LTC2974
4-Channel PMBus Power System Manager
Featuring Accurate Output Current Measurement
FEATURES
DESCRIPTION
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Sequence, Trim, Margin and Supervise Four Power
Supplies
Manage Faults, Monitor Telemetry and Create Fault Logs
PMBus™ Compliant Command Set
Supported by LTpowerPlay
®
GUI
Margin or Trim Supplies to within 0.25% of Target
Fast OV/UV Supervisors Per Channel
Fast Output Current Supervisors Per Channel
Coordinate Sequencing and Fault Management
Across Multiple LTC PSM Devices
Automatic Fault Logging to Internal EEPROM
Operate Autonomously without Additional Software
External Temperature and Input Voltage Supervisors
Accurate Monitoring of Four Output Voltages, Four
Output Currents, Four External Temperatures, Input
Voltage and Internal Die Temperature
I
2
C/SMBus Serial Interface
Can Be Powered from 3.3V, or 4.5V to 15V
Available in 64-Lead 9mm × 9mm QFN Package
APPLICATIONS
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Computers and Network Servers
Industrial Test and Measurement
High Reliability Systems
Medical Imaging
Video
The
LTC
®
2974
is a 4-channel Power System Manager used
to sequence, trim (servo), margin, supervise, manage
faults, provide telemetry and create fault logs. PMBus
commands support power supply sequencing, precision
point-of-load voltage adjustment and margining. DACs
use a proprietary soft-connect algorithm to minimize
supply disturbances. Supervisory functions include over
and under current, voltage and temperature threshold
limits for four power supply output channels as well as
over and under voltage threshold limits for a single power
supply input channel. Programmable fault responses
can disable the power supplies with optional retry after a
fault is detected. Faults that disable a power supply can
automatically trigger black box EEPROM storage of fault
status and associated telemetry. An internal 16-bit ADC
monitors four output voltages, four output currents, four
external temperatures, one input voltage and die tempera-
ture. Output power is also calculated. A programmable
watchdog timer monitors microprocessor activity for a
stalled condition and resets the microprocessor if neces-
sary. A single wire bus synchronizes power supplies across
multiple LTC Power System Management (PSM) devices.
Configuration EEPROM with ECC supports autonomous
operation without additional software.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. patents, including 7382303, 7420359 and 7940091.
TYPICAL APPLICATION
4-Channel PMBus Power System Manager
DC
IN
IN
IBC
OUT
EN
4.5V ≤ V
IBUS
≤ 15V
0.07
V
IN_SNS
AUXFAULTB
* LTC2974 MAY ALSO BE
POWERED DIRECTLY FROM
AN EXTERNAL 3.3V SUPPLY
V
PWR
*
V
DD33
*
I
SENSEM
V
SENSEP
LOAD
R20
R30
R10
I
SENSEP
V
OUT
V
IN
0.06
0.05
0.04
ERROR (%)
0.03
0.02
0.01
0
–0.01
–0.02
THREE TYPICAL PARTS
–0.03
–25
0
25
–50
50
TEMPERATURE (°C)
DC/DC
CONVERTER
V
FB
RUN
ADC Total Unadjusted Error
vs Temperature
LTC2974
SDA
SCL
ALERTB
CONTROL
FAULT
PWRGD
NOTE: SOME DETAILS OMITTED FOR CLARITY
ONLY ONE OF FOUR CHANNELS SHOWN
V
OUT_EN
T
SENSE
V
SENSEM
V
DAC
PMBus
INTERFACE
MMBT3906
75
100
2974 TA01b
Rev. E
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1
LTC2974
TABLE OF CONTENTS
Features ...................................................................1
Applications ..............................................................1
Typical Application ......................................................1
Description................................................................1
Absolute Maximum Ratings ............................................4
Order Information ........................................................4
Pin Configuration ........................................................4
Electrical Characteristics ...............................................5
PMBus Timing Diagram.................................................9
Typical Performance Characteristics ............................... 10
Pin Functions ........................................................... 14
Block Diagram.......................................................... 16
Operation................................................................ 17
LTC2974 Operation Overview ..................................................17
EEPROM .............................................................................18
AUXFAULTB .............................................................................18
RESETB ...................................................................................19
PMBus Serial Digital Interface ................................................19
PMBus ................................................................................19
Device Address...................................................................19
Processing Commands ......................................................20
PMBUS Command Summary ......................................... 23
Summary Table ..................................................................23
Data Formats ......................................................................28
PMBus Command Description ....................................... 29
Addressing and Write Protect .................................................29
PAGE...................................................................................29
WRITE_PROTECT...............................................................30
Write Protect Pin ................................................................30
MFR_PAGE_FF_MASK .......................................................30
MFR_I2C_BASE_ADDRESS ...............................................31
MFR_COMMAND_PLUS ....................................................31
MFR_DATA_PLUS0 and MFR_DATA_PLUS1 ....................31
MFR_STATUS_PLUS0, and MFR_STATUS_PLUS1 ...........31
Reading Fault Log Using Command Plus and
Mfr_data_plus0 ..................................................................32
Peek Operation Using Mfr_data_plus0 ..............................33
Enabling and Disabling Poke Operations............................33
Poke Operation Using Mfr_data_plus0 ..............................33
Command Plus Operations Using Mfr_data_plus1 ............33
On/Off Control, Margining and Configuration .........................34
OPERATION ........................................................................34
ON_OFF_CONFIG ................................................................35
MFR_CONFIG_LTC2974 .....................................................36
Cascade Sequence ON with Time-Based Sequence OFF ....37
MFR_CONFIG2_LTC2974 ...................................................39
MFR_CONFIG3_LTC2974 ...................................................39
Tracking Supplies On and Off .............................................41
Tracking Implementation ....................................................42
MFR_CONFIG_ALL_LTC2974 ............................................43
Programming User EEPROM Space ........................................44
STORE_USER_ALL and RESTORE_USER_ALL ................45
Bulk Programming the User EEPROM Space .....................45
MFR_EE_UNLOCK..............................................................45
MFR_EE_ERASE ................................................................46
MFR_EE_DATA ...................................................................46
Response When Part Is Busy .............................................47
MFR_EE Erase and Write Programming Time ...................47
Input Voltage Commands and Limits ......................................47
VIN_ON, VIN_OFF, VIN_OV_FAULT_LIMIT, VIN_OV_WARN_
LIMIT, VIN_UV_WARN_LIMIT and
VIN_UV_FAULT_LIMIT .......................................................47
Output Voltage Commands and Limits....................................48
VOUT_MODE ......................................................................48
VOUT_COMMAND, VOUT_MAX, VOUT_MARGIN_HIGH,
VOUT_MARGIN_LOW, VOUT_OV_FAULT_LIMIT, VOUT_OV_
WARN_LIMIT, VOUT_UV_WARN_LIMIT, VOUT_UV_FAULT_
LIMIT, POWER_GOOD_ON and POWER_GOOD_OFF ........49
MFR_VOUT_DISCHARGE_THRESHOLD ............................49
MFR_DAC ...........................................................................49
Output Current Commands and Limits....................................50
IOUT_CAL_GAIN ................................................................50
IOUT_OC_FAULT_LIMIT, IOUT_OC_WARN_LIMIT and
IOUT_UC_FAULT_LIMIT .....................................................51
MFR_IOUT_CAL_GAIN_TC ................................................51
External Temperature Commands And Limits.........................52
OT_FAULT_LIMIT, OT_WARN_LIMIT, UT_WARN_LIMIT and
UT_FAULT_LIMIT ...............................................................52
MFR_TEMP_1_GAIN and MFR_TEMP_1_OFFSET ..............52
MFR_T_SELF_HEAT, MFR_IOUT_CAL_GAIN_TAU_INV and
MFR_IOUT_CAL_GAIN_THETA ..........................................53
Sequencing Timing Limits and Clock Sharing.........................55
TON_DELAY, TON_RISE, TON_MAX_FAULT_LIMIT and
TOFF_DELAY ......................................................................55
MFR_RESTART_DELAY .....................................................55
Watchdog Timer and Power Good...........................................56
MFR_PWRGD_EN ..............................................................56
Clock Sharing .....................................................................56
MFR_POWERGOOD_ASSERTION_DELAY.........................57
Watchdog Operation...........................................................57
MFR_WATCHDOG_T_FIRST and MFR_WATCHDOG_T ......57
Fault Responses ......................................................................58
Clearing Latched Faults ......................................................58
VOUT_OV_FAULT_RESPONSE and VOUT_UV_FAULT_
RESPONSE .........................................................................59
IOUT_OC_FAULT_RESPONSE and IOUT_UC_FAULT_
RESPONSE .........................................................................60
OT_FAULT_RESPONSE, UT_FAULT_RESPONSE, VIN_OV_
FAULT_RESPONSE and VIN_UV_FAULT_RESPONSE ........61
TON_MAX_FAULT_RESPONSE..........................................62
MFR_RETRY_DELAY..........................................................62
MFR_RETRY_COUNT .........................................................62
Shared External Faults ............................................................63
MFR_FAULTB0_PROPAGATE and MFR_FAULTB1_
PROPAGATE .......................................................................63
MFR_FAULTB0_RESPONSE and MFR_FAULTB1_
RESPONSE .........................................................................64
Fault Warning and Status ........................................................65
Rev. E
2
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LTC2974
TABLE OF CONTENTS
CLEAR_FAULTS .................................................................65
STATUS_BYTE....................................................................65
STATUS_WORD ..................................................................66
STATUS_VOUT ...................................................................66
STATUS_IOUT ....................................................................67
STATUS_INPUT ..................................................................67
STATUS_TEMPERATURE ...................................................67
STATUS_CML .....................................................................68
STATUS_MFR_SPECIFIC....................................................68
MFR_PADS.........................................................................69
MFR_COMMON ..................................................................69
Telemetry .................................................................................70
READ_VIN ..........................................................................71
READ_VOUT .......................................................................71
READ_IOUT ........................................................................71
READ_TEMPERATURE_1 ...................................................71
READ_TEMPERATURE_2 ...................................................71
READ_POUT .......................................................................71
MFR_READ_IOUT ..............................................................71
MFR_IOUT_SENSE_VOLTAGE ............................................72
MFR_VIN_PEAK .................................................................73
MFR_VOUT_PEAK ..............................................................73
MFR_IOUT_PEAK ...............................................................73
MFR_TEMPERATURE_1_PEAK ..........................................73
MFR_VIN_MIN ...................................................................73
MFR_VOUT_MIN ................................................................73
MFR_IOUT_MIN .................................................................73
MFR_TEMPERATURE_1_MIN ............................................73
Fault Logging ...........................................................................74
Fault Log Operation ............................................................74
MFR_FAULT_LOG_STORE .................................................74
MFR_FAULT_LOG_RESTORE.............................................74
MFR_FAULT_LOG_CLEAR .................................................75
MFR_FAULT_LOG_STATUS ...............................................75
MFR_FAULT_LOG...............................................................75
MFR_FAULT_LOG Read Example .......................................78
Identification/Information .......................................................83
CAPABILITY........................................................................83
PMBUS_REVISION .............................................................83
MFR_SPECIAL_ID ..............................................................83
MFR_SPECIAL_LOT ...........................................................83
MFR_INFO ..........................................................................84
User Scratchpad ......................................................................84
USER_DATA_00, USER_DATA_01, USER_DATA_02,
USER_DATA_03, USER_DATA_04, MFR_LTC_
RESERVED_1 and MFR_LTC_RESERVED_2 ......................84
Applications Information ............................................. 85
Overview..................................................................................85
Powering the LTC2974 ............................................................85
Setting Command Register Values ..........................................85
Sequence, Servo, Margin and Restart Operations ..................85
Command Units On or Off ..................................................85
On Sequencing ...................................................................85
On State Operation .............................................................86
Servo Modes ......................................................................86
DAC Modes .........................................................................87
Margining ...........................................................................87
Off Sequencing ...................................................................87
V
OUT
Off Threshold Voltage................................................87
Automatic Restart via MFR_RESTART_DELAY Command
and CONTROL pin ..............................................................87
Fault Management ...................................................................87
Output Overvoltage, Undervoltage, Overcurrent, and
Undercurrent Faults............................................................87
Output Overvoltage, Undervoltage, and Overcurrent
Warnings ............................................................................88
Configuring the AUXFAULTB Output ..................................88
Multi-Channel Fault Management ......................................89
Interconnect Between Multiple LTC2974’s ..............................89
Application Circuits .................................................................90
Trimming and Margining DC/DC Converters with External
Feedback Resistors ............................................................90
Four-Step Resistor Selection Procedure for DC/DC
Converters with External Feedback Resistors....................90
Trimming and Margining DC/DC Converters with a TRIM
Pin ......................................................................................91
Two-Step Resistor and DAC Full-Scale Voltage Selection
Procedure for DC/DC Converters with a TRIM Pin.............92
Measuring Current with a Sense Resistor ..........................93
Measuring Current with Inductor DCR ...............................93
Single Phase Design Example ............................................93
Measuring Multiphase Currents .........................................93
Multiphase Design Example ...............................................94
Anti-aliasing Filter Considerations .....................................94
Sensing Negative Voltages .................................................94
Connecting the DC1613 USB to I
2
C/SMBus/PMBus
Controller to the LTC2974 in System..................................95
Accurate DCR Temperature Compensation .............................97
LTpowerPlay: An Interactive GUI for Power Managers............98
PCB Assembly and Layout Suggestions .................................99
Bypass Capacitor Placement ..............................................99
Exposed Pad Stencil Design ...............................................99
PCB Board Layout ............................................................100
Unused ADC Sense Inputs ...............................................100
Design Checklist ....................................................................101
I
2
C ....................................................................................101
Output Enables .................................................................101
V
IN
Sense..........................................................................101
External Temperature Sense ............................................101
Logic Signals ....................................................................101
Unused Inputs ..................................................................101
DAC Outputs .....................................................................101
Package Description .................................................102
Revision History ......................................................103
Typical Application ...................................................104
Related Parts ..........................................................104
Rev. E
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3
LTC2974
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
64 V
SENSEM1
63 V
SENSEP1
62 V
SENSEM2
61 V
SENSEP2
60 NC
59 NC
58 V
DAC3
57 V
DAC2
56 NC
55 NC
54 V
DAC1
53 V
DAC0
52 NC
51 NC
50 V
SENSEM3
49 V
SENSEP3
V
SENSEP0
1
V
SENSEM0
2
V
OUT_EN0
3
V
OUT_EN1
4
V
OUT_EN2
5
V
OUT_EN3
6
AUXFAULTB 7
DNC 8
V
IN_SNS
9
V
PWR
10
V
DD33
11
V
DD33
12
V
DD25
13
V
DD25
14
T
SENSE0
15
T
SENSE1
16
65
GND
48 I
SENSEM3
47 I
SENSEP3
46 I
SENSEM2
45 I
SENSEP2
44 I
SENSEM1
43 I
SENSEP1
42 I
SENSEM0
41 I
SENSEP0
40 REFM
39 GND
38 REFP
37 GND
36 ASEL1
35 ASEL0
34 T
SENSE3
33 CONTROL1
UP PACKAGE
64-LEAD (9mm
×
9mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JCtop
= 7°C/W,
θ
JCbottom
= 1°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
Supply Voltages:
V
PWR
...................................................... –0.3V to 15V
V
DD33
.................................................... –0.3V to 3.6V
V
DD25
.................................................. –0.3V to 2.75V
Digital Input/Output Voltages:
ALERTB, SDA, SCL, CONTROL0, CONTROL1,
CONTROL2, CONTROL3 ....................... –0.3V to 3.6V
PWRGD, SHARE_CLK, WDI/RESETB, WP,
FAULTB0, FAULTB1 .............................. –0.3V to 3.6 V
ASEL0, ASEL1 ....................................... –0.3V to 3.6V
Analog Voltages:
REFP ................................................... –0.3V to 1.35V
REFM .................................................... –0.3V to 0.3V
V
IN_SNS
.................................................. –0.3V to 15V
V
SENSEP[3:0]
............................................. –0.3V to 6V
V
SENSEM[3:0]
............................................. –0.3V to 6V
I
SENSEP[3:0]
............................................... –0.3V to 6V
I
SENSEM[3:0]
.............................................. –0.3V to 6V
V
OUT_EN[3:0]
, AUXFAULTB ...................... –0.3V to 15V
V
DAC[3:0]
.................................................. –0.3V to 6V
T
SENSE[3:0]
............................................ –0.3V to 3.6V
Operating Junction Temperature Range:
LTC2974C ................................................ 0°C to 70°C
LTC2974I............................................ –40°C to 105°C
Storage Temperature Range ................ –65°C to 150°C*
Maximum Junction Temperature ........................ 125°C*
*See OPERATION section for detailed EEPROM de-
rating information for junction temperatures in excess
of 105°C.
ORDER INFORMATION
LEAD FREE FINISH
LTC2974CUP#PBF
LTC2974IUP#PBF
TAPE AND REEL
LTC2974CUP#TRPBF
LTC2974IUP#TRPBF
PART MARKING*
LTC2974UP
LTC2974UP
PACKAGE DESCRIPTION
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 105°C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications.
Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
PWRGD 17
SHARE_CLK 18
GND 19
GND 20
GND 21
CONTROL2 22
CONTROL3 23
WDI/RESETB 24
FAULTB0 25
FAULTB1 26
T
SENSE2
27
WP 28
SDA 29
SCL 30
ALERTB 31
CONTROL0 32
Rev. E
4
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LTC2974
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PWR
I
PWR
I
VDD33
V
UVLO_VDD33
PARAMETER
V
PWR
Supply Input Operating Range
V
PWR
Supply Current
V
DD33
Supply Current
V
DD33
Undervoltage Lockout
V
DD33
Undervoltage Lockout
Hysteresis
V
DD33
Supply Input Operating Range
Regulator Output Voltage
V
DD25
t
INIT
V
PWR
= V
DD33
4.5V ≤ V
PWR
≤ 15V
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
PWR
= V
IN_SNS
= 12V, V
DD33
, V
DD25
, REFP and REFM pins floating,
unless otherwise indicated. C
VDD33
= 100nF, C
VDD25
= 100nF and C
REF
= 100nF. (Note 2)
CONDITIONS
V
DD33
Floating
4.5V ≤ V
PWR
≤ 15V, V
DD33
Floating
3.13V ≤ V
DD33
≤ 3.47V, V
PWR
= V
DD33
V
DD33
Ramping Up, V
PWR
= V
DD33
l
l
l
l
MIN
4.5
TYP
MAX
15
UNITS
V
mA
mA
V
mV
Power Supply Characteristics
10
10
2.25
2.55
120
3.13
3.13
75
2.35
30
3.26
90
2.5
55
30
3.47
3.47
140
2.6
80
13
13
2.8
V
V
mA
V
mA
ms
Regulator Output Short-Circuit Current V
PWR
= 4.5V, V
DD33
= 0V
Regulator Output Voltage
3.13V ≤ V
DD33
≤ 3.47V
Regulator Output Short-Circuit Current V
PWR
= V
DD33
= 3.47V, V
DD25
= 0V
Initialization Time
Time from V
IN
applied until the TON_DELAY
timer starts
V
REF
= V
REFP
– V
REFM
, 0 < I
REFP
< 100µA
(Note 4)
Differential Voltage:
V
IN_ADC
= (V
SENSEPn
– V
SENSEMn
)
Single-Ended Voltage: V
SENSEMn
Current Sense Input Range
Single-Ended Voltage: I
SENSEPn
, I
SENSEMn
Differential Current Sense Voltage:
V
IN_ADC
= (I
SENSEPn
– I
SENSEMn
)
Voltage Reference Characteristics
V
REF
Output Voltage (Note 3)
Temperature Coefficient
Hysteresis
ADC Characteristics
V
IN_ADC
Voltage Sense Input Range
l
l
l
l
l
1.220
1.232
3
100
1.244
V
ppm/°C
ppm
0
–0.1
–0.1
–170
122
15.625
31.25
62.5
125
250
6
0.1
6
170
V
V
V
mV
µV/LSB
µA/LSB
µA/LSB
µA/LSB
µA/LSB
µA/LSB
N_ADC
Voltage Sense Resolution
Current Sense Resolution
0V ≤ V
IN_ADC
≤ 6V, READ_VOUT
0mV ≤ |V
IN_ADC
| < 16mV (Note 5)
16mV ≤ |V
IN_ADC
| < 32mV
32mV ≤ |V
IN_ADC
| < 63.9mV
63.9mV ≤ |V
IN_ADC
| < 127.9mV
127.9mV ≤ |V
IN_ADC
|
IOUT_CAL_GAIN = 1000mΩ
Voltage Sense Inputs V
IN_ADC
≥ 1V
Voltage Sense Inputs 0 ≤ V
IN_ADC
≤ 1V
Current Sense Inputs 20mV ≤ |V
IN_ADC
| ≤
170mV
Current Sense Inputs |V
IN_ADC
| ≤ 20mV
I
SENSEPn
and I
SENSEMn
Inputs, V
OS
• IOUT_
CAL_GAIN, IOUT_CAL_GAIN = 1Ω
V
SENSEPn
, V
SENSEMn
, V
IN_SNS
Inputs (Note 6)
I
SENSEPn
and I
SENSEMn
Inputs (Note 6)
Internal Temperature
(READ_TEMPERATURE_2) (Note 6)
l
l
l
l
l
TUE_ADC_
VOLT_SNS
TUE_ADC_
CURR_SNS
V
OS_ADC
t
CONV_ADC
Total Unadjusted Error (Note 3)
Total Unadjusted Error (Note 3)
±0.25
±2.5
±0.3
±60
±35
6.15
24.6
24.6
160
1
62.5
% of Reading
mV
% of Reading
µV
µV
ms
ms
ms
ms
pF
kHz
Rev. E
Offset Error
Conversion Time
t
UPDATE_ADC
C
IN_ADC
f
IN_ADC
Update Time
Input Sampling Capacitance
Input Sampling Frequency
(Note 6)
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