−48 V Hot Swap Controller and Digital
Power Monitor with PMBus Interface
Data Sheet
ADM1075
FEATURES
Constant power foldback for FET SOA protection
Precision (<1.0%) current and voltage measurement
Controls inrush and faults for negative supply voltages
Suitable for wide input range due to internal shunt regulator
25 mV/50 mV full-scale sense voltage
Fine tune current limit to allow use of standard sense resistor
Soft start inrush current limit profiling
1% accurate UVH and OV pins, 1.5% accurate UVL pin
PMBus/I2C interface for control, telemetry, and fault
recording
28-lead LFCSP and TSSOP
−40°C to 105°C junction temperature (TJ) operating range
APPLICATIONS
Telecommunication and data communication equipment
Central office switching
−48 V distributed power systems
Negative power supply control
High availability servers
PRODUCT HIGHLIGHTS
1. Constant Power Foldback.
Maximum FET power set by a PLIM resistor divider. This
eases complexity when designing to maintain FET SOA.
2. Adjustable Current Limit.
The current limit is adjustable via the ISET pin allowing for
the use of a standard value sense resistor.
3. 12-Bit ADC.
Accurate voltage, current, and power measurements. Also
enables calculation of energy consumption over time.
4. PMBus/I2C Interface.
PMBus fast mode compliant interface used to read back
status and data registers and set warning and fault limits.
5. Fault Recording.
Latched status registers provide useful debugging infor-
mation to help trace faults in high reliability systems.
6. Built-In Soft Start.
Soft start capacitor controls inrush current profile with
di/dt control.
FUNCTIONAL BLOCK DIAGRAM
FAULT TIMER
FET POWER
FOLDBACK
CONTROL
DIGITAL
AND
PMBUS
12-BI T ADC
POWER
MULTIPLIER
POWER
ACCUMULATOR
GATE CONTROL
CURRENT LI M IT
DRAIN
RESTART
SHDN
LATCH
GPO1/ALERT1/CONV
GPO2/ALERT2
SDAO
SDAI
SCL
ADR
ADC_AUX
PWRGD
SPLYGD
UNDERVOLTAGE
AND
OVERVOLTAGE
DETECTOR
V
CC
AND
REFERENCE
GENERATOR
VIN
ADC_V
VCAP
UVL
UVH
SENSE+
GATE
PLIM
N-FET
R
SENSE
R
DROP
DC-TO-DC
CONVERTER
5V
12V
3.3V
2.8V
...etc.
GND
–48V RTN ( 0V )
–48V
VEE
SENSE–
ISET
TIMER SS VEE_G VEE
OV
VEE ADuM1250 SDA_ISO
SCL_ISO
CLOAD
09312-001
Figure 1.
Rev. C Document Feedback
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ADM1075 Data Sheet
Rev. C | Page 2 of 52
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Product Highlights ........................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 3
General Description ......................................................................... 4
Specifications ..................................................................................... 5
Serial Bus Timing ......................................................................... 9
Absolute Maximum Ratings .......................................................... 10
Thermal Resistance .................................................................... 10
ESD Caution ................................................................................ 10
Pin Configuration and Function Description ............................ 11
Typical Performance Characteristics ........................................... 13
Theory of Operation ...................................................................... 20
Powering the ADM1075 ............................................................ 20
Current Sense Inputs .................................................................. 21
Current Limit Reference ............................................................ 21
Setting the Current Limit (ISET) ............................................. 22
Soft Start ...................................................................................... 22
Constant Power Foldback (PLIM) ........................................... 22
TIMER ......................................................................................... 23
Setting a Linear Output Voltage Ramp at Power-Up ............. 24
Hot Swap Fault Retry ................................................................. 25
Fast Response to Severe Overcurrent ...................................... 25
UV and OV ................................................................................. 25
PWRGD ....................................................................................... 25
DRAIN ......................................................................................... 26
SPLYGD ....................................................................................... 26
LATCH ......................................................................................... 26
SHDN ........................................................................................... 26
RESTART ..................................................................................... 26
FET Health .................................................................................. 26
Power Monitor ............................................................................ 26
Isolation ....................................................................................... 27
PMBus Interface ............................................................................. 28
Device Addressing ...................................................................... 28
SMBus Protocol Usage ............................................................... 28
Packet Error Checking ............................................................... 28
Partial Transactions on I2C Bus ................................................ 28
SMBus Message Formats ........................................................... 29
Group Commands ..................................................................... 30
Hot Swap Control Commands ................................................. 31
ADM1075 Information Commands ........................................ 31
Status Commands ...................................................................... 31
GPO and Alert Pin Setup Commands .................................... 32
Power Monitor Commands ...................................................... 32
Warning Limit Setup Commands ............................................ 33
PMBus Direct Format Conversion .......................................... 34
Voltage and Current Conversion Using LSB Values .............. 35
ADM1075 Alert Pin Behavior ...................................................... 36
Faults and Warnings .................................................................. 36
Generating an Alert ................................................................... 36
Handling/Clearing an Alert ...................................................... 36
SMBus Alert Response Address ............................................... 37
Example Use of SMBus Alert Response Address ................... 37
Digital Comparator Mode ......................................................... 37
PMBus Command Reference ........................................................ 38
Register Details ............................................................................... 39
Operation Command Register ................................................. 39
Clear Faults Register .................................................................. 39
PMBus Capability Register ....................................................... 39
IOUT OC Warn Limit Register ................................................ 39
VIN OV Warn Limit Register ................................................... 39
VIN UV Warn Limit Register ................................................... 39
PIN OP Warn Limit Register .................................................... 40
Status Byte Register .................................................................... 40
Status Word Register .................................................................. 40
IOUT Status Register ................................................................. 41
Input Status Register .................................................................. 41
Manufacturing Specific Status Register ................................... 42
Read EIN Register ...................................................................... 43
Read VIN Register...................................................................... 43
Read IOUT Register ................................................................... 43
Read PIN Register ...................................................................... 43
PMBus Revision Register .......................................................... 43
Manufacturing ID Register ....................................................... 44
Manufacturing Model Register ................................................ 44
Manufacturing Revision Register ............................................. 44
Peak IOUT Register ................................................................... 44
Peak VIN Register ...................................................................... 45
Data Sheet ADM1075
Peak VAUX Register ................................................................... 45
Power Monitor Control Register ............................................... 45
Power Monitor Configuration Register ................................... 45
ALERT1 Configuration Register ............................................... 46
ALERT2 Configuration Register ............................................... 47
IOUT WARN2 Limit Register ................................................... 48
Device Configuration Register .................................................. 48
Power Cycle Register .................................................................. 49
Peak PIN Register ....................................................................... 49
Read PIN_EXT Register............................................................. 49
Read EIN_EXT Register ............................................................ 49
Read VAUX Register ................................................................... 50
VAUX OV Warn Limit Register ................................................ 50
VAUX UV Warn Limit Register ................................................ 50
VAUX Status Register ................................................................. 50
Outline Dimensions ........................................................................ 51
Ordering Guide ........................................................................... 51
REVISION HISTORY
4/14—Rev. B to Rev. C
Added Setting a Linear Output Voltage Ramp at Power-Up
Section and Figure 51; Renumbered Sequentially ...................... 24
4/13—Rev. A to Rev. B
Changes to Figure 4 ......................................................................... 11
Changes to Figure 43 ...................................................................... 21
Added I Partial Transactions on I2C Bus Section ....................... 28
Change to Bit 14, Table 16 .............................................................. 40
Changes to Table 32 ........................................................................ 45
Change to Bits[1:0], Table 36 ......................................................... 49
3/12—Rev. 0 to Rev. A
Added 28-Lead LFCSP ...................................................... Universal
Changes to Features Section and Product Highlights Section .... 1
Changes to ADC Conversion Time comments in Table 1 .......... 8
Changes to Table 4 .......................................................................... 10
Added Figure 4; Renumbered Sequentially; and changes to
Table 5 ............................................................................................... 11
Changes to Current Limit Reference Section .............................. 21
Changes to Voltage and Current Conversion Using LSB
Values Section .................................................................................. 35
Changes to Table 8 .......................................................................... 38
Changes to Table 20 ........................................................................ 43
Changes to Table 25 through Table 27 ......................................... 44
Changes to Table 32 ........................................................................ 45
Changes to Table 38 and Table 39 ................................................. 49
Changes to Outline Dimensions and Ordering Guide .............. 51
10/11—Revision 0: Initial Version
Rev. C | Page 3 of 52
ADM1075 Data Sheet
GENERAL DESCRIPTION
The ADM1075 is a full feature, negative voltage, hot swap control-
ler with constant power foldback and high accuracy digital current
and voltage measurement that allows boards to be safely inserted
and removed from a live −48 V backplane. The part provides
precise and robust current limiting and protection against both
transient and nontransient short circuits and overvoltage and
undervoltage conditions. The ADM1075 typically operates from
a negative voltage of −35 V to −80 V and, due to shunt regulation,
has excellent voltage transient immunity. The operating range of
the part is flexible due to the shunt regulator, and the part can be
powered directly by a 10 V rail to save shunt power dissipation
(see the Powering the ADM1075 section for more details).
A full-scale current limit of 25 mV or 50 mV can be selected by
choosing the appropriate model. The maximum current limit is
set by the combination of the sense resistor, RSENSE, and the input
voltage on the ISET pin, using external resistors. This allows fine
tuning of the trip voltage so that standard sense resistors can be
used. Inrush current is limited to this programmable value by
controlling the gate drive of an external N-channel FET. A built-
in soft start function allows control of the inrush current profile by
an external capacitor on the soft start (SS) pin.
An external capacitor on the TIMER pin determines the maxi-
mum allowed on-time for when the system is in current limit.
This is based on the safe operating area (SOA) limits of the
MOSFET. A constant power foldback scheme is used to control
the power dissipation in the MOSFET during power-up and
fault conditions. The ADM1075 regulates the current dynami-
cally to ensure that the power in the MOSFET is within SOA
limits as VDS changes. After the timer has expired, the device
shuts down the MOSFET. The level of this power, along with
the TIMER regulation time, can be set to ensure that the
MOSFET remains within the SOA limits.
The ADM1075 employs a limited consecutive retry scheme
when the LATCH pin is tied to the SHDN pin. In this mode,
if the load current reaches the limit, the FET gate is pulled low
after the timer expires and retries after a cooling period for
seven attempts only. If the fault remains, the device latches off,
and the MOSFET is disabled until a manual restart is initiated.
Alternatively, the ADM1075 can be set to retry only once by
isolating the LATCH pin from the SHDN pin. The part can
also be configured to retry an infinite number of times with a
10 second interval between restarts by connecting the GPO2
pin to the RESTART pin.
The ADM1075 has separate UVx and OV pins for undervoltage
and overvoltage detection. The FET is turned off if a nontransient
voltage less than the undervoltage threshold (typically −35 V) is
detected on the UVx pins or if greater than the overvoltage
threshold (typically −80 V) is detected on the OV pin. The
operating voltage range of the ADM1075 is programmable via
resistor networks on the UVx and OV pins. The hysteresis levels
on the overvoltage detectors can also be altered by selecting the
appropriate resistors. There are two separate UVx pins to allow
accurate programming of hysteresis.
In the case of a short circuit, the ADM1075 has a fast response
circuit to detect and respond adequately to this event. If the
sense voltage exceeds 1.5 times the normal current limit, a high
current (750 mA minimum) gate pull-down switch is activated
to shut down the MOSFET as quickly as possible. There is a
default internal glitch filter of 900 ns. If a longer filter time or
different severe overcurrent limit is required, these parameters
can be adjusted via the PMBus™ interface.
The ADM1075 also includes a 12-bit ADC to provide digital
measurement of the voltage and load current. The current is
measured at the output of the internal current sense amplifier
and the voltage from the ADC_V input. This data can be read
across the PMBus interface.
The PMBus interface allows a controller to read current, voltage,
and power measurements from the ADC. Measurements can be
initiated by a PMBus command or can be set up to run continu-
ously. The user can read the latest conversion data whenever it
is required. A power accumulator is also provided to report
total power consumed in a user specified period (total energy).
Up to four unique I2C addresses can be created, depending on
the configuration of the ADR pin.
The GPO1/ALERT1/CONV and GPO2/ALERT2 outputs can
be used as a flag to warn a microcontroller or FPGA of one or
more fault/warning conditions becoming active. The fault type
and level is programmed across the PMBus, and the user can
select which faults/warnings activate the alert.
Other functions include
• PWRGD output, which can be used to enable a power
module (the DRAIN and GATE pins are monitored to
determine when the load capacitance is fully charged)
• SHDN input to manually disable the GATE drive
• RESTART input to remotely initiate a 10 second shutdown
Rev. C | Page 4 of 52
Data Sheet ADM1075
SPECIFICATIONS
VEE = −48 V, VSENSE = (VSENSE+ − VSENSE−) = 0 mV, shunt regulation current = 10 mA, TJ = −40°C to +105°C, unless otherwise noted.
Table 1.
Parameter Min Typ Max Unit Test Conditions/Comments
SYSTEM SUPPLY
Voltage Transient Immunity −200 V
Typical Operating Voltage −80 −35 V Determined by external component, RSHUNT
SHUNT REGULATOR
Operating Supply Voltage Range, VIN 11.5 12.3 13 V Shunt regulation voltage, IIN = 5.5 mA to 30 mA,
maximum IIN dependent on TA, θJA (see the Powering the
ADM1075 section)
Quiescent Supply Current 5.5 mA VIN = 13 V
Undervoltage Lockout, VUVLO_RISING 9.2 V
Undervoltage Lockout Hysteresis 600 mV
Power Directly Without Shunt
9.2
11.5
V
UV PINS—UNDERVOLTAGE DETECTION
Undervoltage Rising Threshold, VUVH 0.99 1.0 1.01 V
Undervoltage Falling Threshold, VUVL 0.887 0.9 0.913 V
Total Undervoltage Hysteresis 100 mV When UVL and UVH are tied together
Undervoltage Fault Filter 3.5 7.5 µs
UV Propagation Delay 5 8 µs UV low to GATE pull-down active
UVL/UVH Input Current 1 50 nA
OV PIN—OVERVOLTAGE DETECTION
Overvoltage Rising Threshold, VOVR 0.99 1.0 1.01 V
Overvoltage Hysteresis Current 4.3 5 5.7 µA
Overvoltage Fault Filter 1.75 3.75 µs
OV Propagation Delay 2 4 µs OV high to GATE pull-down active
OV Input Current 1 50 nA
GATE PIN
Gate Voltage High 11 12 13 V IGATE = −1.0 µA
Gate Voltage Low 10 100 mV IGATE = 100 µA
Pull-Up Current −50 −30 µA VGATE = 0 V to 8 V; VSS = 2 V
Pull-Down Current (Regulation) 100 µA VGATE ≥ 2 V
Pull-Down Current (UV/OV/OC) 5 10 mA VGATE ≥ 2 V
Pull-Down Current (Severe OC) 750 1500 2000 mA VGATE ≥ 6 V
Pull-Down On-Time (Severe OC) 8 16 µs
Gate Hold-Off Resistance 20 Ω 0 V ≤ VIN ≤ 9.2 V
SENSE+, SENSE−
SENSE+, SENSE− Input Current, ISENSEx 100 μA VSENSE ≤ 65 mV for ADM1075-1, per individual pin;
VSENSE ≤ 130 mV for ADM1075-2, per individual pin
SENSE+, SENSE− Input Imbalance, IΔSENSEx 1 μA IΔSENSEx = ISENSE+ − ISENSE−
VCAP
Internally Regulated Voltage, VVCAP 2.66 2.7 2.74 V 0 ≤ IVCAP ≤ 100 μA; CVCAP = 1 μF
ISET
ISET Reference Select Threshold, VISETRSTH 1.35 1.5 1.65 V If VISET > VISETRSTH an internal 1 V reference (VCLREF) is used
ISET Internal Reference, V
CLREF
1
V
Accuracies included in total sense voltage accuracies
Gain of Current Sense Amplifier, AVCSAMP 50/25 V/V Accuracies included in total sense voltage accuracies
ISET Input Current, IISET 100 nA VISET ≤ VCAP
ADM1075-1 ONLY (GAIN = 50)
Hot Swap Sense Voltage
Hot Swap Sense Voltage Current Limit,
VSENSECL
19.4 20 20.6 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
24.5 25 25.5 mV VISET = 1.25 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
19.5 20 20.5 mV VISET = 1.0 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
14.5
15
15.5
mV
V
ISET
= 0.75 V; V
GATE
= 3 V; I
GATE
= 0 μA; V
SS
≥ 2 V; V
PLIM
= 0 V
Rev. C | Page 5 of 52
ADM1075 Data Sheet
Parameter Min Typ Max Unit Test Conditions/Comments
Constant Power Active 9.4 10 11.0 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0.2 V
4.5 5 5.7 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0.4 V
1.4 2 2.6 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 1.2 V
Circuit Breaker Offset, VCBOS 0.6 0.75 0.95 mV Circuit breaker voltage, VCB = VSENSECL − VCBOS
Severe Overcurrent Activates high current gate pull-down
Voltage Threshold, VSENSEOC 23 25 27 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
28 30 32 mV VISET > 1.65 V; VSS ≥ 2 V; default at power-up
38 40 42 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
43 45 47 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
Response Time
Glitch Filter Duration 50 200 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
500 900 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
default at power-up
6.2 10.7 µs VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
44 57 µs VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
Total Response Time 180 300 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
610 950 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
default at power-up
7 13 µs
VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
45 60 µs VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 18 mV to 52 mV;
optional select through PMBus
ADM1075-2 ONLY (GAIN = 25)
Hot Swap Sense Voltage
Hot Swap Sense Voltage Current Limit,
VSENSECL
39.2 40 40.8 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
49.2 50 50.8 mV VISET = 1.25 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
39.2 40 40.8 mV VISET = 1.0 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
29.2 30 30.8 mV VISET = 0.75 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0 V
Constant Power Active 19 20 21.9 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0.2 V
9.2 10 11.2 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 0.4 V
3 4 5.0 mV VISET > 1.65 V; VGATE = 3 V; IGATE = 0 μA; VSS ≥ 2 V; VPLIM = 1.2 V
Circuit Breaker Offset, VCBOS 1.1 1.5 1.9 mV Circuit breaker voltage, VCB = VSENSECL − VCBOS
Severe Overcurrent Activates high current gate pull-down
Voltage Threshold, VSENSEOC1 46 50 54 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
56 60 64 mV VISET > 1.65 V; VSS ≥ 2 V; default at power-up
76 80 84 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
86 90 94 mV VISET > 1.65 V; VSS ≥ 2 V; optional select through PMBus
Response Time
Glitch Filter Duration 50 200 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
optional select through PMBus
400 900 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
default at power-up
6.2
10.7
µs
V
ISET
> 1.65 V; V
SS
≥ 2 V; V
SENSE
step from 36 mV to 104 mV;
optional select through PMBus
44 57 µs VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
optional select through PMBus
Rev. C | Page 6 of 52
Data Sheet ADM1075
Parameter Min Typ Max Unit Test Conditions/Comments
Total Response Time 180 300 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
optional select through PMBus
610 950 ns VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
default at power-up
7 13 µs
VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
optional select through PMBus
45 60 µs VISET > 1.65 V; VSS ≥ 2 V; VSENSE step from 36 mV to 104 mV;
optional select through PMBus
SOFT START
SS Pull-Up Current, ISS −11.5 −10 −8.5 µA VSS = 0V
Default VSENSECL Limit 0.6 1.25 1.9 mV When VSENSE reaches this level, ISS is enabled, ramping;
VSS = 0 V; ADM1075-1 only (gain = 50)
1.2 2.5 3.8 mV When VSENSE reaches this level, ISS is enabled, ramping;
VSS = 0 V; ADM1075-2 only (gain = 25)
SS Pull-Down Current 100 µA VSS = 1 V
TIMER
Timer Pull-Up Current (POR), ITIMERUPPOR −4 −3 −2 µA Initial power-on reset; VTIMER = 0.5 V
Timer Pull-Up Current (OC Fault), ITIMERUPFLT −63 −60 −57 µA Overcurrent fault; 0.05 V ≤ VTIMER ≤ 1 V
Timer Pull-Down Current (Retry), ITIMERDNRT 1.7 2 2.3 µA After a fault when GATE is off; VTIMER = 0.5 V
Timer Retry/OC Fault Current Ratio 3.33 % Defines the limits of the autoretry duty cycle
Timer Pull-Down Current (Hold), ITIMERDNHOLD 100 µA Holds TIMER at 0 V when inactive; VTIMER = 0.5 V
Timer High Threshold, VTIMERH 0.98 1.0 1.02 V
Timer Low Threshold, VTIMERL 0.03 0.05 0.07 V
PLIM
PLIM Active Threshold 0.08 0.09 0.1 V VISET > 1.65 V
Input Current, IPLIM 100 nA VPLIM ≤ 1 V
Minimum Current Clamp, VICLAMP 75 100 125 mV VPLIM = 1.2 V; VSENSE_IMIN = (VICLAMP ÷ gain) = minimum
allowed current control
DRAIN
DRAIN Voltage at Which PWRGD Asserts 1.9 2 2.1 V IDRAIN ≤ 50 µA
ADC_AUX/ADC_V
Input Current 100 nA 0 V ≤ VADC ≤ 1.5 V
SHDN PIN
Input High Voltage, VIH 1.1 V
Input Low Voltage, VIL 0.8 V
Glitch Filter 1 µs
Internal Pull-Up Current 8 µA Pull-up to VIN
RESTART PIN
Input High Voltage, VIH 1.1 V
Input Low Voltage, VIL 0.8 V
Glitch Filter 1 µs
Internal Pull-Up Current 8 µA Pull-up to VIN
SPLYGD PIN
Output Low Voltage, VOL_LATCH 0.4 V ISPLYGD = 1 mA
1.5 V ISPLYGD = 5 mA
Leakage Current 100 nA VSPLYGD ≤ 2 V; SPLYGD pin disabled
1 µA VSPLYGD ≤ 14 V; SPLYGD pin disabled
LATCH PIN
Output Low Voltage, VOL_LATCH 0.4 V ILATCH = 1 mA
1.5 V ILATCH = 5 mA
Leakage Current 100 nA VLATCH ≤ 2 V; LATCH pin disabled
1 µA VLATCH ≤ 14 V; LATCH pin disabled
GPO1/ALERT1/CONV PIN
Output Low Voltage, VOL_GPO1 0.4 V IGPO = 1 mA
1.5 V IGPO = 5 mA
Rev. C | Page 7 of 52
ADM1075 Data Sheet
Parameter Min Typ Max Unit Test Conditions/Comments
Leakage Current 100 nA VGPO ≤ 2 V; GPO disabled
1 µA VGPO = 14 V; GPO disabled
Input High Voltage, VIH 1.1 V Configured as CONV pin
Input Low Voltage, VIL 0.8 V Configured as CONV pin
Glitch Filter 1 µs Configured as CONV pin
GPO2/ALERT2 PIN
Output Low Voltage, VOL_GPO2 0.4 V IGPO = 1 mA
1.5 V IGPO = 5 mA
Leakage Current 100 nA VGPO ≤ 2 V; GPO disabled
1 µA VGPO = 14 V; GPO disabled
PWRGD PIN
Output Low Voltage, VOL_PWRGD 0.4 V IPWRGD = 1 mA
1.5 V IPWRGD = 5 mA
VIN That Guarantees Valid Output 1 V ISINK = 100 μA; VOL_PWRGD = 0.4 V
Leakage Current 100 nA VPWRGD ≤ 2 V; PWRGD active
1 µA VPWRGD = 14 V; PWRGD active
CURRENT AND VOLTAGE MONITORING
Current Sense Absolute Error (ADM1075-1) 25 mV input range; 128 sample averaging (unless
otherwise noted)
−0.01 ±0.7 % VSENSE = 25 mV
0.05
±0.85
%
V
SENSE
= 20 mV
0.07 ±0.85 % VSENSE = 20 mV; 16 sample averaging
0.04 ±2.8 % VSENSE = 20 mV; 1 sample averaging
±1.0 % VSENSE = 15 mV
±1.4 % VSENSE = 10 mV
±2.7 % VSENSE = 5 mV
±5.9 % VSENSE = 2.5 mV
Current Sense Absolute Error (ADM1075-2) 50 mV input range; 128 sample averaging (unless
otherwise noted)
−0.03 ±0.65 % VSENSE = 50 mV
−0.03 ±0.7 % VSENSE = 40 mV
−0.03 ±0.7 % VSENSE = 40 mV; 16 sample averaging
−0.04
±1.35
%
V
SENSE
= 40 mV; 1 sample averaging
±0.75
%
V
SENSE
= 30 mV
±0.9 % VSENSE = 20 mV
±1.7 % VSENSE = 10 mV
±3.0 % VSENSE = 5 mV
ADC_V/ADC_AUX Absolute Accuracy −0.8 +0.8 % 0.6 V ≤ VADC ≤ 1.5 V
ADC Conversion Time 1 sample of voltage and current; from command
received to valid data in register
191 219 µs VAUX disabled
263 301 µs VAUX enabled
16 samples of voltage and current averaged; from
command received to valid data in register
2.830 3.243 ms VAUX disabled
3.987 4.568 ms VAUX enabled
128 samples of voltage and current averaged; from
command received to valid data in register
22.54 25.83 ms VAUX disabled (default on power-up)
31.79 36.43 ms VAUX enabled
Power Multiplication Time 14 µs
Rev. C | Page 8 of 52
Data Sheet ADM1075
Parameter Min Typ Max Unit Test Conditions/Comments
ADR PIN See Table 6
Address Set to 00 0 0.8 V Connect to VEE
Input Current for Address 00 −40 −22 μA VADR = 0 V to 0.8 V
Address Set to 01 135 150 165 kΩ Resistor to VEE
Address Set to 10 −1 +1 μA No connect state; maximum leakage current allowed
Address Set to 11 2.1 V Connect to VCAP
Input Current for Address 11 3 10 μA VADR = 2.0 V to VCAP; must not exceed the maximum
allowable current draw from VCAP
SERIAL BUS DIGITAL INPUTS (SDAI/SDAO, SCL)
Input High Voltage, VIH 1.1 V
Input Low Voltage, VIL 0.8 V
Output Low Voltage, VOL 0.4 V IOL = 4 mA, SDAO only
Input Leakage, ILEAK-PIN −10 +10 μA
−5 +5 μA Device is not powered
Nominal Bus Voltage, VDD 2.7 5.5 V 3 V to 5 V ±10%
Capacitive Load per Bus Segment, CBUS 400 pF
Capacitance for SDAI, SDAO, or SCL Pin, C
PIN
5
pF
Input Glitch Filter, tSP 0 50 ns
SERIAL BUS TIMING
Table 2.
Parameter Description Min Typ Max Unit Test Conditions/Comments
fSCLK Clock frequency 400 kHz
tBUF Bus free time 1.3 µs
tHD;STA Start hold time 0.6 µs
tSU;STA Start setup time 0.6 µs
tSU;STO Stop setup time 0.6 µs
tHD;DAT SDA1 hold time 300 900 ns
t
SU ;DAT
SDA1 setup time
100
ns
tLOW SCL low time 1.3 µs
tHIGH SCL high time 0.6 µs
tR2 SCL, SDA1 rise time 20 300 ns
tF SCL, SDA1 fall time 20 300 ns
tOF SCL, SDA1 output fall time 20 + 0.1 × CBUS 250 ns
1 SDAI and SDAO tied together.
2 tR = (VIL(MAX) – 0.15) to (VIH3V3 + 0.15) and tF = 0.9 VDD to (VIL(MAX) – 0.15); where VIH3V3 = 2.1 V, and VDD = 3.3 V.
t
LOW
t
BUF
t
HD;DAT
t
SU;DAT
t
SU;STA
t
HD;STA
t
HIGH
t
R
t
F
t
SU;STO
PSSP
V
IH
V
IL
V
IH
V
IL
SCL
SDA
09312-002
Figure 2. Serial Bus Timing Diagram
Rev. C | Page 9 of 52
ADM1075 Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
VIN Pin to VEE −0.3 V to +14 V
UVL Pin to VEE
−0.3 V to +4 V
UVH Pin to VEE −0.3 V to +4 V
OV Pin to VEE −0.3 V to +4 V
ADC_V Pin to VEE −0.3 V to +4 V
ADC_AUX Pin to VEE −0.3 V to +4 V
SS Pin to VEE −0.3 V to (VCAP + 0.3 V)
TIMER Pin to VEE
−0.3 V to (VCAP + 0.3 V)
VCAP Pin to VEE −0.3 V to +4 V
ISET Pin to VEE −0.3 V to +4 V
SPLYGD Pin to VEE −0.3 V to +18 V
LATCH Pin to VEE −0.3 V to +18 V
RESTART Pin to VEE −0.3 V to +18 V
SHDN Pin to VEE
−0.3 V to +18 V
PWRGD Pin to VEE −0.3 V to +18 V
DRAIN Pin to VEE −0.3 V to (VCAP + 0.3 V)
SCL Pin to VEE −0.3 V to +6.5 V
SDAI Pin to VEE −0.3 V to +6.5 V
SDAO Pin to VEE
−0.3 V to +6.5 V
ADR Pin to VEE −0.3 V to (VCAP + 0.3 V)
GPO1/ALERT1/CONV Pin to VEE −0.3 V to +18 V
GPO2/ALERT2 Pin to VEE −0.3 V to +18 V
PLIM Pin to VEE
−0.3 V to +4 V
GATE Pin to VEE −0.3 V to +18 V
SENSE+ Pin to VEE −0.3 V to +4 V
SENSE− Pin to VEE −0.3 V to +0.3 V
VEE to VEE_G −0.3 V to +0.3 V
Continuous Current into Any Pin ±10 mA
Storage Temperature Range
−65°C to +125°C
Operating Junction Temperature
Range
−40°C to +105°C
Lead Temperature, Soldering (10 sec) 300°C
Junction Temperature 150°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 4. Thermal Resistance
Package Type θJA1 θJC Unit
28-Lead TSSOP 68 20 °C/W
28-Lead LFCSP 35 4 °C/W
1 Measured on JEDEC 4-layer board in still air.
ESD CAUTION
Rev. C | Page 10 of 52
Data Sheet ADM1075
Rev. C | Page 11 of 52
PIN CONFIGURATION AND FUNCTION DESCRIPTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
VIN
UVH
UVL
VCAP
PLIM
OV
DRAIN
GATE
SENSE+
SENSE–
ADC_AUX
SPLYGD
VEE
A
DC_V
ISET
SS
ADR
SHDN
LATCH
TIMER
PWRGD
SCL
SDAI
GPO1/ALERT1/CONV
RESTART
GPO2/ALERT2
SDAO
VEE_G
TOP VIEW
(No t to Scale)
ADM1075
09312-004
Figure 3. TSSOP Pin Configuration
NOTES
1. EXPOSED PAD. SOL DER THE EXPOSED PAD TO THE BOARD TO
IMPROVE THERMAL DISSIPATION. T HE EXPOSED PAD CAN BE
CO NNE CTED TO VEE.
1OV 2PLIM 3VCAP 4ADC_V 5ISET 6SS 7TIMER
17 PWRGD
18 ADC_AUX
19 SPLYGD
20 VEE
21 SENSE–
16 SCL
15 SDAI
8
LATCH 9
ADR 10
SHDN 11
RESTART 12
GPO1/ALERT1/CONV 13
GPO2/ALERT2 14
SDAO
24 VEE_G
25 DRAIN
26 VIN
27 UVH
28 UVL
23 GATE
22 SENSE+
09312-003
TOP VIEW
(Not to Scale)
ADM1075
Figure 4. LFCSP Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
TSSOP LFCSP Mnemonic Description
1 25 DRAIN Connect to the drain pin of the FET through a resistor. The current in this resistor is used to determine
the VDS of the MOSFET. This is used for PWRGD.
2 26 VIN Shunt Regulated Positive Supply to Chip. Connect to the positive supply rail via a shunt resistor. A
1 μF capacitor to VEE is recommended on the VIN pin.
3 27 UVH Undervoltage Rising Input Pin. An external resistor divider is used from the supply to this pin to allow
an internal comparator to detect if the supply is under the UVH limit.
4 28 UVL Undervoltage Falling Input Pin. An external resistor divider is used from the supply to this pin to
allow an internal comparator to detect if the supply is under the UVL limit.
5 1 OV Overvoltage Input Pin. An external resistor divider is used from the supply to this pin to allow an
internal comparator to detect if the supply is above the OV limit.
6 2 PLIM The voltage on this pin is proportional to the VDS voltage of the FET. As the PLIM voltage changes, the
current limit automatically adjusts to maintain constant power across the FET.
7 3 VCAP A capacitor with a value of 1 μF or greater should be placed on this pin to maintain good accuracy.
This is an internal regulated supply. This pin can be used as a reference to program the ISET pin
voltage.
8 4 ADC_V This pin is used to read back the input voltage using the internal ADC. It can be connected to the OV
string or a separate divider.
9 5 ISET This pin allows the current limit threshold to be programmed. The default limit is set when this pin is
connected directly to VCAP. Alternatively, using a resistor divider from VCAP, the current limit can be
adjusted to achieve a user defined sense voltage. An external reference can also be used.
10 6 SS A capacitor is used on this pin to set the inrush current soft start ramp profile. The voltage on the soft
start pin controls the current sense voltage limit, allowing control over the inrush current profile.
11 7 TIMER Timer Pin. An external capacitor, CTIMER, sets an initial timing cycle delay and a fault delay. The GATE
pin turns off when the voltage on the TIMER pin exceeds the upper threshold.
12 8 LATCH This pin signals the device latching off after an overcurrent fault. This pin is also used to configure the
desired retry scheme. See the Hot Swap Fault Retry section for additional details.
13 9 ADR PMBus Address Pin. This pin can be tied low, tied to VCAP, left floating, or tied low through a resistor
to set four different PMBus addresses.
ADM1075 Data Sheet
Pin No.
TSSOP LFCSP Mnemonic Description
14 10 SHDN Drive this pin low to shut down the gate. Internal weak pull-up to VIN.
This pin is also used to configure the desired retry scheme. See the Hot Swap Fault Retry section for
additional details.
15 11 RESTART Falling Edge Triggered 10 sec Automatic Restart. The gate remains off for 10 seconds, and then
powers back up. Internal weak pull-up to VIN. This pin is also used to configure the desired retry
scheme. See the Hot Swap Fault Retry section for additional details.
16 12 GPO1/ALERT1
/CONV
General-Purpose Digital Output (GPO1).
Alert (ALERT1). This pin can be configured to generate an alert signal when one or more fault or
warning conditions have been detected.
Conversion (CONV). This pin can be used as an input signal to control when a power monitor ADC
sampling cycle begins.
This pin defaults to indicate FET health mode at power-up. There is no internal pull-up on this pin.
17 13 GPO2/ALERT2 General-Purpose Digital Output (GPO2).
Alert (ALERT2). This pin can be configured to generate an alert signal when one or more fault or
warning conditions have been detected.
This pin is also used to configure the desired retry scheme. See the Hot Swap Fault Retry section for
further details. This pin defaults to indicate a seven-attempt fail at power-up.
There is no internal pull-up on this pin.
18 14 SDAO PMBus Serial Data Output. This is a split version of the SDA for easy use with optocouplers.
19 15 SDAI PMBus Serial Data Input. This is a split version of the SDA for easy use with optocouplers.
20 16 SCL PMBus Clock Pin. Open-drain input requires an external resistive pull-up.
21 17 PWRGD Power-Good Signal. This pin is used to indicate that the FET is no longer in the linear region and
capacitors are fully charged. See the PWRGD section for details on assert and deassert.
22 18 ADC_AUX This pin is used to read back a voltage using the internal ADC.
23 19 SPLYGD This pin asserts low when the supply is within the UV and OV limits set by the UVx and OV pins.
24 20 VEE Chip Ground Pin. Must connect to –VIN rail (lowest potential).
25 21 SENSE− Negative Current Sense Input Pin. A sense resistor between the SENSE+ pin and the SENSE− pin sets
the analog current limit. The hot swap operation controls the external FET gate to maintain the
(VSENSE+ − VSENSE−) sense voltage. This pin also connects to the VEE node, but should be routed
separately.
26 22 SENSE+ Positive Current Sense Input Pin. A sense resistor between the SENSE+ pin and the SENSE− pin sets
the analog current limit. The hot swap operation controls the external FET gate to maintain the
(VSENSE+ − VSENSE−) sense voltage. This pin also connects to the FET source node.
27
23
GATE
Gate Output Pin. This pin is the gate drive of an external N-channel FET. It is driven by the FET drive
controller. The FET drive controller regulates to a maximum load current by regulating the GATE pin.
GATE is held low while the supply is out of the voltage range.
28 24 VEE_G Chip Ground Pin. Must connect to –VIN rail (lowest potential). The PCB layout should configure this
pin as the gate pull-down return.
EPAD EPAD Exposed Pad. Solder the exposed pad to the board to improve thermal dissipation. The exposed pad
can be connected to VEE.
Rev. C | Page 12 of 52
Data Sheet ADM1075
TYPICAL PERFORMANCE CHARACTERISTICS
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
IIN (mA)
TEMPERATURE ( °C)
09312-005
Figure 5. IIN vs. Temperature
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
VIN (V)
TEMPERATURE ( °C)
IIN =30mA
IIN = 5.5mA
09312-006
Figure 6. VIN vs. Temperature
0.1
1
10
100
12345678910 11 12 13
IIN (mA)
VIN (V)
+105°C
+85°C
+25°C
–40°C
09312-007
Figure 7. IIN vs. VIN
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
UVLO (V)
TEMPERATURE ( °C)
09312-008
RISING
FALLING
Figure 8. UVLO vs. Temperature
4
5
6
7
8
9
10
–50 –35 –20 –5 10 25 40 55 70 85 100 115
V
GATE
LOW (mV)
TEMPERATURE ( °C)
09312-009
Figure 9. VGATE Low vs. Temperature (IGATE = 100 µA)
0
2
4
6
8
10
12
14
–40 –20 020 40 60 80 100 120
V
GATE
HIG H (V)
TEMPERATURE ( °C)
0µA
5µA
09312-010
Figure 10. VGATE High vs. Temperature
Rev. C | Page 13 of 52
ADM1075 Data Sheet
0
2
4
6
8
10
12
14
–50 –35 –20 –5 10 25 40 55 70 85 100 115
I
GATE
PULL-DOW N ( mA)
TEMPERATURE ( °C)
09312-011
Figure 11. IGATE Pull-Down vs. Temperature
I
GATE
PUL L-DO WN (mA)
V
GATE
(V)
0
2
4
6
8
10
12
0 2 4 6 810 12 14
09312-012
Figure 12. IGATE Pull-Down vs. VGATE
–50
–45
–40
–35
–30
–25
–20
–15
–10
–5
0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
IGATE PULL-UP (µA)
TEMPERATURE ( °C)
09312-013
Figure 13. IGATE Pull-Up vs. Temperature
0
5
10
15
20
25
30
35
40
45
50
0246 8 10 12 14
I
GATE
PULL-UP (µA)
V
GATE
(V)
09312-014
Figure 14. IGATE Pull-Up vs. VGATE
–20
–18
–16
–14
–12
–10
–8
–6
–4
–2
0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
SS PULL-UP CURRENT (µ A)
TEMPERATURE ( °C)
09312-015
Figure 15. SS Pull-Up Current vs. Temperature
–80
–70
–60
–50
–40
–30
–20
–10
0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
I
TIMER
PULL-UP (µA)
TEMPERATURE ( °C)
09312-016
Figure 16. ITIMER Pull-Up vs. Temperature
Rev. C | Page 14 of 52
Data Sheet ADM1075
–10
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
I
TIMER
POR PULL-UP (µA)
TEMPERATURE ( °C)
09312-017
Figure 17. ITIMER POR Pull-Up vs. Temperature
0
1
2
3
4
5
6
–50 –35 –20 –5 10 25 40 55 70 85 100 115
ITIMER RET RY PULL - DOW N ( µA)
TEMPERATURE ( °C)
09312-018
Figure 18. ITIMER Retry Pull-Down vs. Temperature
0
200
400
600
800
1000
–50 –35 –20 –5 10 25 40 55 70 85 100 115
TI MER T HRE S HOL D ( mV )
TEMPERATURE ( °C)
HIGH
LOW
09312-019
Figure 19. TIMER Threshold vs. Temperature
0
20
40
60
80
100
120
140
160
180
200
–50 –35 –20 –5 10 25 40 55 70 85 100 115
PLIM T HRESHOLD (mV)
TEMPERATURE ( °C)
09312-020
Figure 20. PLIM Threshold vs. Temperature
0
20
40
60
80
100
120
140
160
180
200
–50 –35 –20 –5 10 25 40 55 70 85 100 115
PL I M CURRENT CLAM P (mV)
TEMPERATURE ( °C)
09312–021
Figure 21. PLIM Current Clamp vs. Temperature
0
0.5
1.0
1.5
2.0
2.5
3.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
VCAP (V)
TEMPERATURE ( °C)
09312-022
Figure 22. VCAP vs. Temperature (IVCAP = 100 µA)
Rev. C | Page 15 of 52
ADM1075 Data Sheet
0
200
400
600
800
1000
–50 –35 –20 –5 10 25 40 55 70 85 100 115
UVx T HRES HOL D ( mV )
TEMPERATURE ( °C)
UVH
UVL
09312-023
Figure 23. UVx Threshold vs. Temperature
0
200
400
600
800
1000
–50 –35 –20 –5 10 25 40 55 70 85 100 115
OV THRES HOL D ( mV )
TEMPERATURE ( °C)
09312-024
Figure 24. OV Threshold vs. Temperature
–100
–80
–60
–40
–20
0
20
40
60
80
100
020 40 60 80 100 120
I
SENSE
(µA)
V
SENSE
(mV)
SENSE–
SENSE+
09312-025
Figure 25. ISENSE vs. VSENSE
0
2
4
6
8
10
12
14
16
–40 –20 020 40 60 80 100 120
RESTART T IME ( s)
TEMPERATURE ( °C)
09312-026
Figure 26. Restart Time vs. Temperature
0
100
200
300
400
500
600
700
800
900
1000
–50 –35 –20 –5 10 25 40 55 70 85 100 115
SEVERE OC RESPONSE TIME (ns)
TEMPERATURE ( °C)
200ns G LI TCH F ILTER
900ns G LI TCH F ILTER
09312-027
Figure 27. Severe OC Response vs. Temperature
0
10000
20000
30000
40000
50000
60000
–50 –35 –20 –5 10 25 40 55 70 85 100 115
SEVERE OC RESPONSE TIME (ns)
TEMPERATURE ( °C)
10.7µs GLITCH FILTER
57.5µs GLITCH FILTER
09312-028
Figure 28. Severe OC Response vs. Temperature
Rev. C | Page 16 of 52
Data Sheet ADM1075
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
CIRCUI T BREAKE R OF FSET, VCBOS (mV)
TEMPERATURE ( °C)
ISET = 1.65V
ISET = 1.25V
ISET = 1.0V
ISET = 0.75V
ISET = 0.25V
ISET = 0.125V
09312-029
Figure 29. Circuit Breaker Offset vs. Temperature, ADM1075-1
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
–50 –35 –20 –5 10 25 40 55 70 85 100 115
CIRCUI T BREAKE R OF FSET, VCBOS (mV)
TEMPERATURE ( °C)
ISET = 1.65V
ISET = 1.25V
ISET = 1.0V
ISET = 0.75V
ISET = 0.25V
ISET = 0.125V
09312-030
Figure 30. Circuit Breaker Offset vs. Temperature, ADM1075-2
0
5
10
15
20
25
30
35
40
45
50
–50 –35 –20 –5 10 25 40 55 70 85 100 115
V
SENSECL
(mV)
TEMPERATURE ( °C)
ADM1075-1
ADM1075-2
09312-031
Figure 31. VSENSECL vs. Temperature, ISET = 1.65 V
0
5
10
15
20
25
30
35
40
45
50
1.21.11.00.90.80.70.60.50.40.30.20.10
V
SENSECL
(mV)
V
PLIM
(V)
ADM1075-2 + 85°C
ADM1075-2 + 25°C
ADM1075-2 –40°C
ADM1075-1 + 85°C
ADM1075-1 + 25°C
ADM1075-1 –40°C
09312-032
Figure 32. VSENSECL vs. PLIM
ADM1075-1
ADM1075-2
0
5
10
15
20
25
00.5 1.0 1.5
ACCURACY (%)
ISET (V)
09312-132
Figure 33. Worst-Case Hot Swap VSENSE Accuracy vs. ISET
ADM1075-1
ADM1075-2
0
10
20
30
40
50
60
00.5 1.0 1.5
VSENSECL (mV)
ISET (V)
09312-133
Figure 34. Typical Hot Swap VSENSECL vs. ISET
Rev. C | Page 17 of 52
ADM1075 Data Sheet
0
5
10
15
20
25
30
35
40
45
50
–50 –35 –20 –5 10 25 40 55 70 85 100 115
SEVERE OC THRESHOLD (mV)
TEMPERATURE ( °C)
125%
150%
200%
225%
09312-035
Figure 35. Severe OC Threshold vs. Temperature, ADM1075-1, ISET = 1.65 V
–50 –35 –20 –5 10
25 40 55 70 85 100 115
SEVERE OC THRESHOLD (mV)
TEMPERATURE ( °C)
125%
150%
200%
225%
09312-036
0
10
20
30
40
50
60
70
80
90
100
Figure 36. Severe OC Threshold vs. Temperature, ADM1075-2, ISET = 1.65 V
125%
225%
ISET (V)
0
10
20
30
40
50
60
70
0.25 0.45 0.65 0.85 1.05 1.25 1.45 1.65
SEVERE OC THRESHOLD (mV)
200%
150%
09312-136
ISE T UNDEFI NE D
IN G REYAREA
Figure 37. Severe OC Threshold vs. ISET, ADM1075-1
ISET (V)
0
20
40
60
80
100
120
140
0.25 0.45 0.65 0.85 1.05 1.25 1.45 1.65
SEVERE OC THRESHOLD (mV)
09312-237
125%
225%
ISE T UNDEFI NE D
IN G REYAREA
200%
150%
Figure 38. Severe OC Threshold vs. ISET, ADM1075-2
0
1
2
3
4
5
6
7
010 20 30 40 50 60
ACCURACY (%)
SENSE VOLTAGE (mV)
ADM1075-1
ADM1075-2
09312-138
Figure 39. Worst-Case Current Sense Power Monitor Error vs. Current Sense
Voltage (VSENSE)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 1 2 3 4 5 6 78 9 10
V
OL
(V)
I
OL
(mA)
PWRGD
GPO1
GPO2
LATCH
SPLYGD
09312-040
Figure 40. VOL vs. IOL
Rev. C | Page 18 of 52
Data Sheet ADM1075
0
0.5
1.0
1.5
2.0
2.5
3.0
–25 –20 –15 –10 –5 05
VADR (V)
IADR (µ A)
00 DECODE 01 DECODE 10 DECODE 11 DECODE
09312-041
Figure 41. VADR vs. IADR
Rev. C | Page 19 of 52
ADM1075 Data Sheet
THEORY OF OPERATION
When circuit boards are inserted into a live backplane,
discharged supply bypass capacitors draw large transient
currents from the backplane power bus as they charge. Such
transient currents can cause permanent damage to connector
pins, as well as dips on the backplane supply that can reset other
boards in the system.
The ADM1075 is intended to control the powering on and off
of a board in a controlled manner, allowing the board to be
removed from, or inserted into, a live backplane by protecting it
from excess currents. The ADM1075 can reside either on the
backplane or on the removable board.
A minimal load current requirement is assumed when charging
the load capacitance. If the load current is too large relative to
the regulation current, it may not be possible to charge the load
capacitance. The PWRGD pin can be used to disable the load
until the load capacitance is fully charged.
POWERING THE ADM1075
The ADM1075 typically operates from a negative supply of
−35 V to −80 V and can tolerate transient voltages of up to
−200 V. The VIN pin is a positive supply pin with respect to
chip ground. It is a current-driven supply and is shunt regulated
to 12 V internally. It should be connected to the most positive
supply terminal (usually −48 V RTN or 0 V) through a dropper
resistor. The resistor should be chosen such that it always
supplies enough current to overcome the maximum quiescent
supply current of the chip while not exceeding the maximum
allowable shunt current. After the system supply range has been
established, an appropriate value for the dropper resistor can be
calculated.
MAXSHUNT
MINSHUNT
MAXIN
MINSHUNT
I
VV
R
_
_
_
_
/
=
MINSHUNT
MAX
SHUNT
MIN
IN
MAXSHUNT
I
VV
R
_
_
_
_
/
=
where:
VIN_MIN and VIN_MAX are the supply voltage extremes (that is, 35 V,
80 V).
VSHUNT_MIN and VSHUNT_MAX are the shunt regulator voltage data
sheet specifications (see Table 1).
ISHUNT_MIN is the maximum quiescent supply current (minimum
shunt current).
ISHUNT_MAX is the maximum shunt input current.
ISHUNT_MAX can be calculated based on the maximum ambient
temperature (TA(MAX)) in the application, the maximum junction
temperature (TJ(MAX) = 105°C), and the θJA value of the package
from Table 4. Worst-case internal power is at VIN(MAX) from
Table 1.
)(
JA
)()(
_
MAX
MAXAMAXJ
MAXSHUNT
VIN
TT
I×
/
=
θ
For example, the maximum shunt current with a TSSOP device
at 80°C maximum ambient can be calculated as
mA28
V13C/W68
80105
_=
×°
°/°
=CC
IMAXSHUNT
Toler ance of supplies and resistors should also be accounted for
to ensure that the shunt current is always within the desired range.
Care must be taken to ensure that the power rating of the shunt
resistor is sufficient. The power may be as high as 2 W at
extreme supply conditions. Multiple shunt resistors can be used
in series or in parallel to share power between resistors.
MAX
MINSHUNT
MAXIN
SHUNTRIVVVIP×/== )( _
_
_
where:
SHUNT
MINSHUNT
MAXIN
MAX
R
VV
I
_
_
/
=
The power dissipation in the shunt resistor can be saved if a
suitable voltage rail is available to power the chip directly. This
voltage rail must be well regulated to ensure that it is always
greater than the UVLO threshold but less than the minimum
shunt regulation voltage. The power directly without shunt
specification in Table 1 shows the limits this voltage rail must
meet. Note that this voltage is referenced to VEE.
The VIN pin provides the majority of the bias current for the
device. The remainder of the current needed to control the gate
drive and to best regulate the VGS voltage is supplied by the
SENSE± pins. The VEE and SENSE− pins are connected to the
same voltage rail, although through separate traces to prevent
accuracy loss in the sense voltage measurement (see Figure 42).
R
SENSE
Q1
SENSE–
VEE
GATE
VIN
R
SHUNT
SENSE+
ADM1075
–48V RTN
VEE
C
LOAD
1µF
09312-042
Figure 42. Powering the ADM1075
The available shunt current range should be wide enough to
accommodate most telecommunication input voltage ranges.
In an application where a wider input voltage range is possible,
some external circuitry may be required to meet the shunt
regulation current specifications. The applications diagram in
Figure 43 shows an example of such a circuit, using a Zener
diode and a bipolar junction transistor (BJT) device as an
external pre-regulator on the −48 V supply. This ensures that
the shunt regulation current is always within specification even
at the extremes of supply voltage.
Rev. C | Page 20 of 52
Data Sheet ADM1075
RSENSE
Q1
SENSE–
VEE
GATE
VIN
SENSE+
ADM1075
RDROP = 15Ω
–48V RT N
–48V
11V
VEE
1µF
Rb1 = 100kΩ Rb2 = 640Ω
Ib = 6µ A TO 33µA
10.3V (5.5mA)
CIN
CLOAD
18V
TO
75V
09312-137
Figure 43. Wide Input Supply Range
CURRENT SENSE INPUTS
The load current is monitored by measuring the voltage drop
across an external sense resistor, RSENSE. An internal current
sense amplifier provides a gain of 25 or 50 (depending on the
model) to the voltage drop detected across RSENSE. The result is
compared to an internal reference and detects when an
overcurrent condition occurs.
RSENSE
Q1
SENSE–
VEE
GATE
VIN
SENSE+
ADM1075
OVER-
CURRENT
1V REF
×25/50
+
+
–
–
09312-043
Figure 44. Hot-Swap Current Sense Amplifier
The SENSE± inputs can be connected to multiple parallel sense
resistors, which can affect the voltage drop detected by the
ADM1075. The current flowing through the sense resistors
creates an offset, resulting in reduced accuracy. To achieve
better accuracy, averaging resistors should be used to sum the
sense nodes of each sense resistor, as shown in Figure 45. The
typical value for the averaging resistors is 10 Ω. The value of the
averaging resistors is chosen to be much greater than the trace
resistance between the sense resistor terminals and the inputs to
the ADM1075. This greatly reduces the effects of differences in
the trace resistances.
Q1
SENSE–
VEE
GATE
VIN
SENSE+
ADM1075
BIAS
CURRENT
09312-044
Figure 45. Connection of Multiple Sense Resistors to SENSE± Pins
CURRENT LIMIT REFERENCE
The current limit reference voltage determines the load current
level to which the ADM1075 limits the current during an
overcurrent event. This is the reference voltage to which the
gained up current sense voltage is compared to determine if the
limit is reached. This current limit voltage, shown in Figure 46,
is then converted to a gate current to regulate the GATE pin.
m
LIMCURR
GATE
gVI ×=
_
where gm, the gate transconductance, = 660 µS.
An internal current limit reference selector block continuously
compares the ISET, soft start, and foldback (derived from PLIM)
voltages, determines which is the lowest at any given time, and
uses it as the current limit reference. This ensures that the
programmed current limit, ISET, is used in normal operation
and the soft start and foldback features reduce the current limit
when required.
The foldback and soft start voltages change during different
stages of operation and are clamped to a lower level of 100 mV
(typical) to prevent zero current flow due to the current limit
being too low.
GATE
SENSE+
ADM1075
VEE
SENSE–
SS
CURRENT
LIMIT
VOLTAGE
FLB
( = 0.1/PLIM)
ISET
TIMEOUT
CURRENT
LIMIT
CONTROL
REF
SELECT
1.0V
CURRENT
LIMIT
VCAP
10µA
GATE
DRIVE
LOGIC
PLIM
–
×25/50
+
+
–
09312-045
Figure 46. Current Limit Reference Selection
Rev. C | Page 21 of 52
ADM1075 Data Sheet
09312-046
SS
FLB
ISET1V
0
.1V
V
t
CURRENT LIM IT
REFERENCE
Figure 47. Interaction of Soft Start, Foldback, and ISET Current Limits
SETTING THE CURRENT LIMIT (ISET)
The maximum current limit is partially determined by selecting
a sense resistor to match the current sense voltage limit on the
controller for the desired load current. However, as currents
become larger, the sense resistor value becomes smaller and
resolution can be difficult to achieve when selecting the appropri-
ate sense resistor value. The ADM1075 provides an adjustable
sense voltage limit to deal with this issue. The device allows the
user to program the required current sense voltage limit from
15 mV to 25 mV for the ADM1075-1 and from 30 mV to 50 mV
for the ADM1075-2.
The default value of 20 mV/40 mV is achieved by connecting
the ISET pin directly to the VCAP pin (VCAP > 1.65 V ISET
reference select threshold). This configures the device to use an
internal 1 V reference, which equates to 20 mV/40 mV at the
sense inputs (see Figure 48(a)).
ADM1075
(PARTIAL)
VCAP
ISET
C1
VEE VEE
(A) (B)
VCAP
ISET
C1 R1
R2
ADM1075
(PARTIAL)
09312-047
Figure 48. (a) Fixed 20 mV/40 mV Current Sense Limit
(b) Adjustable 15 mV to 50 mV Current Sense Limit
To set the sense voltage in the 15 mV to 50 mV range, a resistor
divider is used to apply a reference voltage to the ISET pin (see
Figure 48(b)). The VCAP pin has a 2.7 V internally generated
voltage that can be used to set a voltage at the ISET pin.
Assuming VISET equals the voltage on the ISET pin, the resistor
divider should be sized to set the ISET voltage as follows:
VISET = (VSENSE × 50) for ADM1075-1 or
VISET = (VSENSE × 25) for ADM1075-2
where VSENSE is the sense voltage limit. The VCAP rail can also
be used as the pull-up supply for setting the I2C address. The
VCAP pin should not be used for any other purpose. To
guarantee accuracy specifications, care must be taken to not
load the VCAP pin by more than 100 µA.
SOFT START
A capacitor connected to the SS pin determines the inrush
current profile. Before the FET is enabled, the output voltage of
the current limit reference selector block is clamped at 100 m V.
This, in turn, holds the current limit reference at approximately
2 mV for the ADM1075-1 or 4 mV for the ADM1075-2. When
the FET is requested to turn on, the SS pin is held at ground
until the voltage between the SENSE+ and SENSE− pins
(VSENSE) reaches the circuit breaker voltage, VCB.
VCB = VSENSECL − VCBOS
When the load current generates a sense voltage equal to VCB, a
10 µA current source is enabled, which charges the SS capacitor
and results in a linear ramping voltage on the SS pin. The
current limit reference also ramps up accordingly, allowing the
regulated load current to ramp up, while avoiding sudden
transients during power-up. The SS capacitor value is given by
ISET
SS
SS
V
tI
C×
=
where ISS = 10 µA, and t is the SS ramp time.
For example, a 10 nF capacitor gives a soft start time of 1 ms.
Note that the SS voltage may intersect with the PLIM or
foldback (FLB) voltage, and the current limit reference may
change to follow PLIM (see Figure 47). This has minimal
impact on startup because the output voltage rises at a similar
rate to SS.
CONSTANT POWER FOLDBACK (PLIM)
Foldback is a method that actively reduces the current limit as
the voltage drop across the FET increases. It keeps the power
across the FET below the programmed value during power-up,
overcurrent, or short-circuit events. This allows a smaller FET
to be used, resulting in significant cost savings. The foldback
method employed is a constant power foldback scheme, meaning
power in the FET is held constant regardless of the VDS of the
FET. This simplifies the task of ensuring that the FET is always
operating within the SOA region.
The ADM1075 detects the voltage drop across the FET by
monitoring the voltage on the drain of the FET (via the PLIM
pin). The device relies on the principle that the source of the
FET is at the most negative expected supply voltage, and the
magnitude of the drain voltage is relative to that of the VDS of
the FET. Using a resistor divider from the drain of the FET to
Rev. C | Page 22 of 52
Data Sheet ADM1075
the PLIM pin, the relationship of VDS to VPLIM can be controlled.
The foldback voltage, VFLB, is the input to the current limit
reference selector block and is defined as
VFLB = 0.1/VPLIM
The resistor divider should be designed to generate a VFLB
voltage equal to ISET when the VDS of the FET (and thus VPLIM)
rises above the desired power level. If ISET = 1 V, V PLIM needs to
be 0.1 V at the point where constant power takes over (VFLB =
ISET). For example, to generate a 200 W constant power limit at
10 A current limit, the maximum VDS is required to be 20 V at
the current limit. Therefore, the resistor divider must be 200:1
to generate a 0.1 V PLIM voltage at VDS = 20 V. A s VPLIM
continues to increase, the current limit reference follows VFLB
because it is now the lowest voltage input to the current limit
reference selector block. This results in a reduction of the
current limit, and, therefore, the regulated load current. To
prevent complete current flow restriction, a clamp becomes
active when the current limit reference reaches 100 m V. T h e
current limit cannot drop below this level. This 200 W constant
power example is illustrated in terms of FET SOA and real
scope plots in Figure 49 and Figure 50.
When VFLB has control of the current limit reference, the
regulation current through the FET is
ID = VFLB/(Gain × RSENSE)
where ID is the external FET drain current, and Gain is the sense
amplifier gain.
ID = 0.1/(VPLIM × Gain × RSENSE)
ID = 0.1/(VDS × D × Gain × RSENSE)
where D is the resistor divider factor on PLIM.
Therefore, the FET power is calculated as
PFET = ID × VDS = 0.1/(D × Gain × RSENSE)
Because PFET does not have any dependency on VDS, it remains
constant. Therefore, the FET power for a given system can be
set by adjusting the divider (D) driving the PLIM pin.
The limits to the constant power system are when VFLB > ISET (or
1 V if VISET > VISETRSTH) or when VFLB < 100 mV (100 mV max
clamp on VCLREF). With an ISET voltage of 1 V, this gives a 10:1
foldback current range.
1000
100
10
1
0.1
0.1 110 100 1000
V
DS
(V)
I
D
(A)
09312-143
MAX 200W
POWER
DISSIPATION
60V × 3. 33A = 200W
20V × 10A = 200W
1µs
10µs
100µs
1ms
10ms
DC
Figure 49. FET SOA
3,4
1,2
CURRENT LI M IT ADJUS TI NG
VIN
I
IN
V
DS
200W CONST ANT POW E R
GATE
M1
09312-144
Figure 50. 200 W Constant Power Scope Plot, CH1 = VIN; CH2 = VDS;
CH3 = GATE; CH4 = System Current; M1 = FET Power
TIMER
The TIMER pin handles several timing functions with an
external capacitor, CTIMER. There are two comparator thresholds:
VTIMERH (1.0 V) and VTIMERL (0.05 V). The four timing current
sources are a 3 μA pull-up, a 60 μA pull-up, a 2 μA pull-down,
and a 100 μA pull-down.
These current and voltage levels, together with the value of
CTIMER chosen by the user, determine the initial timing cycle
time, the fault current limit time, and the hot swap retry duty
cycle. The TIMER capacitor value is determined using the
following equation:
CTIMER = (tON × 60 μA)/VTIMERH
where tON is the time that the FET is allowed to spend in
regulation. The choice of CTIMER is based on matching this time
with the SOA requirements of the FET. Foldback can be used
here to simplify selection.
When VIN is connected to the backplane supply, the internal
supply of the ADM1075 must be charged up. A very short time
later when the internal supply is fully up and above the undervolt-
age lockout voltage (UVLO), the device comes out of reset.
During this first short reset period, the GATE and TIMER pins
are both held low. The ADM1075 then goes through an initial
Rev. C | Page 23 of 52
ADM1075 Data Sheet
timing cycle. The TIMER pin is pulled up with 3 μA. When the
TIMER reaches the VTIMERH threshold (1.0 V), the first portion
of the initial cycle is complete. The 100 μA current source then
pulls down the TIMER pin until it reaches VTIMERL (0.05 V). The
initial cycle duration is related to CTIMER by the following equation:
μA100
)(
μA3
TIMERTIMERLTIMERHTIMERTIMERH
INITIAL
CVVCV
t×/
+
×
=
For example, a 470 nF capacitor results in a power-up delay of
approximately 160 ms. Provided the UV and OV detectors are
inactive when the initial timing cycle terminates, the device is
ready to start a hot swap operation.
When the voltage across the sense resistor reaches the circuit
breaker trip voltage, VCB, the 60 µA timer pull-up current is
activated, and the gate begins to regulate the current at the current
limit. This initiates a ramp-up on the TIMER pin. If the sense
voltage falls below this circuit breaker trip voltage before the
TIMER pin reaches VTIMERH (1.0 V), the 60 µA pull-up is
disabled, and the 2 µA pull-down is enabled.
The circuit breaker trip voltage is not the same as the hot swap
sense voltage current limit. There is a small circuit breaker
offset, VCBOS, which means that the timer actually starts a short
time before the current reaches the defined current limit.
However, if the overcurrent condition is continuous and the
sense voltage remains above the circuit breaker trip voltage, the
60 µA pull-up remains active and the FET remains in regulation.
This allows the TIMER pin to reach VTIMERH and initiate the
GATE shutdown. The LATCH pin is pulled low immediately.
In latch-off mode, the TIMER pin is switched to the 2 µA pull-
down when it reaches the VTIMERH threshold. The LATCH pin
remains low. While the TIMER pin is being pulled down, the
hot swap controller is kept off and cannot be turned back on.
When the voltage on the TIMER pin goes below the VTIMERL
threshold, the hot swap controller can be reenabled by toggling
the UVx pin or by using the PMBus OPERATION command to
toggle the ON bit from on to off and then on again.
SETTING A LINEAR OUTPUT VOLTAGE RAMP AT
POWER-UP
The ADM1075 standard method of operation is to control a constant
power in the MOSFET during power-up into the load. This can
result in non-linear output voltage ramps and often requires
many retry attempts to charge larger load capacitances, due to
MOSFET SOA limitations. However, there is a way to configure
a single linear voltage ramp on the output which allows a constant
inrush current to be maintained. For a typical power-up using
constant power, as the output voltage increases in magnitude,
the controlled current also increases to maintain a constant power
in the pass MOSFET. This can be a challenge for maintaining
MOSFET SOA, where higher drain currents limit energy transfer
more than lower currents. However, if the output voltage is
programmed to result in a linear ramp, the inrush into the load
capacitance remains somewhat constant. This can have the
advantage of setting very low inrush currents where required by
combination of large output capacitance and FET SOA limitations.
The object of such a design is to allow a linear monotonic
power-up event without the restrictions of the system fault
timer. To achieve this, a power-up ramp is set so that the inrush
is low enough not to reach the circuit breaker current limit, or
constant power current limit. This allows power-up to continue
without the timer running. When using this method, take
separate care to ensure the power in the MOSFET during this
event meets the SOA requirements. The components labeled
RGD, CGD and CG on the gate pin in Figure 51 show the required
extra components.
0V
VIN
ADM1075
VEE GATE
PLIM
R
PLIM2
R
PLIM1
C
G
C
LOAD
C
GD
R
GD
R
SENSE
10Ω D
S
–48V
09312-151
Figure 51. Required Extra Components
To ensure the inrush current does not approach or exceed the
active current limit level, the output voltage ramp can be set by
selecting the appropriate value for CGD as follows:
CGD = (IGATEUP/IINRUSH) × CLOAD
where IGATEUP is the gate pull-up current specified.
Add margin and tolerance as necessary to ensure a robust
design. Subtract any parasitic CGD of the MOSFETS from the
total to determine the additional external capacitance required.
The power-up ramp time can now be approximated by:
tRAMP = (VIN × CLOAD)/IINRUSH
Check the SOA of the MOSFET for conditions and the duration
of this power-up ramp.
RGD and CG are used to limit the impact of sudden transients on
the MOSFET Drain pin being coupled to the GATE pin through
CGD. RG is chosen such that IGATEUP has minimal voltage drop
impact. Typical values would be 1 K. As a rule, CG is recommended
to be about 10× the value of CGD, to a maximum of 470 nF. CG
must be minimized and must not exceed 470 nF to avoid slowing
down gate shutdown in response to severe overcurrent events.
This capacitance results in slowing down the gate ramp through
VTH and therefore the trans-conductance current ramp. This
delay must also be considered when checking SOA during
power-up into a fault. When using this method, always remove
the SS cap, and TIMER can be minimized to provide a simple
fault filtering solution.
Rev. C | Page 24 of 52
Data Sheet ADM1075
HOT SWAP FAULT RETRY
The ADM1075 turns off the FET after an overcurrent fault.
With the default pin configuration, the part latches off after an
overcurrent fault and LATCH goes active low. This condition
can then be reset by either a power cycling event or a low signal
to either the SHDN input or RESTART input. It can also be
reset by toggling the UVx pin, using the PMBus operation
command or the PMBus power cycle command.
If the LATCH pin is connected to the SHDN pin, the part
makes seven attempts to hot swap before latching off. In this
mode, the part uses the TIMER pin to time a delay between
each attempt. In this way, a large load capacitance can be
charged using consecutive current limit periods.
The part can also be configured to autoretry an infinite number of
times with a 10 second cooling period between each retry. Connect-
ing LATCH to RESTART means that the part makes one hot
swap attempt between each cooling period. Connecting LATCH
to SHDN and GPO2/ALERT2 to RESTART means that the part
makes seven hot swap attempts between each cooling period.
The duty cycle of the automatic retry cycle is set by the ratio of
2 µA/60 µA, which approximates to being on ~4% of the time.
The value of the timer capacitor determines the on time of this
cycle, which is calculated as follows:
tON = VTIMERH × (CTIMER/60 μA)
tOFF = (VTIMERH − VTIMERL) × (CTIMER/2 μA)
A 470 nF capacitor on the TIMER pin gives ~8 ms of on time
(for example, to meet 10 ms SOA), and ~220 ms off time.
FAST RESPONSE TO SEVERE OVERCURRENT
The ADM1075 features a very fast detection circuit that quickly
responds to severe overcurrent events such as short circuits.
Such an event may cause catastrophic damage if not controlled
ver y quickly. A fast response circuit ensures that the ADM1075
detects an overcurrent event at approximately 150% of the normal
current limit (ISET) and responds and controls the current
within 1 µs in most cases. The severe overcurrent threshold
and glitch filter times are digitally programmable through the
PMBus. The threshold can be selected as 125%, 150%, 200%, or
225% of the normal current limit, and the glitch filter time can
be set to 200 ns, 900 ns, 10.7 μs, or 57 μs. This sets a maximum
response time of 300 ns, 950 ns, 13 μs, or 60 μs.
UV AND OV
The ADM1075 monitors the supply voltage for undervoltage
(UV) and overvoltage (OV) conditions. The OV pin is con-
nected to the input of an internal voltage comparator, and its
voltage level is internally compared with a 1 V voltage reference.
The user can program the value of the OV hysteresis by varying
the top resistor of the resistor divider on the pin. This impedance
in combination with the 5 μA OV hysteresis current (current
turned on after OV trips) sets the OV hysteresis voltage.
BOTTOM
BOTTOMTOP
THRESHOLD
RISING R
RR
OVOV +
×=
)μA
5( ×
/≈ TOP
RISING
FALLING R
OVOV
The UV detector is split into two separate pins, UVH and UVL.
The voltage on the UVH pin is compared internally to a 1 V
reference, whereas the UVL pin is compared to a 0.9 V reference.
Therefore, if the pins are tied together, the UV hysteresis is 100 mV.
The hysteresis can be adjusted by placing a resistor between
UVL and UVH.
Figure 52 illustrates the positive voltage monitoring input
connection. An external resistor network divides the supply
voltage for monitoring. An undervoltage event is detected when
the voltage connected to the UVL pin falls below 0.9 V, and the
gate is shut down using the 10 mA pull-down device. The fault
is cleared after UVH pin rises above 1.0 V.
Similarly, when an overvoltage event occurs and the voltage on
the OV pin exceeds 1 V, the gate is shut down using the 10 mA
pull-down device.
R
SENSE
Q1
C1
SENSE–
VEE
GATE
VIN
SENSE+
ADM1075
–48V RT N ( 0V )
R
SHUNT
UVH
UVL
OV
–48V
+
–
+
–
+
–
GATE
ENABLE
LOGIC
1V
0.9V
1V
09312-048
Figure 52. Undervoltage and Overvoltage Supply Monitoring
The maximum rating on the UVH pin is 4 V and the UVH
threshold is 1 V. This limits the maximum input voltage to
minimum input voltage ratio to 4:1. For example, if the UVH
threshold is set at 20 V, the maximum input voltage is 80 V so
as not to exceed the maximum ratings of the pin. If a wider
input range is required, some protection circuitry is required
on the UV pins to limit them to less than 4 V.
PWRGD
The PWRGD output indicates the status of the output voltage.
As shown in Figure 53, the PWRGD output is derived from the
DRAIN pin voltage. It is an open-drain output that pulls low
when the voltage on DRAIN is less than 2 V and the GATE pin
voltage is near its 12 V rail (power good). When a fault occurs
or hot swap is turned off, the open-drain pull-down is disabled,
allowing PWRGD to go high (power bad). PWRGD is guaran-
teed to be in a valid state for VIN ≥ 1 V.
Rev. C | Page 25 of 52
ADM1075 Data Sheet
FET
DRAIN
HOT SWAP
DISABLE
SIGNAL
DIO DE CLAMP S
DRAIN TO 2V
S
R
Q
Q
R
DRAIN
I
DRAIN
=
50µA MAX
DRAIN
2V
11V
GATE
PWRGD
09312-049
Figure 53. Generation of PWRGD Signal
DRAIN
Because the source of the FET is always at or near the most
negative system supply, the drain voltage is a close approxima-
tion to the VDS of the FET. When the voltage at the DRAIN pin
is less than 2 V, it is assumed the FET is turned on. The DRAIN
pin is used by the power-good circuitry to determine when
PWRGD can be asserted. A resistor is required on the DRAIN
pin to limit current on the pin to 50 μA. A 2 MΩ resistor is
suitable to limit the current in most cases.
SPLYGD
The SPLYGD output indicates when the input supply is within
the programmed voltage window. This is an open-drain output.
An external pull-up resistor is required on this pin.
LATCH
The LATCH output signals that the device has latched off after
an overcurrent fault. This pin is also used to configure the
desired retry scheme. See the Hot Swap Fault Retry section
for additional details.
SHDN
The SHDN pin is a level-triggered input that allows the user to
command a shutdown of the hot swap function. When this
input is set low, the GATE output is switched to VEE to turn the
FET off. This pin has an internal pull-up of approximately 8 µA,
allowing it to be driven by an open-drain pull-down output or a
push-pull output. The input threshold is ~1 V.
This pin is also used to configure the desired retry scheme. See
the Hot Swap Fault Retry section for additional details.
Take care if using the SHDN pin as an on/off pin. Pulling the
SHDN low always turns off the gate. However, taking SHDN
high again turns on hot swap only if there have been less than
seven faults/shutdown events within a 10 second period. The
retry scheme is configured to set GPO2/ALERT2 low after
seven faults. The SHDN pin cannot clear the GPO2/ALERT2
fault. The retry counter is cleared after 10 seconds of power
good. Therefore, this is not an issue if there is never going to be
more than seven SHDN events within a 10 second period.
The UVH or UVL pin may work better as a system on/off pin if
required. Toggling the UVx pin clears any faults (including
GPO2/ALERT2 low after seven retry attempts). A switch
shorting UVH or UVL to VEE works as an on/off switch.
RESTART
The RESTART pin is a falling edge triggered input that allows
the user to command a 10 second automatic restart. When this
input is set low, the gate turns off for 10 seconds, and then powers
back up. The pin is falling edge triggered; therefore, holding
RESTART low for more than 10 seconds generates only one
restart. This pin has an internal pull-up of approximately 8 µA,
allowing it to be driven by an open-drain pull-down output or a
push-pull output. The input threshold is ~1 V.
This pin is also used to configure the desired retry scheme. See
the Hot Swap Fault Retry section for additional details.
FET HEALTH
The ADM1075 features a method of detecting a shorted pass
FET. The FET health status can be used to generate an alert on
the GPO1/ALERT1/CONV and GPO2/ALERT2 pins. By default,
at power-up, an alert is generated on GPO1/ALERT1/CONV if
the FET health status indicates a bad FET is present. FET health
is considered bad if all of the following conditions are true:
• The ADM1075 is holding the FET off, for example, during
the initial power-on cycle time.
• VSENSE > 2 mV for the ADM1075-1 and 4 mV for the
ADM1075-2.
• VGATE < ~1 V.
POWER MONITOR
The ADM1075 features an integrated ADC that accurately
measures the current sense voltage and the ADC_V voltage.
It can also optionally monitor the ADC_AUX voltage. The
measured input voltage (ADC_V) and the current being
delivered to the load are multiplied to give a power value that
can be read back. Each power value is also added to an accumula-
tor that can be read back to allow an external device to calculate
the energy consumption of the load.
The PEAK_IOUT, PEAK_VIN, and PEAK_VAUX commands
can be used to read the highest peak current or voltage since the
value was last cleared.
An averaging function is provided for voltage and current that
allows a number of samples to be averaged by the ADM1075.
This function reduces the need for postprocessing of sampled
data by the host processor. The number of samples that can be
averaged is 2N, where N is in the range of 0 to 7.
The power monitor current sense amplifier is bipolar and can
measure both positive and negative currents. It has two input
ranges and can be selected using the PMBus interface. The
input ranges are ±25 mV and ±50 m V.
The two basic modes of operation for the power monitor are
single shot and continuous. In single-shot mode, the power
monitor samples the input voltage and current a number of
times, depending on the averaging value selected by the user.
Rev. C | Page 26 of 52
Data Sheet ADM1075
The ADM1075 returns a single value corresponding to the
average voltage and current measured. When configured for
continuous mode, the power monitor continuously samples
voltage and current, making the most recent sample available
to be read. The ADC runs in continuous mode by default at
power-up.
The single-shot mode can be triggered in a number of ways.
The simplest is by selecting the single-shot mode using the
PMON_CONFIG command and writing to the CONVERT bit
using the PMON_CONTROL command. The CONVERT bit
can also be written as part of a PMBus group command. Using a
group command allows multiple devices to be written to as part
of the same I2C bus transaction, with all devices executing the
command when the stop condition appears on the bus. In this
way, several devices can be triggered to sample at the same time.
When the GPO1/ALERT1/CONV pin is set to the convert
(CONV) mode, an external hardware signal can be used to
trigger the single-shot sampling of one or more parts at the
same time.
Each time a current sense and input voltage measurement is
taken, a power calculation is performed, multiplying the two
measurements together. This can be read from the device using
the READ_PIN command, returning the input power.
At the same time, the calculated power value is added to a
power accumulator register that may increment a rollover
counter if the value exceeds the maximum accumulator value,
and that also increments a power sample counter.
The power accumulator and power sample counter are read
back using the same READ_EIN command to ensure that the
accumulated value and sample count are from the same point in
time. The bus host reading the data assigns a timestamp to show
when the data is read. By calculating the time difference between
consecutive uses of READ_EIN and determining the delta in
power consumed, it is possible for the host to determine the
total energy consumed over that period.
ISOLATION
Isolation is usually required in −48 V systems because there can
be a large voltage difference between different ground planes in
the system. The ADM1075 is referenced to −48 V, whereas the
MCU is usually referenced to 0 V. In almost all cases, the I2C signals
must be isolated. Any other ADM1075 digital input and output
signals that go to or come from the MCU must also be isolated.
Analog Devices, Inc., provide a range of digital isolators using
iCoupler® technology. iCoupler technology is based on chip
scale transformers rather than the LEDs and photodiodes used
in optocouplers. The ADuM1250 is a dual I2C isolator and can
be used in conjunction with the ADM1075 for I2C isolation.
In cases where more digital signals need to be isolated, the
ADuM3200 is a dual-channel digital isolator whereas the
ADuM5404 is a quad-channel isolator with isoPower®, an
integrated, isolated dc-to-dc converter.
VDD1
SCL2
SCL1
GND1
VDD2
SDA2
SCL2
GND2
–48V
–48V
GND_ISO
GND_ISO
5V_ISO
5V 100nF 100nF
SDA SDA_ISO
SCL SCL_ISO
ISOLATED SIDE
(SECONDARY)
–48V SI DE
(PRIMARY)
VDD1 10kΩ
10kΩ
ADuM1250
09312-147
Figure 54. ADuM1250 I2C Isolation
The ADuM1250 and ADuM3200 must be powered from both the
primary and secondary sides. The ADuM5404 only needs to be
powered from the secondary side and can provide power across
the isolation barrier via the integrated dc-to-dc converter. There-
fore, the ADuM5404 can be used to power the primary side of
the ADuM1250 if both are used on the board. Some extra care
is required if using the ADuM5404 to power the ADuM3200. If
the power at the secondary side is enabled by the ADM1075, the
isoPower solution may not work. Because isoPower is unpowered
in this case, the ADuM3200 outputs are in an undefined state. If
the SHDN input comes from the ADuM3200, it may be held
low, and the ADM1075 never turns on the FET or enables
power at the secondary side.
isoPower uses high frequency switching elements to transfer
power through its transformer. Special precautions must be
taken during printed circuit board (PCB) layout to meet
emissions standards. See the AN-0971 Application Note for
board layout recommendations.
Powering the iCouplers from the secondary side is usually
straightforward because there is often a suitable voltage rail
available. However, there is not always a suitable voltage rail
available on the primary side (−48 V side). If the ADuM5404 is
not used on the system, the ADuM1250 can be powered on the
primary side in a number of different ways.
If a voltage rail is available on the primary side (3.3 V or 5 V
referenced to VEE), that can be used to power the chip directly.
Otherwise, the ADM1075 shunt voltage and/or the −48 V
supply can be regulated down to power the part. A simple
emitter follower circuit achieves this, as shown in Figure 55.
12V (S HUNT) –48V RT N
–48V
–48V
5V AUX
20kΩ1kΩ
0.33W
1µF
20k
6V
09312-148
Figure 55. Powering iCoupler from −48 V Supply
Rev. C | Page 27 of 52
ADM1075 Data Sheet
PMBus INTERFACE
The I2C bus is a common, simple serial bus used by many devices
to communicate. It defines the electrical specifications, the bus
timing, the physical layer, and some basic protocol rules.
SMBus is based on I2C and aims to provide a more robust and
fault-tolerant bus. Functions such as bus timeout and packet
error checking are added to help achieve this robustness, along
with more specific definitions of the bus messages used to read
and write data to devices on the bus.
PMBus is layered on top of SMBus and, in turn, on I2C. Using the
SMBus defined bus messages, PMBus defines a set of standard
commands that can be used to control a device that is part of a
power chain.
The ADM1075 command set is based upon the PMBus™ Power
System Management Protocol Specification, Part I and Part II,
Revision 1.2. This version of the standard is intended to provide
a common set of commands for communicating with dc-to-dc
type devices. However, many of the standard PMBus commands
can be mapped directly to the functions of a hot swap controller.
Part I and Part II of the PMBus standard describe the basic
commands and how they can be used in a typical PMBus setup.
The following sections describe how the PMBus standard and
the ADM1075 specific commands are used.
DEVICE ADDRESSING
The ADM1075 is available in two models: the ADM1075-1 and
ADM1075-2. The PMBus address is seven bits in size. The
upper five bits (MSBs) of the address word are fixed and are
different for each model, as follows:
• ADM1075-1: Base address is 00100xx (0x10)
• ADM1075-2: Base address is 00110xx (0x18)
The ADM1075-1 and ADM1075-2 have a single ADR pin that
is used to select one of four possible addresses for a given
model. The ADR pin connection selects the lowest two bits
(LSBs) of the 7-bit address word (see Tabl e 6).
Table 6. PMBus Addresses and ADR Pin Connection
Value of Address LSBs ADR Pin Connection
00 Connect to VEE
01 150 kΩ resistor to VEE
10 No connection (floating)
11 Connect to VCAP
SMBus PROTOCOL USAGE
All I2C transactions on the ADM1075 are performed using
SMBus defined bus protocols. The following SMBus protocols
are implemented by the ADM1075:
• Send byte
• Receive byte
• Write byte
• Read byte
• Write word
• Read word
• Block read
PACKET ERROR CHECKING
The ADM1075 PMBus interface supports the use of the packet
error checking (PEC) byte that is defined in the SMBus standard.
The PEC byte is transmitted by the ADM1075 during a read
transaction or sent by the bus host to the ADM1075 during a
write transaction. The ADM1075 supports the use of PEC with
all the SMBus protocols that it implements.
The use of the PEC byte is optional. The bus host can decide
whether to use the PEC byte with the ADM1075 on a message-
by-message basis. There is no need to enable or disable PEC in
the ADM1075.
The PEC byte is used by the bus host or the ADM1075 to detect
errors during a bus transaction, depending on whether the trans-
action is a read or a write. If the host determines that the PEC
byte read during a read transaction is incorrect, it can decide to
repeat the read if necessary. If the ADM1075 determines that the
PEC byte sent during a write transaction is incorrect, it ignores
the command (does not execute it) and sets a status flag.
Within a group command, the host can choose to send or not
send a PEC byte as part of the message to the ADM1075.
PARTIAL TRANSACTIONS ON I2C BUS
In the event of a specific sequence of events occurring on the
I2C bus, it is possible for the I2C interface on the device to go
into a state where it fails to ACK the next I2C transaction directed
to it. There are two ways that this behavior can be triggered:
• A partial I2C transaction consisting of a start condition,
followed by a single SCL clock pulse and stop condition.
• If the I2C bus master does not follow the 300 ns SDA data
hold time when signaling the ACK/NACK bit at the end of
a transaction. The device sees this as a single SCL clock
partial transaction.
In the event that the device NACKs a transaction, then the I2C
interface on the device can be reset by sending a series of up to
16 SCL clock pulses, or performing a dummy transaction to
another I2C address on the bus.
Rev. C | Page 28 of 52
Data Sheet ADM1075
Rev. C | Page 29 of 52
SMBus MESSAGE FORMATS
Figure 56 to Figure 64 show all the SMBus protocols supported
by the ADM1075, along with the PEC variant. In these figures,
unshaded cells indicate that the bus host is actively driving the
bus; shaded cells indicate that the ADM1075 is driving the bus.
Figure 56 to Figure 64 use the following abbreviations:
S = start condition
Sr = repeated start condition
P = stop condition
R = read bit
W = write bit
A = acknowledge bit (0)
A = acknowledge bit (1)
A represents the ACK (acknowledge) bit. The ACK bit is typi-
cally active low (Logic 0) if the transmitted byte is successfully
received by a device. However, when the receiving device is the
bus master, the acknowledge bit for the last byte read is a Logic 1,
indicated by A.
SPAAWSLAVE ADDRES S DATA BYTE
S PAAWSLAVE ADDRES S DATA BYTE PEC A
MASTER TO SLAVE
SLAVE TO MASTER
09312-050
Figure 56. Send Byte and Send Byte with PEC
SPAARSLAVE ADDRES S DATA BYT E
S PAARSLAVE ADDRES S DATA BYT E PEC
MASTER TO SLAVE
SLAVE TO MASTER
A
09312-051
Figure 57. Receive Byte and Receive Byte with PEC
SAAWSL AVE ADDRESS COM M AND CODE DATA BYT E PA
SAAWSL AVE ADDRESS COM M AND CODE DATA BYTE PA PEC A
MASTER TO SLAVE
SLAVE TO MASTER
09312-052
Figure 58. Write Byte and Write Byte with PEC
A
SLAVE ADDRESS RDATA BYTE
Sr A
A
SA
AWSLAVE ADDRE SS CO M MAND CODE PA
PEC
SAAWSLAVE ADDRES S COM M A ND CODE SLAVE ADDRES S PRDATA BYTE
Sr A
MASTER TO SLAVE
SLAVE TO MASTER
09312-053
Figure 59. Read Byte and Read Byte with PEC
P
SAAWSLAVE ADDRESS CO M M AND CO DE DATA BYTE L OW A A
SAAWSLAVE ADDRESS CO M M AND CO DE DATA BYTE L OW ADATA BYTE HIGH
DATA BYTE HIGH
APA
PEC
MASTER TO SLAVE
SLAVE TO MASTER
09312-054
Figure 60. Write Word and Write Word with PEC
SrA SLAVE ADDRESS ARSAWSLAVE ADDRESS COM M AND CODE A
DATA BYTE LOW
PA
AA
DATA BYTE HI GH
SrA SLAVE ADDRESS ARSAWSLAVE ADDRESS COM M AND CODE ADATA BYTE LOW
DATA BYTE HI GH P
PEC
MASTER TO SLAVE
SLAVE TO MASTER
09312-055
Figure 61. Read Word and Read Word with PEC
ADM1075 Data Sheet
Rev. C | Page 30 of 52
SrA SLAVE ADDRESS ARSAWSLAVE ADDRESS COM MAND CO DE ABYT E COUNT = N
A
DATA BYTE 1 PDATA BYTE NA
DATA BYTE 2
SrA SLAVE ADDRESS ARSAWSLAVE ADDRESS COM M AN D CODE ABY TE COUNT = N
A
DATA BYTE 1 ADATA BYTE N PPECA
DATA BYTE 2
MASTER TO SLAVE
SLAVE TO MASTER
A
A
09312-056
Figure 62. Block Read and Block Read with PEC
MASTER TO SLAVE
SLAVE TO MASTER
ALOW DATA BYTE ASAWDEVICE 1 ADD RESS COMMAND CODE 1 AHIGH DATA BYTE
ONE OR MORE DATA BYTES
ALOW DATA BYTE ASr AWDEVICE 2 ADDRESS COMMAND CODE 2 AHIGH DATA BYTE
ONE OR MORE DATA BYTES
ALOW DATA BYTE ASr AWDEVICE N AD DRE SS COMMAND C ODE N APHIGH DATA BYTE
ONE OR MORE DATA BYTES
09312-057
Figure 63. Group Command
MASTER TO SLAVE
SLAVE TO MASTER
APEC 1
P
A LOW DATA BYTE ASAWDEV ICE 1 ADDRE SS COMM AN D C ODE 1 AHI GH DATA BYTE
ONE OR M ORE DATA BYTES
APEC 2
A LOW DATA BYTE ASr AWDE V ICE 2 ADDRESS COM M AN D C ODE 2 AHIGH DATA BYTE
ONE OR M ORE DATA BYTES
A
PEC N
A LOW DATA BYTE ASr AWDE VICE N ADDRE S S COMMAND CO DE N AHI GH DATA BYTE
ONE OR M ORE DATA BYTES
09312-058
Figure 64. Group Command with PEC
GROUP COMMANDS
The PMBus standard defines what are known as group
commands. Group commands are single bus transactions that
send commands or data to more than one device at the same
time. Each device is addressed separately, using its own address;
there is no special group command address. A group command
transaction can contain only write commands that send data to
a device. It is not possible to use a group command to read data
from devices.
From an I2C protocol point of view, a normal write command
consists of the following:
I2C start condition
Slave address bits and a write bit (followed by ACK from
the slave device)
One or more data bytes (each of which is followed by ACK
from the slave device)
I2C stop condition to end the transaction
A group command differs from a nongroup command in that,
after the data is written to one slave device, a repeated start
condition is put on the bus followed by the address of the next
slave device and data. This continues until all the devices have
been written to, at which point the stop condition is put on the
bus by the master device.
The format of a group command and a group command with
PEC is shown in Figure 64.
Each device that is written to as part of the group command
does not immediately execute the command written. The device
must wait until the stop condition appears on the bus. At that
point, all devices execute their commands at the same time.
Using a group command, it is possible, for example, to turn
multiple PMBus devices on or off at the same time. In the case
of the ADM1075, it is also possible to issue a power monitor
command that initiates a conversion, causing multiple ADM1075
devices to sample together at the same time. This is analogous
to connecting the GPO1/ALERT1/CONV pins together and
configuring the pin in the convert (CONV) mode to drive the
power monitor sampling.
Data Sheet ADM1075
HOT SWAP CONTROL COMMANDS
OPERATION Command
The GATE pin that drives the FET is controlled by a dedicated
hot swap state machine. The UVH, UVL, and OV input pins,
along with the TIMER and SS pins and the current sense, all
feed into the state machine and control when and how strongly
the gate is turned off.
It is also possible to control the hot swap GATE output using
commands over the PMBus interface. The OPERATION com-
mand can be used to request the hot swap output to turn on.
However, if the UV pin indicates that the input supply is less
than required, the hot swap output is not turned on, even if the
OPERATION command indicates that the output should be
enabled.
If the OPERATION command is used to disable the hot swap
output, the GATE pin is held low, even if all hot swap state
machine control inputs indicate that it can be enabled.
The default state of the OPERATION command ON bit is 1;
therefore, the hot swap output is always enabled when the
ADM1075 comes out of UVLO. If the ON bit is never changed,
the UV input is the hot swap master on/off control signal.
By default, at power-up, the OPERATION command is disabled
and must be enabled using the DEVICE_CONFIG command.
This prevents inadvertent shutdowns of the hot swap controller
by software.
If the ON bit is set to 0 while the UV signal is high, the hot swap
output is turned off. If the UV signal is low or if the OV signal is
high, the hot swap output is already off and the status of the ON
bit has no effect.
If the ON bit is set to 1, the hot swap output is requested to turn
on. If the UV signal is low or if the OV signal is high, setting the
ON bit to 1 has no effect, and the hot swap output remains off.
It is possible to determine at any time whether the hot swap output
is enabled using the STATUS_BYTE or the STATUS_WORD
command (see the Status Commands section).
The OPERATION command can also be used to clear any latched
faults in the status registers. To clear latched faults, set the ON
bit to 0, and then reset it to 1.
DEVICE_CONFIG Command
The DEVICE_CONFIG command is used to configure certain
settings within the ADM1075, for example, to modify the
duration of the severe overcurrent glitch filter and to set the trip
threshold. This command is also used to configure the polarity
of the second IOUT current warnings.
At power-up, the OPERATION command is disabled, and
the ADM1075 responds with a NACK if the OPERATION
command is received. To allow use of the OPERATION
command, the OPERATION_CMD_EN bit must be set
using the DEVICE_CONFIG command.
POWER_CYCLE Command
The POWER_CYCLE command can be used to request that
the ADM1075 be turned off for ~10 seconds and then back on.
This command can be useful if the processor that controls the
ADM1075 is also powered off when the part is turned off. This
command allows the processor to request that the ADM1075 turn
off and back on again as part of a single command.
ADM1075 INFORMATION COMMANDS
CAPABILITY Command
The CAPABILITY command can be used by host processors
to determine the I2C bus features supported by the ADM1075.
The features reported are the maximum bus speed and whether
the device supports the packet error checking (PEC) byte and
the SMBAlert reporting function.
PMBUS_REVISION Command
The PMBUS_REVISION command reports the version of Part I
and Part II of the PMBus standard.
MFR_ID, MFR_MODEL, and MFR_REVISION Commands
The MFR_ID, MFR_MODEL, and MFR_REVISION
commands return ASCII strings that can be used to facilitate
detection and identification of the ADM1075 on the bus.
These commands are read using the SMBus block read message
type. This message type requires that the ADM1075 return a
byte count corresponding to the length of the string data that is
to be read back.
STATUS COMMANDS
The ADM1075 provides a number of status bits that are used
to report faults and warnings from the hot swap controller and
the power monitor. These status bits are located in six different
registers that are arranged in a hierarchy. The STATUS_BYTE
and STATUS_WORD commands provide eight bits and 16 bits
of high level information, respectively. The STATUS_BYTE and
STATUS_WORD commands contain the most important status
bits, as well as pointer bits that indicate whether any of the four
other status registers need to be read for more detailed status
information.
In the ADM1075, a particular distinction is made between
faults and warnings. A fault is always generated by the hot swap
controller and is defined by hardware component values. Three
events can generate a fault.
• Overcurrent condition that causes the hot swap timer to
time out
• Overvoltage condition on the OV pin
• Undervoltage condition on the UVx pin
When a fault occurs, the hot swap controller always takes some
action, usually to turn off the GATE pin, which is driving the
FET. A fault can also generate an SMBAlert on one or both of
the GPOx/ALERTx pins.
Rev. C | Page 31 of 52
ADM1075 Data Sheet
All warnings in the ADM1075 are generated by the power
monitor sampling voltage and current and then comparing
these measurements to the threshold values set by the various
limit commands. A warning has no effect on the hot swap
controller, but it may generate an SMBAlert on one or both of
the GPOx/ALERTx output pins.
When a fault or warning status bit is set, it always means that the
status condition—fault or warning—is active or was active at some
point in the past. When a fault or warning bit is set, it is latched
until it is explicitly cleared using either the OPERATION or the
CLEAR_FAULTS command. Some other status bits are live, that
is, they always reflect a status condition and are never latched.
STATUS_BYTE and STATUS_WORD Commands
The STATUS_BYTE and STATUS_WORD commands can
be used to obtain a snapshot of the overall part status. These
commands indicate whether it is necessary to read more
detailed information using the other status commands.
The low byte of the word returned by the STATUS_WORD
command is the same byte returned by the STATUS_BYTE
command. The high byte of the word returned by the STATUS_
WORD command provides a number of bits that can be used to
determine which of the other status commands must be issued
to obtain all active status bits.
STATUS_INPUT Command
The STATUS_INPUT command returns a number of bits
relating to voltage faults and warnings and power warnings on
the input supply.
STATUS_IOUT Command
The STATUS_IOUT command returns a number of bits
relating to current faults and warnings on the output supply.
STATUS_VAUX Command
The STATUS_VAUX command returns a number of bits
relating to current faults and warnings on the output supply.
STATUS_MFR_SPECIFIC Command
The STATUS_MFR_SPECIFIC command is a standard PMBus
command, but the contents of the byte returned is specific to
the ADM1075.
CLEAR_FAULTS Command
The CLEAR_FAULTS command is used to clear fault and
warnings bits when they are set. Fault and warnings bits are
latched when they are set. In this way, a host can read the bits
any time after the fault or warning condition occurs and
determine which problem actually occurred.
If the CLEAR_FAULTS command is issued and the fault or warn-
ing condition is no longer active, the status bit is cleared. If the
condition is still active—for example, if an input voltage is below
the undervoltage threshold of the UV pin—the CLEAR_FAULTS
command attempts to clear the status bit, but that status bit is
immediately set again.
GPO AND ALERT PIN SETUP COMMANDS
Two multipurpose pins are provided on the ADM1075:
GPO1/ALERT1/CONV and GPO2/ALERT2.
The GPO1/ALERT1/CONV and GPO2/ALERT2 pins have
two output modes of operation. These pins can be configured
independently over the PMBus as general-purpose digital
outputs. They can both be configured to generate an SMBAlert
when one or more fault/warning status bits become active in the
PMBus status registers. For an example of how to configure these
pins to generate an SMBAlert and how to respond and clear the
condition, see the Example Use of SMBus Alert Response
Address section.
The GPO1/ALERT1/CONV pin can also be configured as an
input (CONV) to drive the power monitor in single-shot run
mode and to control when a power monitor ADC sampling
cycle begins. This function can be used to synchronize sampling
across multiple ADM1075 devices, if required.
ALERT1_CONFIG and ALERT2_CONFIG Commands
Using combinations of bit masks, the ALERT1_CONFIG and
ALERT2_CONFIG commands can be used to select the status
bits that, when set, generate an SMBAlert signal to a processor.
They can also be used to set a GPO mode on the pin, so that it
is under software control. If this mode is set, the SMBAlert
masking bits are ignored.
On the ADM1075, one of the inputs can also be configured
as a hardware-based convert control signal. If this mode is set,
the GPO and SMBAlert masking bits are ignored.
POWER MONITOR COMMANDS
The ADM1075 provides a high accuracy, 12-bit current and
voltage power monitor. The power monitor can be configured
in a number of different modes of operation and can run in
either continuous mode or single-shot mode with a number
of different sample averaging options.
The power monitor can measure the following:
• Input voltage (VIN)
• Output current (IOUT)
• Auxiliary voltage (VAUX)
The following quantities are then calculated:
• Input power (PIN)
• Input energy (EIN)
PMON_CONFIG Command
The power monitor can run in a number of different modes with
different input voltage range settings. The PMON_CONFIG
command is used to set up the power monitor.
Rev. C | Page 32 of 52
Data Sheet ADM1075
The settings that can be configured are as follows:
• Single-shot or continuous sampling
• Enable VAU X sampling
• Current input range
• Current and voltage sample averaging
Modifying the power monitor settings while the power monitor
is sampling is not recommended because it may cause spurious
data or warnings to be generated.
PMON_CONTROL Command
Power monitor sampling can be initiated via software or via
hardware, as follows:
• PMON_CONTROL command. This command can be
used with single-shot or continuous mode.
• GPO1/ALERT1/CONV pin. If this pin is configured for
convert mode, an external hardware signal can be used to
take this pin high, triggering the single-shot sampling of
one or more parts together.
READ_VIN, READ_VAUX, and READ_IOUT Commands
The ADM1075 power monitor measures the voltage developed
across the sense resistor to provide a current measurement. The
input voltage from the ADC_V pin is always measured, and the
user can choose whether or not to measure the output voltage
present on the ADC_AUX pin as well.
READ_PIN, READ_PIN_EXT, READ_EIN, and
READ_EIN_EXT Commands
The VIN input voltage (12-bit) and IOUT current (12-bit)
measurement values are multiplied by the ADM1075 to give the
input power value. This is done using fixed point arithmetic and
produces a 24-bit value. It is assumed that the numbers are of
the 12.0 format, meaning there is no fractional part. It should
be noted that only positive IOUT values are used to avoid
returning a negative power.
This 24-bit value can be read from the ADM1075 using the
READ_PIN_EXT command, where the most significant bit
(MSB) is always a zero because PIN_EXT is a twos complement
binary value that is always positive.
The 16 most significant bits of the 24-bit value are used as the
value for input power (PIN). The MSB of the 16-bit PIN word is
always zero because PIN is a twos complement binary value that
is always positive.
Each time a power calculation is performed, the 24-bit power
value is added to a 24-bit energy accumulator register. This is a
twos complement representation as well; therefore, the MSB is
always zero. Each time this energy accumulator register rolls
over from 0x7FFFFF to 0x000000, a 16-bit rollover counter is
incremented. The rollover counter is straight binary, with a
maximum value of 0xFFFF before it rolls over.
There is also a 24-bit straight binary power sample counter that
is incremented by one each time a power value is calculated and
added to the energy accumulator.
These registers can be read back using one of two commands,
depending on the level of accuracy required for the energy
accumulator and the desire to limit the frequency of reads from
the ADM1075.
A bus host can read these values, and, using some difference
calculations, determine the amount of energy consumed since
the last read and the number of samples in that time. The bus
host, using an external real-time clock, can then determine the
power used in the last time period.
To avoid the loss of data, the bus host must read at a rate that
ensures the rollover counter does not wrap around more than
once and, if it does wrap around, that the next rollover value is
less than the previous one.
The READ_EIN command returns the top 16 bits of the energy
accumulator, the lower eight bits of the rollover counter, and the
full 24 bits of the sample counter.
The READ_EIN_EXT command returns the full 24 bits of the
energy accumulator, the full 16 bits of the rollover counter, and
the full 24 bits of the sample counter. The use of the longer
rollover counter means that the time interval between reads of
the part to ensure that no data is lost can be increased from
seconds to minutes.
PEAK_IOUT, PEAK_VIN, PEAK_VAUX, and PEAK_PIN
Commands
In addition to the standard PMBus commands for reading
voltage and current, the ADM1075 provides commands that
can report the maximum peak voltage, current, or power value
since the peak value was last cleared.
The peak values are updated only after the power monitor has
sampled and averaged the current and voltage measurements.
Individual peak values are cleared by writing a 0 value with the
corresponding commands.
WARNING LIMIT SETUP COMMANDS
The ADM1075 power monitor can monitor a number of
different warning conditions simultaneously and report any
current or voltage values that exceed the user-defined
thresholds using the status commands.
All comparisons performed by the power monitor require the
measured voltage or current value to be strictly greater or less
than the threshold value.
At power-up, all threshold limits are set to either minimum
scale (for undervoltage or undercurrent conditions) or to
maximum scale (for overvoltage, overcurrent or overpower
conditions). This effectively disables the generation of any
status warnings by default; warning bits are not set in the status
registers until the user explicitly sets the threshold values.
VIN_OV_WARN_LIMIT and VIN_UV_WARN_LIMIT
Commands
The VIN_OV_WARN_LIMIT and VIN_UV_WARN_LIMIT
commands are used to set the OV and UV thresholds on the
input voltage, as measured at the ADC_V pin.
Rev. C | Page 33 of 52
ADM1075 Data Sheet
VAUX_OV_WARN_LIMIT and VAUX_UV_WARN_LIMIT
Commands
The VAUX_OV_WARN_LIMIT and VAUX_UV_WARN_
LIMIT commands are used to set the OV and UV thresholds
on the output voltage, as measured at the A D C _ VAU X pin on
the ADM1075.
PIN_OP_WARN_LIMIT Command
The PIN_OP_WARN_LIMIT command is used to set the
overpower (OP) threshold for the power measurement register.
IOUT_OC_WARN_LIMIT Command
The IOUT_OC_WARN_LIMIT command is used to set the
overcurrent (OC) threshold for the current flowing through the
sense resistor.
IOUT_WARN2_LIMIT Command
The IOUT_WARN2_LIMIT command provides a second
current warning threshold that can be programmed. The
polarity of this warning can be set to overcurrent or
undercurrent using the DEVICE_CONFIG command.
PMBus DIRECT FORMAT CONVERSION
The ADM1075 uses the PMBus direct format internally to
represent real-world quantities such as voltage, current, and
power values. A direct format number takes the form of a
2-byte, twos complement binary integer value.
It is possible to convert between direct format value and real-world
quantities using the following equations. Equation 1 converts from
real-world quantities to PMBus direct values, and Equation 2
converts PMBus direct format values to real-world values.
Y = (mX + b) × 10R (1)
X = 1/m × (Y × 10−R − b) (2)
where:
Y is the value in PMBus direct format.
X is the real-world value.
m is the slope coefficient, a 2-byte, twos complement integer.
b is the offset, a 2-byte, twos complement integer.
R is a scaling exponent, a 1-byte, twos complement integer.
The same equations are used for voltage, current, and power
conversions, the only difference being the values of the m, b,
and R coefficients used.
Table 7 lists all the coefficients required for the ADM1075. The
coefficients shown are dependent on the value of the external
sense resistor used in a given application. This means that an
additional calculation must be performed to take the sense
resistor value into account to obtain the coefficients for a
specific sense resistor value. The resistor divider scaling factor
on VIN/VAUX also needs to be taken into account when
performing a voltage or power calculation (see Example 4).
The sense resistor value used in the calculations to obtain the
coefficients is expressed in milliohms. The m coefficients are
defined as 2-byte twos complement numbers in the PMBus stand-
ard; therefore, the maximum positive value that can be represented
is 32,767. If the m value is greater than that, and is to be stored
in PMBus standard form, the m coefficients should be divided
by 10, and the R coefficient increased by a value of 1. For example,
if performing a power calculation on the ADM1075-1 with a
10 mΩ sense resistor, the m coefficient is 8549, and the R
coefficient is 0.
Example 1
IOUT_OC_WARN_LIMIT requires a current limit value
expressed in direct format.
If the required current limit is 10 A, and the sense resistor is
2 mΩ, the first step is to determine the voltage coefficient. For
an ADM1075-1, this is simply m = 806 × 2, giving 1612.
Using Equation 1, and expressing X, in units of amps,
Y = ((1612 × 10) + 20,475) × 10−1
Y = 3659.5 = 3660 (rounded up to integer form)
Writing a value of 3660 with the IOUT_OC_WARN_LIMIT
command sets an overcurrent warning at 10 A.
Example 2
The READ_IOUT command returns a direct format value of 3341,
representing the current flowing through a sense resistor of 1 mΩ.
To convert this value to the current flowing, use Equation 2,
with m = 806 × 1 (for the ADM1075-1):
X = 1/806 × (3341 × 101 – 20,475)
X = 16.05 A
This means that when READ_IOUT returns a value of 3341,
16.05 A is flowing in the sense resistor.
Note the following:
• The same calculations that are used to convert power
values also apply to the energy accumulator value returned
by the READ_EIN command because the energy
accumulator is a summation of multiple power values.
• The READ_PIN_EXT and READ_EIN_EXT commands
return 24-bit extended precision versions of the 16-bit
values returned by READ_PIN and READ_EIN. The direct
format values must be divided by 256 prior to being con-
verted with the coefficients shown in Tabl e 7.
Rev. C | Page 34 of 52
Data Sheet ADM1075
Table 7. PMBus Conversion to Real-World Coefficients
Coefficient Voltage (V)
Current (A) Power (W)—Resistor Scaled
ADM1075-1 ADM1075-2 ADM1075-1 ADM1075-2
m 27,169 806 × RSENSE 404 × RSENSE 8549 × RSENSE 4279 × RSENSE
b 0 20,475 20,475 0 0
R −1 −1 −1 −1 −1
Example 3
The READ_VIN command returns a direct format value of 1726.
The ADC_V pin is shorted to the OV pin, which is connected
to the input supply via an 820 kΩ/11 kΩ resistor divider.
To convert this value to the input voltage, use Equation 2
X = 1/27,169 × (1726 × 101 – 0)
X = 0.635 V
This corresponds to 0.635 V at the ADC_V pin. To obtain the
input voltage, this must be amplified by the resistor divider ratio,
X = 0.635 V × (820 kΩ + 11 kΩ)/11 kΩ = 47.99 V
Example 4
The PIN_OP_WARN_LIMIT command requires a power limit
value expressed in direct format.
If the required power limit is 350 W and the sense resistor is
1 mΩ, the first step is to determine the m coefficient. Assuming
an ADM1075-1 device, m = 8549 × 1 = 8549. The resistor
divider on VIN scales down the power limit referenced to the
ADC input. Assuming a 49 kΩ and 1 kΩ resistor divider on
VIN, this gives a scaling factor of 0.02.
Using Equation 1,
Y = (8549 × (350 × 0.02)) × 10−1
Y = 5984.3 = 5984 (rounded to the nearest integer)
Writing a value of 5984 with the PIN_OP_WARN_LIMIT
command sets an overpower warning at 350 W.
VOLTAGE AND CURRENT CONVERSION USING
LSB VALUES
The direct format voltage and current values returned by the
READ_VIN, READ_VAUX, and READ_IOUT commands, and
the corresponding peak versions are the actual data output
directly from the ADM1075 ADC. Because the voltages and
currents are a 12-bit ADC output code, they can also be
converted to real-world values with knowledge of the size of the
LSB on the ADC.
The m, b, and R coefficients defined for the PMBus conversion
are required to be whole integers by the standard and have
therefore been rounded off slightly. Using this alternative
method, with the exact LSB values, can provide slightly more
accurate numerical conversions.
To convert an ADC code to current in amperes, the following
formulas can be used:
VSENSE = LSBxmV × (IADC − 2048)
IOUT = VSENSE/(RSENSE × 0.001)
where:
VSENSE = (VSENSE+) − (VSENSE−).
LSB25mV = 12.4 µ V.
LSB50mV = 24.77 µ V.
IADC is the 12-bit ADC code.
IOUT is the measured current value in amperes.
RSENSE is the value of the sense resistor in milliohms.
To convert an ADC code to a voltage, the following formula can
be used:
VM = LSBINPUTV × (VADC + 0.5)
where:
VM is the measured value in volts.
VADC is the 12-bit ADC code.
LSBINPUTV = 368 μV.
To convert a current in amperes to a 12-bit value, the following
formulas can be used (round the result to the nearest integer):
VSENSE = IA × RSENSE × 0.001
ICODE = 2048 + (VSENSE/LSBxmV)
where:
VSENSE = (VSENSE+) − (VSENSE−).
IA is the current value in amperes.
RSENSE is the value of the sense resistor in milliohms.
ICODE is the 12-bit ADC code.
LSB25mV = 12.4 µ V.
LSB50mV = 24.77 µ V.
To convert a voltage to a 12-bit value, the following formula can
be used (round the result to the nearest integer):
VCODE = (VA/LSBINPUTV) − 0.5
where:
VCODE is the 12-bit ADC code.
VA is the voltage value in volts.
LSBINPUTV = 368 μV.
Rev. C | Page 35 of 52
ADM1075 Data Sheet
ADM1075 ALERT PIN BEHAVIOR
The ADM1075 provides a very flexible alert system, whereby
one or more fault/warning conditions can be indicated to an
external device.
FAULTS AND WARNINGS
A PMBus fault on the ADM1075 is always generated due to an
analog event and causes a change in state in the hot swap output,
turning it off. The three defined fault sources are as follows:
• Undervoltage (UV) event detected on the UVH and UVL
pins
• Overvoltage (OV) event detected on the OV pin
• Overcurrent (OC) event that causes a hot swap timeout
Faults are continuously monitored, and, as long as power is
applied to the device, they cannot be disabled. When a fault
occurs, a corresponding status bit is set in one or more
STATUS_xxx registers.
A value of 1 in a status register bit field always indicates a fault
or warning condition. Fault and warning bits in the status
registers are latched when set to 1. To clear a latched bit to 0—
provided that the fault condition is no longer active—use the
CLEAR_FAULTS command or use the OPERATION command
to turn the hot swap output off and then on again.
The latched status registers provide fault recording functionality.
In the event of a fault, the HS_SHUTDOWN_CAUSE bits in
the manufacturing specific status register (0x80) can be used to
identify the fault source (UV, OV, or OC). Other status registers
can also be checked for more fault and warning information.
A warning is less severe than a fault and never causes a change
in the state of the hot swap controller. The eight sources of a
warning are defined as follows:
• CML: a communications error occurred on the I2C bus
• HS timer was active (HSTA): the current regulation was
active but does not necessarily shut the system down
• IOUT OC warning from the ADC
• IOUT Warning 2 from the ADC
• VIN UV warning from the ADC
• VIN OV warning from the ADC
• VAUX UV warning from the ADC
• VAUX OV warning from the ADC
• PIN OP warning from the ADC
GENERATING AN ALERT
A host device can periodically poll the ADM1075 using the
status commands to determine whether a fault/warning is
active. However, this polling is very inefficient in terms of
software and processor resources. The ADM1075 has two
GPOx/ALERTx output pins that can be used to generate
interrupts to a host processor, GPO1/ALERT1/CONV and
GPO2/ALERT2.
By default, at power-up, the open-drain GPOx/ALERTx
outputs are high impedance; therefore, the pins can be pulled
high through resistors. No faults or warnings are enabled on the
GPO2/ALERT2 pin at power-up; the user must explicitly enable
the faults or warnings to be monitored. The FET health bad
warning is active by default on the GPO1/ALERT1/CONV pin
at power-up.
Any one or more of the faults and warnings listed in the Faults
and Warnings section can be enabled and cause an alert, making
the corresponding GPOx/ALERTx pin active. By default, the
active state of a GPOx/ALERTx pin is low.
For example, to use GPO1/ALERT1/CONV to monitor the
IOUT OC warning from the ADC, the followings steps must be
performed:
1. Set a threshold level with the IOUT_OC_WARN_LIMIT
command.
2. Set the IOUT_OC_WARN_EN1 bit in the
ALERT1_CONFIG register
3. Start the power monitor sampling on IOUT.
If an IOUT sample is taken that is above the configured
IOUT OC value, the GPO1/ALERT1/CONV pin is taken
low, signaling an interrupt to a processor.
HANDLING/CLEARING AN ALERT
When faults/warnings are configured on the GPOx/ALERTx pins,
the pins become active to signal an interrupt to the processor.
(These pins are active low, unless inversion is enabled.) The
GPOx/ALERTx signal performs the function of an SMBAlert.
Note that the GPOx/ALERTx pins can become active indepen-
dently of each other, but they are always made inactive together.
A processor can respond to the interrupt in one of two basic ways:
• If there is only one device on the bus, the processor can
simply read the status bytes and issue a CLEAR_FAULTS
command to clear all the status bits, which causes the
deassertion of the GPOx/ALERTx line. If there is a persistent
fault—for example, an undervoltage on the input—the status
bits remain set after the CLEAR_FAULTS command is
executed because the fault has not been removed. However,
the GPOx/ALERTx line is not pulled low unless a new fault/
warning becomes active. If the cause of the SMBAlert is a
power monitor generated warning and the power monitor
is running continuously, the next sample generates a new
SMBAlert after the CLEAR_FAULTS command is issued.
• If there are many devices on the bus, the processor can issue
an SMBus alert response address command to find out
which device asserted the SMBAlert line. The processor
can read the status bytes from that device and issue a
CLEAR_FAULTS command.
Rev. C | Page 36 of 52
Data Sheet ADM1075
SMBus ALERT RESPONSE ADDRESS
The SMBus alert response address (ARA) is a special address
that can be used by the bus host to locate any devices that need
to talk to it. A host typically uses a hardware interrupt pin to
monitor the SMBus alert pins of a number of devices. When the
host interrupt occurs, the host issues a message on the bus using
the SMBus receive byte or receive byte with PEC protocol.
The special address used by the host is 0x0C. Any devices that
have an SMBAlert signal return their own 7-bit address as the
seven MSBs of the data byte. The LSB value is not used and can
be either 1 or 0. The host reads the device address from the
received data byte and proceeds to handle the alert condition.
More than one device may have an active SMBAlert signal and
attempt to communicate with the host. In this case, the device
with the lowest address dominates the bus and succeeds in
transmitting its address to the host. The device that succeeds
disables its SMBusAlert signal. If the host sees that the SMBus
alert signal is still low, it continues to read addresses until all
devices that need to talk to it have successfully transmitted their
addresses.
EXAMPLE USE OF SMBus ALERT RESPONSE
ADDRESS
The full sequence of steps that occurs when an SMBAlert is
generated and cleared is as follows:
1. A fault or warning is enabled using the ALERT1_CONFIG
command, and the corresponding status bit for the fault or
warning goes from 0 to 1, indicating that the fault/warning
has just become active.
2. The GPO1/ALERT1/CONV or GPO2/ALERT2 pin
becomes active (low) to signal that an SMBAlert is active.
3. The host processor issues an SMBus alert response address
to determine which device has an active alert.
4. If there are no other active alerts from devices with lower
I2C addresses, this device makes the GPO1/ALERT1/CONV
or GPO2/ALERT2 pin inactive (high) during the NACK
bit period after it sends its address to the host processor.
5. If the GPO1/ALERT1/CONV or GPO2/ALERT2 pin stays
low, the host processor must continue to issue SMBus alert
response address commands to devices to find out the
addresses of all devices whose status it must check.
6. The ADM1075 continues to operate with the GPO1/ALERT1/
CONV or GPO2/ALERT2 pin inactive and the contents of
the status bytes unchanged until the host reads the status
bytes and clears them, or until a new fault occurs. That is, if
a status bit for a fault/warning that is enabled on the
GPO1/ALERT1/CONV or GPO2/ALERT2 pin and that
was not already active (equal to 1) goes from 0 to 1, a new
alert is generated, causing the GPO1/ALERT1/CONV or
GPO2/ALERT2 pin to become active again.
DIGITAL COMPARATOR MODE
The GPO1/ALERT1/CONV and GPO2/ALERT2 pins can be
configured to indicate if a user defined threshold for voltage,
current, or power is being exceeded. In this mode, the output
pin is live and is not latched when a warning threshold is
exceeded. In effect, the pin acts as a digital comparator where
the threshold is set using the warning limit threshold commands.
The ALERTx_CONFIG command is used, as for the SMBAlert
configuration, to select the specific warning threshold to be
monitored. The GPO1/ALERT1/CONV or GPO2/ALERT2 pin
then indicates if the measured value is above or below the
threshold.
Rev. C | Page 37 of 52
ADM1075 Data Sheet
PMBus COMMAND REFERENCE
Register addresses are in hexadecimal format.
Table 8. PMBus Command Summary
Command Code Command Name SMBus Transaction Type Number of Data Bytes Reset
0x01 OPERATION Read/write byte 1 0x00
0x03 CLEAR_FAULTS Send byte 0 Not applicable
0x19 CAPABILITY Read byte 1 0xB0
0x4A IOUT_OC_WARN_LIMIT Read/write word 2 0x0FFF
0x57 VIN_OV_WARN_LIMIT Read/write word 2 0x0FFF
0x58 VIN_UV_WARN_LIMIT Read/write word 2 0x0000
0x6B PIN_OP_WARN_LIMIT Read/write word 2 0x7FFF
0x78 STATUS_BYTE Read byte 1 0x00
0x79 STATUS_WORD Read word 2 0x0000
0x7B STATUS_IOUT Read byte 1 0x00
0x7C STATUS_INPUT Read byte 1 0x00
0x80 STATUS_MFR_SPECIFIC Read byte 1 0x00
0x86 READ_EIN Block read 1 (byte count) + 6 (data) 0x06000000000000
0x88 READ_VIN Read word 2 0x0000
0x8C READ_IOUT Read word 2 0x0000
0x97 READ_PIN Read word 2 0x0000
0x98 PMBUS_REVISION Read byte 1 0x22
0x99 MFR_ID Block read 1 (byte count) + 3 (data) 0x03 + ASCII “ADI”
0x9A MFR_MODEL Block read 1 (byte count) + 9 (data) 0x09 + ASCII “ADM1075-1” or “ADM1075-2”
0x9B MFR_REVISION Block read 1 (byte count) + 1 (data) 0x01 + ASCII “1”
0xD0 PEAK_IOUT Read/write word 2 0x0000
0xD1 PEAK_VIN Read/write word 2 0x0000
0xD2 PEAK_VAUX Read/write word 2 0x0000
0xD3 PMON_CONTROL Read/write byte 1 0x01
0xD4 PMON_CONFIG Read/write byte 1 0x8F for ADM1075-1; 0x97 for ADM1075-2
0xD5 ALERT1_CONFIG Read/write word 2 0x8000
0xD6 ALERT2_CONFIG Read/write word 2 0x0004
0xD7 IOUT_WARN2_LIMIT Read/write word 2 0x0000
0xD8 DEVICE_CONFIG Read/write byte 1 0x00
0xD9 POWER_CYCLE Send byte 0 Not applicable
0xDA PEAK_PIN Read/write word 2 0x0000
0xDB READ_PIN_EXT Block read 1 (byte count) + 3 (data) 0x03000000
0xDC READ_EIN_EXT Block read 1 (byte count) + 8 (data) 0x080000000000000000
0xDD READ_VAUX Read word 2 0x0000
0xDE VAUX_OV_WARN_LIMIT Read/write word 2 0x0FFF
0xDF VAUX_UV_WARN_LIMIT Read/write word 2 0x0000
0xF6 STATUS_VAUX Read byte 1 0x00
Rev. C | Page 38 of 52
Data Sheet ADM1075
Rev. C | Page 39 of 52
REGISTER DETAILS
OPERATION COMMAND REGISTER
Address: 0x01, Reset: 0x00, Name: OPERATION
Table 9. Bit Descriptions for OPERATION
Bits Bit Name Settings Description Reset Access
7 ON Hot swap enable. 0x0 RW
0 Hot swap output disabled.
1 Hot swap output enabled.
[6:0] RESERVED Always reads as 0000000. 0x0 R
CLEAR FAULTS REGISTER
Address: 0x03, Send Byte, No Data, Name: CLEAR_FAULTS
PMBUS CAPABILITY REGISTER
Address: 0x19, Reset: 0xB0, Name: CAPABILITY
Table 10. Bit Descriptions for CAPABILITY
Bits Bit Name Settings Description Reset Access
7 PEC_SUPPORT Always reads as 1. Packet error checking (PEC) is supported. 0x1 R
[6:5] MAX_BUS_SPEED Always reads as 01. Maximum supported bus speed is 400 kHz. 0x01 R
4 SMBALERT_SUPPORT Always reads as 1. Device supports SMBAlert and alert response
address (ARA).
0x1 R
[3:0] RESERVED Always reads as 0000. 0x0000 R
IOUT OC WARN LIMIT REGISTER
Address: 0x4A, Reset: 0x0FFF, Name: IOUT_OC_WARN_LIMIT
Table 11. Bit Descriptions for IOUT_OC_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] IOUT_OC_WARN_LIMIT Overcurrent threshold for the IOUT measurement through the sense
resistor, expressed in ADC codes.
0xFFF RW
VIN OV WARN LIMIT REGISTER
Address: 0x57, Reset: 0x0FFF, Name: VIN_OV_WARN_LIMIT
Table 12. Bit Descriptions for VIN_OV_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] VIN_OV_WARN_LIMIT Overvoltage threshold for the ADC_V pin measurement, expressed
in ADC codes.
0xFFF RW
VIN UV WARN LIMIT REGISTER
Address: 0x58, Reset: 0x0000, Name: VIN_UV_WARN_LIMIT
Table 13. Bit Descriptions for VIN_UV_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] VIN_UV_WARN_LIMIT Undervoltage threshold for the ADC_V pin measurement, expressed
in ADC codes.
0x0 RW
ADM1075 Data Sheet
Rev. C | Page 40 of 52
PIN OP WARN LIMIT REGISTER
Address: 0x6B, Reset: 0x7FFF, Name: PIN_OP_WARN_LIMIT
Table 14. Bit Descriptions for PIN_OP_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
15 RESERVED Always reads as 0. 0x0 R
[14:0] PIN_OP_WARN_LIMIT Overpower threshold for the PMBus power measurement, expressed
in ADC codes.
0x7FFF RW
STATUS BYTE REGISTER
Address: 0x78, Reset: 0x00, Name: STATUS_BYTE
Table 15. Bit Descriptions for STATUS_BYTE
Bits Bit Name Settings Description Reset Access
7 RESERVED Always reads as 0. 0x0 R
6 HOTSWAP_OFF Live register. 0x0 R
0 The hot swap gate drive output is enabled.
1
The hot swap gate drive output is disabled, and the GATE pin is
pulled down. This can be due to, for example, an overcurrent fault
that causes the ADM1075 to latch off, an undervoltage condition on
the UVx pin, or the use of the OPERATION command to turn the
output off.
5 RESERVED Always reads as 0. 0x0 R
4 IOUT_OC_FAULT Latched register. 0x0 R
0 No overcurrent output fault detected.
1
The hot swap controller detected an overcurrent condition and the
time limit set by the capacitor on the TIMER pin has elapsed, causing
the hot swap gate drive to shut down.
3 VIN_UV_FAULT Latched register. 0x0 R
0 No undervoltage input fault detected on the UVH/UVL pins.
1 An undervoltage input fault was detected on the UVH/UVL pins.
2 RESERVED Always reads as 0. 0x0 R
1 CML_FAULT Latched register. 0x0 R
0 No communications error detected on the I2C/PMBus interface.
1
An error was detected on the I2C/PMBus interface. Errors detected
are unsupported command, invalid PEC byte, and incorrectly
structured message.
0 NONE_OF_THE_ABOVE Live register. 0x0 R
0
No other active status bit to be reported by any other status
command.
1
Active status bits are waiting to be read by one or more status
commands.
STATUS WORD REGISTER
Address: 0x79, Reset: 0x0000, Name: STATUS_WORD
Table 16. Bit Descriptions for STATUS_WORD
Bits Bit Name Settings Description Reset Access
15 RESERVED Always reads as 0. 0x0 R
14 IOUT_STATUS Live register. 0x0 R
0 There are no active status bits to be read by STATUS_IOUT.
1 There are one or more active status bits to be read by STATUS_IOUT.
Data Sheet ADM1075
Rev. C | Page 41 of 52
Bits Bit Name Settings Description Reset Access
13 INPUT_STATUS Live register. 0x0 R
0 There are no active status bits to be read by STATUS_INPUT.
1 There are one or more active status bits to be read by STATUS_INPUT.
12 MFR_STATUS Live register. 0x0 R
0 There are no active status bits to be read by STATUS_MFR_SPECIFIC.
1
There are one or more active status bits to be read by
STATUS_MFR_SPECIFIC.
11 PGB_STATUS Live register. 0x0 R
0
The voltage on the DRAIN pin is above the required threshold,
indicating that output power is considered good. This bit is the
logical inversion of the PWRGD pin on the part.
1
The voltage on the DRAIN pin is below the required threshold,
indicating that output power is considered bad.
[10:8] RESERVED Always reads as 000. 0x0 R
[7:0] STATUS_BYTE This byte is the same as the byte returned by the STATUS_BYTE
command.
0x0 R
IOUT STATUS REGISTER
Address: 0x7B, Reset: 0x00, Name: STATUS_IOUT
Table 17. Bit Descriptions for STATUS_IOUT
Bits Bit Name Settings Description Reset Access
7 IOUT_OC_FAULT Latched register. 0x0 R
0 No overcurrent output fault detected.
1
The hot swap controller detected an overcurrent condition and the
time limit set by the capacitor on the TIMER pin has elapsed, causing
the hot swap gate drive to shut down.
6 RESERVED Always reads as 0. 0x0 R
5 IOUT_OC_WARN Latched register. 0x0 R
0
No overcurrent condition on the output supply detected by the
power monitor using the IOUT_OC_WARN_LIMIT command.
1
An overcurrent condition was detected by the power monitor using
the IOUT_OC_WARN_LIMIT command.
[4:0] RESERVED Always reads as 00000. 0x0 R
INPUT STATUS REGISTER
Address: 0x7C, Reset: 0x00, Name: STATUS_INPUT
Table 18. Bit Descriptions for STATUS_INPUT
Bits Bit Name Settings Description Reset Access
7 VIN_OV_FAULT Latched register. 0x0 R
0 No overvoltage detected on the OV pin.
1 An overvoltage was detected on the OV pin.
6 VIN_OV_WARN Latched register. 0x0 R
0
No overvoltage condition on the input supply detected by the
power monitor.
1
An overvoltage condition on the input supply was detected by the
power monitor.
5 VIN_UV_WARN Latched register. 0x0 R
0
No undervoltage condition on the input supply detected by the
power monitor.
1
An undervoltage condition on the input supply was detected by the
power monitor.
ADM1075 Data Sheet
Rev. C | Page 42 of 52
Bits Bit Name Settings Description Reset Access
4 VIN_UV_FAULT Latched register. 0x0 R
0 No undervoltage detected on the UVx pin.
1 An undervoltage was detected on the UVx pin.
[3:1] RESERVED Always reads as 000. 0x0 R
0 PIN_OP_WARN Latched register. 0x0 R
0
No overpower condition on the input supply detected by the power
monitor.
1
An overpower condition on the input supply was detected by the
power monitor.
MANUFACTURING SPECIFIC STATUS REGISTER
Address: 0x80, Reset: 0x00, Name: STATUS_MFR_SPECIFIC
Table 19. Bit Descriptions for STATUS_MFR_SPECIFIC
Bits Bit Name Settings Description Reset Access
7 FET_HEALTH_BAD Latched register. 0x0 R
0 FET behavior appears to be as expected.
1 FET behavior suggests that the FET may be shorted.
6 UV_CMP_OUT Live register. 0x0 R
0 Input voltage to UVx pin is above threshold.
1 Input voltage to UVx pin is below threshold.
5 OV_CMP_OUT Live register. 0x0 R
0 Input voltage to OV pin is below threshold.
1 Input voltage to OV pin is above threshold.
4 VAUX_STATUS Latched register. 0x0 R
0 There are no active status bits to be read by STATUS_VAUX.
1 There are one or more active status bits to be read by STATUS_VAUX.
3 HS_INLIM_FAULT Latched register. 0x0 R
0 The ADM1075 has not actively limited the current into the load.
1
The ADM1075 has actively limited current into the load. This bit
differs from the IOUT_OC_FAULT bit in that the HS_INLIM bit is set
immediately, whereas the IOUT_OC_FAULT bit is not set unless the
time limit set by the capacitor on the TIMER pin elapses.
[2:1] HS_SHUTDOWN_CAUSE Latched register. 0x0 R
00
The ADM1075 is either enabled and working correctly, or has been
shut down using the OPERATION command.
01
An IOUT_OC_FAULT condition occurred that caused the ADM1075
to shut down.
10
A VIN_UV_FAULT condition occurred that caused the ADM1075 to
shut down.
11
A VIN_OV_FAULT condition occurred that caused the ADM1075 to
shut down.
0 IOUT_WARN2 Latched register. 0x0 R
0
No overcurrent condition on the output supply detected by the
power monitor using the IOUT_WARN2_LIMIT command.
1
An undercurrent or overcurrent condition on the output supply was
detected by the power monitor using the IOUT_WARN2_LIMIT
command. The polarity of the threshold condition is set by the
IOUT_WARN2_OC_SELECT bit using the DEVICE_CONFIG command.
Data Sheet ADM1075
Rev. C | Page 43 of 52
READ EIN REGISTER
Address: 0x86, Reset: 0x06, 0x0000, 0x00, 0x000000, Name: READ_EIN
Table 20. Bit Descriptions for READ_EIN
Byte Bit Name Settings Description Reset Access
[0] BYTE_COUNT Always reads as 0x06, the number of data bytes that the block read
command should expect to read.
0x6 R
[2:1] ENERGY_COUNT Energy accumulator value in direct format. Byte 2 is the high byte, and
Byte 1 is the low byte. Internally, the energy accumulator is a 24-bit
value, but only the most significant 16 bits are returned with this
command. Use the READ_EIN_EXT to access the nontruncated version.
0x0 R
[3] ROLLOVER_COUNT Number of times that the energy count has rolled over, from 0x7FFF to
0x0000. This is a straight 8-bit binary value.
0x0 R
[6:4] SAMPLE_COUNT This is the total number of PIN samples acquired and accumulated in
the energy count accumulator. Byte 6 is the high byte, Byte 5 is the
middle byte, and Byte 4 is the low byte.
0x0 R
READ VIN REGISTER
Address: 0x88, Reset: 0x0000, Name: READ_VIN
Table 21. Bit Descriptions for READ_VIN
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] READ_VIN Input voltage from the ADC_V pin measurement, expressed in ADC
codes.
0x0 R
READ IOUT REGISTER
Address: 0x8C, Reset: 0x0000, Name: READ_IOUT
Table 22. Bit Descriptions for READ_IOUT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] READ_IOUT Output current measurement through the sense resistor. 0x0 R
READ PIN REGISTER
Address: 0x97, Reset: 0x0000, Name: READ_PIN
Table 23. Bit Descriptions for READ_PIN
Bits Bit Name Settings Description Reset Access
[15:0] READ_PIN Input power from the VIN × IOUT calculation. 0x0 R
PMBus REVISION REGISTER
Address: 0x98, Reset: 0x22, Name: PMBUS_REVISION
Table 24. Bit Descriptions for PMBUS_REVISION
Bits Bit Name Settings Description Reset Access
[7:4] PMBUS_P1_REVISION Always reads as 0010, PMBus Specification Part I, Revision 1.2. 0x2 R
[3:0] PMBUS_P2_REVISION Always reads as 0010, PMBus Specification Part II, Revision 1.2. 0x2 R
0000 Rev1.0.
0001 Rev1.1.
0010 Rev1.2.
ADM1075 Data Sheet
Rev. C | Page 44 of 52
MANUFACTURING ID REGISTER
Address: 0x99, Reset: 0x03 + ASCII “ADI”, Name: MFR_ID
Table 25. Bit Descriptions for MFR_ID
Byte Bit Name Settings Description Reset Access
0 BYTE_COUNT Always reads as 0x03, the number of data bytes that the block read
command should expect to read.
0x3 R
1 CHARACTER1 Always reads as 0x41 = “A”. 0x41 R
2 CHARACTER2 Always reads as 0x44 = “D”. 0x44 R
3 CHARACTER3 Always reads as 0x49 = “I”. 0x49 R
MANUFACTURING MODEL REGISTER
Address: 0x9A, Reset: 0x09 + ASCII “ADM1075-x”, Name: MFR_MODEL
Table 26. Bit Descriptions for MFR_MODEL
Byte Bit Name Settings Description Reset Access
0 BYTE_COUNT Always reads as 0x03, the number of data bytes that the block read
command should expect to read.
0x9 R
1 CHARACTER1 Always reads as 0x41 = “A”. 0x41 R
2 CHARACTER2 Always reads as 0x44 = “D”. 0x44 R
3 CHARACTER3 Always reads as 0x4D = “M”. 0x4D R
4 CHARACTER4 Always reads as 0x31 = “1”. 0x31 R
5 CHARACTER5 Always reads as 0x30 = “0”. 0x30 R
6 CHARACTER6 Always reads as 0x37 = “7”. 0x37 R
7 CHARACTER7 Always reads as 0x35 = “5”. 0x35 R
8 CHARACTER8 Always reads as 0x2D = “-”. 0x2D R
9 CHARACTER9 Always reads as 0x31 = “1” for ADM1075-1.
Always reads as 0x32 = “2” for ADM1075-2.
0x31 or
0x32
R
MANUFACTURING REVISION REGISTER
Address: 0x9B, Reset: 0x01 + ASCII “1”, Name: MFR_REVISION
Table 27. Bit Descriptions for MFR_REVISION
Byte Bit Name Settings Description Reset Access
0 BYTE_COUNT Always reads as 0x01, the number of data bytes that the block read
command should expect to read.
0x1 R
1 CHARACTER1 Always reads as 0x31, Revision 1 of ADM1075. 0x31 R
PEAK IOUT REGISTER
Address: 0xD0, Reset: 0x0000, Name: PEAK_IOUT (writing 0x0000 clears the peak value)
Table 28. Bit Descriptions for PEAK_IOUT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] PEAK_IOUT Returns the peak IOUT current since the register was last cleared. 0x0 R
Data Sheet ADM1075
Rev. C | Page 45 of 52
PEAK VIN REGISTER
Address: 0xD1, Reset: 0x0000, Name: PEAK_VIN (writing 0x0000 clears the peak value)
Table 29. Bit Descriptions for PEAK_VIN
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] PEAK_VIN Returns the peak VIN voltage since the register was last cleared. 0x0 R
PEAK VAUX REGISTER
Address: 0xD2, Reset: 0x0000, Name: PEAK_VAUX (writing 0x0000 clears the peak value)
Table 30. Bit Descriptions for PEAK_VAUX
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] PEAK_VAUX Returns the peak VAUX voltage since the register was last cleared. 0x0 R
POWER MONITOR CONTROL REGISTER
Address: 0xD3, Reset: 0x01, Name: PMON_CONTROL
Table 31. Bit Descriptions for PMON_CONTROL
Bits Bit Name Settings Description Reset Access
[7:1] RESERVED Always reads as 0000000. 0x0 R
0 CONVERT 0x1 RW
0 Power monitor is not running.
1
Default. Starts the sampling of current and voltage with the power
monitor. In single-shot mode, this bit clears itself after one complete cycle.
In continuous mode, this bit must be written to 0 to stop sampling.
POWER MONITOR CONFIGURATION REGISTER
Address: 0xD4, Reset: 0x8F, Name: PMON_CONFIG
Table 32. Bit Descriptions for PMON_CONFIG
Bits Bit Name Settings Description Reset Access
7 PMON_MODE 0x1 RW
0 This setting selects single-shot sampling mode.
1 Default. This setting selects continuous sampling mode.
6 VAUX_ENABLE 0x0 RW
0
Default. The power monitor samples the input voltage on ADC_V and
IOUT.
1 The power monitor also samples the voltage on the ADC_AUX pin.
5 RESERVED Always reads as 0. 0x0 RW
[4:3] IRANGE 0x1 or
0x2
RW
00 Reserved.
01 Sets current sense range to 25 mV. Default for ADM1075-1.
10 Sets current sense range to 50 mV. Default for ADM1075-2.
11 Reserved.
[2:0] AVERAGING 0x7 RW
000 Disables sample averaging for current and voltage.
001 Sets sample averaging for current and voltage to two samples.
010 Sets sample averaging for current and voltage to four samples.
011 Sets sample averaging for current and voltage to eight samples.
100 Sets sample averaging for current and voltage to 16 samples.
101 Sets sample averaging for current and voltage to 32 samples.
110 Sets sample averaging for current and voltage to 64 samples.
111 Default. Sets sample averaging for current and voltage to 128 samples.
ADM1075 Data Sheet
Rev. C | Page 46 of 52
ALERT1 CONFIGURATION REGISTER
Address: 0xD5, Reset: 0x8000, Name: ALERT1_CONFIG
Table 33. Bit Descriptions for ALERT1_CONFIG
Bits Bit Name Settings Description Reset Access
15 FET_HEALTH_BAD_EN1 0x1 RW
0
Disables generation of SMBAlert when the FET_HEALTH_BAD bit
is set.
1
Default. Generates SMBAlert when the FET_HEALTH_BAD bit is
set. This bit is active from power-up so that a FET problem can be
detected and flagged immediately without the need for software
to set this bit.
14 IOUT_OC_FAULT_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
IOUT_OC_FAULT bit is set.
1 Generates SMBAlert when the IOUT_OC_FAULT bit is set.
13 VIN_OV_FAULT_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_OV_FAULT bit is set.
1 Generates SMBAlert when the VIN_OV_FAULT bit is set.
12 VIN_UV_FAULT_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_UV_FAULT bit is set.
1 Generates SMBAlert when the VIN_UV_FAULT bit is set.
11 CML_ERROR_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the CML_FAULT
bit is set.
1 Generates SMBAlert when the CML_ FAULT bit is set.
10 IOUT_OC_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
IOUT_OC_WARN bit is set.
1 Generates SMBAlert when the IOUT_OC_WARN bit is set.
9 IOUT_WARN2_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the IOUT_WARN2
bit is set.
1 Generates SMBAlert when the IOUT_WARN2 bit is set.
8 VIN_OV_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_OV_WARN bit is set.
1 Generates SMBAlert when the VIN_OV_WARN bit is set.
7 VIN_UV_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_UV_WARN bit is set.
1 Generates SMBAlert when the VIN_UV_WARN bit is set.
6 VAUX_OV_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VAUX_OV_WARN bit is set.
1 Generates SMBAlert when the VAUX_OV_WARN bit is set.
5 VAUX_UV_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
VAUX_UV_WARN bit is set.
1 Generates SMBAlert when the VAUX_UV_WARN bit is set.
4 HS_INLIM_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
HS_INLIM_FAULT bit is set.
1 Generates SMBAlert when the HS_INLIM_FAULT bit is set.
Data Sheet ADM1075
Rev. C | Page 47 of 52
Bits Bit Name Settings Description Reset Access
3 PIN_OP_WARN_EN1 0x0 RW
0
Default. Disables generation of SMBAlert when the
PIN_OP_WARN bit is set.
1 Generates SMBAlert when the PIN_OP_WARN bit is set.
[2:1] GPO1_MODE 0x0 RW
00 Default. GPO1 is configured to generate SMBAlerts.
01
GPO1 can be used a general-purpose digital output pin. The
GPO1_INVERT bit is used to change the output state.
10 GPO1 is configured as a convert (CONV) input pin.
11
This is digital comparator mode. The output pin now reflects the
live status of the warning or fault bit selected for the output. In
effect, this is a nonlatched SMBAlert.
0 GPO1_INVERT 0x0 RW
0 Default. In GPO mode, the GPO1 pin is active low.
1 In GPO mode, the GPO1 pin is active high.
ALERT2 CONFIGURATION REGISTER
Address: 0xD6, Reset: 0x0004, Name: ALERT2_CONFIG
Table 34. Bit Descriptions for ALERT2_CONFIG
Bits Bit Name Settings Description Reset Access
15 FET_HEALTH_BAD_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
FET_HEALTH_BAD bit is set.
1
Generates SMBAlert when the FET_HEALTH_BAD bit is set. This bit
is active from power-up so that a FET problem can be detected
and flagged immediately without the need for software to set
this bit.
14 IOUT_OC_FAULT_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
IOUT_OC_FAULT bit is set.
1 Generates SMBAlert when the IOUT_OC_FAULT bit is set.
13 VIN_OV_FAULT_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_OV_FAULT bit is set.
1 Generates SMBAlert when the VIN_OV_FAULT bit is set.
12 VIN_UV_FAULT_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_UV_FAULT bit is set.
1 Generates SMBAlert when the VIN_UV_FAULT bit is set.
11 CML_ERROR_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the CML_FAULT
bit is set.
1 Generates SMBAlert when the CML_FAULT bit is set.
10 IOUT_OC_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
IOUT_OC_WARN bit is set.
1 Generates SMBAlert when the IOUT_OC_WARN bit is set.
9 IOUT_WARN2_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the IOUT_WARN2
bit is set.
1 Generates SMBAlert when the IOUT_WARN2 bit is set.
8 VIN_OV_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_OV_WARN bit is set.
1 Generates SMBAlert when the VIN_OV_WARN bit is set.
ADM1075 Data Sheet
Rev. C | Page 48 of 52
Bits Bit Name Settings Description Reset Access
7 VIN_UV_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VIN_UV_WARN bit is set.
1 Generates SMBAlert when the VIN_UV_WARN bit is set.
6 VAUX_OV_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VAUX_OV_WARN bit is set.
1 Generates SMBAlert when the VAUX_OV_WARN bit is set.
5 VAUX_UV_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
VAUX_UV_WARN bit is set.
1 Generates SMBAlert when the VAUX_UV_WARN bit is set.
4 HS_INLIM_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
HS_INLIM_FAULT bit is set.
1 Generates SMBAlert when the HS_INLIM_FAULT bit is set.
3 PIN_OP_WARN_EN2 0x0 RW
0
Default. Disables generation of SMBAlert when the
PIN_OP_WARN bit is set.
1 Generates SMBAlert when the PIN_OP_WARN bit is set.
[2:1] GPO2_MODE 0x2 RW
00 GPO2 is configured to generate SMBAlerts.
01
GPO2 can be used a general-purpose digital output pin. The
GPO2_INVERT bit is used to change the output state.
10 Default. GPO2 is configured as a retry fail output.
11
This is digital comparator mode. The output pin now reflects the
live status of the warning or fault bit selected for the output. In
effect, this is a nonlatched SMBAlert.
0 GPO2_INVERT 0x0 RW
0 Default. In GPO mode, the GPO2 pin is active low.
1 In GPO mode, the GPO2 pin is active high.
IOUT WARN2 LIMIT REGISTER
Address: 0xD7, Reset: 0x0000, Name: IOUT_WARN2_LIMIT
Table 35. Bit Descriptions for IOUT_WARN2_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] IOUT_WARN2_LIMIT Threshold for the IOUT measurement through the sense resistor,
expressed in ADC codes. This value can be either an undercurrent
or overcurrent, depending on the state of the
IOUT_WARN2_OC_SELECT bit set using the DEVICE_CONFIG
command.
0x0 RW
DEVICE CONFIGURATION REGISTER
Address: 0xD8, Reset: 0x00, Name: DEVICE_CONFIG
Table 36. Bit Descriptions for DEVICE_CONFIG
Bits Bit Name Settings Description Reset Access
[7:6] RESERVED Always reads as 00. 0x00 R
5 OPERATION_CMD_ENABLE Enable operation command. 0x0 RW
0
The OPERATION command is disabled, and the ADM1075 issues a
NACK if the command is received. This setting provides some
protection against a card accidentally turning itself off
1
The OPERATION command is enabled, and the ADM1075
responds to it.
Data Sheet ADM1075
Rev. C | Page 49 of 52
Bits Bit Name Settings Description Reset Access
4 IOUT_WARN2_OC_SELECT Sets IOUT Warning 2 limit to OC or UC. 0x0 RW
0 Configures IOUT_WARN2_LIMIT as an undercurrent threshold.
1 Configured IOUT_WARN2_LIMIT as an overcurrent threshold.
[3:2] OC_TRIP_SELECT Sets severe OC trip threshold. 0x0 RW
00 125%.
01 150%. Default.
10 200%.
11 225%.
[1:0] OC_FILT_SELECT Sets severe OC filter time. 0x0 RW
00 200 ns. Default.
01 900 ns.
10 10.7 μs.
11 57 μs.
POWER CYCLE REGISTER
Address: 0xD9, Send Byte, No Data, Name: POWER_CYCLE
PEAK PIN REGISTER
Address: 0xDA, Reset: 0x0000, Name: PEAK_PIN (writing 0x0000 clears the peak value)
Table 37. Bit Descriptions for PEAK_PIN
Bits Bit Name Settings Description Reset Access
[15:0] PEAK_PIN Returns the peak input power since the register was last cleared. 0x0 R
READ PIN_EXT REGISTER
Address: 0xDB, Reset: 0x03, 0x000000, Name: READ_PIN_EXT
Table 38. Bit Descriptions for READ_PIN_EXT
Byte Bit Name Settings Description Reset Access
[0] BYTE_COUNT Always reads as 0x03, the number of data bytes that the block
read command should expect to read.
0x3 R
[3:1] READ_PIN_EXT This is the result of the VIN × IOUT calculation that has not been
truncated. Byte 3 is the high byte, Byte 2 is the middle byte, and
Byte 1 is the low byte.
0x0 R
READ EIN_EXT REGISTER
Address: 0xDC, Reset: 0x08, 0x000000, 0x0000, 0x000000, Name: READ_EIN_EXT
Table 39. Bit Descriptions for READ_EIN_EXT
Byte Bit Name Settings Description Reset Access
[0] BYTE_COUNT Always reads as 0x08, the number of data bytes that the block
read command should expect to read.
0x8 R
[3:1] ENERGY_EXT This is the 24-bit energy accumulator in direct format. Byte 3 is
the high byte, Byte 2 is the middle byte, and Byte 1 is the low
byte.
0x0 R
[5:4] ROLLOVER_EXT Number of times that the energy count has rolled over, from
0x7FFF to 0x0000. This is a straight 16-bit binary value. Byte 5 is
the high byte, Byte 4 is the low byte.
0x0 R
[8:6] SAMPLE_COUNT This is the total number of PIN samples acquired and
accumulated in the energy count accumulator. Byte 8 is the high
byte, Byte 7 is the middle byte, and Byte 6 is the low byte.
0x0 R
ADM1075 Data Sheet
Rev. C | Page 50 of 52
READ VAUX REGISTER
Address: 0xDD, Reset: 0x0000, Name: READ_VAUX
Table 40. Bit Descriptions for READ_VAUX
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] READ_VAUX Output voltage from the ADC_AUX pin measurement, expressed in
ADC codes.
0x0 R
VAUX OV WARN LIMIT REGISTER
Address: 0xDE, Reset: 0x0FFF, Name: VAUX_OV_WARN_LIMIT
Table 41. Bit Descriptions for VAUX_OV_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] VAUX_OV_WARN_LIMIT Overvoltage threshold for the ADC_AUX pin measurement,
expressed in ADC codes.
0xFFF RW
VAUX UV WARN LIMIT REGISTER
Address: 0xDF, Reset: 0x0000, Name: VAUX_UV_WARN_LIMIT
Table 42. Bit Descriptions for VAUX_UV_WARN_LIMIT
Bits Bit Name Settings Description Reset Access
[15:12] RESERVED Always reads as 0000. 0x0 R
[11:0] VAUX_UV_WARN_LIMIT Undervoltage threshold for the ADC_AUX pin measurement,
expressed in ADC codes.
0x0 RW
VAUX STATUS REGISTER
Address: 0xF6, Reset: 0x00, Name: STATUS_VAUX
Table 43. Bit Descriptions for STATUS_VAUX
Bits Bit Name Settings Description Reset Access
7 VAUX_OV_WARN Latched register. 0x0 R
0
No overvoltage condition was detected on the ADC_AUX pin by the
power monitor using the VAUX_OV_WARN_LIMIT command.
1
An overvoltage condition was detected on the ADC_AUX pin by the
power monitor using the VAUX_OV_WARN_LIMIT command.
6 VAUX_UV_WARN Latched register. 0x0 R
0
No undervoltage condition was detected on the ADC_AUX pin by
the power monitor using the VAUX_UV_WARN_LIMIT command.
1
An undervoltage condition was detected on the ADC_AUX pin by
the power monitor using the VAUX_UV_WARN_LIMIT command.
[5:0] RESERVED Always reads as 000000. 0x0 R
Data Sheet ADM1075
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC STANDARDS MO-153-AE
28 15
141
8°
0°
SEATING
PLANE
COPLANARITY
0.10
1.20 MAX
6.40 BSC
0.65
BSC
PIN 1
0.30
0.19 0.20
0.09
4.50
4.40
4.30
0.75
0.60
0.45
9.80
9.70
9.60
0.15
0.05
Figure 65. 28-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-28)
Dimensions shown in millimeters
1
0.50
BSC
BOTTOM VIEWTOP VIEW
28
8
14
15
21
22
7
EXPOSED
PAD
PIN 1
INDICATOR
3.40
3.30 SQ
3.20
0.50
0.40
0.30
SEATING
PLANE
0.80
0.75
0.70 0. 05 MAX
0.02 NO M
0.203 REF
COPLANARITY
0.08
PIN 1
INDICATOR
0.30
0.25
0.18
FOR PRO P E R CONNECTI ON OF
THE EXPOSED PAD, REFER TO
THE P IN CO NFI GURAT ION AND
FUNCTION DES CRIPTIONS
SECTION OF THIS DATA SHEET.
COMPLIANT
TO
JEDEC STANDARDS M O-220- WHHD-3.
5.10
5.00 SQ
4.90
05-23-2012-B
0.20 M IN
Figure 66. 28-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
5 mm × 5 mm Body, Very Very Thin Quad
(CP-28-6)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range2 Package Description Package Option
ADM1075-1ACPZ −40°C to +85°C 28-Lead LFCSP_WQ (25 mV full-scale VSENSE) CP-28-6
ADM1075-1ACPZ-RL7 −40°C to +85°C 28-Lead LFCSP_WQ (25 mV full-scale VSENSE) CP-28-6
ADM1075-1ARUZ −40°C to +85°C 28-Lead TSSOP (25 mV full-scale VSENSE) RU-28
ADM1075-1ARUZ-RL7
−40°C to +85°C
28-Lead TSSOP (25 mV full-scale V
SENSE
)
RU-28
ADM1075-2ACPZ −40°C to +85°C 28-Lead LFCSP_WQ (50 mV full-scale VSENSE) CP-28-6
ADM1075-2ACPZ-RL7 −40°C to +85°C 28-Lead LFCSP_WQ (50 mV full-scale VSENSE) CP-28-6
ADM1075-2ARUZ −40°C to +85°C 28-Lead TSSOP (50 mV full-scale VSENSE) RU-28
ADM1075-2ARUZ-RL7 −40°C to +85°C
28-Lead TSSOP (50 mV full-scale VSENSE) RU-28
EVAL-ADM1075EBZ Evaluation Board
1 Z = RoHS Compliant Part.
2 Operating junction temperature is −40°C to +105°C.
Rev. C | Page 51 of 52
ADM1075 Data Sheet
Rev. C | Page 52 of 52
NOTES
I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).
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D09312-0-4/14(C)
