15
20
RPWR
16
12
14
8
RPWR
4
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20
Figure 7.
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 8.
PGD Low Voltage
UVLO Threshold
42
1.17
38
UVLO THRESHOLD (V)
PGD LOW VOLTAGE (mV)
=25K; CL = GND
0
-40 -20
34
30
26
VIN = 2.9 to 12V
1.16
VIN = 17V
22
PGD Sink Current = 2mA
18
-60 -40 -20 0 20 40 60 80 100120140
1.15
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 9.
Figure 10.
UVLO Hysteresis Current
FB Threshold
24.0
1.172
1.171
23.8
1.170
FB THRESHOLD (V)
UVLO HYSTERESIS CURRENT ( A)
=50K; CL = VDD
1.169
23.6
1.168
1.167
23.4
1.166
1.165
23.2
1.164
1.163
23.0
-60 -40 -20 0 20 40 60 80 100120140
1.162
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 11.
Figure 12.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12V. All graphs show junction temperature.
OVLO Threshold
OVLO Hysteresis
-16
OVLO HYSTERESIS CURRENT ( A)
1.167
OVLO THRESHOLD (V)
VIN = 2.9V
1.166
VIN = 12V
1.165
1.164
1.163
VIN = 17V
1.162
-18
-20
-22
VIN = 12V to 17V
-24
-26
-28
-30
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 13.
Figure 14.
FB Pin Hysteresis
Current Limit Threshold
27.0
CURRENT LIMIT THRESHOLD (mV)
-23.0
FB HYSTERESIS ( A)
-23.5
-24.0
-24.5
-25.0
-25.5
26.5
26.0
25.5
VIN = 5V to 17V
25.0
24.5
24.0
VIN = 2.9V
23.5
23.0
-26.0
-60 -40 -20 0 20 40 60 80 100120140
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 15.
Figure 16.
CURRENT LIMIT THRESHOLD (mV)
49
48
47
VIN = 5V to 17V
46
45
44
VIN = 2.9V
43
42
41
40
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Circuit Breaker Threshold (CL = VDD)
CIRCUIT BREAKER THRESHOLD (mV)
Current Limit Threshold
50
200
180
160
CL = VDD, CB = VDD
140
120
CL = GND, CB = VDD
100
80
60
CL = GND, CB = GND
40
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
Figure 17.
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Figure 18.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12V. All graphs show junction temperature.
Reference Voltage
Startup (Insertion Delay)
2.75
INSERTION DELAY = 140 ms
VREF (V)
2.74
2.73
2.72
TIMER
1V/DIV
VIN
10V/DIV
10V/DIV
GATE
2.71
VOUT
10V/DIV
2.70
100 ms/DIV
-60 -40 -20 0 20 40 60 80 100120140
TEMPERATURE (°C)
Figure 19.
Figure 20.
Startup (Short circuit VOUT)
Startup (5A Load)
TIMER
1V/DIV
TIMER
VIN
1V/DIV
10V/DIV
RETRY PERIOD = 1.10s
GATE
10V/DIV
10V/DIV
GATE
10V/DIV
VOUT
VOUT
10V/DIV
2.5A/DIV
ILOAD
1 ms/DIV
400 ms/DIV
Figure 21.
Figure 22.
Startup (UVLO, OVLO)
Startup (PGOOD)
PGOOD
5V/DIV
OVLO = 15.2V
GATE
VIN
hyst = 1.2V
5V/DIV
10.7V
10.25V
5V/DIV
VIN
hyst = 0.2V
VOUT
UVLO = 2.9V
40 ms/DIV
40 ms/DIV
Figure 23.
Figure 24.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = 25°C, VIN = 12V. All graphs show junction temperature.
Current Limit Event (CL = GND)
Circuit Breaker Event (CL = CB = GND)
1V/DIV
TIMER
TIMER
TIMEOUT PERIOD
= 8.3 ms
GATE
1V/DIV
GATE
10V/DIV
VOUT
10V/DIV
VOUT
10V/DIV
>50A
10V/DIV
ILOAD
> 90A Triggers
Circuit Breaker
25A/DIV
ILOAD
50A/DIV
1 ms/DIV
4 ms/DIV
Figure 25.
Figure 26.
Retry Event (Retry = GND)
Latch Off (Retry = VDD)
RETRY PERIOD = 1.1s
1V/DIV
TIMER
TIMER
1V/DIV
GATE
10V/DIV
VOUT
VOUT
10V/DIV
ILOAD
10V/DIV
ILOAD
25A/DIV
25A/DIV
100 ms/DIV
Figure 27.
Figure 28.
IIN Measurement Accuracy
(VIN - SENSE = 25 mV)
PIN Measurement Accuracy
(VIN - SENSE = 25 mV)
0.5
1.0
0.4
0.8
0.3
0.6
PIN ERROR (% OF FSR)
IIN ERROR ( % OF FSR)
400 ms/DIV
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-0.5
-15 -5
0.4
-1.0
5 15 25 35 45 55 65 75 85
TEMPERATURE ( °C)
-15 -5
Figure 29.
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5 15 25 35 45 55 65 75 85
TEMPERATURE (°C)
Figure 30.
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24 A
LM25066I/A
VDD
REG
VDD
REF
GEN
1.167V
UV
OV
S/H
AMUX
1/16
ID
25 mV
VAUX
1M
SCL
SMBUS
INTERFACE
VDS
10 A
Diode
Temp
Sense
Gate
Control
2 mA
190
mA
Power Limit
Threshold
GATE
18.8V
Current Limit/
Power Limit
Control
5.5 A
Insertion
Timer
SnapShot
MEASUREMENT/
AVERAGING
FAULT REGISTERS
SDA
22 A
Current Limit
Threshold
Gain = 2.3V/V
DIODE
Charge
Pump
1/16
12bit
ADC
VREF
PGD
FB
OUT
SENSE
VIN
BLOCK DIAGRAM
90 A
23 A
Fault
Timer
TIMER
TELEMETRY
STATE
MACHINE
1.16V
TIMER AND GATE
LOGIC CONTROL
1.16V
SMBA
1.9 mA
End
Insertion
Time
2.8 A
Fault
Discharge
1.72V
ADDRESS
DECODER
1.0V
23 A
0.3V
2.5V
ADR0
VDD
ADR1
POR
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RETRY
CB
GND
UVLO/EN
PWR
OVLO
ADR2
CL
2.6V
VIN
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FUNCTIONAL DESCRIPTION
The inline protection functionality of the LM25066I/A is designed to control the in-rush current to the load upon
insertion of a circuit card into a live backplane or other “hot” power source, thereby limiting the voltage sag on the
backplane’s supply voltage and the dV/dt of the voltage applied to the load. Effects on other circuits in the
system are minimized, preventing possible unintended resets. A controlled shutdown when the circuit card is
removed can also be implemented using the LM25066I/A.
In addition to a programmable current limit, the LM25066I/A monitors and limits the maximum power dissipation
in the series pass device to maintain operation within the device Safe Operating Area (SOA). Either current
limiting or power limiting for an extended period of time results in the shutdown of the series pass device. In this
event, the LM25066I/A can latch off or repetitively retry based on the hardware setting of the RETRY pin. Once
started, the number of retries can be set to none, 1, 2, 4, 8, 16, or infinite. The circuit breaker function quickly
switches off the series pass device upon detection of a severe over-current condition. Programmable undervoltage lockout (UVLO) and over-voltage lockout (OVLO) circuits shut down the LM25066I/A when the system
input voltage is outside the desired operating range.
The telemetry capability of the LM25066I/A provides intelligent monitoring of the input voltage, output voltage,
input current, input power, temperature, and an auxiliary input. The LM25066I/A also provides a peak capture of
the input power and programmable hardware averaging of the input voltage, current, power, and output voltage.
Warning thresholds which trigger the SMBA pin may be programmed for input and output voltage, current, power
and temperature via the PMBus interface. Additionally, the LM25066I/A is capable of detecting damage to the
external MOSFET, Q1.
Q2
VIN
CIN
VOUT
RS
Q1
DZ
R1
VIN
SENSE
CLOAD
GATE
OUT
R4
DIODE
UVLO/EN
UVLO/EN
R2
FB
VDD
R5
OVLO
R3
RPG
VDD
ADR2
N/C
ADR1
N/C
ADR0
PGD
LM25066I/A
VAUX
RETRY
SMBA
SMBus
Interface
Auxillary ADC Input
(0V - 1.16V)
CB
SDA
CL
SCL
VDD
CVDD
VREF
CVREF
GND
TIMER
PWR
RPWR
CT
Figure 31. Typical Application Circuit
Power Up Sequence
The VIN operating range of the LM25066I/A is +2.9V to +17V, with transient capability to +24V. Referring to
Figure 31 and Figure 32, as the voltage at VIN initially increases, the external N-channel MOSFET (Q1) is held
off by an internal 190 mA pulldown current at the GATE pin. The strong pulldown current at the GATE pin
prevents an inadvertent turn-on as the MOSFET’s gate-to-drain (Miller) capacitance is charged. Additionally, the
TIMER pin is initially held at ground. When the VIN voltage reaches the POR threshold, the insertion time begins.
During the insertion time, the capacitor at the TIMER pin (CT) is charged by a 5.5 µA current source and Q1 is
held off by a 2 mA pulldown current at the GATE pin regardless of the input voltage. The insertion time delay
allows ringing and transients at VIN to settle before Q1 is enabled. The insertion time ends when the TIMER pin
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voltage reaches 1.7V. CT is then quickly discharged by an internal 1.9 mA pulldown current. The GATE pin then
switches on Q1 when VSYS, the input supply voltage, exceeds the UVLO threshold. If VSYS is above the UVLO
threshold at the end of the insertion time, Q1 switches on at that time. The GATE pin charge pump sources 22
µA to charge the gate capacitance of Q1. The maximum voltage at the GATE pin with respect to ground is limited
by an internal 18.8V zener diode.
As the voltage at the OUT pin increases, the LM25066I/A monitors the drain current and power dissipation of
MOSFET Q1. Inrush current limiting and/or power limiting circuits actively control the current delivered to the
load. During the inrush limiting interval (t2 in Figure 32), an internal 90 µA fault timer current source charges CT.
If Q1’s power dissipation and the input current reduce below their respective limiting thresholds before the TIMER
pin reaches 1.7V, the 90 µA current source is switched off and CT is discharged by the internal 2.8 µA current
sink (t3 in Figure 32). The PGD pin switches high when FB exceeds its rising threshold of 1.167V.
If the TIMER pin voltage reaches 1.7V before inrush current limiting or power limiting ceases during t2, a fault is
declared and Q1 is turned off. See Fault Timer and Restart for a complete description of the fault mode.
The LM25066I/A will pull the SMBA pin low after the input voltage has exceeded its POR threshold to indicate
that the volatile memory and device settings are in their default state. The CONFIG_PRESET bit within the
STATUS_MFR_SPECIFIC register (80h) indicates default configuration of warning thresholds and device
operation and will remain set until a CLEAR_FAULTS command is received.
VSYS
VIN
UVLO
POR
1.7V
5.5 PA
90 PA
2.8 PA
TIMER
Pin
GATE
Pin
190 mA
pull-down
2 mA pull-down
22 PA source
ILIMIT
Load
Current
Output
Voltage
(OUT Pin)
PGD
t1
Insertion Time
t2
t3
In rush
Limiting
Normal Operation
Figure 32. Power Up Sequence (Current Limit Only)
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Gate Control
A charge pump provides the voltage at the GATE pin to enhance the N-Channel MOSFET’s gate. During normal
operating conditions (t3 in )Figure 32) the gate of Q1 is held charged by an internal 22 µA current source. The
voltage at the GATE pin (with respect to ground) is limited by an internal 18.8 V zener diode. See the graph
“GATE Pin Voltage” shown previously. Since the gate-to-source voltage applied to Q1 could be as high as 18.8 V
during various conditions, a zener diode with the appropriate voltage rating must be added between the GATE
and OUT pins if the maximum VGS rating of the selected MOSFET is less than 18.8 V. The external zener diode
must have a forward current rating of at least 190 mA. When the system voltage is initially applied, the GATE pin
is held low by a 190 mA pulldown current. This helps prevent an inadvertent turn-on of the MOSFET through its
drain-gate capacitance as the applied system voltage increases.
During the insertion time (t1 in Figure 32) the GATE pin is held low by a 2 mA pulldown current. This maintains
Q1 in the off-state until the end of t1, regardless of the voltage at VIN or UVLO. Following the insertion time (t2 in
Figure 32), the gate voltage of Q1 is controlled to keep the current or power dissipation level from exceeding the
programmed levels. While in the current or power limiting mode, the TIMER pin capacitor is charging. If the
current and power limiting cease before the TIMER pin reaches 1.7V, the TIMER pin capacitor then discharges,
and the circuit begins normal operation. If the inrush limiting condition persists such that the TIMER pin reached
1.7V during t2, the GATE pin is then pulled low by the 190 mA pulldown current. The GATE pin is then held low
until either a power up sequence is initiated (RETRY pin to VDD), or an automatic retry is attempted (RETRY pin
to GROUND). See Fault Timer and Restart. If the system input voltage falls below the UVLO threshold or rises
above the OVLO threshold, the GATE pin is pulled low by the 2 mA pulldown current to switch off Q1.
Current Limit
The current limit threshold is reached when the voltage across the sense resistor RS (VIN to SENSE) exceeds
the internal voltage limit of 25 mV or 46 mV depending on whether the CL pin is connected to GND or VDD,
respectively. In the current limiting condition, the GATE voltage is controlled to limit the current in MOSFET Q1.
While the current limit circuit is active, the fault timer is active as described in Fault Timer and Restart. If the load
current falls below the current limit threshold before the end of the Fault Timeout Period, the LM25066I/A
resumes normal operation. If the current limit condition persists for longer than the Fault Timeout Period set by
the timer capacitor, CT, the IIN OC FAULT bit in the STATUS_INPUT (7Ch) register, the INPUT bit in the
STATUS_WORD (79h) register, and the IIN_OC/PFET_OP_FAULT bit in the DIAGNOSTIC_WORD (E1h)
register will be toggled high and SMBA pin will be pulled low unless this feature is disabled using the
ALERT_MASK (D8h) register. For proper operation, the RS resistor value should be less than 200 mΩ. Higher
values may create instability in the current limit control loop. The current limit threshold pin value may be
overridden by setting appropriate bits in the DEVICE_SETUP register (D9h).
Circuit Breaker
If the load current increases rapidly (e.g. the load is short circuited), the current in the sense resistor (RS) may
exceed the current limit threshold before the current limit control loop is able to respond. If the current exceeds
1.8 or 3.6 times (user settable) the current limit threshold, Q1 is quickly switched off by the 190 mA pulldown
current at the GATE pin, and a Fault Timeout Period begins. When the voltage across RS falls below the
threshold the 190 mA pulldown current at the GATE pin is switched off and the gate voltage of Q1 is then
determined by the current limit or power limit functions. If the TIMER pin reaches 1.7V before the current limiting
or power limiting condition ceases, Q1 is switched off by the 2 mA pulldown current at the GATE pin as described
in Fault Timer and Restart. A circuit breaker event will cause the CIRCUIT BREAKER FAULT bit in the
STATUS_MFR_SPECIFIC (80h) and DIAGNOSTIC_WORD (E1h) registers to be toggled high and SMBA pin will
be pulled low unless this feature is disabled using the ALERT_MASK (D8h) register. The circuit breaker pin
configuration may be overridden by setting appropriate bits in the DEVICE_SETUP (D9h) register.
Power Limit
An important feature of the LM25066I/A is the MOSFET power limiting. The Power Limit function can be used to
maintain the maximum power dissipation of MOSFET Q1 within the device SOA rating. The LM25066I/A
determines the power dissipation in Q1 by monitoring its drain-source voltage (SENSE to OUT), and the drain
current through RS (VIN to SENSE). The product of the current and voltage is compared to the power limit
threshold programmed by the resistor at the PWR pin. If the power dissipation reaches the limiting threshold, the
GATE voltage is controlled to regulate the current in Q1. While the power limiting circuit is active, the fault timer is
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active as described in Fault Timer and Restart. If the power limit condition persists for longer than the Fault
Timeout Period set by the timer capacitor, CT, the IIN_OC_FAULT bit in the STATUS_INPUT (7Ch) register, the
INPUT bit in the STATUS_WORD (79h) register, and the IIN_OC/PFET_OP_FAULT bit in the
DIAGNOSTIC_WORD (E1h) register will be toggled high and SMBA pin will be pulled low unless this feature is
disabled using the ALERT_MASK (D8h) register.
Fault Timer and Restart
When the current limit or power limit threshold is reached during turn-on, or as a result of a fault condition, the
gate-to-source voltage of Q1 is controlled to regulate the load current and power dissipation in Q1. When either
limiting function is active, a 90 µA fault timer current source charges the external capacitor (CT) at the TIMER pin
as shown in Figure 32 (Fault Timeout Period). If the fault condition subsides during the Fault Timeout Period
before the TIMER pin reaches 1.7V, the LM25066I/A returns to the normal operating mode and CT is discharged
by the 1.9 mA current sink. If the TIMER pin reaches 1.7V during the Fault Timeout Period, Q1 is switched off by
a 2 mA pulldown current at the GATE pin. The subsequent restart procedure then depends on the selected retry
configuration.
If the RETRY pin is high, the LM25066I/A latches the GATE pin low at the end of the Fault Timeout Period. CT is
then discharged to ground by the 2.8 µA fault current sink. The GATE pin is held low by the 2 mA pulldown
current until a power up sequence is externally initiated by cycling the input voltage (VSYS), or momentarily pulling
the UVLO/EN pin below its threshold with an open-collector or open-drain device as shown in Figure 33. The
voltage at the TIMER pin must be <0.3V for the restart procedure to be effective. The TIMER_LATCHED_OFF
bit in the DIAGNOSTIC_WORD (E1h) register will remain high while the latched off condition persists.
VSYS
VIN
R1
UVLO/EN
Restart
Control
LM25066I/A
R2
OVLO
R3
GND
Figure 33. Latched Fault Restart Control
The LM25066I/A provides an automatic restart sequence which consists of the TIMER pin cycling between 1.7V
and 1V seven times after the Fault Timeout Period, as shown in Figure 34. The period of each cycle is
determined by the 90 µA charging current, and the 2.8 µA discharge current, and the value of the capacitor CT.
When the TIMER pin reaches 0.3V during the eighth high-to-low ramp, the 22 µA current source at the GATE pin
turns on Q1. If the fault condition is still present, the Fault Timeout Period and the restart sequence repeat. The
RETRY pin allows selecting no retries or infinite retries. Finer control of the retry behavior can be achieved
through the DEVICE_SETUP (D9h) register. Retry counts of 0, 1, 2, 4, 8, 16 or infinite may be selected by
setting the appropriate bits in the DEVICE_SETUP (D9h) register.
Fault
Detection
ILIMIT
Load
Current
22 PA
Gate Charge
2 mA pulldown
GATE
Pin
2.8 PA
1.7V
90 PA
TIMER
Pin
1V
1
2
3
7
8
0.3V
t RESTART
Fault Timeout
Period
Figure 34. Restart Sequence
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Under-Voltage Lockout (UVLO)
The series pass MOSFET (Q1) is enabled when the input supply voltage (VSYS) is within the operating range
defined by the programmable under-voltage lockout (UVLO) and over-voltage lockout (OVLO) levels. Typically
the UVLO level at VSYS is set with a resistor divider (R1-R3) as shown in Figure 35. Refering to the Block
Diagram when VSYS is below the UVLO level, the internal 23 µA current source at UVLO is enabled, the current
source at OVLO is off, and Q1 is held off by the 2 mA pulldown current at the GATE pin. As VSYS is increased,
raising the voltage at UVLO above its threshold the 23 µA current source at UVLO is switched off, increasing the
voltage at UVLO, providing hysteresis for this threshold. With the UVLO/EN pin above its threshold, Q1 is
switched on by the 22 µA current source at the GATE pin if the insertion time delay has expired.
See Applications Section for a procedure to calculate the values of the threshold setting resistors (R1-R3). The
minimum possible UVLO level at VSYS can be set by connecting the UVLO/EN pin to VIN. In this case, Q1 is
enabled after the insertion time when the voltage at VIN reaches the POR threshold. After power up, an UVLO
condition will toggle high the VIN UV FAULT bit in the STATUS_INPUT (7Ch), the INPUT bit in the
STATUS_WORD register, and the VIN_UNDERVOLTAGE_FAULT bit in the DIAGNOSTIC_WORD (E1h)
register, and SMBA pin will be pulled low unless this feature is disabled using the ALERT_MASK (D8h) register.
Over-Voltage Lockout (OVLO)
The series pass MOSFET (Q1) is enabled when the input supply voltage (VSYS) is within the operating range
defined by the programmable under-voltage lockout (UVLO) and over-voltage lockout (OVLO) levels. If VSYS
raises the OVLO pin voltage above its threshold, Q1 is switched off by the 2 mA pulldown current at the GATE
pin, denying power to the load. When the OVLO pin is above its threshold, the internal 23 µA current source at
OVLO is switched on, raising the voltage at OVLO to provide threshold hysteresis. When VSYS is reduced below
the OVLO level, Q1 is re-enabled. An OVLO condition will toggle high the VIN OV FAULT bit in the
STATUS_INPUT (7Ch), the INPUT bit in the STATUS_WORD register, and the VIN_OVERVOLTAGE_FAULT bit
in the DIAGNOSTIC_WORD (E1h) register, and the SMBA pin will be pulled low unless this feature is disabled
using the ALERT_MASK (D8h) register.
See Applications Section for a procedure to calculate the threshold setting resistor values.
Shutdown Control
The load current can be remotely switched off by taking the UVLO/EN pin below its threshold with an open
collector or open drain device, as shown in Figure 35. Upon releasing the UVLO/EN pin, the LM25066I/A
switches on the load current with inrush current and power limiting.
VSYS
R1
VIN
UVLO/EN
Shutdown
Control
LM25066I/A
R2
OVLO
R3
GND
Figure 35. Shutdown Control
Power Good
The Power Good indicator (PGD) is connected to the drain of an internal N-channel MOSFET capable of
sustaining 17V in the off-state, and transients up to 20V. An external pullup resistor is required at PGD to an
appropriate voltage to indicate the status to downstream circuitry. The off-state voltage at the PGD pin can be
higher or lower than the voltages at VIN and OUT. PGD is switched high when the voltage at the FB pin exceeds
the PGD threshold voltage. Typically, the output voltage threshold is set with a resistor divider from output to
feedback, although the monitored voltage need not be the output voltage. Any other voltage can be monitored as
long as the voltage at the FB pin does not exceed its maximum rating. Referring to the Block Diagram, when the
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voltage at the FB pin is below its threshold, the 24 µA current source at FB is disabled. As the output voltage
increases, taking FB above its threshold, the current source is enabled, sourcing current out of the pin, raising
the voltage at FB to provide threshold hysteresis. The PGD output is forced low when either the UVLO/EN pin is
below its threshold or the OVLO pin is above its threshold. The status of the PGD pin can be read via the PMBus
interface in either the STATUS_WORD (79h) or DIAGNOSTIC_WORD (E1h) registers.
VDD Sub-Regulator
The LM25066I/A contains an internal linear sub-regulator which steps down the input voltage to generate a 4.5V
rail used for powering low voltage circuitry. When the input voltage is below 4.5V, VDD will track VIN. For input
voltages 3.3V and below, VDD should be tied directly to VIN to avoid the dropout of the sub-regulator. The VDD
sub-regulator should be used as the pullup supply for the CL, CB, RETRY, ADR2, ADR1, ADR0 pins if they are
to be tied high. It may also be used as the pullup supply for the PGD and the SMBus signals (SDA, SCL, SMBA).
The VDD sub-regulator is not designed to drive high currents and should not be loaded with other integrated
circuits. The VDD pin is current limited to 45mA in order to protect the LM25066I/A in the event of a short. The
sub-regulator requires a bypass capacitance having a value between 1 µF and 4.7 µF to be placed as close to
the VDD pin as the PCB layout allows.
Remote Temperature Sensing
The LM25066I/A is designed to measure temperature remotely using an MMBT3904 NPN transistor. The base
and collector of the MMBT3904 is connected to the DIODE pin and the emitter is grounded. Place the
MMBT3904 near the device whose temperature is to be monitored. If the temperature of the hot-swap pass
MOSFET, Q1, is to be measured, the MMBT3904 should be placed as close to Q1 as the layout allows. The
temperature is measured by means of a change in the diode voltage in response to a step in current supplied by
the DIODE pin. The DIODE pin sources a constant 9.4 µA but pulses 250 µA once every millisecond in order to
measure the diode temperature. Care must be taken in the PCB layout to keep the parasitic resistance between
the DIODE pin and the MMBT3904 low so as not to degrade the measurement. Additionally, a small 1000 pF
bypass capacitor should be placed in parallel with the MMBT3904 to reduce the effects of noise. The
temperature can be read using the READ_TEMPERATURE_1 PMBus command (8Dh). The default limits of the
LM25066I/A will cause SMBA pin to be pulled low if the measured temperature exceeds 125°C and will disable
the hot-swap pass MOSFET if the temperature exceeds 150°C. These thresholds can be reprogrammed via the
PMBus interface using the OT_WARN_LIMIT (51h) and OT_FAULT_LIMIT (4Fh) commands. If the temperature
measurement and protection capability of the LM25066I/A is not used, the DIODE pin should be grounded.
Damaged MOSFET Detection
The LM25066I/A is able to detect whether the external MOSFET, Q1, is damaged under certain conditions. If the
voltage across the sense resistor exceeds 4mV while the GATE voltage is low or the internal logic indicates that
the GATE should be low, the EXT_MOSFET_SHORTED bit in the STATUS_MFR_SPECIFIC (80h) and
DIAGNOSTIC_WORD (E1h) registers will be toggled high and the SMBA pin will be pulled low unless this
feature is disabled using the ALERT_MASK register (D8h). This method effectively determines whether Q1 is
shorted because of damage present between the drain and gate and/or drain and source of the external
MOSFET.
Enabling, Disabling, and Resetting
The output can be disabled at any time during normal operation by either pulling the UVLO/EN pin to below its
threshold or the OVLO pin above its threshold, causing the GATE voltage to be forced low with a pulldown
strength of 2mA. Toggling the UVLO/EN pin will also reset the LM25066I/A from a latched-off state due to an
over-current or over-power limit condition which has caused the maximum allowed number of retries to be
exceeded. While the UVLO/EN or OVLO pins can be used to disable the output, they have no effect on the
volatile memory or address location of the LM25066I/A. User stored values for address, device operation, and
warning and fault levels programmed via the SMBus are preserved while the LM25066I/A is powered regardless
of the state of the UVLO/EN and OVLO pins. The output may also be enabled or disabled by writing 80h or 0h to
the OPERATION (03h) register. To re-enable after a fault, the fault condition should be cleared and the
OPERATION (03h) register should be written to 0h and then 80h.
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The SMBus address of the LM25066I/A is captured based on the states of the ADR0, ADR1, and ADR2 pins
(GND, NC, VDD) during turn-on and is latched into a volatile register once VDD has exceeded its POR threshold
of 2.6V. Reassigning or postponing the address capture is accomplished by holding the VREF pin to ground.
Pulling the VREF pin low will also reset the logic and erase the volatile memory of the LM25066I/A. Once
released, the VREF pin will charge up to its final value and the address will be latched into a volatile register
once the voltage at the VREF exceeds 2.4V.
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APPLICATIONS SECTION
MMBT3904
12V
SMCJ15A
0.5 m:
VOUT
PSMN1R2-25YL
330 PF
25 k:
10 k:
VIN
SENSE
GATE
UVLO/EN
UVLO/EN
2.1 k:
OUT
OUT
DIODE
FB
1.3 k:
OVLO
2.1 k:
10 k:
VDD
ADR2
N/C
ADR1
N/C
ADR0
PGD
LM25066I/IA
VAUX
Auxillary ADC Input
(0V - 1.16V)
RETRY
SMBA
SMBus
Interface
VDD
CB
SDA
CL
SCL
VDD
VREF
1 PF
1 PF
GND
TIMER
PWR
0.47 PF
6.98 k:
Figure 36. Typical Application Circuit
DESIGN-IN PROCEDURE
(Refer to Figure 36 for Typical Application Circuit) Shown here is the step-by-step procedure for hardware design
of the LM25066I/A. This procedure refers to sections that provide detailed information on the following design
steps. The recommended design-in procedure is as follows:
MOSFET Selection: Determine MOSFET value based on breakdown voltage, current and power ratings.
Current Limit, RS: Determine the current limit threshold (ILIM). This threshold must be higher than the normal
maximum load current, allowing for tolerances in the current sense resistor value and the LM25066I/A Current
Limit threshold voltage. Use Equation 1 to determine the value for RS.
Power Limit Threshold: Determine the maximum allowable power dissipation for the series pass MOSFET (Q1)
using the device’s SOA information. Use Equation 2 to determine the value for RPWR.
Turn-On Time and TIMER Capacitor, CT: Determine the value for the timing capacitor at the TIMER pin (CT)
using Equation 8. The fault timeout period (tFAULT) MUST be longer than the circuit’s turn-on-time. The turn-on
time can be estimated using the equations in TURN-ON TIME, but should be verified experimentally. Review the
resulting insertion time, and the restart timing if retry is enabled.
UVLO, OVLO: Choose option A, B, C, or D from UVLO, OVLO to set the UVLO and OVLO thresholds and
hysteresis. Use the procedure for the appropriate option to determine the resistor values at the UVLO/EN and
OVLO pins.
Power Good: Choose the appropriate output voltage and calculate the required resistor divider from the output
voltage to the FB pin. Choose either VDD or OUT to connect properly sized pullup resistor for the Power Good
output (PGD).
Refer to Programming Guide section: After all hardware design is complete, refer to the programming guide
for a step by step procedure regarding software.
MOSFET SELECTION
It is recommended that the external MOSFET (Q1) selection be based on the following criteria:
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•
•
•
•
•
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The BVDSS rating should be greater than the maximum system voltage (VSYS), plus ringing and transients
which can occur at VSYS when the circuit card, or adjacent cards, are inserted or removed.
The maximum continuous current rating should be based on the current limit threshold (e.g. 25 mV/RS), not
the maximum load current, since the circuit can operate near the current limit threshold continuously.
The Pulsed Drain Current spec (IDM) must be greater than the current threshold for the circuit breaker function
(45 mV/RS when CL = CB = GND).
The SOA (Safe Operating Area) chart of the device and its thermal properties should be used to determine
the maximum power dissipation threshold set by the RPWR resistor. The programmed maximum power
dissipation should have a reasonable margin from the maximum power defined by the MOSFET’s SOA curve
(if the device is set to infinitely retry, the MOSFET will be repeatedly stressed during fault restart cycles). The
MOSFET manufacturer should be consulted for guidelines.
RDS(on) should be sufficiently low such that the power dissipation at maximum load current (ILIM2 x RDS(on))
does not raise its junction temperature above the manufacturer’s recommendation.
The gate-to-source voltage provided by the LM25066I/A can be as high as 18.8V at turn-on when the output
voltage is zero. At turn-off, the reverse gate-to-source voltage will be equal to the output voltage at the instant
the GATE pin is pulled low. If the device chosen for Q1 is not rated for these voltages, an external zener
diode must be added from its gate to source, with the zener voltage less than the device maximum VGS
rating. The zener diode’s working voltage protects the MOSFET during turn-on, and its forward voltage
protects the MOSFET during shutoff. The zener diode’s forward current rating must be at least 190 mA to
conduct the GATE pulldown current when a circuit breaker condition is detected.
CURRENT LIMIT (RS)
The LM25066I/A monitors the current in the external MOSFET Q1 by measuring the voltage across the sense
resistor (RS), connected from VIN to SENSE. The required resistor value is calculated from:
RS =
VCL
ILIM
(1)
where ILIM is the desired current limit threshold. If the voltage across RS reaches VCL, the current limit circuit
modulates the gate of Q1 to regulate the current at ILIM. While the current limiting circuit is active, the fault timer is
active as described in Fault Timer and Restart. For proper operation, RS must be less than 200 mΩ.
VCL can be set to either 25mV or 46mV via hardware and/or software. This setting defaults to use of CL pin
which when grounded is 25mV or high is 46mV. The value when powered can be set via PMBus™ with the
MFR_SPECIFIC_DEVICE_SETUP command, which defaults to the 25mV setting.
Once the desired setting is known, calculate the shunt based on that input voltage and maximum current. While
the maximum load current in normal operation can be used to determine the required power rating for resistor
RS, basing it on the current limit value provides a more reliable design since the circuit can operate near the
current limit threshold continuously. The resistor’s surge capability must also be considered since the circuit
breaker threshold is 1.8 or 3.6 times the current limit threshold.
Connections from RS to the LM25066I/A should be made using Kelvin techniques. In the suggested layout of
Figure 37, the small pads at the lower corners of the sense resistor connect only to the sense resistor terminals
and not to the traces carrying the high current. With this technique, only the voltage across the sense resistor is
applied to VIN and SENSE, eliminating the voltage drop across the high current solder connections.
HIGH CURRENT PATH
TO DRAIN OF
FROM SYSTEM
INPUT VOLTAGE
SENSE
RESISTOR
MOSFET Q1
RS
VIN
SENSE
Figure 37. Sense Resistor Connections
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POWER LIMIT THRESHOLD
The LM25066I/A determines the power dissipation in the external MOSFET (Q1) by monitoring the drain current
(the current in RS), and the VDS of Q1 (SENSE to OUT pins). The resistor at the PWR pin (RPWR) sets the
maximum power dissipation for Q1 and is calculated from Equation 2:
RPWR = 1.71 x 105 x RS x PMOSFET(LIM)
(2)
where PMOSFET(LIM) is the desired power limit threshold for Q1 and RS is the current sense resistor described in
Current Limit. For example, if RS is 10 mΩ and the desired power limit threshold is 20W, RPWR calculates to 34.2
kΩ. If Q1’s power dissipation reaches the threshold, Q1’s gate is controlled to regulate the load current, keeping
Q1’s power from exceeding the threshold. For proper operation of the power limiting feature, RPWR must be ≤150
kΩ. While the power limiting circuit is active, the fault timer is active as described in Fault Timer and Restart.
Typically, power limit is reached during startup, or if the output voltage falls because of a severe overload or
short circuit. The programmed maximum power dissipation should have a reasonable margin from the maximum
power defined by the SOA chart, especially if retry is enabled since the MOSFET will be repeatedly stressed
during fault restart cycles. The MOSFET manufacturer should be consulted for guidelines. If the application does
not require use of the power limit function, the PWR pin can be left open. The accuracy of the power limit
function at turn-on may degrade if a very low value power dissipation limit is set. The reason for this caution is
that the voltage across the sense resistor, which is monitored and regulated by the power limit circuit, is lowest at
turn-on when the regulated current is at a minimum. The voltage across the sense resistor during power limit can
be expressed as follows:
VSENSE = IL x RS =
RPWR
1.71 x 105 x VDS
=
RS x PFET(LIM)
VDS
(3)
where IL is the current in RS and VDS is the voltage across Q1. For example, if the power limit is set at 20W with
RS = 10 mΩ and VDS = 15V, the sense resistor voltage calculates to 13.3 mV, which is comfortably regulated by
the LM25066I/A. However, if the power limit is set lower (e.g. 2W), the sense resistor voltage calculates to 1.33
mV. At this low level, noise and offsets within the LM25066I/A may degrade the power limit accuracy. To
maintain accuracy, the sense resistor voltage should not be less than 5 mV.
TURN-ON TIME
The output turn-on time depends on whether the LM25066I/A operates in current limit, or in both power limit and
current limit, during turn-on.
A) Turn-on with current limit only: The current limit threshold (ILIM) is determined by the current sense resistor
(RS). If the current limit threshold is less than the current defined by the power limit threshold at maximum VDS,
the circuit operates at the current limit threshold only during turn-on. Referring to Figure 39A, as the load current
reaches ILIM, the gate-to-source voltage is controlled at VGSL to maintain the current at ILIM. As the output voltage
reaches its final value (VDS ≊ 0V) the drain current reduces to its normal operating value. The time for the OUT
pin voltage to transition from zero volts to VSYS is equal to:
tON =
VSYS x CL
ILIM
(4)
where CL is the load capacitance. For example, if VSYS = 12V, CL = 1000 µF, and ILIM = 1A, tON calculates to 12
ms. The maximum instantaneous power dissipated in the MOSFET is 12W. This calculation assumes the time
from t1 to t2 in Figure 40(a) is small compared to tON and the load does not draw any current until after the output
voltage has reached its final value, and PGD switches high (Figure 39A). The Fault Timeout Period must be set
longer than tON to prevent a fault shutdown before the turn-on sequence is complete.
If the load draws current during the turn-on sequence (Figure 39B), the turn-on time is longer than the above
calculation and is approximately equal to:
tON = -(RL x CL) x In
(ILIM x RL) - VSYS
(ILIM x RL)
(5)
where RL is the load resistance. The Fault Timeout Period must be set longer than tON to prevent a fault
shutdown before the turn-on sequence is complete.
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RS
Q1
VSYS
OUT
SENSE
VIN
PGD
LM25066I/A
RL
CL
GND
GND
Figure 38. A. No Load Current During Turn-On
RS
Q1
VSYS
SENSE
VIN
OUT
CL
PGD
RL
LM25066I/A
GND
GND
Load Draws Current During Turn-On
Figure 39. Current During Turn-On
B) Turn-On with Power Limit and Current Limit: The maximum allowed power dissipation in Q1 (PMOSFET(LIM))
is defined by the resistor at the PWR pin, and the current sense resistor RS. See POWER LIMIT THRESHOLD. If
the current limit threshold (ILIM) is higher than the current defined by the power limit threshold at maximum VDS
(PMOSFET(LIM)/VSYS), the circuit operates initially in the power limit mode when the VDS of Q1 is high and then
transitions to current limit mode as the current increases to ILIM and VDS decreases. Assuming the load (RL) is not
connected during turn-on, the time for the output voltage to reach its final value is approximately equal to:
tON =
CL x VSYS2
2 x PMOSFET(LIM)
+
CL x PMOSFET(LIM)
2 x ILIM2
(6)
For example, if VSYS = 12V, CL = 1000 µF, ILIM = 1A, and PMOSFET(LIM) = 10W, tON calculates to ≊12.2 ms, and the
initial current level (IP) is approximately 0.83A. The Fault Timeout Period must be set longer than tON.
VSYS
VSYS
VDS
VDS
Drain Current
ILIM
Drain Current
ILIM
IP
0
0
VGATE
VGATE
Gate- to - Source Voltage
VGSL
VGSL
VTH
VTH
t ON
0
0
t3
t1 t2
a) Current Limit Only
t ON
0
0
b) Power Limit and Current Limit
Figure 40. MOSFET Power Up Waveforms
TIMER CAPACITOR, CT
The TIMER pin capacitor (CT) sets the timing for the insertion time delay, fault timeout period, and the restart
timing of the LM25066I/A.
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A) Insertion Delay -Upon applying the system voltage (VSYS) to the circuit, the external MOSFET (Q1) is held off
during the insertion time (t1 in Figure 32) to allow ringing and transients at VSYS to settle. Since each backplane’s
response to a circuit card plug-in is unique, the worst case settling time must be determined for each application.
The insertion time starts when VIN reaches the POR threshold, at which time the internal 5.5 µA current source
charges CT from 0V to 1.7V. The required capacitor value is calculated from:
CT =
t1 x 5.5 PA
= t1 x 3.2 x 10-6
1.7V
(7)
For example, if the desired insertion delay is 250 ms, CT calculates to 0.8 µF. At the end of the insertion delay,
CT is quickly discharged by a 1.9 mA current sink.
B) Fault Timeout Period -During inrush current limiting or upon detection of a fault condition where the current
limit and/or power limit circuits regulate the current through Q1, the fault timer current source (90 µA) is switched
on to charge CT. The Fault Timeout Period is the time required for the TIMER pin voltage to reach 1.7V, at which
time Q1 is switched off. The required capacitor value for the desired Fault Timeout Period tFAULT is calculated
from:
CT =
tFAULT x 90 PA
1.7V
= tFAULT x 5.3 x 10-5
(8)
For example, if the desired Fault Timeout Period is 15 ms, CT calculates to 0.8 µF. CT is discharged by the 2.8
µA current sink at the end of the Fault Timeout Period. After the Fault Timeout Period, if retry is disabled, the
LM25066I/A latches the GATE pin low until a power up sequence is initiated by external circuitry. When the Fault
Timeout Period of the LM25066I/A expires, a restart sequence starts as described below (Restart Timing).
During consecutive cycles of the restart sequence, the fault timeout period is shorter than the initial fault timeout
period described above by approximately 20% since the voltage at the TIMER pin starts ramping up from 0.3V
rather than ground.
Since the LM25066I/A normally operates in power limit and/or current limit during a power up sequence, the
Fault Timeout Period MUST be longer than the time required for the output voltage to reach its final value. See
TURN-ON TIME.
C) Restart Timing - For the LM25066I/A, after the Fault Timeout Period described above, CT is discharged by
the 2.8 µA current sink to 1V. The TIMER pin then cycles through seven additional charge/discharge cycles
between 1V and 1.7V as shown in Figure 34. The restart time ends when the TIMER pin voltage reaches 0.3V
during the final high-to-low ramp. The restart time, after the Fault Timeout Period, is equal to:
tRESTART = CT x
1.4V
7 x 0.7V
7 x 0.7V
+
+
2.8 PA
90 PA
2.8 PA
(9)
(10)
6
= CT x 2.3 x 10
For example, if CT = 0.8 µF, tRESTART = 2 seconds. At the end of the restart time, Q1 is switched on. If the fault is
still present, the fault timeout and restart sequence repeats. The on-time duty cycle of Q1 is approximately 0.67%
in this mode.
UVLO, OVLO
By programming the UVLO and OVLO thresholds the LM25066I/A enables the series pass device (Q1) when the
input supply voltage (VSYS) is within the desired operational range. If VSYS is below the UVLO threshold, or above
the OVLO threshold, Q1 is switched off, denying power to the load. Hysteresis is provided for each threshold.
Option A: The configuration shown in Figure 41 requires three resistors (R1-R3) to set the thresholds.
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VSYS
VIN
23 PA
R1
UVLO/EN
1.16V
R2
1.16V
TIMER AND
GATE
LOGIC CONTROL
OVLO
R3
23 PA
GND
LM25066I/A
Figure 41. UVLO and OVLO Thresholds Set By R1-R3
The procedure to calculate the resistor values is as follows:
• Choose the upper UVLO threshold (VUVH), and the lower UVLO threshold (VUVL).
• Choose the upper OVLO threshold (VOVH).
• The lower OVLO threshold (VOVL) cannot be chosen in advance in this case, but is determined after the
values for R1-R3 are determined. If VOVL must be accurately defined in addition to the other three thresholds,
see Option B below. The resistors are calculated as follows:
R1 =
R3 =
R2 =
VUVH - VUVL VUV(HYS)
=
23 PA
23 PA
(11)
1.16V x R1 x VUVL
VOVH x (VUVL ± 1.16V)
(12)
1.16V x R1
- R3
VUVL - 1.16V
(13)
The lower OVLO threshold is calculated from:
VOVL = [(R1 + R2) x ((1.16V) - 23 PA)] + 1.16V
R3
(14)
As an example, assume the application requires the following thresholds: VUVH = 8V, VUVL = 7V, VOVH = 15V.
R1 =
8V - 7V
1V
= 43.5 k:
=
23 PA
23 PA
(15)
1.16V x R1 x 7V
R3 =
= 4.03 k:
15V x (7V - 1.16V)
(16)
1.16V x R1
- R3 = 4.61 k:
R2 =
(7V ± 1.16V)
(17)
The lower OVLO threshold calculates to 12.03V and the OVLO hysteresis is 2.97V. Note that the OVLO
hysteresis is always slightly greater than the UVLO hysteresis in this configuration. When the R1-R3 resistor
values are known, the threshold voltages and hysteresis are calculated from the following:
VUVH = 1.16V + [R1 x (23 PA +
1.16V
)]
(R2 + R3)
(18)
1.16V x (R1 + R2 + R3)
VUVL =
R2 + R3
(19)
(20)
VUV(HYS) = R1 x 23µA
VOVH =
1.16V x (R1 + R2 + R3)
R3
(21)
VOVL = [(R1 + R2) x (1.16V) - 23 PA)] + 1.16V
R3
(22)
(23)
VOV(HYS) = (R1 + R2) x 23µA
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Option B: If all four thresholds must be accurately defined, the configuration in Figure 42 can be used.
VSYS
VIN
23 PA
R1
UVLO/EN
1.16V
TIMER AND
GATE
LOGIC CONTROL
R2
R3
OVLO
1.16V
R4
GND
23 PA
LM25066I/A
Figure 42. Programming the Four Thresholds
The four resistor values are calculated as follows: - Choose the upper and lower UVLO thresholds (VUVH) and
(VUVL).
R1 =
VUVH - VUVL VUV(HYS)
=
23 PA
23 PA
(24)
1.16V x R1
R2 =
(VUVL - 1.16V)
(25)
- Choose the upper and lower OVLO threshold (VOVH) and (VOVL).
R3 =
VOV(HYS)
VOVH - VOVL
=
23 PA
23 PA
(26)
1.16V x R3
R4 =
(VOVH - 1.16V)
(27)
As an example, assume the application requires the following thresholds: VUVH = 8V, VUVL = 7V, VOVH = 15.5V,
and VOVL = 14V. Therefore VUV(HYS) = 1V and VOV(HYS) = 1.5V. The resistor values are:
R1 = 43.5 kΩ, R2 = 8.64 kΩ
R3 = 65.2 kΩ, R4 = 5.27 kΩ
When the R1-R4 resistor values are known, the threshold voltages and hysteresis are calculated from the
following:
VUVH = 1.16V + [R1 x (1.16V + 23 PA)]
R2
VUVL =
(28)
1.16V x (R1 + R2)
R2
(29)
(30)
VUV(HYS) = R1 x 23 µA
VOVH =
1.16V x (R3 + R4)
R4
(31)
VOVL = 1.16V + [R3 x (1.16V - 23 PA)]
R4
(32)
(33)
VOV(HYS) = R3 x 23 µA
Option C: The minimum UVLO level is obtained by connecting the UVLO/EN pin to VIN as shown in Figure 43.
Q1 is switched on when the VIN voltage reaches the POR threshold (≊2.6V). The OVLO thresholds are set using
R3, R4. Their values are calculated using the procedure in Option B.
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VSYS
VIN
23 A
10k
UVLO/EN
1.16V
R3
1.16V
TIMER AND
GATE
LOGIC CONTROL
OVLO
R4
GND
23 A
LM25066I/A
Figure 43. UVLO = POR
Option D: The OVLO function can be disabled by grounding the OVLO pin. The UVLO thresholds are set as
described in Option B or Option C.
POWER GOOD
When the voltage at the FB pin increases above its threshold, the internal pulldown acting on the PGD pin is
disabled allowing PGD to rise to VPGD through the pullup resistor, RPG, as shown in Figure 45. The pullup voltage
(VPGD) can be as high as 17V, and can be higher or lower than the voltages at VIN and OUT. VDD is a
convenient choice for VPGD as it allows interface to low voltage logic and avoids glitching on PGD during powerup. If a delay is required at PGD, suggested circuits are shown in Figure 46 In Figure 46A, capacitor CPG adds
delay to the rising edge, but not to the falling edge. In Figure 46B, the rising edge is delayed by RPG1 + RPG2 and
CPG, while the falling edge is delayed a lesser amount by RPG2 and CPG. Adding a diode across RPG2
(Figure 46C) allows for equal delays at the two edges, or a short delay at the rising edge and a long delay at the
falling edge.
Setting the output threshold for the PGD pin requires two resistors (R4, R5) as shown in Figure 44. While
monitoring the output voltage is shown in Figure 44. R4 can be connected to any other voltage which requires
monitoring.
The resistor values are calculated as follows:
Choose the upper and lower threshold (VPGDH) and (VPGDL) at VOUT.
R4 =
VPGDH - VPGDL VPGD(HYS)
=
24 PA
24 PA
R5 =
1.167V x R4
(VPGDH - 1.167V)
(34)
As an example, assume the application requires the following thresholds: VPGDH = 10.14V, and VPGDL = 9.9V.
Therefore VPGD(HYS) = 0.24V. The resistor values are:
R4 = 10 kΩ, R5 = 1.3 kΩ
Where the R4 and R5 resistor values are known, the threshold voltages and hysteresis are calculated from the
following:
VPGDH =
1.167V x (R4 + R5)
R5
VPGDL = 1.167V + [R4 x (1.167V + 24 PA)]
R5
VPGD(HYS) = R4 x 24 PA
(35)
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Q1
VOUT
GATE
LM25066I/A
OUT
R4
1.167V
FB
R5
24uA
PGD
from UVLO
from OVLO
GND
Figure 44. Programming the PGD Threshold
VPGD
LM25066I/A
RPG
Power Good
GND
Figure 45. Power Good Output
VPGD
LM25066I/A
VPGD
RPG1
LM25066I/A
PGD
VPGD
PGD
Power
Good
LM25066I/A
RPG1
RPG2
PGD
Power
Good
RPG2
CPG
CPG
GND
B) Long Delay at Rising Edge,
Short Delay at Falling Edge
Power
Good
CPG
GND
A) Delay at Rising Edge Only
RPG1
GND
C) Short Delay at Rising Edge and
Long Delay at Falling Edge or
Equal Delays
Figure 46. Adding Delay to the Power Good Output Pin
SYSTEM CONSIDERATIONS
A) Continued proper operation of the LM25066I/A hot-swap circuit normally dictates that capacitance be present
on the supply side of the connector into which the hot-swap circuit is plugged in, as depicted in Figure 47. The
capacitor in the “LIVE POWER SOURCE” section is necessary to absorb the transient generated whenever the
hot-swap circuit shuts off the load current. If the capacitance is not present, parasitic inductance of the supply
lines will generate a voltage transient at shut-off which may exceed the absolute maximum rating of the
LM25066I/A, resulting in its destruction. A TVS device with appropriate voltage and power ratings can also be
connected from VIN to GND to clamp the voltage spike (see application note AN-2100 SNVA464).
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B) If the load powered by the LM25066I/A hot-swap circuit has inductive characteristics, a Schottky diode is
required across the LM25066I/A’s output along with some load capacitance. The capacitance and diode are
necessary to limit the negative excursion at the OUT pin when the load current is shut off. If the OUT pin
transitions more than 0.3V negative, the LM25066I/A will internally reset, erasing the volatile setting for retries
and warning thresholds. See Figure 47. To alleviate this, a small gate resistance (e.g. 10Ω) can be used. This
resistor has the added benefit of damping any high frequency gate voltage oscillations, particularly in paralleled
FET arrangements.
RS
VSYS
Q1
VOUT
+12V
LIVE
POWER
SOURCE
TVS
D1
VIN
SENSE GATE OUT
Schottky
D2
CL
Inductive
Load
LM25066I/A
GND
GND
PLUG-IN BOARD
Figure 47. Output Diode Required for Inductive Loads
PC BOARD GUIDELINES
The following guidelines should be followed when designing the PC board for the LM25066I/A:
• Place the LM25066I/A close to the board’s input connector to minimize trace inductance from the connector
to the MOSFET.
• Place a small capacitor, CIN (1nF), directly adjacent to the VIN and GND pins of the LM25066I/A to help
minimize transients which may occur on the input supply line. Transients of several volts can easily occur
when the load current is shut off. ASIDE: note that if the current drawn by such capacitor is deemed
unacceptable, input voltage spike transients can be appropriately miniminzed by proper placement of a TVS
device and operation without this CIN capacitor becomes feasible.
• Place a 1 µF capacitor as close as possible to VREF pin.
• Place a 1 µF capacitor as close as possible to VDD pin.
• The sense resistor (RS) should be placed close to the LM25066I/A. In particular, the trace to the VIN pin
should be made as low resistance as practical to ensure maximum current and power measurement
accuracy. Connect RS using the Kelvin techniques shown in Figure 37.
• The high current path from the board’s input to the load (via Q1) and the return path should be parallel and
close to each other to minimize parasitic loop inductance.
• The ground connections for the various components around the LM25066I/A should be connected directly to
each other and to the LM25066I/A’s GND pin and then connected to the system ground at one point. Do not
connect the various component grounds to each other through the high current ground line. For more details,
see application note AN-2100 SNVA464.
• Provide adequate heat sinking for the series pass device (Q1) to help reduce stresses during turn-on and
turn-off.
• Keep the gate trace from the LM25066I/A to the pass MOSFET short and direct.
• The board’s edge connector can be designed such that the LM25066I/A detects via the UVLO/EN pin that the
board is being removed and responds by turning off the load before the supply voltage is disconnected. For
example, in Figure 48, the voltage at the UVLO/EN pin goes to ground before VSYS is removed from the
LM25066I/A because of the shorter edge connector pin. When the board is inserted into the edge connector,
the system voltage is applied to the LM25066I/A’s VIN pin before the UVLO voltage is taken high, thereby
allowing the LM25066I/A to turn on the output in a controlled fashion.
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GND
VSYS
To
Load
RS
Q1
R1
GATE
SENSE
VIN
UVLO
OVLO
GND
SDA
R2
R3
ADD2
ADD1
ADD0
VDD
CL
CB
FB
SCL
OUT
SMBA
PGD
VREF LM25066I/A PWR
DIODE
TIMER
RETRY
VAUX
PLUG-IN CARD
CARD EDGE
CONNECTOR
Figure 48. Recommended Board Connector Design
PMBus™ Command Support
The device features an SMBus interface that allows the use of PMBus™ commands to set warn levels, error
masks, and get telemetry on VIN, VOUT, IIN, VAUX, and PIN. The supported PMBus™ commands are shown in
Table 1.
Table 1. Supported PMBus™ Commands
Code
Name
Function
R/W
Number
Of Data
Bytes
Default
Value
80h
01h
OPERATION
Retrieves or stores the operation status.
R/W
1
03h
CLEAR_FAULTS
Clears the status registers and re-arms the black box registers
for updating.
Send
Byte
0
19h
CAPABILITY
Retrieves the device capability.
R
1
B0h
43h
VOUT_UV_WARN_LIMIT
Retrieves or stores output under-voltage warn limit threshold.
R/W
2
0000h
4Fh
OT_FAULT_LIMIT
Retrieves or stores over-temperature fault limit threshold.
R/W
2
0FFFh
(256°C)
51h
OT_WARN_LIMIT
Retrieves or stores over-temperature warn limit threshold.
R/W
2
0FFFh
(256°C)
57h
VIN_OV_WARN_LIMIT
Retrieves or stores input over-voltage warn limit threshold.
R/W
2
0FFFh
58h
VIN_UV_WARN_LIMIT
Retrieves or stores input under-voltage warn limit threshold.
R/W
2
0000h
5Dh
IIN_OC_WARN_LIMIT
Retrieves or stores input current warn limit threshold (mirror at
D3h)
R/W
2
0FFFh
78h
STATUS_BYTE
Retrieves information about the part operating status.
R
1
01h
79h
STATUS_WORD
Retrieves information about the part operating status.
R
2
0801h
7Ah
STATUS_VOUT
Retrieves information about output voltage status.
R
1
00h
7Ch
STATUS_INPUT
Retrieves information about input status.
R
1
10h
7Dh
STATUS_TEMPERATURE
Retrieves information about temperature status.
R
1
00h
7Eh
STATUS_CML
Retrieves information about communications status.
R
1
00h
7Fh
STATUS_OTHER
Retrieves other status information
R
1
00h
80h
STATUS_MFR_SPECIFIC
Retrieves information about circuit breaker and MOSFET
shorted status.
R
1
10h
86h
READ_EIN
Retrieves energy meter measurement.
R
6
00h 00h
00h 00h
00h 00h
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Table 1. Supported PMBus™ Commands (continued)
Function
R/W
Number
Of Data
Bytes
Default
Value
READ_VIN
Retrieves input voltage measurement.
R
2
0000h
READ_IIN
Retrieves input current measurement (Mirror at D1h).
R
2
0000h
Code
Name
88h
89h
32
8Bh
READ_VOUT
Retrieves output voltage measurement.
R
2
0000h
8Dh
READ_TEMPERATURE_1
Retrieves temperature measurement.
R
2
0000h
97h
READ _PIN
Retrieves averaged input power measurement (mirror at DFh).
R
2
0000h
98h
PMBUS_Revision
Retrieves PMBus Revision
R
1
22h
99h
MFR_ID
Retrieves manufacturer ID in ASCII characters (TI).
R
2
54h
49h
9Ah
MFR_MODEL
Retrieves Part number in ASCII characters. (LM25066I).
R
8
4Ch
4Dh
32h
35h
30h
36h
36h
49h
9Bh
MFR_REVISION
Retrieves part revision letter/number in ASCII (e.g. AA).
R
2
41h A
41h A
D0h
MFR_SPECIFIC_00
READ_VAUX
Retrieves auxiliary voltage measurement.
R
2
0000h
D1h
MFR_SPECIFIC_01
MFR_READ_IIN
Retrieves input current measurement. (Mirror at 89h)
R
2
0000h
D2h
MFR_SPECIFIC_02
MFR_READ_PIN
Retrieves input power measurement.
R
2
0000h
D3h
MFR_SPECIFIC_03
MFR_IIN_OC_WARN_LIMIT
Retrieves or stores input current limit warn threshold. (Mirror at
5Dh)
R/W
2
0FFFh
D4h
MFR_SPECIFIC_04
MFR_PIN_OP_WARN_LIMIT
Retrieves or stores input power limit warn threshold.
R/W
2
0FFFh
D5h
MFR_SPECIFIC_05
READ_PIN_PEAK
Retrieves measured maximum input power measurement.
R
2
0000h
D6h
MFR_SPECIFIC_06
CLEAR_PIN_PEAK
Resets the contents of the peak input power register to zero.
Send
Byte
0
D7h
MFR_SPECIFIC_07
GATE_MASK
Disables external MOSFET gate control for FAULTs.
R/W
1
0000h
D8h
MFR_SPECIFIC_08
ALERT_MASK
Retrieves or stores user user fault mask.
R/W
2
FD04h
D9h
MFR_SPECIFIC_09
DEVICE_SETUP
Retrieves or stores information about number of retry attempts.
R/W
1
0000h
DAh
MFR_SPECIFIC_10
BLOCK_READ
Retrieves most recent diagnostic and telemetry information in a
single transaction.
R
12
0460h
0000h
0000h
0000h
0000h
0000h
DBh
MFR_SPECIFIC_11
SAMPLES_FOR_AVG
2^n number of samples to be averaged, range = 00h to 0Ch .
R/W
1
08h
DCh
MFR_SPECIFIC_12
READ_AVG_VIN
Retrieves averaged input voltage measurement.
R
2
0000h
DDh
MFR_SPECIFIC_13
READ_AVG_VOUT
Retrieves averaged output voltage measurement.
R
2
0000h
DEh
MFR_SPECIFIC_14
READ_AVG_IIN
Retrieves averaged input current measurement.
R
2
0000h
DFh
MFR_SPECIFIC_15
READ_AVG_PIN
Retrieves averaged input power measurement. (Mirror at 97h)
R
2
0000h
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Table 1. Supported PMBus™ Commands (continued)
Code
Name
Function
R/W
Number
Of Data
Bytes
E0h
MFR_SPECIFIC_16
BLACK_BOX_READ
Captures diagnostic and telemetry information which are
latched when the first SMBA alert occurs after faults have been
cleared.
R
12
0000h
0000h
0000h
0000h
0000h
0000h
MFR_SPECIFIC_17
Manufacturer-specific parallel of the STATUS_WORD to convey
READ_DIAGNOSTIC_WORD
all FAULT/WARN data in a single transaction.
R
2
0880h
R
12
0880h
0000h
0000h
0000h
0000h
0000h
E1h
E2h
MFR_SPECIFIC_18
AVG_BLOCK_READ
Retrieves most recent average telemetry and diagnostic
information in a single transaction.
Default
Value
Standard PMBus™ Commands
OPERATION (01h)
The OPERATION command is a standard PMBus™ command that controls the MOSFET switch. This command
may be used to switch the MOSFET ON and OFF under host control. It is also used to re-enable the MOSFET
after a fault triggered shutdown. Writing an OFF command followed by an ON command will clear all faults.
Writing only an ON command after a fault triggered shutdown will not clear the fault registers. The OPERATION
command is issued with the write byte protocol.
Table 2. Recognized OPERATION Command Values
Value
Meaning
Default
80h
Switch ON
80h
00h
Switch OFF
n/a
CLEAR_FAULTS (03h)
The CLEAR_FAULTS command is a standard PMBus™ command that resets all stored warning and fault flags
and the SMBA signal. If a fault or warning condition still exists when the CLEAR_FAULTS command is issued,
the SMBA signal may not clear or will re-assert almost immediately. Issuing a CLEAR_FAULTS command will
not cause the MOSFET to switch back on in the event of a fault turn-off: that must be done by issuing an
OPERATION command after the fault condition is cleared. This command uses the PMBus™ send byte protocol.
CAPABILITY (19h)
The CAPABILITY command is a standard PMBus™ command that returns information about the PMBus™
functions supported by the LM25066I/A. This command is read with the PMBus™ read byte protocol.
Table 3. CAPABILITY Register
Value
Meaning
Default
B0h
Supports Packet Error Check, 400Kbits/sec, Supports SMBus Alert
B0h
VOUT_UV_WARN_LIMIT (43h)
The VOUT_UV_WARN_LIMIT command is a standard PMBus™ command that allows configuring or reading the
threshold for the VOUT Under-voltage Warning detection. Reading and writing to this register should use the
coefficients shown in Table 44. Accesses to this command should use the PMBus™ read or write word protocol.
If the measured value of VOUT falls below the value in this register, VOUT UV Warn Limit flags are set in the
respective registers, and the SMBA signal is asserted.
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Table 4. VOUT_UV_WARN_LIMIT Register
Value
Meaning
Default
1h – 0FFFh
VOUT Under-voltage Warning detection threshold
0000h (disabled)
0000h
VOUT Under-voltage Warning disabled
n/a
OT_FAULT_LIMIT (4Fh)
The OT_FAULT_LIMIT is a standard PMBus™ command that allows configuring or reading the threshold for the
Overtemperature Fault detection. Reading and writing to this register should use the coefficients shown in
Table 44. Accesses to this command should use the PMBus™ read or write word protocol. If the measured
temperature exceeds this value, an overtemperature fault is triggered, the MOSFET is switched off, OT Fault
flags are set in the respective registers, and the SMBA signal is asserted. After the measured temperature falls
below the value in this register, the MOSFET may be switched back on with the OPERATION command. A
single temperature measurement is an average of 16 milliseconds of data. Therefore, the temperature fault
detection time maybe up to 16 ms.
Table 5. OT_FAULT_LIMIT Register
Value
Meaning
Default
0h – 0FFFh
Overtemperature Fault Threshold Value
0FFFh (256°C)
0FFFh
Overtemperature Fault detection disabled
n/a
OT_WARN_LIMIT (51h)
The OT_WARN_LIMIT is a standard PMBus™ command that allows configuring or reading the threshold for the
Overtemperature Warning detection. Reading and writing to this register should use the coefficients shown in
Table 44. Accesses to this command should use the PMBus™ read or write word protocol. If the measured
temperature exceeds this value, an overtemperature warning is triggered, the OT Warn flags are set in the
respective registers, and the SMBA signal is asserted. A single temperature measurement is an average of 16
milliseconds of data. Therefore, the temperature warn detection time maybe up to 16 ms.
Table 6. OT_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFFh
Overtemperature Warn Threshold Value
0FFFh (256°C)
0FFFh
Overtemperature Warn detection disabled
n/a
VIN_OV_WARN_LIMIT (57h)
The VIN_OV_WARN_LIMIT is a standard PMBus™ command that allows configuring or reading the threshold for
the VIN Over-voltage Warning detection. Reading and writing to this register should use the coefficients shown in
Table 44. Accesses to this command should use the PMBus™ read or write word protocol. If the measured value
of VIN rises above the value in this register, VIN OV Warn flags are set in the respective registers, and the
SMBA signal is asserted.
Table 7. VIN_OV_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFFh
VIN Over-voltage Warning detection threshold
0FFFh (disabled)
0FFFh
VIN Over-voltage Warning disabled
n/a
VIN_UV_WARN_LIMIT (58h)
The VIN_UV_WARN_LIMIT is a standard PMBus™ command that allows configuring or reading the threshold for
the VIN Under-voltage Warning detection. Reading and writing to this register should use the coefficients shown
in Table 44. Accesses to this command should use the PMBus™ read or write word protocol. If the measured
value of VIN falls below the value in this register, VIN UV Warn flags are set in the respective registers, and the
SMBA signal is asserted.
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Table 8. VIN_UV_WARN_LIMIT Register
Value
Meaning
Default
1h – 0FFFh
VIN Under-voltage Warning detection
threshold
0000h (disabled)
0000h
VIN Under-voltage Warning disabled
n/a
IIN_OC_WARN_LIMIT (5Dh)
The IIN_OC_WARN_LIMIT command is a standard PMBus command that allows configuring or reading the
threshold for the input current, over current warning. For access to this command use the PMBus Read or Write
word protocol. The coefficients show in table 43. To read data use the SMBus Read Word protocol. To write data
use the SMBus Write Word protocol. Sets the input current threshold above which a warning will be generated.
(Mirror at D3h)
STATUS_BYTE (78h)
The STATUS_BYTE command is a standard PMBus™ command that returns the value of a number of flags
indicating the state of the LM25066I/A. Accesses to this command should use the PMBus™ read byte protocol.
To clear bits in this register, the underlying fault should be removed and a CLEAR_FAULTS command issued.
Table 9. STATUS_BYTE Definitions
Bit
NAME
Meaning
Default
7
BUSY
Not Supported, always 0
0
6
OFF
This bit is asserted if the MOSFET is not switched on for any reason.
0
5
VOUT OV
Not Supported, always 0
0
4
IOUT OC
OC Fault or OP Fault
0
3
VIN UV FAULT
A VIN Under-voltage Fault has occurred
0
2
TEMPERATURE
A Temperature Fault or Warning has occurred
0
1
CML
A Communication Fault has occurred
0
0
None of the Above
A fault or warning not listed in bits [7:1] has occurred
1
STATUS_WORD (79h)
The STATUS_WORD command is a standard PMBus™ command that returns the value of a number of flags
indicating the state of the LM25066I/A. Accesses to this command should use the PMBus™ read word protocol.
To clear bits in this register, the underlying fault should be removed and a CLEAR_FAULTS command issued.
The INPUT and VIN UV FAULT flags will default to 1 on startup. However, they will be cleared to 0 after the first
time the input voltage exceeds the resistor programmed UVLO threshold.
Table 10. STATUS_WORD Definitions
Bit
NAME
Meaning
Default
15
VOUT
An output voltage fault or warning has occurred
0
14
IOUT/POUT
Not Supported, always 0
0
13
INPUT
An input voltage or current fault has occurred
0
12
FET Fail
FET Fail
0
11
POWER GOOD
The Power Good signal has been negated
1
10
FANS
Not Supported, always 0
0
9
CB Fault
Circuit Breaker Fault has occurred
0
8
UNKNOWN
Not Supported, always 0
0
7
BUSY
Not Supported, always 0
0
6
OFF
This bit is asserted if the MOSFET is not switched on for any reason.
0
5
VOUT OV
Not Supported, always 0
0
4
IOUT OC/OP
IIN overcurrent fault or FET dissapation fault
0
3
VIN UV FAULT
A VIN Under-voltage Fault has occurred
0
2
TEMPERATURE
A Temperature Fault or Warning has occurred
0
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Table 10. STATUS_WORD Definitions (continued)
Bit
NAME
Meaning
Default
1
CML
A Communication Fault has occurred
0
0
None of the Above
A fault or warning not listed in bits [7:1] has occurred
1
STATUS_VOUT (7Ah)
The STATUS_VOUT command is a standard PMBus™ command that returns the value of the VOUT UV Warning
flag. Accesses to this command should use the PMBus™ read byte protocol. To clear bits in this register, the
underlying fault should be removed and a CLEAR_FAULTS command issued.
Table 11. STATUS_VOUT Definitions
Bit
NAME
Meaning
Default
7
VOUT OV Fault
Not Supported, always 0
0
6
VOUT OV Warn
Not Supported, always 0
0
5
VOUT UV Warn
A VOUT Under-voltage Warning has occurred
0
4
VOUT UV Fault
Not Supported, always 0
0
3
VOUT Max
Not Supported, always 0
0
2
TON Max Fault
Not Supported, always 0
0
1
TOFF Max Fault
Not Supported, always 0
0
0
VOUT Tracking Error
Not Supported, always 0
0
STATUS_INPUT (7Ch)
The STATUS_INPUT command is a standard PMBus™ command that returns the value of a number of flags
related to input voltage, current, and power. Accesses to this command should use the PMBus™ read byte
protocol. To clear bits in this register, the underlying fault should be removed and a CLEAR_FAULTS command
issued. The VIN UV Warn flag will default to 1 on startup. However, it will be cleared to 0 after the first time the
input voltage exceeds the resistor programmed UVLO threshold.
Table 12. STATUS_INPUT Definitions
Bit
NAME
Meaning
Default
7
VIN OV Fault
A VIN Over-voltage Fault has occurred
0
6
VIN OV Warn
A VIN Over-voltage Warning has occurred
0
5
VIN UV Warn
A VIN Under-voltage Warning has occurred
1
4
VIN UV Fault
A VIN Under-voltage Fault has occurred
0
3
Insufficient Voltage
Not Supported, always 0
0
2
IIN OC Fault
An IIN Over-current Fault has occurred
0
1
IIN OC Warn
An IIN Over-current Warning has occurred
0
0
PIN OP Warn
A PIN Over-power Warning has occurred
0
STATUS_TEMPERATURE (7Dh)
The STATUS_TEMPERATURE is a standard PMBus™ command that returns the value of the of a number of
flags related to the temperature telemetry value. Accesses to this command should use the PMBus™ read byte
protocol. To clear bits in this register, the underlying fault should be removed and a CLEAR_FAULTS command
issued.
Table 13. STATUS_TEMPERATURE Definitions
36
Bit
NAME
Meaning
Default
7
Overtemp Fault
An Overtemperature Fault has occurred
0
6
Overtemp Warn
An Overtemperature Warning has occurred
0
5
Undertemp Warn
Not Supported, always 0
0
4
Undertemp Fault
Not Supported, always 0
0
3
reserved
Not Supported, always 0
0
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Table 13. STATUS_TEMPERATURE Definitions (continued)
Bit
NAME
Meaning
Default
2
reserved
Not Supported, always 0
0
1
reserved
Not Supported, always 0
0
0
reserved
Not Supported, always 0
0
STATUS_CML (7Eh)
The STATUS_CML command is a standard PMBus™ command that returns the value of a number of flags
related to communication faults. Accesses to this command should use the PMBus™ read byte protocol. To clear
bits in this register, a CLEAR_FAULTS command should be issued.
Table 14. STATUS_CML Definitions
Bit
NAME
Default
7
Invalid or unsupported command received
0
6
Invalid or unsupported data received
0
5
Packet Error Check failed
0
4
Memory Fault Detected Not supported, always 0
0
3
Processor Fault Detected Not supported, always 0
0
2
Reserved, always 0
0
1
Miscellaneous communications fault has occurred
0
0
Other memory or logic fault detected Not supported, always 0
0
STATUS_OTHER (7Fh)
Bit
NAME
Default
7
Reserved: always 0
0
6
Reserved: always 0
0
5
CB Fault
0
4
Not supported: Always 0
0
3
Not supported: Always 0
0
2
Not supported: Always 0
0
1
Not supported: Always 0
0
0
Not supported: Always 0
0
STATUS_MFR_SPECIFIC (80h)
The STATUS_MFR_SPECIFIC command is a standard PMBus™ command that contains manufacturer specific
status information. Accesses to this command should use the PMBus™ read byte protocol. To clear bits in this
register, the underlying fault should be removed and a CLEAR_FAULTS command should be issued. The default
loaded status does not create an SMB Alert State.
Table 15. STATUS_MFR_SPECIFIC Definitions
(1)
Bit
Meaning
Default
7
Circuit breaker fault
0
6
Ext. MOSFET shorted fault
0
5
Not Supported, Always 0
0
4
Defaults loaded (1)
1
3
Not supported: Always 0
0
2
Not supported: Always 0
0
1
Not supported: Always 0
0
0
Not supported: Always 0
0
Bit 4, Defaults loaded, does not set an SMBAlert.
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READ_EIN (86h)
The READ_EIN command is a standard PMBus command that returns information the host can use to calculate
average input power consumption. Accesses to this command should use the PMBus Block Read protocol.
Information provided by this command is independent of any device specific averaging period. Six bytes of data
are returned by this command. The first two bytes are the two's complement, signed output of an accumulator
that continuously sums samples of the instantaneous input power. These two data bytes are formatted in the
DIRECT format. The third data byte is a count of the rollover events for the accumulator. This byte is an
unsigned integer indicating the number of times that the accumulator has rolled over from it's maximum positive
value (7FFFh) to zero. The last three data bytes are a 24 bit unsigned integer that counts the number of samples
of the instantaneous input power that have been applied to the accumulator.
The combination of the accumulator and the rollover count may overflow within a few seconds. It is left to the
host software to detect this overflow and handle it appropriately. Similarly, the sample count value will overflow,
but this event only occurs once every few hours.
To convert the data obtained with the READ_EIN command to average power, first convert the accumulator and
rollover count to an unsigned integer:
Accumulator_23 = (rollover_count << 15) + accumulator
overflow detection and handling should be done on the 23 bits of accumulator data and the sample count now.
Data from the previous calculation should be saved and will be used in this calculation to get the unscaled
average power:
Accumulator_23 [n] - A ccumulator_23 [n-1]
Sample_count [n] - Sample_count [n-1]
(36)
Where:
accumulator_23 [n] = overflow corrected, 23 bit accumulator data from this read
Sample_count [n] = Sample count data from this read
accumulator_23[n-1]= overflow corrected, 23 bit accumulator data from previous read
Sample_count [n-1] = Sample Count data from previous read
unscaled Average Power is now in the same units as the data from the READ_PIN command. Coefficients from
Table 43 are used to convert the Unscaled Average Power to Watts.
Table 16. READ_EIN
Bit
Meaning
Default
0
Sample Count High byte
0
1
Sample Count Mid byte
0
2
Sample Count Low byte
0
3
Power Accumulator Rollover Count
0
4
Power Accumulator High Byte
0
5
Power Accumulator Low Byte
0
6
Number of Bytes
6
READ_VIN (88h)
The READ_VIN command is a standard PMBus™ command that returns the 12-bit measured value of the input
voltage. Reading this register should use the coefficients shown in Table 44. Accesses to this command should
use the PMBus™ read word protocol. This value is also used internally for the VIN Over and Under Voltage
Warning detection.
Table 17. READ_VIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for VIN
0000h
38
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READ_VOUT (8Bh)
The READ_VOUT command is a standard PMBus™ command that returns the 12-bit measured value of the
output voltage. Reading this register should use the coefficients shown in Table 44. Accesses to this command
should use the PMBus™ read word protocol. This value is also used internally for the VOUT Under Voltage
Warning detection.
Table 18. READ_VOUT Register
Value
Meaning
Default
0h – 0FFFh
Measured value for VOUT
0000h
READ_IIN (89h)
The READ_IIN command is a standard PMBus™ command that returns the 12-bit measured value of the input
current. Returns instantaneous current. Reading this register should use the coefficients shown in Table 44.
Accesses to this command should use the PMBus™ read word protocol. This value is also mirrored at (D1H)
Table 19. READ_IIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for IIN
0000h
READ_PIN (97h)
The READ_IIN command is a standard PMBus™ command that returns the 12-bit measured value of the input
current. Returns average power Reading this register should use the coefficients shown in Table 44. Accesses to
this command should use the PMBus™ read word protocol. This value is also mirrored at (DFh)
Table 20. READ_PIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for PIN
0000h
READ_TEMPERATURE_1 (8Dh)
The READ_TEMPERATURE _1 command is a standard PMBus™ command that returns the signed value of the
temperature measured by the external temperature sense diode. Reading this register should use the coefficients
shown in Table 44. Accesses to this command should use the PMBus™ read word protocol. This value is also
used internally for the Over Temperature Fault and Warning detection. This data has a range of -256°C to +
255°C after the coefficients are applied.
Table 21. READ_TEMPERATURE_1 Register
Value
Meaning
Default
0h – 0FFFh
Measured value for TEMPERATURE
0000h
MFR_ID (99h)
The MFR_ID command is a standard PMBus™ command that returns the identification of the manufacturer. To
read the MFR_ID, use the PMBus™ block read protocol.
Table 22. MFR_ID Register
Byte
Name
0
Number of bytes
02h
1
MFR ID-1
54h ‘T’
2
MFR ID-2
49h ‘I’
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MFR_MODEL (9Ah)
The MFR_MODEL command is a standard PMBus™ command that returns the part number of the chip. To read
the MFR_MODEL, use the PMBus™ block read protocol.
Table 23. MFR_MODEL Register
Byte
Name
0
Number of bytes
Value
08h
1
MFR ID-1
4Ch ‘L’
2
MFR ID-2
4Dh ‘M’
3
MFR ID-3
32h ‘2’
4
MFR ID-4
35h ‘5’
5
MFR ID-5
30h ‘0’
6
MFR ID-6
36h ‘6’
7
MFR ID-7
36h ‘6’
8
MFR ID-8
49h ‘I’
MFR_REVISION (9Bh)
The MFR_REVISION command is a standard PMBus™ command that returns the revision level of the part. To
read the MFR_REVISION, use the PMBus™ block read protocol.
Table 24. MFR_REVISION Register
Byte
Name
Value
0
Number of bytes
02h
1
MFR ID-1
41h ‘A’
2
MFR ID-2
41h ‘A’
Manufacturer Specific PMBus™ Commands
MFR_SPECIFIC_00: READ_VAUX (D0h)
The READ_VAUX command will report the 12-bit ADC measured auxiliary voltage. Voltages greater than or
equal to 1.16V to ground will be reported at plus full scale (0FFFh). Voltages less than or equal to 0V referenced
to ground will be reported as 0 (0000h). Coefficients for the VAUX value are dependent on the value of the
external divider (if used). To read data from the READ_VAUX command, use the PMBus™ Read Word protocol.
Table 25. READ_VAUX Register
Value
Meaning
Default
0h – 0FFFh
Measured value for VAUX input
0000h
MFR_SPECIFIC_01: MFR_READ_IIN (D1h)
The MFR_READ_IIN command will report the 12-bit ADC measured current sense voltage. To read data from
the MFR_READ_IIN command, use the PMBus™ Read Word protocol. Reading this register should use the
coefficients shown in Table 44. Please see the section on coefficient calculations to calculate the values to use.
Table 26. MFR_READ_IIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for input current sense voltage
0000h
40
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MFR_SPECIFIC_02: MFR_READ_PIN (D2h)
The MFR_ READ_PIN command will report the upper 12 bits of the VIN x IIN product as measured by the 12-bit
ADC. To read data from the MFR_READ_PIN command, use the PMBus™ Read Word protocol. Reading this
register should use the coefficients shown in Table 44. Please see the section on coefficient calculations to
calculate the values to use.
Table 27. MFR_READ_PIN Register
Value
Meaning
Default
0h – 0FFFh
Value for input current x input voltage
0000h
MFR_SPECIFIC_03: MFR_IN_OC_WARN_LIMIT (D3h)
The MFR_IIN_OC_ WARN_LIMIT PMBus™ command sets the input over-current warning threshold. In the event
that the input current rises above the value set in this register, the IIN over-current flags are set in the status
registers and the SMBA is asserted. To access the MFR_IIN_ OC_WARN_LIMIT register, use the PMBus™
Read/Write Word protocol. Reading/writing to this register should use the coefficients shown in Table 44.
Table 28. MFR_IIN_OC_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFFh
Value for input over-current warn limit
0FFFh
0FFFh
Input over-current warning disabled
n/a
MFR_SPECIFIC_04: MFR_PIN_OP_WARN_LIMIT (D4h)
The MFR_PIN_OP_WARN_LIMIT PMBus™ command sets the input over-power warning threshold. In the event
that the input power rises above the value set in this register, the PIN Over-power flags are set in the status
registers and the SMBA is asserted. To access the MFR_PIN_OP_WARN_LIMIT register, use the PMBus™
Read/Write Word protocol. Reading/writing to this register should use the coefficients shown in Table 44.
Table 29. MFR_PIN_OP_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFFh
Value for input over-power warn limit
0FFFh
0FFFh
Input over-power warning disabled
n/a
MFR_SPECIFIC_05: READ_PIN_PEAK (D5h)
The READ_PIN_PEAK command will report the maximum input power measured since a Power-On-Reset or the
last CLEAR_PIN_PEAK command. To access the READ_PIN_PEAK command, use the PMBus™ Read Word
protocol. Use the coefficients shown in Table 44.
Table 30. READ_PIN_PEAK Register
Value
Meaning
Default
0h – 0FFFh
Maximum value for input current x input voltage since reset or last clear
0h
MFR_SPECIFIC_06: CLEAR_PIN_PEAK (D6h)
The CLEAR_PIN_PEAK command will clear the PIN_PEAK register. This command uses the PMBus™ Send
Byte protocol.
MFR_SPECIFIC_07: GATE_MASK (D7h)
The GATE_MASK register allows the hardware to prevent fault conditions from switching off the MOSFET. When
the bit is high, the corresponding FAULT has no control over the MOSFET gate. All status registers will still be
updated (STATUS, DIAGNOSTIC) and an SMBA will still be issued. This register is accessed with the PMBus™
Read / Write Byte protocol.
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WARNING
Inhibiting the MOSFET switch off in response to over-current or circuit breaker
fault conditions will likely result in the destruction of the MOSFET! This
functionality should be used with great care and supervision!
Table 31. GATE_MASK Register
Bit
NAME
Default
7
Not used, always 0
0
6
Not used, always 0
0
5
VIN UV FAULT
0
4
VIN OV FAULT
0
3
IIN/PFET FAULT
0
2
OVERTEMP FAULT
0
1
Not used, always 0
0
0
CIRCUIT BREAKER FAULT
0
The IIN/PFET Fault refers to the input current fault and the MOSFET power dissipation fault. There is no input
power fault detection, only input power warning detection.
MFR_SPECIFIC_08: ALERT_MASK (D8h)
The ALERT_MASK is used to mask the SMBA when a specific fault or warning has occurred. Each bit
corresponds to one of the 14 different analog and digital faults or warnings that would normally result in an
SMBA being set. When the corresponding bit is high, that condition will not cause the SMBA to be asserted. If
that condition occurs, the registers where that condition is captured will still be updated (STATUS registers,
DIAGNOSTIC_WORD) and the external MOSFET gate control will still be active (VIN_OV_FAULT,
VIN_UV_FAULT, IIN/PFET_FAULT, CB_FAULT, OT_FAULT). This register is accessed with the PMBus™ Read
/ Write Word protocol. The VIN UNDERVOLTGE FAULT flag will default to 1 on startup. However, it will be
cleared to 0 after the first time the input voltage exceeds the resistor programmed UVLO threshold.
Table 32. ALERT_MASK Definitions
(1)
42
BIT
NAME
DEFAULT
15
VOUT UNDERVOLTAGE WARN
1
14
IIN LIMIT Warn
1
13
VIN UNDERVOLTAGE WARN
1
12
VIN OVERVOLTAGE WARN
1
11
POWER GOOD
1
10
OVERTEMP WARN
1
9
Not Used, always 0
0
8
OVERPOWER LIMIT WARN
1
7
Not Used, always 0
0
6
EXT_MOSFET_SHORTED
0
5
VIN UNDERVOLTAGE FAULT (1)
0
4
VIN OVERVOLTAGE FAULT
0
3
IIN/PFET FAULT
0
2
OVERTEMPERATURE FAULT
1
1
CML FAULT (Communications Fault)
0
0
CIRCUIT BREAKER FAULT
0
VIN_UV_FAULT initializes after power up as masked. When VIN exceeds the hardware threshold the mask bit is automatically cleared.
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MFR_SPECIFIC_09: DEVICE_SETUP (D9h)
The DEVICE_SETUP command may be used to override pin settings to define operation of the LM25066I/A
under host control. This command is accessed with the PMBus™ read / write byte protocol.
Table 33. DEVICE_SETUP Byte Format
Bit
Name
Meaning
7:5
Retry setting
111 = Unlimited retries
110 = Retry 16 times
101 = Retry 8 times
100 = Retry 4 times
011 = Retry 2 times
010 = Retry 1 time
001 = No retries
000 = Pin configured retries
4
Current limit setting
3
CB/CL Ratio
0 = Low setting (25mV)
1 = High setting (46mV)
0 = Low setting (1.8x)
1 = High setting (3.6x)
2
Current limit Configuration
0 = Use pin settings
1 = Use SMBus settings
1
Circuit Breaker Configuration
0 = Use pin settings
1 = Use SMBus settings
0
Unused
In order to configure the Current Limit Setting via this register, it is necessary to set the Current Limit
Configuration bit (2) to 1 to enable the register to control the current limit function and the Current Limit Setting
bit (4) to select the desired setting. Similarly, in order to control the Circuit Breaker via this register, it is
necessary to set the Circuit Breaker Configuration bit (1) to 1 to enable the register to control the Circuit Breaker
Setting, and the Circuit Breaker / Current Limit Ratio bit (3) to the desired value. If the respective Configuration
bits are not set, the Settings will be ignored and the pin set values used.
The Current Limit Configuration effects the coefficients used for the Current and Power measurements and
warning registers.
MFR_SPECIFIC_10: BLOCK_READ (DAh)
The BLOCK_READ command concatenates the DIAGNOSTIC_WORD with input and output telemetry
information (IIN, VOUT, VIN, PIN) as well as TEMPERATURE to capture all of the operating information of the
LM25066I/A in a single SMBus transaction. The block is 12 bytes long with telemetry information being sent out
in the same manner as if an individual READ_XXX command had been issued (shown below). The contents of
the block read register are updated every clock cycle (85ns) as long as the SMBus interface is idle.
BLOCK_READ also specifies that the VIN, VOUT, IIN and PIN measurements are all time-aligned whereas there
is a chance they may not be if read with individual PMBus™ commands.
The BLOCK_READ command is read via the PMBus™ block read protocol.
Table 34. BLOCK_READ Register Format
Byte Count (always 12)
(1 byte)
DIAGNOSTIC_WORD
(1 Word)
IIN_BLOCK
(1 Word)
VOUT_BLOCK
(1 Word)
VIN_BLOCK
(1 Word)
PIN_BLOCK
(1 Word)
TEMP_BLOCK
(1 Word)
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MFR_SPECIFIC_11: SAMPLES_FOR_AVG (DBh)
The SAMPLES_FOR_AVERAGE is a manufacturer specific command for setting the number of samples used in
computing the average values for IIN, VIN, VOUT, PIN. The decimal equivalent of the AVGN nibble is the power
of 2 samples (e.g. AVGN=12 equates to 4096 samples used in computing the average). The LM25066I/A
supports average numbers of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096. The SAMPLES_FOR_AVG
number applies to average values of IIN, VIN, VOUT, PIN simultaneously. The LM25066I/A uses simple
averaging. This is accomplished by summing consecutive results up to the number programmed, then dividing by
the number of samples. Averaging is calculated according to the following sequence:
Y = (X(N) + X(N-1) + ... + X(0)) / 2AVGN
(37)
When the averaging has reached the end of a sequence (for example, 4096 samples are averaged), then a
whole new sequence begins that will require the same number of samples (in this example, 4096) to be taken
before the new average is ready.
Table 35. SAMPLES_FOR_AVG Register
AVGN
N=2AVGN averages
Averaging/Register Update Period (ms)
0000
1
1
0001
2
2
0010
4
4
0011
8
8
0100
16
16
0101
32
32
0110
64
64
0111
128
128
1000
256
256
1001
512
512
1010
1024
1024
1011
2048
2048
1100
4096
4096
Note that a change in the SAMPLES_FOR_AVG register will not be reflected in the average telemetry
measurements until the present averaging interval has completed. The default setting for AVGN is 0000 and
therefore the average telemetry will mirror the instantaneous telemetry until a value higher than zero is
programmed.
The SAMPLES_FOR_AVG register is accessed via the PMBus™ read / write byte protocol.
Table 36. SAMPLES_FOR_AVG Register
Value
Meaning
Default
0h – 0Ch
Exponent (AVGN) for number of samples to average over
00h
MFR_SPECIFIC_12: READ_AVG_VIN (DCh)
The READ_AVG_VIN command will report the 12-bit ADC measured input average voltage. If the data is not
ready, the returned value will be the previous averaged data. However, if there is no previously averaged data,
the default value (0000h) will be returned. This data is read with the PMBus™ Read Word protocol. This register
should use the coefficients shown in Table 44.
Table 37. READ_AVG_VIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for input voltage
0000h
44
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MFR_SPECIFIC_13: READ_AVG_VOUT (DDh)
The READ_AVG_VOUT command will report the 12-bit ADC measured average output voltage. The returned
value will be the default value (0000h) or previous data when the average data is not ready. This data is read
with the PMBus™ Read Word protocol. This register should use the coefficients shown in Table 44.
Table 38. READ_AVG_VOUT Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for output voltage
0000h
MFR_SPECIFIC_14: READ_AVG_IIN (DEh)
The READ AVG_IIN command will report the 12-bit ADC measured current sense average voltage. The returned
value will be the default value (0000h) or previous data when the average data is not ready. This data is read
with the PMBus™ Read Word protocol. This register should use the coefficients shown in Table 44.
Table 39. READ_AVG_IIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for current sense voltage
0000h
MFR_SPECIFIC_15: READ_AVG_PIN (DFh)
The READ_AVG_PIN command will report the upper 12 bits of the average VIN x IIN product as measured by
the 12-bit ADC. You will read the default value (0000h) or previous data when the average data is not ready.
This data is read with the PMBus™ Read Word protocol. This register should use the coefficients shown in
Table 44.
Table 40. READ_AVG_PIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured value for input voltage x input current sense voltage
0000h
MFR_SPECIFIC_16: BLACK_BOX_READ (E0h)
The BLACK_BOX_READ command retrieves the BLOCK_READ data which was latched in at the first assertion
of SMBA. It is re-armed with the CLEAR_FAULTS command. It is the same format as the BLOCK_READ
registers, the only difference being that its contents are updated with the SMBA edge rather than the internal
clock edge. This command is read with the PMBus™ Block Read protocol.
MFR_SPECIFIC_17: READ_DIAGNOSTIC_WORD (E1h)
The READ_DIAGNOSTIC_WORD PMBus command will report all of the LM25066I/A faults and warnings in a
single read operation. The standard response to the assertion of the SMBA signal of issuing multiple read
requests to various status registers can be replaced by a single word read to the DIAGNOSTIC_WORD register.
The READ_DIAGNOSTIC_WORD command should be read with the PMBus™ Read Word protocol. The
DIAGNOSTIC_WORD is also returned in the BLOCK_READ, BLACK_BOX_READ, and AVG_BLOCK_READ
operations.
Table 41. READ_DIAGNOSTIC_WORD Format
Bit
Meaning
Default
15
VOUT_UNDERVOLTAGE_WARN
0
14
IIN_OP_WARN
0
13
VIN_UNDERVOLTAGE_WARN
0
12
VIN_OVERVOLTAGE_WARN
0
11
POWER GOOD
1
10
OVER_TEMPERATURE_WARN
0
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Table 41. READ_DIAGNOSTIC_WORD Format (continued)
Bit
Meaning
Default
9
TIMER_LATCHED_OFF
0
8
EXT_MOSFET_SHORTED
0
7
CONFIG_PRESET
1
6
DEVICE_OFF
1
5
VIN_UNDERVOLTAGE_FAULT
1
4
VIN_OVERVOLTAGE_FAULT
0
3
IIN_OC/PFET_OP_FAULT
0
2
OVER_TEMPERATURE_FAULT
0
1
CML_FAULT
0
0
CIRCUIT_BREAKER_FAULT
0
MFR_SPECIFIC_18: AVG_BLOCK_READ (E2h)
The AVG_BLOCK_READ command concatenates the DIAGNOSTIC_WORD with input and output average
telemetry information (IIN, VOUT, VIN, PIN) as well as TEMPERATURE to capture all of the operating
information of the part in a single PMBus™ transaction. The block is 12 bytes long with telemetry information
being sent out in the same manner as if an individual READ_AVG_XXX command had been issued (shown
below). AVG_BLOCK_READ also specifies that the VIN, VOUT, PIN, and IIN measurements are all time-aligned
whereas there is a chance they may not be if read with individual PMBus™ commands. To read data from the
AVG_BLOCK_READ command, use the SMBus Block Read protocol.
Table 42. AVG_BLOCK_READ Register Format
46
Byte Count (always 12)
(1 byte)
DIAGNOSTIC_WORD
(1 word)
AVG_IIN
(1 word)
AVG_VOUT
(1 word)
AVG_VIN
(1 word)
AVG_PIN
(1 word)
TEMPERATURE
(1 word)
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DIOD E
VIN
IIN
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R EAD _VAUX D 0h
PEAK-HOLD
C LEAR_PIN_PEAK D6h
READ_ PIN_ PEAK D5 h
AVERAGED
DATA
R EAD _VOU T 8Bh
CMP
CMP
CMP
CMP
CMP
CMP
CMP
CMP
CMP
PMBus Interface
WARNING
LIMITS
OT_WARNING_LIMIT 51h
VOUT_UV_WARN_ LIMIT 4 3h
PIN_OP_WAR N_LIMIT D4h
IIN _OC_WAR N_LIMIT 5Dh an d D3h
VIN _UV_WARN_L IMIT 58 h
VIN_ OV_WARN_ LIMIT 57 h
MOSFET STATUS
C IRC UIT
BREAKER
MOSFET
DISSIPATION
L IMIT
CUR RENT L IMIT
VOUT
1.16
WARNING
SYSTEM
OT_WAR NING_ LIMIT
STATUS_TEMPERATURE 7Dh
VOUT_UV WAR NIN G
STATUS_VOU T 7Ah
PIN_OP WARNING
STATUS_INPUT 7Ch
IIN _OC WARNING
STATUS_INPUT 7Ch
VIN_U V WAR NING
STATUS_ INPU T 7Ch
CMP
OT_ FAUL T_ LIMIT
4Fh
C MP
C MP
GATE MASK
1.16
VIN_OV WARNING
STATUS_INPUT 7Ch
To loa d
OT_ FAUL T_ LIMIT
STATU S_ TEMPERATURE 7Dh
STATU S_ WORD 79h
STATU S_ BYTE 78h
FAULT
SYSTEM
FET Shorted FAULT
STATUS_ MFR_ SPECIFIC 80 h
C ircuit Breaker FAU LT
STATU S_MFR _SPECIFIC 80h
IIN _OC FAULT
STATUS_ INPU T 7Ch
VIN_UV_FAULT
STATUS_INPUT 7Ch
STATUS_WORD 79h
STATUS_BYTE 7 8h
VIN_ OV_FAULT
STATUS_INPUT 7C h
www.ti.com
READ_TEMPERATU RE_1 8Dh
READ_AVG_PIN DFh
READ_ AVG_VOUT DD h
READ_PIN 97h an dDFh
SAMPLES_FOR_AVG DBh
ADC
OVLO
READ_AVG_IIN DEh
MUX
UVLO
READ_ IIN 89h an d D1h
S/H
SENSE
READ _AVG_VIN DCh
READ_EIN 86h
DATA
OUTPUT
VAUX
+
READ_VIN 88h
+12
LM25066I, LM25066IA
SNVS824C – JUNE 2012 – REVISED MARCH 2013
Figure 49. Command/Register and Alert Flow Diagram
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Reading and Writing Telemetry Data and Warning Thresholds
All measured telemetry data and user programmed warning thresholds are communicated in 12 bit two’s
compliment binary numbers read/written in 2 byte increments conforming to the Direct format as described in
section 8.3.3 of the PMBus™ Power System Management Protocol Specification 1.1 (Part II). The organization
of the bits in the telemetry or warning word is shown in Table 43, where Bit_11 is the most significant bit (MSB)
and Bit_0 is the least significant bit (LSB). The decimal equivalent of all warning and telemetry words are
constrained to be within the range of 0 to 4095, with the exception of temperature. The decimal equivalent value
of the temperature word ranges from 0 to 65535.
Table 43. Telemetry and Warning Word Format
Byte
B7
B6
B5
B4
1
Bit_7
Bit_6
Bit_5
Bit_4
2
0
0
0
0
B3
B2
B1
B0
Bit_3
Bit_2
Bit_1
Bit_0
Bit_11
Bit_10
Bit_9
Bit_8
Conversion from direct format to real world dimensions of current, voltage, power, and temperature is
accomplished by determining appropriate coefficients as described in section 7.2.1 of the PMBus™ Power
System Management Protocol Specification 1.1 (Part II). According to this specification, the host system converts
the values received into a reading of volts, amperes, watts, or other units using the following relationship:
X=
1
(Y x 10-R - b)
m
(38)
where:
X: the calculated "real world" value (volts, amps, watt, etc.)
m: the slope coefficient
Y: a two byte two's complement integer received from device
b: the offset, a two byte two's complement integer
R: the exponent, a one byte two's complement integer
R is only necessary in systems where m is required to be an integer (for example, where m may be stored in a
register in an integrated circuit). In those cases, R only needs to be large enough to yield the desired accuracy.
Table 44. Current, Power and Warning Conversion Coefficients (RS in mΩ)
Commands
Condition
Format
Number of
Data Bytes
m
b
R
Unit
READ_VIN, READ_AVG_VIN
VIN_OV_WARN_LIMIT
VIN_UV_WARN_LIMIT
DIRECT
2
22070
-1800
-2
V
READ_VOUT, READ_AVG_VOUT
VOUT_UV_WARN_LIMIT
DIRECT
2
22070
-1800
-2
V
DIRECT
2
3546
-3
0
V
READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
READ_VAUX
CL = GND
DIRECT
2
13661 x RS
-5200
-2
A
READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
CL = VDD
DIRECT
2
6854 x RS
-3100
-2
A
READ_PIN, READ_AVG_PIN,
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
CL = GND
DIRECT
2
736 x RS
-3300
-2
W
READ_PIN, READ_AVG_PIN,
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
CL = VDD
DIRECT
2
369 x RS
-1900
-2
W
DIRECT
2
16000
0
-3
°C
DIRECT
2
369 x RS
-1900
-2
W
READ_TEMPERATURE_1
OT_WARN_LIMIT
OT_FAULT_LIMIT
READ_PIN, READ_AVG_PIN,
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
48
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CL = VDD
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Table 45. Current, Power and Warning Conversion Coefficients (RS in mΩ)
Commands
Condition
Format
Number of
Data Bytes
m
b
R
Unit
*READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
CL = GND
DIRECT
2
13661 x RS
-5200
-2
A
*READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
CL = VDD
DIRECT
2
6854 x RS
-3100
-2
A
*READ_PIN, READ_AVG_PIN,
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
CL = GND
DIRECT
2
736 x RS
-3300
-2
W
Care must be taken to adjust the exponent coefficient, R, such that the value of m remains within the range of 32768 to +32767. For example, if a 5 mΩ sense resistor is used, the correct coefficients for the READ_IIN
command with CL = VDD would be m = 6830, b = -310, R = -1.
A Note on the "b" Coefficient
Since b coefficients represent offset, for simplification b is set to zero in the following discussions.
Determining Telemetry Coefficients Empirically with Linear Fit
The coefficients for telemetry measurements and warning thresholds presented in Table 44 are adequate for the
majority of applications. Current and power coefficients must be calculated per application as they are dependent
on the value of the sense resistor, RS, used. Table 45 provides the equations necessary for calculating the
current and power coefficients for the general case. The small signal nature of the current measurement make it
and the power measurement more susceptible to PCB parasitics than other telemetry channels. This may cause
slight variations in the optimum coefficients (m, b, R) for converting from Direct Format digital values to real-world
values (e.g. Amps and Watts). The optimum coefficients can be determined empirically for a specific application
and PCB layout using two or more measurements of the telemetry channel of interest. The current coefficients
can be determined using the following method:
1. While the LM25066I/A is in normal operation, measure the voltage across the sense resistor using kelvin test
points and a high accuracy DVM while controlling the load current. Record the integer value returned by the
READ_AVG_IIN command (with the SAMPLES_FOR_AVG set to a value greater than 0) for two or more
voltages across the sense resistor. For best results, the individual READ_AVG_IIN measurements should
span nearly the full scale range of the current (for example, voltage across RS of 5 mV and 20 mV).
2. Convert the measured voltages to currents by dividing them by the value of RS. For best accuracy, the value
of RS should be measured. Table 46 assumes a sense resistor value of 5 mΩ.
Table 46. Measurements for linear fit determination of current coefficients
Measured voltage across
RS (V)
Measured Current (A)
READ_AVG_IIN
(integer value)
0.005
1
648
0.01
2
1331
0.02
4
2698
3. Using the spreadsheet or math program of your choice, determine the slope and the y-intercept values
returned by the READ_AVG_IIN command versus the measured current. For the data shown in Table 46:
– READ_AVG_IIN value = slope x (Measured Current) + (y-intercept)
– slope = 683.4
– y-intercept = -35.5
4. To determine the ‘m’ coefficient, simply shift the decimal point of the calculated slope to arrive at an integer
with a suitable number of significant digits for accuracy (typically 4) while staying with the range of -32768 to
+32767. This shift in the decimal point equates to the ‘R’ coefficient. For the slope value shown above, the
decimal point would be shifted to the right once hence R = -1.
5. Once the ‘R’ coefficient has been determined, the ‘b’ coefficient is found by multiplying the y-intercept by 10R
. In this case the value of b = -355.
– Calculated Current Coefficients:
– m = 6834
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– b = -355
– R = -1
X=
1
(Y x 10-R - b)
m
(39)
where:
X: the calculated "real world" value (volts, amps, watts, temperature)
m: the slope coefficient, a the two byte two's complement integer
Y: a two byte, two's complement integer received from device
b: the offset, a two byte two's complement integer
R: the exponent, a one byte two's complement integer
The above procedure can be repeated to determine the coefficients of any telemetry channel simply by
substituting measured current for some other parameter (e.g. power, voltage, etc.).
Writing Telemetry Data
There are several locations that will require writing data if their optional usage is desired. Use the same
coefficients previously calculated for your application and apply them using this method as prescribed by the
PMBus™ revision section 7.2.2 "Sending a Value"
Y = (mX + b) x 10R
(40)
where:
X: the calculated "real world" value (volts, amps, watts, temperature)
m: the slope coefficient, a two byte two's complement integer
Y: a two byte two's complement integer received from device
b: the offset, a two byte two's complement integer
R: the exponent, a one byte two's complement integer
PMBus™ Address Lines (ADR0, ADR1, ADR2)
The three address lines are to be set high (connect to VDD), low (connect to GND),open (connect to GND) to
select one of 27 addresses for communicating with the LM25066I/A. Table 47 depicts 7-bit addresses (eighth bit
is read/write bit):
Table 47. Device Addressing
50
ADR2
ADR1
ADR0
Decoded Address
Z
Z
Z
40h
Z
Z
0
41h
Z
Z
1
42h
Z
0
Z
43h
Z
0
0
44h
Z
0
1
45h
Z
1
Z
46h
Z
1
0
47h
Z
1
1
10h
0
Z
Z
11h
0
Z
0
12h
0
Z
1
13h
0
0
Z
14h
0
0
0
15h
0
0
1
16h
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LM25066I, LM25066IA
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
Table 47. Device Addressing (continued)
ADR2
ADR1
ADR0
Decoded Address
0
1
Z
17h
0
1
0
50h
0
1
1
51h
1
Z
Z
52h
1
Z
0
53h
1
Z
1
54h
1
0
Z
55h
1
0
0
56h
1
0
1
57h
1
1
Z
58h
1
1
0
59h
1
1
1
5Ah
SMBus Communications Timing Requirements
tR
SCL
tF
tLOW
VIH
VIL
tHIGH
tHD;DAT
tHD;STA
tSU;STA
tSU;STO
tSU;DAT
SDA
VIH
VIL
tBUF
P
S
S
P
Figure 50. SMBus Timing Diagram
Table 48. SMBus Timing Definition
(1)
(2)
Symbol
Parameter
Limits
Unit
Min
Max
FSMB
SMBus Operating Frequency
10
400
TBUF
Bus free time between Stop and Start Condition
1.3
µs
THD:STA
Hold time after (Repeated) Start Condition. After this
period, the first clock is generated.
0.6
µs
TSU:STA
Repeated Start Condition setup time
0.6
µs
TSU:STO
Stop Condition setup time
0.6
µs
THD:DAT
Data hold time
300
ns
TSU:DAT
Data setup time
100
TTIMEOUT
Clock low time-out
25
TLOW
Clock low period
1.5
µs
THIGH
Clock high period
0.6
µs
Comments
kHz
ns
35
ms
(1)
(2)
Devices participating in a transfer will timeout when any clock low exceeds the value of TTIMEOUT,MIN of 25 ms. Devices that have
detected a timeout condition must reset the communication no later than TTIMEOUT,MAX of 35 ms. The maximum value must be adhered
to by both a master and a slave as it incorporates the cumulative stretch limit for both a master (10ms) and a slave (25ms).
THIGH MAX provides a simple method for devices to detect bus idle conditions.
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Table 48. SMBus Timing Definition (continued)
Symbol
Parameter
Limits
Min
(3)
(4)
(5)
Unit
Comments
Max
TLOW:SEXT
Cumulative clock low extend time (slave device)
25
ms
(3)
TLOW:MEXT
Cumulative low extend time (master device)
10
ms
(4)
TF
Clock or Data Fall Time
20
300
ns
(5)
TR
Clock or Data Rise Time
20
300
ns
(5)
TLOW:SEXT is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start to the stop. If
a slave exceeds this time, it is expected to release both its clock and data lines and reset itself.
TLOW:MEXT is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as defined from
start-to-ack, ack-to-ack, or ack-to-stop.
Rise and fall time is defined as follows:• TR = ( VILMAX – 0.15) to (VIHMIN + 0.15)• TF = 0.9 VDD to (VILMAX – 0.15)
SMBA Response
The SMBA effectively has two masks:
1. The Alert Mask Register at D8h, and
2. The ARA Automatic Mask.
The ARA Automatic Mask is a mask that is set in response to a successful ARA read. An ARA read operation
returns the PMBus™ address of the lowest addressed part on the bus that has its SMBA asserted. A successful
ARA read means that THIS part was the one that returned its address. When a part responds to the ARA read, it
releases the SMBA signal. When the last part on the bus that has an SMBA set has successfully reported its
address, the SMBA signal will de-assert.
The way that the LM25066I/A releases the SMBA signal is by setting the ARA Automatic mask bit for all fault
conditions present at the time of the ARA read. All status registers will still show the fault condition, but it will not
generate an SMBA on that fault again until the ARA Automatic mask is cleared by the host issuing a Clear Fault
command to this part. This should be done as a routine part of servicing an SMBA condition on a part, even if the
ARA read is not done. Figure 51 depicts a schematic version of this flow.
From other
fault inputs
SMBA
Fault Condition
Alert Mask D8h
From PMBus
Set
ARA Operation Flag Succeeded
CLEAR_FAULT Command Received
ARA Auto Mask
Clear
Figure 51. Typical Flow Schematic for SMBA Fault
52
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SNVS824C – JUNE 2012 – REVISED MARCH 2013
REVISION HISTORY
Changes from Revision B (March 2013) to Revision C
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 52
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PACKAGE OPTION ADDENDUM
www.ti.com
27-Jun-2016
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM25066IAPSQ/NOPB
ACTIVE
WQFN
NHZ
24
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IA
LM25066IAPSQE/NOPB
ACTIVE
WQFN
NHZ
24
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IA
LM25066IAPSQX/NOPB
ACTIVE
WQFN
NHZ
24
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IA
LM25066IPSQ/NOPB
ACTIVE
WQFN
NHZ
24
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IS
LM25066IPSQE/NOPB
ACTIVE
WQFN
NHZ
24
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IS
LM25066IPSQX/NOPB
ACTIVE
WQFN
NHZ
24
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
25066IS
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
27-Jun-2016
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
26-Mar-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
LM25066IAPSQ/NOPB
WQFN
NHZ
24
LM25066IAPSQE/NOPB
WQFN
NHZ
LM25066IAPSQX/NOPB
WQFN
NHZ
LM25066IPSQ/NOPB
WQFN
LM25066IPSQE/NOPB
LM25066IPSQX/NOPB
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1000
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
24
250
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
24
4500
330.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
NHZ
24
1000
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
WQFN
NHZ
24
250
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
WQFN
NHZ
24
4500
330.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
26-Mar-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM25066IAPSQ/NOPB
WQFN
NHZ
24
1000
213.0
191.0
55.0
LM25066IAPSQE/NOPB
WQFN
NHZ
24
250
213.0
191.0
55.0
LM25066IAPSQX/NOPB
WQFN
NHZ
24
4500
367.0
367.0
35.0
LM25066IPSQ/NOPB
WQFN
NHZ
24
1000
213.0
191.0
55.0
LM25066IPSQE/NOPB
WQFN
NHZ
24
250
213.0
191.0
55.0
LM25066IPSQX/NOPB
WQFN
NHZ
24
4500
367.0
367.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
NHZ0024B
SQA24B (Rev A)
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