FeaTures
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LTC2978A
8-Channel PMBus Power
System Manager Featuring Accurate
Output Voltage Measurement
DescripTion
The
LTC
®
2978A
is an 8-channel Power System Manager
used to sequence, trim (servo), margin, supervise, man-
age 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 overvoltage
and undervoltage threshold limits for eight power supply
output channels and one power supply input channel, as
well as over and under temperature limits. 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 eight output voltages, one input voltage,
and die temperature. In addition, odd numbered chan-
nels can be configured to measure the voltage across a
current sense resistor. A programmable watchdog timer
monitors microprocessor activity for a stalled condition and
resets the microprocessor if necessary. A single wire bus
synchronizes power supplies across multiple LTC power
system management devices. Configuration EEPROM sup-
ports autonomous operation without additional software.
L,
LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo are registered trademarks and
LTpowerPlay ia a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents including 7382303, 7420359 and 7940091.
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Sequence, Trim, Margin and Supervise Eight Power Supplies
Manage Faults, Monitor Telemetry and Create Fault Logs
PMBus Compliant Command Set
Supported by LTpowerPlay™ GUI
Margin or Trim Supplies to 0.25% Accuracy
Fast OV/UV Supervisors per Channel
Coordinate Sequencing and Fault Management
Across Multiple Chips
Automatic Fault Logging to Internal EEPROM
Operate Autonomously without Additional Software
Internal Temperature and Input Voltage Supervisors
Accurate Monitoring of Eight Output Voltages, Input
Voltage and Internal Die Temperature
I
2
C/SMBus Serial Interface
Can Be Powered from 3.3V, or 4.5V to 15V
Programmable Watchdog Timer
100% Compatible with the LTC2978
Available in 64-pin 9mm
×
9mm QFN Package
applicaTions
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Computers and Network Servers
Industrial Test and Measurement
High Reliability Systems
Medical Imaging
Video
Typical applicaTion
8-Channel PMBus Power System Manager
4.5V < V
IBUS
< 15V**
V
PWR
3.3V**
TO INTERMEDIATE
BUS CONVERTER ENABLE
PMBus
INTERFACE
V
DD33
V
IN_EN
SDA
SCL
ALERTB
CONTROL0
WRITE-PROTECT
TO/FROM OTHER
LTC2978s
WP
FAULTB00
SHARE_CLK
GND
2978a TA01a
Typical ADC Total Unadjusted
Error vs Temperature
V
IN
0.035
0.030
0.025
ERROR (%)
0.020
0.015
0.010
0.005
0
–50 –35 –20 –5 10 25 40 55 70 85 100
TEMPERATURE (°C)
2978a TA01b
ADC V
IN
= 1.8V
V
IN_SNS
V
DACP0
V
SENSEP0
LTC2978A*
V
DACM0
V
SENSEM0
V
OUT_EN0
PWRGD
WDI/RESETB
ASEL0
ASEL1
TO µP RESETB INPUT
WATCHDOG
TIMER INTERRUPT
LOAD
R10
R30
R20
V
OUT
DIGITALLY
MANAGED
POWER
SUPPLY
V
FB
SGND
RUN/SS
GND
*SOME DETAILS OMITTED FOR CLARITY
ONLY ONE OF EIGHT CHANNELS SHOWN
**LTC2978A MAY BE POWERED FROM EITHER AN
EXTERNAL 3.3V SUPPLY OR THE INTERMEDIATE BUS
2978af
For more information
www.linear.com/LTC2978A
1
LTC2978A
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 .............................................. 15
Block Diagram............................................. 17
Operation................................................... 18
Operation Overview ................................................ 18
EEPROM ............................................................. 18
Reset ...................................................................... 19
Write-Protect Pin .................................................... 19
Other Operations .................................................... 19
Clock Sharing ..................................................... 19
PMBus Serial Digital Interface ................................20
PMBus ................................................................20
Device Address ...................................................23
Processing Commands....................................... 24
Summary Table...................................................25
PMBus Command Summary ............................ 25
Data Formats ......................................................29
PMBus Command Description .......................... 30
Operation, Mode and EEPROM Commands ............30
PAGE ..................................................................30
OPERATION ........................................................ 31
ON_OFF_CONFIG ................................................ 32
CLEAR_FAULTS.................................................. 32
WRITE_PROTECT ...............................................33
STORE_USER_ALL and RESTORE_USER_ALL .33
CAPABILITY........................................................33
VOUT_MODE ......................................................34
Output Voltage Related Commands ........................34
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 ..................34
Input Voltage Related Commands...........................34
VIN_ON, VIN_OFF, VIN_OV_FAULT_LIMIT, VIN_
OV_WARN_LIMIT, VIN_UV_WARN_LIMIT and
VIN_UV_FAULT_LIMIT .......................................34
Temperature Related Commands ............................35
OT_FAULT_LIMIT, OT_WARN_LIMIT, UT_WARN_
LIMIT and UT_FAULT_LIMIT...............................35
Timer Limits ...........................................................35
TON_DELAY, TON_RISE, TON_MAX_FAULT_
LIMIT and TOFF_DELAY......................................35
Fault Response for Voltages Measured by the High
Speed Supervisor ...................................................36
VOUT_OV_FAULT_RESPONSE and VOUT_UV_
FAULT_RESPONSE .............................................36
Fault Response for Values Measured by the ADC ... 37
OT_FAULT_RESPONSE, UT_FAULT_RESPONSE,
VIN_OV_FAULT_RESPONSE and VIN_UV_FAULT_
RESPONSE ......................................................... 37
Timed Fault Response ............................................ 37
TON_MAX_FAULT_RESPONSE .......................... 37
Status Commands ..................................................38
STATUS_BYTE:...................................................38
STATUS_WORD: .................................................39
STATUS_VOUT ................................................... 39
STATUS_INPUT ..................................................40
STATUS_TEMPERATURE ....................................40
STATUS_CML ..................................................... 41
STATUS_MFR_SPECIFIC .................................... 41
ADC Monitoring Commands ................................... 42
READ_VIN .......................................................... 42
READ_VOUT ....................................................... 42
READ_TEMPERATURE_1 .................................. 42
PMBUS_REVISION ............................................. 42
Manufacturer Specific Commands ..........................43
MFR_CONFIG_LTC2978 .....................................43
MFR_CONFIG_ALL_LTC2978 ............................44
MFR_FAULTBz0_PROPAGATE, MFR_FAULTBz1_
PROPAGATE .......................................................45
MFR_PWRGD_EN ..............................................46
MFR_FAULTB00_RESPONSE, MFR_FAULTB01_
RESPONSE, MFR_FAULTB10_RESPONSE and
MFR_FAULTB11_RESPONSE .............................. 47
2978af
2
For more information
www.linear.com/LTC2978A
LTC2978A
Table oF conTenTs
MFR_VINEN_OV_FAULT_RESPONSE .................48
MFR_VINEN_UV_FAULT_RESPONSE ................. 49
MFR_RETRY_DELAY .......................................... 49
MFR_RESTART_DELAY ......................................50
MFR_VOUT_PEAK ..............................................50
MFR_VIN_PEAK .................................................50
MFR_TEMPERATURE_PEAK ..............................50
MFR_DAC ........................................................... 51
MFR_POWERGOOD_ASSERTION_DELAY ......... 51
Watchdog Operation ............................................... 51
MFR_WATCHDOG_T_FIRST and MFR_
WATCHDOG_T .................................................... 51
MFR_PAGE_FF_MASK ....................................... 52
MFR_PADS.........................................................53
MFR_I2C_BASE_ADDRESS ...............................53
MFR_SPECIAL_ID ..............................................53
MFR_SPECIAL_LOT ...........................................54
MFR_VOUT_DISCHARGE_THRESHOLD .............54
MFR_COMMON ..................................................54
MFR_SPARE_0, MFR_SPARE_1, MFR_SPARE_2,
MFR_SPARE_3 ..................................................54
MFR_VOUT_MIN ................................................55
MFR_VIN_MIN ...................................................55
MFR_TEMPERATURE_MIN ................................55
Fault Log Operation ................................................55
MFR_FAULT_LOG_STORE .................................56
MFR_FAULT_LOG_RESTORE .............................56
MFR_FAULT_LOG_CLEAR..................................56
MFR_FAULT_LOG_STATUS ................................56
MFR_FAULT_LOG ............................................... 57
Applications Information ................................ 63
Overview .................................................................63
Powering the LTC2978A .........................................63
Setting Command Register Values .........................63
Sequence, Servo, Margin and Restart Operations ..63
Command Units On or Off ..................................63
On Sequencing ...................................................64
On State Operation .............................................64
Servo Modes ......................................................64
DAC Modes.........................................................64
Margining ...........................................................65
Off Sequencing ...................................................65
V
OUT
Off Threshold Voltage ................................65
Automatic Restart Via MFR_RESTART_DELAY
Command and CONTROLn pin ...........................65
Fault Management ..................................................65
Output Overvoltage and Undervoltage Faults .....65
Output Overvoltage and Undervoltage Warnings 66
Configuring the V
IN_EN
Output............................66
Multichannel Fault Management ........................68
Interconnect Between Multiple LTC2978A’s ............68
Application Circuits ................................................. 70
Trimming and Margining DC/DC Converters with
External Feedback Resistors............................... 70
Four-Step Resistor Selection Procedure for DC/DC
Converters with External Feedback Resistors..... 70
Trimming and Margining DC/DC Converters with a
TRIM Pin ............................................................ 71
Two-Step Resistor and DAC Full-Scale Voltage
Selection Procedure for DC/DC Converters with a
TRIM Pin ............................................................ 71
Measuring Current .............................................. 72
Measuring Current with a Sense Resistor...........72
Measuring Current with Inductor DCR................ 72
Single Phase Design Example ............................73
Measuring Multiphase Currents..........................73
Multiphase Design Example ...............................73
Anti-aliasing Filter Considerations ...................... 74
Sensing Negative Voltages ................................. 74
Connecting the DC1613 USB to I
2
C/SMBus/PMBus
Controller to the LTC2978A in System .................... 75
LTpowerPlay: An Interactive GUI for Power System
Managers ................................................................77
PCB Assembly and Layout Suggestions ................. 78
Bypass Capacitor Placement .............................. 78
Exposed Pad Stencil Design ............................... 78
PC Board Layout................................................. 78
Unused ADC Sense Inputs.................................. 78
Package Description ..................................... 79
Typical Application ....................................... 80
Related Parts .............................................. 80
2978af
For more information
www.linear.com/LTC2978A
3
LTC2978A
absoluTe MaxiMuM raTings
Supply Voltages:
V
PWR
to GND ......................................... –0.3V to 15V
V
DD33
to GND ....................................... –0.3V to 3.6V
V
DD25
to GND ..................................... –0.3V to 2.75V
Digital Input/Output Voltages:
ALERTB, SDA, SCL, CONTROL0,
CONTROL1............................................ –0.3V to 5.5V
PWRGD, SHARE_CLK,
WDI/RESETB, WP ....................–0.3V to V
DD33
+ 0.3V
FAULTB00, FAULTB01, FAULTB10,
FAULTB11 ................................–0.3V to V
DD33
+ 0.3V
ASEL0, ASEL1 ..........................–0.3V to V
DD33
+ 0.3V
Analog Voltages:
REFP ................................................... –0.3V to 1.35V
REFM to GND........................................ –0.3V to 0.3V
V
IN_SNS
to GND...................................... –0.3V to 15V
V
SENSEP[7:0]
to GND ................................. –0.3V to 6V
V
SENSEM[7:0]
to GND ................................ –0.3V to 6V
V
OUT_EN[3:0]
, V
IN_EN
to GND .................. –0.3V to 15V
V
OUT_EN[7:4]
to GND ................................. –0.3V to 6V
V
DACP[7:0]
to GND .................................... –0.3V to 6V
V
DACM[7:0]
to GND ................................ –0.3V to 0.3V
Operating Junction Temperature Range:
LTC2978AC .............................................. 0°C to 70°C
LTC2978AI ...........................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
Maximum Junction Temperature ........................ 125°C*
*See OPERATION section for detailed EEPROM de-
rating information for junction temperatures in excess
of 85°C.
(Notes 1, 2)
pin conFiguraTion
64 V
SENSEP6
63 V
SENSEM5
62 V
SENSEP5
61 V
DACM7
60 V
DACP7
59 V
DACP6
58 V
DACM6
57 V
DACM5
56 V
DACP5
55 V
DACP4
54 V
DACM4
53 V
SENSEM4
52 V
SENSEP4
51 V
DACM3
50 V
DACP3
49 V
SENSEM3
V
SENSEM6
1
V
SENSEP7
2
V
SENSEM7
3
V
OUT_EN0
4
V
OUT_EN1
5
V
OUT_EN2
6
V
OUT_EN3
7
V
OUT_EN4
8
V
OUT_EN5
9
V
OUT_EN6
10
V
OUT_EN7
11
V
IN_EN
12
DNC 13
V
IN_SNS
14
V
PWR
15
V
DD33
16
65
GND
48 V
SENSEP3
47 V
SENSEM2
46 V
SENSEP2
45 V
DACM2
44 V
DACP2
43 V
SENSEM1
42 V
SENSEP1
41 V
DACM1
40 V
DACP1
39 V
DACP0
38 V
DACM0
37 V
SENSEM0
36 V
SENSEP0
35 REFM
34 REFP
33 ASEL1
UP PACKAGE
64-LEAD (9mm
×
9mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA-TOP
= 28°C/W,
θ
JC-BOTTOM
= 1°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
orDer inForMaTion
LEAD FREE FINISH
LTC2978ACUP#PBF
LTC2978AIUP#PBF
TAPE AND REEL
LTC2978ACUP#TRPBF
LTC2978AIUP#TRPBF
PART MARKING*
LTC2978AUP
LTC2978AUP
PACKAGE DESCRIPTION
64-Lead (9mm
×
9mm) Plastic QFN
64-Lead (9mm
×
9mm) Plastic QFN
JUNCTION TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container. Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
V
DD33
17
V
DD25
18
WP 19
PWRGD 20
SHARE_CLK 21
WDI/RESETB 22
FAULTB00 23
FAULTB01 24
FAULTB10 25
FAULTB11 26
SDA 27
SCL 28
ALERTB 29
CONTROL0 30
CONTROL1 31
ASEL0 32
2978af
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For more information
www.linear.com/LTC2978A
LTC2978A
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
Regulator Output Voltage
Initialization Time
V
PWR
= V
DD33
4.5V ≤ V
PWR
≤ 15V
3.13V ≤ V
DD33
≤ 3.47V
Time from V
IN
Applied Until the
TON_DELAY Timer Starts
V
REF
= V
REFP
– V
REFM
, 0 < I
REFP
< 100µA
(Note 3)
Differential Voltage:
V
IN_ADC
= (V
SENSEPn
– V
SENSEMn
)
Single-Ended Voltage: V
SENSEMn
Current Sense Input Range (Odd
Numbered Channels Only)
N_ADC
Voltage Sense Resolution (Uses L16
Format)
Current Sense Resolution (Odd
Numbered Channels Only)
Single-Ended Voltage: V
SENSEPn
, V
SENSEMn
Differential Voltage: V
IN_ADC
0V ≤ V
IN_ADC
≤ 6V
0mV ≤ |V
IN_ADC
| < 16mV (Note13)
16mV ≤ |V
IN_ADC
| < 32mV
32mV ≤ |V
IN_ADC
| < 63.9mV
63.9mV ≤ |V
IN_ADC
| < 127.9mV
127.9mV ≤ |V
IN_ADC
|
V
IN_ADC
≥ 1.8V (Note 4)
Voltage Sense Mode (Note 5)
Current Sense Mode, Odd Numbered
Channels Only, 15.6µV/LSB (Note 5)
DNL_ADC
Differential Nonlinearity
Voltage Sense Mode
Current Sense Mode, Odd Numbered
Channels Only
V
OS_ADC
Offset Error
Voltage Sense Mode
Current Sense Mode, Odd Numbered
Channels Only
GAIN_ADC
Gain Error
Voltage Sense Mode, V
IN_ADC
= 6V
Current Sense Mode, Odd Numbered
Channels Only, V
IN_ADC
= ±0.17V
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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.
CONDITIONS
l
MIN
4.5
TYP
MAX
15
UNITS
V
mA
mA
V
mV
Power-Supply Characteristics
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
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l
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10
10
2.35
2.55
120
3.13
3.13
75
2.35
30
3.26
90
2.5
55
135
13
13
2.8
3.47
3.47
140
2.6
80
V
V
mA
V
mA
ms
Regulator Output Short-Circuit Current V
PWR
= 4.5V, V
DD33
= 0V
Regulator Output Short-Circuit Current V
PWR
= V
DD33
= 3.47V, V
DD25
= 0V
Voltage Reference Characteristics
V
REF
Output Voltage
Temperature Coefficient
Hysteresis
ADC Characteristics
V
IN_ADC
Voltage Sense Input Range
0
–0.1
–0.1
–170
122
15.625
31.25
62.5
125
250
±0.25
±854
±31.3
±400
±31.3
±250
±35
±0.2
±0.2
6
0.1
6
170
V
V
V
mV
µV/LSB
µV/LSB
µV/LSB
µV/LSB
µV/LSB
µV/LSB
%
µV
µV
µV
µV
µV
µV
%
%
2978af
1.232
3
100
V
ppm/°C
ppm
TUE_ADC
INL_ADC
Total Unadjusted Error
Integral Nonlinearity
For more information
www.linear.com/LTC2978A
5
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