System Power Measurement IC with PMBus. (Rev. A)

System Power Measurement IC with PMBus. (Rev. A)
LM25056A
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SNVS785A – JANUARY 2011 – REVISED APRIL 2013
LM25056A System Power Measurement IC with PMBus
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FEATURES
APPLICATIONS
• Input Voltage Range: 3V to 17V
• I2C/SMBus Interface with PMBus Compliant
Command Structure
• Remote Temperature Sensing with
Programmable Warning and Shutdown
Thresholds
• Real Time Monitoring of VIN, IIN, PIN, VAUX with
12-bit Resolution and 1 kHz Sampling Rate
• Current Measurement Error: ±0.5%: +10°C to
+85°C
• Voltage Measurement Error: ±1.0%: +10°C
to+85°C
• Power Measurement Error: ±1.5%: +10°C to
+85°C
• True Input Power Measurement Using
Simultaneous Sampling of VIN and IIN
Accurately Averages Dynamic Power Readings
• Averaging of VIN, IIN, PIN, and VAUX Over
Programmable Interval Ranging from 0.001 to
4 Seconds
• User Programmable WARN and FAULT
Thresholds with SMBA Notification
• Black Box Capture of Telemetry
Measurements and Device Status Triggered by
WARN and FAULT Conditions
• Full Featured Application Development
Software
• WQFN-24 Package
•
•
•
1
234
Server Backplane Systems
Base Station Power Distribution Systems
Subsystem Power Measurement
DESCRIPTION
The LM25056A combines high performance analog
and digital technology with a PMBus™ compliant
SMBus™/I2C interface to accurately measure the
operating conditions of electrical systems including
computing and storage blades connected to a
backplane power bus. The LM25056A continuously
supplies real-time power, voltage, current, and
temperature data to the system management host via
the SMBus interface.
The LM25056A monitoring block captures both realtime and average values of subsystem operating
parameters (VIN, IIN, PIN, VAUX) as well as peak
power.
Accurate
power
measurement
is
accomplished by measuring the product of the input
voltage and current through a shunt resistor.
LM25056A current measurement has a ±0.5%
accuracy over the temperature range of +10°C to
+85°C with operation from -40°C to +125°C. A black
box (Telemetry/Fault Snapshot) function captures and
stores telemetry data and device status in the event
of a warning or a fault.
1
2
3
4
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SMBus is a trademark of Intel Corp..
PMBus is a trademark of SMIF, Inc..
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011–2013, Texas Instruments Incorporated
LM25056A
SNVS785A – JANUARY 2011 – REVISED APRIL 2013
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Typical Application Schematic
RS
+12V
MMBT3904
VIN
VOUT
POL
REGULATOR
CIN
VIN
VDD
VS- DIODE
VS+
ADR2
NC
ADR1
NC
ADR0
VAUX
VREF
LM25056
ENABLE
CVREF
SMBA
SMBus
Interface
VDD
SDA
CVDD
SCL
DGND
AGND
VAUX
NC
NC
NC
AGND
NC
DGND
Connection Diagram
SDA
ENABLE
SCL
VIN
SMBA
NC
NC
NC
VS-
VDD
DIODE
ADR0
VS+
ADR1
VREF
ADR2
24
NC
Exposed Pad
1
Solder exposed pad to ground.
Figure 1. Top View
WQFN-24
2
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PIN DESCRIPTIONS
Pin
No.
Name
Description
Applications Information
PAD
Exposed
Pad
Exposed pad of WQFN
package
No internal electrical connections. Solder to the ground plane to reduce thermal
resistance.
1
ADR2
SMBus address line 2
3 - state address line. Should be connected to GND, VDD, or left floating.
2
ADR1
SMBus address line 1
3 - state address line. Should be connected to GND, VDD, or left floating.
3
ADR0
SMBus address line 0
3 - state address line. Should be connected to GND, VDD, or left floating.
4
VDD
Internal sub-regulator
output
Internally sub-regulated 3.7V bias supply. Connect a 1 µF capacitor on this pin to ground
for bypassing. VDD can be driven from an external voltage for low voltage operation.
5
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
6
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
7
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
8
VS-
Current sense input (-)
Negative IIN sense amplifer input. The voltage across the current sense resistor (RS) is
measured from VS+ to this pin.
9
VS+
Current sense input (+)
Positive IIN sense amplifier input. The voltage across the current sense resistor (RS) is
measured from this pin to VS-.
10
NC
No Connect
11
VIN
Positive supply input
Not bonded to die. Can be connected to the ground plane.
12
ENABLE
Enable
13
VAUX
Auxiliary voltage input
14
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
15
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
16
NC
No Connect
Not bonded to die. Can be connected to the ground plane.
17
AGND
Analog ground
18
NC
No Connect
19
DGND
Digital ground
20
SDA
SMBus data pin
Data pin for SMBus.
21
SCL
SMBus clock
Clock pin for SMBus.
22
SMBA
SMBus alert line
Alert pin for SMBus. Active low.
23
VREF
Internal reference
Internally generated precision 2.82V reference used for analog to digital conversion.
Connect a 1 µF ceramic capacitor on this pin to ground for bypassing.
24
DIODE
External diode
A small 0.1 µF ceramic bypass capacitor close to this pin is recommended. VIN is
measured from this pin.
Enable pin. This pin has a rising threshold of +1.2V to enable the LM25056A. Lowering
this pin below the 75mV hysteresis from the +1.2V threshold will put the part into power
down mode.
Auxiliary pin allows voltage telemetry from an external source. Full scale input of 1.2V
Connect analog ground to digital ground and then to a quiet system ground. Be sure to
avoid high current return ground lines.
Not bonded to die. Can be connected to the ground plane.
Connect analog ground to digital ground and then to a clean system ground. Be sure to
avoid high current return ground lines.
Connect this to a diode-configured MMBT3904 NPN transistor for temperature monitoring.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1) (2)
VIN, VS-, VS+ to AGND/DGND
-0.3V to 24V
SCL, SDA, SMBA, ADR0, ADR1, ADR2, VDD, VAUX, DIODE, ENABLE to AGND/DGND
VS+ to VSESD Rating (3)
-0.3V to 6V
-0.3V to +0.3V
Human Body Model
2kV
Storage Temperature
-65°C to +150°C
Junction Temperature
+150°C
(1)
(2)
(3)
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional. For specifications and conditions see the Electrical Characteristics.
If Military/Aerospace specified devices are required, please contact the TI Office/Distributors for availability and specifications.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
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Operating Ratings
VIN, VS-, VS+ voltage
3V to 17V
VDD
3V to 5.5V
Junction Temperature
-40°C to +125°C
Electrical Characteristics
Limits in standard type are for TJ = +25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = +25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and (2).
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
Input (VIN Pin)
ISUPPLY-EN
Supply current, enabled
ENABLE > 1.2V
1.7
2.8
mA
ISUPPLY-DIS
Supply current, disabled
ENABLE < 1.2V
10
100
µA
VREF Reference
VREF
Reference voltage
2.82
V
VDD Regulator (VDD pin)
VDD
IVDDLIM
3.1
3.7
4.1
V
VDD current limit
VIN = 12V
50
mA
PORVDD
Power on reset threshold at VDD
VDD increasing
2.4
PORHYS
POR hysteresis
VDD decreasing
90
mV
12
Bits
Acquisition round robin time
Update all telemetry channels
1
ms
3.0
V
ADC and MUX
Resolution
tRR
Telemetry Accuracy
20
µA
IINFSR
IINIB
Current sense full scale range, VSENSE = GAIN = 0
VS+ − VSGAIN = 1
29.68
mV
60.88
mV
IINLSB
Current sense input LSB
GAIN = 0
7.25
µV
GAIN = 1
14.87
µV
1.199
V
VAUXFSR
VAUX input full scale range (ADC native
range)
VAUXLSB
VAUX input LSB
4
For calculation only, observe maximum
voltage ratings.
293
µV
25.13
V
6.14
mV
VINFSR
Supply voltage measurement full scale
range
VINLSB
Supply voltage measurement LSB
IINERR
Current sense measurement error
GAIN = 0, VSENSE = 25 mV,
+10°C to +85C
-0.5
+0.5
%
IINERR
Current sense measurement error
GAIN = 0, VSENSE = 25 mV
-1.5
+1.5
%
IINERR
Current sense measurement error
GAIN = 0, VSENSE = 5 mV,
+10°C to +85C
-5
+5
%
IINERR
Current sense measurement error
GAIN = 1, VSENSE = 55 mV,
PERR
Input power measurement error
GAIN = 0, VIN = 12V, VSENSE = 25 mV,
+10°C to +85C
-1.5
PERR
Input power measurement error
GAIN = 0, VIN = 12V, VSENSE = 25 mV
-3
PERR
Input power measurement error
GAIN = 1, VIN = 12V, VSENSE = 55 mV
VINERR
Input voltage measurement error
VIN = 12V, +10°C to +85C
-1.0
+1.0
%
VINERR
Input voltage measurement error
VIN = 12V
-1.5
+1.5
%
Auxiliary measurement error
VAUX = 1V, +10°C to +85C
-1.5
+1.5
%
VAUXERR
(1)
(2)
Current sense input bias current
1
%
+1.5
%
+3
%
2
%
Current out of a pin is indicated as a negative value.
All electrical characteristics having room temperature limits are tested during production at TA = +25°C. All bold limits are specified by
correlating the electrical characteristics to process and temperature variations and applying statistical process control.
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Electrical Characteristics (continued)
Limits in standard type are for TJ = +25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C
to +85°C unless otherwise stated. Minimum and Maximum limits are specified through test, design, or statistical correlation.
Typical values represent the most likely parametric norm at TJ = +25°C, and are provided for reference purposes only. Unless
otherwise stated the following conditions apply: VIN = 12V. See (1) and (2).
Symbol
VAUXERR
Parameter
Conditions
Auxiliary measurement error
VAUX = 1V
Min.
Typ.
-2.5
Max.
Units
+2.5
%
Remote Diode Temperature Sensor
TACC
Temperature accuracy using local diode
3
Remote diode resolution
IDIODE
°C
9
External diode current source
High Level
240
Low Level
9.2
Diode Current
Ratio
bits
325
µA
µA
26
PMBus Pin Thresholds (SMBA, SDA, SCL)
VIL
Data, clock input low voltage
VIH
Data, clock input high voltage
VOL
Data output low voltage
IPULLUP = 5 mA
ILEAK
Input leakage current
SDA, SMBA, SCL = 5.5V
ENABLE threshold voltage
Rising threshold
0.9
V
2.1
5.5
V
0
0.4
V
1
µA
ENABLE Pin
VEN
VEN-HYS
ILEAK
IPULLUP
ENABLE threshold voltage hysteresis
Input Leakage Current
1.4
1.2
V
75
mV
ENABLE = 5V
ENABLE pin pullup current
1
2.8
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mA
µA
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Typical Performance Characteristics
Unless otherwise specified the following conditions apply: TJ = +25°C, VIN = 12V. All graphs show junction temperature.
VIN Pin Current (Enabled)
VIN Pin Current (Disabled)
1.8
14
17V
5V, 12V, 17V
12
CURRENT ( A)
CURRENT (mA)
1.7
1.6
1.5
1.4
10
12V
8
5V
6
1.3
1.2
-40 -20
3V
3V
4
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20
Figure 2.
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 3.
VS+ Pin Input Bias Current (Enabled)
VS- Pin Input Bias Current (Enabled)
12
25
CURRENT ( A)
CURRENT ( A)
24
11
10
23
22
21
9
20
-40 -20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20
Figure 4.
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure .
POR Threshold
ENABLE Threshold
2.50
1.30
2.46
1.25
VOLTAGE (V)
VOLTAGE (V)
Rising
2.40
2.35
2.30
Falling
Rising
1.20
1.15
2.25
2.20
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Falling
1.10
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 5.
6
Figure 6.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = +25°C, VIN = 12V. All graphs show junction temperature.
VREF Voltage
VDD Voltage
2.840
3.73
2.835
3.72
VOLTAGE (V)
VOLTAGE (V)
2.830
2.825
2.820
2.815
3.71
3.70
3.69
2.810
3.68
2.805
2.800
3.67
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 7.
Figure 8.
VIN Error, VIN=12V
VAUX Error, VAUX=1V
1.0
1.0
0.8
0.8
VAUX ERROR (%)
VIN ERROR (%)
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
0.6
0.4
0.2
0.0
-0.2
-0.8
-0.4
-1.0
-0.6
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 9.
Figure 10.
IIN Error, GAIN=0, VSENSE=25mV
PIN Error, GAIN=0, VIN=12V, VSENSE=25mV
0.4
0.8
0.6
0.4
PIN ERROR (%)
IIN ERROR (%)
0.2
0.0
-0.2
-0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-0.6
-1.0
-0.8
-1.2
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 11.
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 12.
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Typical Performance Characteristics (continued)
Unless otherwise specified the following conditions apply: TJ = +25°C, VIN = 12V. All graphs show junction temperature.
PIN Error, GAIN=1, VIN=12V, VSENSE=55mV
0.8
0.3
0.6
0.2
0.4
0.1
0.2
PIN ERROR (%)
IIN ERROR (%)
IIN Error, GAIN=1, VSENSE=55mV
0.4
0.0
-0.1
-0.2
-0.3
0.0
-0.2
-0.4
-0.6
-0.4
-0.8
-0.5
-1.0
-0.6
-1.2
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 13.
8
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
Figure 14.
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VS-
VS+
VIN
VDD
3.7V
Block Diagram
VDD
REG
VREF
2.82V
1.2V
2.35x
REF
GEN
BUF
1/21
12 bit
ADC
S/H
AMUX
20x, GAIN=0
40x, GAIN=1
ENABLE
Black Box
SMBA
SMBus
Interface
Telemetry State
Machine
SDA
VAUX
Measurement/
Averaging
Warning Registers
ADR0
ADR2
DGND
ADR1
Address
Decoder
Diode
Temp
Sense
AGND
DIODE
SCL
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FUNCTIONAL DESCRIPTION
The LM25056A provides intelligent monitoring of the input voltage, input current, input power, temperature, and
an auxiliary input. The LM25056A also provides a peak capture of the input power and programmable hardware
averaging of the input voltage, current, power, temperature, and the auxiliary voltage. Warning thresholds which
trigger the SMBA pin may be programmed for input and auxiliary voltage, current, power, and temperature via
the PMBus interface.
Enabling/Disabling and Resetting
The LM25056A has an ENABLE pin that can be used to power on and off the device. If desired, the LM25056A
can be kept in shutdown until the supply reaches a particular threshold using ENABLE with a resistor divider or
with an active control as shown in Figure 15.
+12V
VIN
ENABLE
LM25056
SHUTDOWN
CONTROL
GND
Figure 15. ENABLE Control
When taken low, this logic pin will reduce the quiescent current for the device and will no longer respond to
PMBus commands. Also, taking the ENABLE low is a functional reset of the LM25056A. Raising ENABLE sets
the part to its default operation. If this functionality is not used, then ENABLE should be left floating (an internal
pull-up will maintain its operation) or tied to an external VDD voltage. Do not tie ENABLE to the onboard VDD.
The VDD power-up is delayed and when power is first applied, and VDD starts low. This in turn will keep
ENABLE low and the LM25056A will not start up.
VDD and VREF also have a power-on-reset (POR) circuit that holds the LM25056A in reset until it reaches the
operating state. Note that if either of these output lines are inadvertently pulled low, the device is reset to its
initial default state, erasing the volatile memory the same as ENABLE pulled low. Once VDD and VREF have
reached the POR threshold of 2.4V, the device comes out of reset.
As an example, the SMBus address of the LM25056A is captured based on the states (GND, NC, VDD) of the
ADR0, ADR1, and ADR2 pins during turn on and is latched into a volatile register once the ENABLE pin is
determined to be high and the VDD and VREF has exceeded its POR threshold of 2.4V. Reassigning or
postponing the address capture can be accomplished by holding the ENABLE pin to AGND. For more
information on the operation of these pins, please see the PMBus Address Lines section of this datasheet.
The logic and volatile memory can also be reset with a PMBus write to the MFR_DEVICE_SETUP (D9h) register
into the software reset bit. However, this software reset will not trigger a read of the states of the address pins as
the ENABLE pin or VDD and VREF POR events will.
VDD Sub-Regulator
The LM25056A contains an internal linear sub-regulator which steps down the input voltage to generate a 3.7V
rail used for powering low voltage and low power circuitry. When the input voltage is below 3.7V, VDD will track
VIN. For input voltages 3.3V and below, VDD should be tied directly to VIN to avoid the dropout of the subregulator. The VDD sub-regulator should be used as the pull-up supply for the ADR2, ADR1, and ADR0 pins if
they are to be tied high. It may also be used as the pull-up supply for SMBus signals (SDA, SCL, SMBA). The
VDD sub-regulator is not designed to drive high currents and should not be loaded to drive high current circuits.
The VDD pin is current limited to 50 mA in order to protect the LM25056A in the event of a short. The subregulator requires a ceramic bypass capacitance of 1 µF or greater to be placed as close to VDD as the PCB
layout allows.
10
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Additionally, VDD can be driven from an external source to maintain telemetry readings for VIN and temperature
if the VIN drops below its operation point. To do this, use an external 5V supply driving the VDD through a
Schottky diode. This allows for telemetry readings down to VIN=0. A large capacitor (100uF) can also be placed
at on the VDD line to momentarily supply current to the device to similarly maintain telemetry readings that would
normally shutdown and reset the device. Note that when using an external VDD drive, ENABLE will not operate
independently. To use this functionality, simply connect the external VDD source to ENABLE and lower this
source to put the LM25056A into low power mode.
Remote Temperature Sensing
The LM25056A is designed to measure temperature remotely using an MMBT3904 NPN transistor. The base
and collector of the MMBT3904 should be connected to the DIODE pin and the emitter of the MMBT3904
connected to AGND. Place the MMBT3904 near the device whose temperature is to be monitored. In noisy
environments with large currents or switching noise, it is especially important to bring this connection back to
AGND and not just to the nearest ground plane. If the temperature of a pass MOSFET is to be measured, the
MMBT3904 should be placed as close to device as the layout allows. The temperature is measured by means of
a change in an external diode voltage in response to a step in current supplied by DIODE. DIODE sources 9.2
µA but pulses 240 µA once every millisecond in order to measure the diode temperature. Care must be taken in
the PCB layout to keep the parasitic resistance between DIODE and the MMBT3904 low so as not to degrade
the measurement. Additionally, a small 100 pF bypass capacitor can be placed in parallel with the MMBT3904 to
reduce the effects of noise. The temperature can be read using the READ_TEMPERATURE_1 PMBus command
(8Dh). The default warning limit of the LM25056A will cause SMBA to be pulled low if the measured temperature
code exceeds 07D0h. The PMBus will also indicate an over temperature fault if the measured temperature code
exceeds 0960h. These thresholds can be reprogrammed via the PMBus interface using the OT_WARN_LIMIT
(51h) and OT_FAULT_LIMIT (4Fh) commands. If the temperature measurement and protection capability of the
LM25056A is not used the DIODE pin should be grounded.
Application Section
RS
+12V
MMBT3904
VIN
VOUT
POL
REGULATOR
CIN
VIN
VDD
VS+
VS- DIODE
ADR2
NC
ADR1
NC
ADR0
VAUX
VREF
ENABLE
LM25056
SMBA
SMBus
Interface
CVREF
VDD
SDA
CVDD
SCL
DGND
AGND
Figure 16. Typical Application Circuit
DESIGN-IN PROCEDURE
(Refer to Figure 16 for Typical Application Circuit) Shown here is the step-by-step procedure for hardware design
of the LM25056A. This procedure refers to section numbers that provide detailed information on the following
design steps. The recommended design-in procedure is as follows:
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Current Range, RS: Determine the current range based on the voltage dropped across the sense resistor (RS).
Depending on the GAIN setting, the voltage across the sense resistor to get a full scale reading for the current
measurement should be 30 mV for GAIN=0 and 60 mV for GAIN=1. Use the Equation 1 to determine the value
for RS.
Refer to Programming Guide section: After all hardware design is complete, refer to the programming guide
for a step by step procedure regarding software.
CURRENT RANGE, (RS)
The LM25056A monitors current by measuring the voltage across the sense resistor (RS) connected from VS+ to
VS -. The required resistor value is calculated from:
(1)
where IFS is the expected full scale current range based on the current sense gain setting (GAIN). If the voltage
across RS reaches VS, the current measurement will reach the full scale measurement. As mentioned before, it is
important to limit the current to the full scale reading. While there is internal circuitry intended to maintain the
integrity of the other readings in the telemetry, the ADC and MUX are shared and overranging an input may
compromise the integrity of the other readings.
VS can be set to either 30 mV or 60 mV through software commands. This setting defaults to the sense voltage
full scale of 30 mV (GAIN = 0), or it can be set to 60 mV (GAIN = 1). The value can be set via the PMBus with
the MFR_DEVICE_SETUP (D9h) command, which defaults to the 30 mV setting. Once the current measurement
full scale is known and the VS range is chosen, calculate the shunt based on that input voltage and maximum
current range. The maximum load current in normal operation can be used to determine the required power
rating for resistor RS.
Connections from RS to the LM25056A should be made using Kelvin techniques. In the suggested layout of
Figure 17, the small pads at the lower corners of the sense resistor connect only to the sense resistor terminals
and not to the traces carrying the high current. With this technique, only the voltage across the sense resistor is
applied to VS+ and VS-, eliminating the voltage drop across the high current solder connections.
SENSE CURRENT PATH
FROM SYSTEM
INPUT VOLTAGE
TO LOAD
SENSE
RESISTOR
RS
VS+
VS-
Figure 17. Sense Resistor Connections
PC BOARD GUIDELINES
The following guidelines should be followed when designing the PC board for the LM25056A:
• Place the LM25056A close to the board’s input connector to minimize trace inductance from the connector to
following devices.
• Place a small capacitor, CIN, (0.1µF) directly adjacent to the VIN and AGND and DGND pins of the
LM25056A to help minimize transients which may occur on the input supply line. Transients of several volts
can easily occur when the load current is shut off.
• Place a 1 µF capacitor as close as possible to VREF pin.
• Place a 1 µF capacitor as close as possible to VDD pin.
• The sense resistor (RS) should be placed close to the LM25056A. In particular, the traces to the VS+, VS-,
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and VIN pins should be made as low resistance as practical to ensure maximum current and power
measurement accuracy. Connect RS using the Kelvin techniques shown in Figure 17.
The high current path from the board’s input to the load and the return path should be parallel and close to
each other to minimize loop inductance.
The ground connections for the various components around the LM25056A should be connected directly to
each other, and to the LM25056A’s DGND and AGND pins, and then connected to the system ground at one
point. Do not connect the various component grounds to each other through the high current ground line. The
ground of the MMBT3904 should also be connected to the AGND pin to prevent corruption of the temperature
diode measurement.
PMBus Command Support
The device features an SMBus interface that allows the use of PMBus commands to set warn levels, error
masks, and get telemetry on VIN, VAUX, IIN, PIN, and temperature. The supported PMBus commands are shown in
Table 1.
Table 1. Supported PMBus Commands
Number
Of Data
Bytes
Code
Name
Function
R/W
03h
CLEAR_FAULTS
Clears the status registers and re-arms the black box
registers for updating.
Send
Byte
0
Default
Value
19h
CAPABILITY
Retrieves the device capability.
R
1
B0h
4Fh
OT_FAULT_LIMIT
Retrieves or stores over temperature fault limit
threshold.
R/W
2
0960h
51h
OT_WARN_LIMIT
Retrieves or stores over temperature warn limit
threshold.
R/W
2
07D0h
57h
VIN_OV_WARN_LIMIT
Retrieves or stores input over-voltage warn limit
threshold.
R/W
2
0FFFh
58h
VIN_UV_WARN_LIMIT
Retrieves or stores input under-voltage warn limit
threshold.
R/W
2
0000h
78h
STATUS BYTE
Retrieves information about the parts operating status.
R
1
01h
79h
STATUS_WORD
Retrieves information about the parts operating status.
R
2
1001h
7Ch
STATUS_INPUT
Retrieves information about input status.
R
1
00h
7Dh
STATUS_TEMPERATURE
Retrieves information about temperature status.
R
1
00h
7Eh
STATUS_CML
Retrieves information about communications status.
R
1
00h
80h
STATUS_MFR_SPECIFIC
Retrieves information about manufacturer specific
device status.
R
1
10h
88h
READ_VIN
Retrieves input voltage measurement.
R
2
0000h
8Dh
READ_TEMPERATURE_1
Retrieves temperature measurement.
R
2
0000h
99h
MFR_ID
Retrieves manufacturer ID in ASCII characters (NSC).
R
3
4Eh
53h
43h
9Ah
MFR_MODEL
Retrieves Part number in ASCII characters.
(LM25056A).
R
8
4Ch
4Dh
32h
35h
30h
35h
36h
00h
9Bh
MFR_REVISION
Retrieves part revision letter/number in ASCII (e.g., AA).
R
2
41h
41h
D0h
MFR_SPECIFIC_00
MFR_READ_VAUX
Retrieves auxiliary voltage measurement.
R
2
0000h
D1h
MFR_SPECIFIC_01
MFR_READ_IIN
Retrieves input current measurement.
R
2
0000h
D2h
MFR_SPECIFIC_02
MFR_READ_PIN
Retrieves input power measurement.
R
2
0000h
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Table 1. Supported PMBus Commands (continued)
Code
Name
Function
R/W
Number
Of Data
Bytes
Default
Value
D3h
MFR_SPEICIFIC_03
MFR_IIN_OC_WARN_LIMIT
Retrieves or stores input current limit warn threshold.
R/W
2
0FFFh
D4h
MFR_SPECIFIC_04
MFR_PIN_OP_WARN_LIMIT
Retrieves or stores input power limit warn threshold.
R/W
2
0FFFh
D5h
MFR_SPECIFIC_05
MFR_READ_PIN_PEAK
Retrieves maximum input power measurement.
R
2
0000h
D6h
MFR_SPECIFIC_06
MFR_CLEAR_PIN_PEAK
Resets the contents of the peak input power register to
zero.
Send
Byte
0
D8h
MFR_SPECIFIC_08
MFR_ALERT_MASK
Retrieves or stores user SMBA fault mask.
R/W
2
0000h
D9h
MFR_SPECIFIC_09
MFR_DEVICE_SETUP
Retrieves or stores information about the LM25056A
setup.
R/W
1
0000h
DAh
MFR_SPECIFIC_10
MFR_BLOCK_READ
Retrieves most recent diagnostic and telemetry
information in a single transaction.
R
12
0080h
0000h
0000h
0000h
0000h
0000h
DBh
MFR_SPECIFIC_11
MFR_SAMPLES_FOR_AVG
Exponent value AVGN for number of samples to be
averaged, range = 00h to 0Ch .
R/W
1
00h
DCh
MFR_SPECIFIC_12
MFR_READ_AVG_VIN
Retrieves averaged input voltage measurement.
R
2
0000h
DDh
MFR_SPECIFIC_13
MFR_READ_AVG_VAUX
Retrieves averaged auxiliary voltage measurement.
R
2
0000h
DEh
MFR_SPECIFIC_14
MFR_READ_AVG_IIN
Retrieves averaged input current measurement.
R
2
0000h
DFh
MFR_SPECIFIC_15
MFR_READ_AVG_PIN
Retrieves averaged input power measurement.
R
2
0000h
E0h
MFR_SPECIFIC_16
MFR_BLACK_BOX_READ
Captures diagnostic and telemetry information which are
latched when an SMBA occurs after faults have been
cleared.
R
12
0080h
0000h
0000h
0000h
0000h
0000h
E1h
MFR_SPECIFIC_17
MFR_DIAGNOSTIC_WORD_READ
Manufacturer-specific parallel of the STATUS_WORD to
convey all FAULT/WARN data in a single transaction.
R
2
0080h
E2h
MFR_SPECIFIC_18
MFR_AVG_BLOCK_READ
Retrieves most recent average telemetry and diagnostic
information in a single transaction.
R
12
0080h
0000h
0000h
0000h
0000h
0000h
E3h
MFR_SPECIFIC_19
MFR_VAUX_OV_WARN_LIMIT
Retrieves or stores auxiliary over-voltage warn limit
threshold.
R
2
0FFFh
E4h
MFR_SPECIFIC_20
MFR_VAUX_UV_WARN_LIMIT
Retrieves or stores auxiliary under-voltage warn limit
threshold.
R
2
0000h
STANDARD PMBus Commands
CLEAR_FAULTS (03h)
The CLEAR_FAULTS command is a standard PMBus command that resets all stored warning and fault flags
and the SMBA signal. If a fault or warning condition still exists when the CLEAR_FAULTS command is issued,
the SMBA signal may not clear or will re-assert almost immediately. This command uses the PMBus send byte
protocol.
CAPABILITY (19h)
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The CAPABILITY command is a standard PMBus command that returns information about the PMBus functions
supported by the LM25056A. This command is read with the PMBus read byte protocol.
Table 2. CAPABILITY Register
Value
Meaning
Default
B0h
Supports Packet Error Check, 400Kbits/sec, Supports SMBus
Alert
B0h
OT_FAULT_LIMIT (4Fh)
The OT_FAULT_LIMIT is a standard PMBus command that allows configuring or reading the threshold for the
overtemperature fault detection. Reading and writing to this register should use the coefficients shown in the
Telemetry and Warning Conversion Coefficients Table. Accesses to this command should use the PMBus read
or write word protocol. If the measured temperature exceeds this value, an Overtemperature fault is triggered,
OT Fault flags are set and the SMBA signal is asserted.
Table 3. OT_FAULT_LIMIT Register
Value
Meaning
Default
0h – 0FFEh
Overtemperature Fault Threshold Value
0960h
0FFFh
Overtemperature Fault detection disabled
n/a
OT_WARN_LIMIT (51h)
The OT_WARN_LIMIT is a standard PMBus command that allows configuring or reading the threshold for the
overtemperature warning detection. Reading and writing to this register should use the coefficients shown in the
Telemetry and Warning Conversion Coefficients Table. Accesses to this command should use the PMBus read
or write word protocol. If the measured temperature exceeds this value, an Overtemperature warning is triggered
and the OT Warning flags are set and the SMBA signal is asserted.
Table 4. OT_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFEh
Overtemperature Warn Threshold Value
07D0h
0FFFh
Overtemperature Warn detection disabled
n/a
VIN_OV_WARN_LIMIT (57h)
The VIN_OV_WARN_LIMIT is a standard PMBus command that allows configuring or reading the threshold for
the VIN overvoltage warning detection. Reading and writing to this register should use the coefficients shown in
the Telemetry and Warning Conversion Coefficients Table. Accesses to this command should use the PMBus
read or write word protocol. If the measured value of VIN rises above the value in this register, VIN OV Warn
flags are set and the SMBA signal is asserted.
Table 5. VIN_OV_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFEh
VIN Overvoltage Warning detection threshold
0FFFh (disabled)
0FFFh
VIN Overvoltage Warning disabled
n/a
VIN_UV_WARN_LIMIT (58h)
The VIN_UV_WARN_LIMIT is a standard PMBus command that allows configuring or reading the threshold for
the VIN undervoltage warning detection. Reading and writing to this register should use the coefficients shown in
the Telemetry and Warning Conversion Coefficients Table. Accesses to this command should use the PMBus
read or write word protocol. If the measured value of VIN falls below the value in this register, VIN UV Warn flags
are set and the SMBA signal is asserted.
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Table 6. VIN_UV_WARN_LIMIT Register
Value
Meaning
Default
1h – 0FFFh
VIN Undervoltage Warning detection threshold
0000h (disabled)
0000h
VIN Undervoltage Warning disabled
n/a
STATUS_BYTE (78h)
The STATUS_BYTE is a standard PMBus command that returns the value of a number of flags indicating the
state of the LM25056A. Accesses to this command should use the PMBus read byte protocol. To clear bits in this
register, the underlying fault should be cleared and a CLEAR_FAULTS command issued.
Table 7. STATUS_BYTE Definitions
Bit
Name
Meaning
Default
7
BUSY
Not supported
0
6
OFF
Not supported
0
5
VOUT_OV
Not supported
0
4
IOUT_OC
Not supported
0
3
VIN_UV
An input undervoltage fault has occurred
0
2
TEMPERATURE
A temperature fault or warning has occurred
0
1
CML
A Communication Fault has occurred
0
0
NONE OF THE ABOVE
A fault or warning not listed in bits [7:1] has occurred
1
STATUS_WORD (79h)
The STATUS_WORD is a standard PMBus command that returns the value of a number of flags indicating the
state of the LM25056A. Accesses to this command should use the PMBus read word protocol. To clear bits in
this register, the underlying fault should be cleared and a CLEAR_FAULTS command issued. The INPUT and
VIN UV flags will default to 1 on startup.
Table 8. STATUS_WORD Definitions
Bit
16
Name
Meaning
Default
15
VOUT
Not supported
0
14
IOUT/POUT
Not supported
0
13
INPUT
An input voltage or current fault has occurred
0
12
MFR
A manufacturer specific fault or warning has occurred
1
11
POWER_GOOD#
Not supported
0
10
FANS
Not supported
0
9
OTHER
Not supported
0
8
UNKNOWN
Not supported
0
7
BUSY
Not supported
0
6
OFF
Not supported
0
5
VOUT_OV
Not supported
0
4
IOUT_OC
Not supported
0
3
VIN_UV
An input undervoltage fault has occurred
0
2
TEMPERATURE
A temperature fault or warning has occurred
0
1
CML
A communication fault has occurred
0
0
NONE OF THE ABOVE
A fault or warning not listed in bits [7:1] has occurred
1
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STATUS_INPUT (7Ch)
The STATUS_INPUT is a standard PMBus command that returns the value of the of a number of flags related to
input voltage, current, and power. Accesses to this command should use the PMBus read byte protocol. To clear
bits in this register, the underlying fault should be cleared and a CLEAR_FAULTS command issued.
Table 9. STATUS_INPUT Definitions
Bit
Name
Meaning
Default
7
VIN OV Fault
Not supported
0
6
VIN OV Warn
An input overvoltage warning has occurred
0
5
VIN UV Warn
An input undervoltage warning has occurred
0
4
VIN UV Fault
Not supported
0
3
Insufficient Voltage
Not supported
0
2
IIN OC Fault
Not supported
0
1
IIN OC Warn
An input overcurrent warning has occurred
0
0
PIN OP Warn
An input overpower warning has occurred
0
STATUS_TEMPERATURE (7Dh)
The STATUS TEMPERATURE is a standard PMBus command that returns the value of the of a number of flags
related to the temperature telemetry value. Accesses to this command should use the PMBus read byte protocol.
To clear bits in this register, the underlying fault should be cleared and a CLEAR_FAULTS command issued.
Table 10. STATUS_TEMPERATURE Definitions
Bit
Name
Meaning
Default
7
OT FAULT
An overtemperature fault has occurred
0
6
OT WARN
An overtemperature warning has occurred
0
5
UT WARN
Not supported
0
4
UT FAULT
Not supported
0
3
reserved
Not supported
0
2
reserved
Not supported
0
1
reserved
Not supported
0
0
reserved
Not supported
0
STATUS_CML (7Eh)
The STATUS_CML is a standard PMBus command that returns the value of a number of flags related to
communication faults. Accesses to this command should use the PMBus read byte protocol. To clear bits in this
register, a CLEAR FAULTS command should be issued.
Table 11. STATUS_CML Definitions
Bit
Meaning
Default
7
Invalid or unsupported command received
0
6
Invalid or unsupported data received
0
5
Packet Error Check failed
0
4
Not supported
0
3
Not supported
0
2
Reserved
0
1
Miscellaneous communications fault has occurred
0
0
Not supported
0
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STATUS_MFR_SPECIFIC (80h)
The STATUS_MFR_SPECIFIC command, is a standard PMBus command that contains manufacturer specific
status information. Accesses to this command should use the PMBus read byte protocol. To clear bits in this
register, the underlying fault should be cleared and a CLEAR_FAULTS command should be issued.
Table 12. STATUS_MFR_SPECIFIC Definitions
Bit
Meaning
Default
7
Not supported
0
6
Not supported
0
5
Not supported
0
4
Defaults loaded
1
3
Not supported
0
2
Not supported
0
1
A VAUX Overvoltage Warning has occurred
0
0
A VAUX Undervoltage Warning has occurred
0
READ_VIN (88h)
The READ_VIN is a standard PMBus command that returns the 12 bit measured value of the input voltage as
read from the VIN pin. Reading this register should use the coefficients shown in the Telemetry and Warning
Conversion Coefficients Table. Accesses to this command should use the PMBus read word protocol. This value
is also used internally for the VIN Over and Under Voltage Warning detection.
Table 13. READ_VIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for VIN
0000h
READ_TEMPERATURE_1 (8Dh)
The READ_TEMPERATURE_1 is a standard PMBus command that returns the signed value of the temperature
measured by the external temperature sense diode. Reading this register should use the coefficients shown in
the Telemetry and Warning Conversion Coefficients Table. Accesses to this command should use the PMBus
read word protocol. This value is also used internally for the Over Temperature Fault and Warning detection. This
data has a range of -256°C to + 255°C after the coefficients are applied.
Table 14. READ_TEMPERATURE_1 Register
Value
Meaning
Default
0h – 0FFFh
Measured value for TEMPERATURE
0000h
MFR_ID (99h)
The MFR_ID is a standard PMBus command that returns the identification of the manufacturer. To read the
manufacturer ID, use the PMBus block read protocol.
Table 15. MFR_ID Register
Byte
Name
0
Number of bytes
Value
03h
1
MFR ID-1
4Eh ‘N’
2
MFR ID-2
53h ‘S’
3
MFR ID-3
43h ‘C’
MFR_MODEL (9Ah)
The MFR_MODEL is a standard PMBus command that returns the part number of the chip. To read the
manufacturer model, use the PMBus block read protocol.
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Table 16. MFR_MODEL Register
Byte
Name
Value
0
Number of bytes
08h
1
MFR ID-1
4Ch ‘L’
2
MFR ID-2
4Dh ‘M’
3
MFR ID-3
32h ‘2’
4
MFR ID-4
35h ‘5’
5
MFR ID-5
30h ‘0’
6
MFR ID-6
35h ‘5’
7
MFR ID-7
36h ‘6’
8
MFR ID-8
00h
MFR_REVISION (9Bh)
The MFR_REVISION is a standard PMBus command that returns the revision level of the part. To read the
manufacturer revision, use the PMBus block read protocol.
Table 17. MFR_REVISION Register
Byte
Name
Value
0
Number of bytes
02h
1
MFR ID-1
41h ‘A’
2
MFR ID-2
41h ‘A’
Manufacturer Specific PMBus Commands
MFR_SPECIFIC_00: MFR_READ_VAUX (D0h)
The MFR_READ_VAUX command will report the 12-bit ADC measured auxiliary voltage. Voltages greater than
or equal to 1.199V to AGND will be reported at plus full scale (0FFFh). Voltages less than or equal to 0V
referenced to AGND will be reported as 0 (0000h). Coefficients for the VAUX value are dependent on the value
of the external divider (if used). To read data from the MFR_READ_VAUX command, use the PMBus Read Word
protocol.
Table 18. MFR_READ_VAUX Register
Value
Meaning
Default
0h – 0FFFh
Measured value for AUX input
0000h
MFR_SPECIFIC_01: MFR_READ_IIN (D1h)
The MFR_READ_IIN command will report the 12-bit ADC measured current sense voltage. To read data from
the MFR_READ_IIN command, use the PMBus Read Word protocol. Reading this register should use the
coefficients shown in the Telemetry and Warning Conversion Coefficients Table. Please see the section on
coefficient calculations to calculate the values to use.
Table 19. MFR_READ_IIN Register
Value
Meaning
Default
0h – 0FFFh
Measured value for input current sense voltage
0000h
MFR_SPECIFIC_02: MFR_READ_PIN (D2h)
The MFR_READ_PIN command will report the upper 12-bits of the VIN x IIN product as measured by the 12-bit
ADC. To read data from the MFR_READ_PIN command, use the PMBus Read Word protocol. Reading this
register should use the coefficients shown in the Telemetry and Warning Conversion Coefficients Table.
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Table 20. MFR_READ_PIN Register
Value
Meaning
Default
0h – 0FFFh
Value for input current x input voltage
0000h
MFR_SPECIFIC_03: MFR_IIN_OC_WARN_LIMIT (D3h)
The MFR_IIN_OC_WARN_LIMIT PMBus command sets the input overcurrent warning threshold. In the event
that the input current rises above the value set in this register, the IIN Overcurrent flags are set in the status
registers and the SMBA is asserted. To access the MFR_IIN_OC_WARN_LIMIT register, use the PMBus
Read/Write Word protocol. Reading/writing to this register should use the coefficients shown in the Telemetry
and Warning Conversion Coefficients Table.
Table 21. MFR_IIN_OC_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFEh
Value for input over current warn limit
0FFFh
0FFFh
Input over current warning disabled
n/a
MFR_SPECIFIC_04: MFR_PIN_OP_WARN_LIMIT (D4h)
The MFR_PIN_OP_WARN_LIMIT PMBus command sets the input overpower warning threshold. In the event
that the input power rises above the value set in this register, the PIN Overpower flags are set in the status
registers and the SMBA is asserted. To access the MFR_PIN_OP_WARN_LIMIT register, use the PMBus
Read/Write Word protocol. Reading/writing to this register should use the coefficients shown in the Telemetry
and Warning Conversion Coefficients Table.
Table 22. MFR_PIN_OP_WARN_LIMIT Register
Value
Meaning
Default
0h – 0FFEh
Value for input over power warn limit
0FFFh
0FFFh
Input over power warning disabled
n/a
MFR_SPECIFIC_05: MFR_READ_PIN_PEAK (D5h)
The MFR_READ_PIN_PEAK command will report the maximum input power measured since a Power On reset
or the last MFR_CLEAR_PIN_PEAK command. To access the MFR_READ_PIN_PEAK command, use the
PMBus Read Word protocol. Use the coefficients shown in the Telemetry and Warning Conversion Coefficients
Table.
Table 23. MFR_READ_PIN_PEAK Register
Value
Meaning
Default
0h – 0FFEh
Maximum Value for input current x input voltage since reset or
last clear
0000h
MFR_SPECIFIC_06: MFR_CLEAR_PIN_PEAK (D6h)
The MFR_CLEAR_PIN_PEAK command will clear the MFR_READ_PIN_PEAK register. This command uses the
PMBus Send Byte protocol.
MFR_SPECIFIC_08: MFR_ALERT_MASK (D8h)
The MFR_ALERT_MASK is used to mask the SMBA when a specific fault or warning has occurred. Each bit
corresponds to one of the 9 different analog and digital faults or warnings that would normally result in an SMBA
being asserted. When the corresponding bit is high, that condition will not cause the SMBA to be asserted. If that
condition occurs, the registers where that condition is captured will still be updated (STATUS registers,
MFR_DIAGNOSTIC_WORD, OT_FAULT_LIMIT). This register is accessed with the PMBus Read / Write Word
protocol.
20
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Table 24. MFR_ALERT_MASK Definitions
BIT
NAME
DEFAULT
15
VAUX UNDERVOLTAGE WARN
0
14
IIN LIMIT WARN
0
13
VIN UNDERVOLTAGE WARN
0
12
VIN OVERVOLTAGE WARN
0
11
Reserved, always set to 0
0
10
OVERTEMPERATURE WARN
0
9
VAUX OVERVOLTAGE WARN
0
8
OVERPOWER LIMIT WARN
0
7
Reserved, always set to 0
0
6
Reserved, always set to 0
0
5
Reserved, always set to 0
0
4
Reserved, always set to 0
0
3
Reserved, always set to 0
0
2
OVERTEMPERATURE FAULT
0
1
CML FAULT (Communications Fault)
0
0
Reserved, always set to 0
0
MFR_SPECIFIC_09: MFR_DEVICE_SETUP (D9h)
The MFR_DEVICE_SETUP command may be used to define operation or reset the LM25056A under host
control. This command is accessed with the PMBus read / write byte protocol.
Table 25. MFR_DEVICE_SETUP Byte Format
Bit
Name
7
Reserved, always set to 0
6
Reserved, always set to 0
5
Reserved, always set to 0
4
Current sense gain
3
Reserved, always set to 0
2
Reserved, always set to 0
1
Reserved, always set to 0
0
Software reset
Meaning
GAIN = 0, Low setting (30mV)
GAIN = 1, High setting (60mV)
0 = Default
1 = Reset
Within this command byte, the current sense gain bit changes the range and coefficients used for current and
power measurements as well as relevant warning registers. The software reset bit is used to reset the
LM25056A. Writing a 1 to this bit will reset the device back to its default startup values.
MFR_SPECIFIC_10: MFR_BLOCK_READ (DAh)
The MFR_BLOCK_READ command concatenates the MFR_DIAGNOSTIC_WORD_READ with input telemetry
information (IIN, VAUX, VIN, PIN) as well as READ_TEMPERATURE_1 to capture all of the operating
information of the LM25056A in a single SMBus transaction. The block is 12 bytes long with telemetry
information being sent out in the same manner as if an individual READ_XXX command had been issued (shown
below). The contents of the block read register are updated every clock cycle (85 ns) as long as the SMBus
interface is idle. MFR_BLOCK_READ also specifies that the VIN, VAUX, IIN and PIN measurements are all timealigned whereas there is a chance they may not be if retrieved with individual PMBus commands.
The Block Read command is read via the PMBus block read protocol.
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Table 26. MFR_BLOCK_READ Register Format
Byte Count (always 12)
(1 byte)
DIAGNOSTIC WORD
(1 Word)
IIN_BLOCK
(1 Word)
VAUX_BLOCK
(1 Word)
VIN_BLOCK
(1 Word)
PIN_BLOCK
(1 Word)
TEMP_BLOCK
(1 Word)
MFR_SPECIFIC_11: MFR_SAMPLES_FOR_AVG (DBh)
The MFR_SAMPLES_FOR AVG is a manufacturer specific command for setting the number of samples used in
computing the average values for IIN, VIN, VAUX, PIN. The decimal equivalent of the AVGN nibble is the power
of 2 samples (e.g. AVGN=12 equates to 4096 samples used in computing the average). The LM25056A supports
average numbers of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096. The MFR_SAMPLES_FOR_AVG
number applies to average values of IIN, VIN, VAUX, PIN simultaneously. The LM25056A uses simple
averaging. This is accomplished by summing consecutive results up to the number programmed, then dividing by
the number of samples. Averaging is calculated according to the following sequence:
Y = (X(N) + X(N-1) + ... + X(0)) / N
(2)
When the averaging has reached the end of a sequence (for example, 4096 samples are averaged), then a
whole new sequence begins that will require the same number of samples (in this example, 4096) to be taken
before the new average is ready.
Table 27. MFR_SAMPLES_FOR_AVERAGE
AVGN
N = 2AVGN
Averaging/Register Update Period
(ms)
0000
1
1
0001
2
2
0010
4
4
0011
8
8
0100
16
16
0101
32
32
0110
64
64
0111
128
128
1000
256
256
1001
512
512
1010
1024
1024
1011
2048
2048
1100
4096
4096
Note that a change in the MFR_SAMPLES_FOR_AVG register will not be reflected in the average telemetry
measurements until the present averaging interval has completed. The default setting for AVGN is 0000 and
therefore the average telemetry will mirror the instantaneous telemetry until a value higher than zero is
programmed.
The MFR_SAMPLES_FOR_AVG register is accessed via the PMBus read / write byte protocol.
Table 28. MFR_SAMPLES_FOR_AVG Register
22
Value
Meaning
Default
0h – 0Ch
Exponent for number of samples to average over
00h
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MFR_SPECIFIC_12: MFR_READ_AVG_VIN (DCh)
The MFR_READ_AVG_VIN command will report the 12-bit ADC measured input average voltage. If the data is
not ready, the returned value will be the previous averaged data. However, if there is no previously averaged
data the default value (0000h) will be returned. This data is read with the PMBus Read Word protocol. This
register should use the coefficients shown in the Telemetry and Warning Conversion Coefficients Table.
Table 29. MFR_READ_AVG_VIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for input voltage
0000h
MFR_SPECIFIC_13: MFR_READ_AVG_VAUX (DDh)
The MFR_READ_AVG_AUX command will report the 12-bit ADC measured auxiliary average voltage. If the data
is not ready, the returned value will be the previous averaged data. However, if there is no previously averaged
data the default value (0000h) will be returned. This data is read with the PMBus Read Word protocol. This
register should use the coefficients shown in the Telemetry and Warning Conversion Coefficients Table.
Table 30. MFR_READ_AVG_VAUX Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for auxiliary voltage
0000h
MFR_SPECIFIC_14: MFR_READ_AVG_IIN (DEh)
The MFR_READ_AVG_IIN command will report the 12-bit ADC measured current sense average voltage. If the
data is not ready, the returned value will be the previous averaged data. However, if there is no previously
averaged data the default value (0000h) will be returned. This data is read with the PMBus Read Word protocol.
This register should use the coefficients shown in the Telemetry and Warning Conversion Coefficients Table.
Table 31. MFR_READ_AVG_IIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured values for current sense voltage
0000h
MFR_SPECIFIC_15: MFR_READ_AVG_PIN (DFh)
The MFR_READ_AVG_PIN command will report the upper 12-bits of the average VIN x IIN product as measured
by the 12-bit ADC. If the data is not ready, the returned value will be the previous averaged data. However, if
there is no previously averaged data the default value (0000h) will be returned. This data is read with the PMBus
Read Word protocol. This register should use the coefficients shown in the Telemetry and Warning Conversion
Coefficients Table.
Table 32. MFR_READ_AVG_PIN Register
Value
Meaning
Default
0h – 0FFFh
Average of measured value for input voltage x input current sense
voltage
0000h
MFR_SPECIFIC_16: MFR_BLACK_BOX_READ (E0h)
The MFR_BLACK_BOX_READ command retrieves the MFR_BLOCK_READ data which was latched in at the
first assertion of SMBA. It is re-armed with the CLEAR_FAULTS command. It is the same format as the
MFR_BLOCK_READ registers, the only difference being that its contents are updated with the SMBA edge
rather than the internal clock edge. This command is read with the PMBus Block Read protocol.
MFR_SPECIFIC_17: MFR_DIAGNOSTIC_WORD_READ (E1h)
The MFR_DIAGNOSTIC_WORD_READ PMBus command will report all of the LM25056A faults and warnings in
a single read operation. The standard response to the assertion of the SMBA signal of issuing multiple read
requests to various status registers can be replaced by a single word read to the
MFR_DIAGNOSTIC_WORD_READ register. The MFR_DIAGNOSTIC_WORD_READ command should be read
with the PMBus Read Word protocol. The MFR_DIAGNOSTIC_WORD_READ register is also returned in the
MFR_BLOCK_READ, MFR_BLACK_BOX_READ, and MFR_AVG_BLOCK_READ operations.
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Table 33. MFR_DIAGNOSTIC_WORD_READ Format
Bit
Name
15
Reserved
Meaning
Default
14
MFR_IIN_OC_WARN or MFR_PIN_OP_WARN
Input Overcurrent or Overpower Warning
0
13
VIN_UV_WARN
Input Undervoltage Warning
0
12
VIN_OV_WARN
Input Overvoltage Warning
0
11
Reserved
0
0
10
OT_WARN
Overtemperature Warning
0
9
MFR_VAUX_UNDERVOLTAGE_WARN
VAUX Undervoltage Warning
0
8
MFR_VAUX_OVERVOLTAGE_WARN
VAUX Overvoltage Warning
0
7
CONFIG_PRESET
1
6
Reserved
0
5
Reserved
0
4
Reserved
0
3
Reserved
2
OT__FAULT
Over Temperature Fault
0
1
CML_FAULT
Communications Fault
0
0
Reserved
0
0
MFR_SPECIFIC_18: MFR_AVG_BLOCK_READ (E2h)
The MFR_AVG_BLOCK_READ command concatenates the DIAGNOSTIC_WORD with input average telemetry
information (IIN, VAUX, VIN, PIN) as well as TEMPERATURE to capture all of the operating information of the
part in a single PMBus transaction. The block is 12 bytes long with telemetry information being sent out in the
same manner as if an individual READ_AVG_XXX command had been issued (shown below).
AVG_BLOCK_READ also specifies that the VIN, VAUX, IIN, and PIN measurements are all time-aligned
whereas there is a chance they may not be if read with individual PMBus commands. To read data from the
AVG_BLOCK_READ command, use the SMBus Block Read protocol.
Table 34. MFR_AVG_BLOCK_READ Register Format
Byte Count (always 12)
(1 byte)
DIAGNOSTIC WORD
(1 word)
AVG_IIN
(1 word)
AVG_VAUX
(1 word)
AVG_VIN
(1 word)
AVG_PIN
(1 word)
TEMPERATURE
(1 word)
MFR_SPECIFIC_19: VAUX_OV_WARN_LIMIT (E3h)
The VAUX_OV_WARN_LIMIT command allows configuring or reading the threshold for the VAUX overvoltage
warning detection. Reading and writing to this register should use the coefficients shown in the Telemetry and
Warning Conversion Coefficients Table. Accesses to this command should use the PMBus read or write word
protocol. If the measured value of VAUX rises above the value in this register, VAUX OV Warn flags are set and
the SMBA signal is asserted.
Table 35. VAUX_OV_WARN_LIMIT Register
24
Value
Meaning
Default
0h – 0FFEh
VAUX Overvoltage Warning detection threshold
0FFFh (disabled)
0FFFh
VAUX Overvoltage Warning disabled
n/a
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MFR_SPECIFIC_20: VAUX_UV_WARN_LIMIT (E4h)
The VAUX_UV_WARN_LIMIT command allows configuring or reading the threshold for the VAUX undervoltage
warning detection. Reading and writing to this register should use the coefficients shown in the Telemetry and
Warning Conversion Coefficients Table. Accesses to this command should use the PMBus read or write word
protocol. If the measured value of VAUX falls below the value in this register, VAUX UV Warn flags are set and
the SMBA signal is asserted.
Table 36. VAUX_UV_WARN_LIMIT Register
Value
Meaning
Default
1h – 0FFFh
VAUX Undervoltage Warning detection threshold
0000h (disabled)
0000h
VAUX Undervoltage Warning disabled
n/a
+12V
To load
VIN
VS-
VS+
+
VAUX
IIN
VIN
WARNING
LIMITS
S/H
WARNING
SYSTEM
ADC
MUX
DIODE
VIN_OV_WARN_LIMIT 57h
DATA
OUTPUT
VIN_UV_WARN_LIMIT 58h
MFR_SAMPLES_FOR_AVG DBh
READ_VIN 88h
MFR_READ_AVG_VIN DCh
MFR_READ_IIN D1h
MFR_READ_AVG_IIN DEh
MFR_READ_PIN D2h
READ_AVG_PIN DFh
MFR_READ_VAUX D0h
READ_AVG_VAUX DDh
MFR_IIN_OC_WARN_LIMIT D3h
MFR_PIN_OP_WARN_LIMIT D4h
MFR_VAUX_OV_WARN_LIMIT E3h
CMP
VIN_OV WARNING
STATUS_INPUT 7Ch
CMP
VIN_UV WARNING
STATUS_INPUT 7Ch
STATUS_BYTE 78h
CMP
IIN_OC WARNING
STATUS_INPUT 7Ch
CMP
PIN_OP WARNING
STATUS_INPUT 7Ch
CMP
VAUX_OV WARNING
STATUS_MFR_SPECIFIC 80h
CMP
VAUX_UV WARNING
STATUS_MFR_SPECIFIC 80h
CMP
OT_WARNING_LIMIT
STATUS_WORD 79h
STATUS_TEMPERATURE 7Dh
CMP
OT_FAULT_LIMIT
STATUS_WORD 79h
STATUS_TEMPERATURE 7Dh
READ_TEMPERATURE_1 8Dh
AVERAGED
DATA
MFR_VAUX_UV_WARN_LIMIT E4h
OT_WARNING_LIMIT 51h
READ_PIN_PEAK D5h
CLEAR_PIN_PEAK D6h
PEAK-HOLD
OT_FAULT_LIMIT 4Fh
MFR_DIAGNOSTIC_WORD_READ E1h
PMBus Interface
Figure 18. Command/Register and Alert Flow Diagram
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Reading and Writing Telemetry Data and Warning Thresholds
All measured telemetry data and user programmed warning thresholds are communicated in 12 bit two’s
compliment binary numbers read/written in 2 byte increments conforming to the Direct format as described in
section 8.3.3 of the PMBus Power System Management Protocol Specification 1.1 (Part II). The organization of
the bits in the telemetry or warning word is shown in Table 37, where Bit_11 is the most significant bit (MSB) and
Bit_0 is the least significant bit (LSB). The decimal equivalent of all warning and telemetry words are constrained
to be within the range of 0 to 4095, with the exception of temperature. The decimal equivalent value of the
temperature word ranges from 0 to 65535.
Table 37. Telemetry and Warning Word Format
Byte
B7
B6
B5
B4
B3
1
Bit_7
Bit_6
Bit_5
Bit_4
2
0
0
0
0
B2
B1
B0
Bit_3
Bit_2
Bit_1
Bit_0
Bit_11
Bit_10
Bit_9
Bit_8
Conversion from direct format to real world dimensions of current, voltage, power, and temperature is
accomplished by determining appropriate coefficients as described in section 7.2.1 of the PMBus Power System
Management Protocol Specification 1.1 (Part II). According to this specification, the host system converts the
values received into a reading of volts, amperes, watts, or other units using the following relationship:
Where:
•
•
•
•
•
X: the calculated "real world" value (volts, amps, watt, etc.)
m: the slope coefficient
Y: a two byte two's complement integer received from device
b: the offset, a two byte, two's complement integer
R: the exponent, a one byte two's complement integer
R is only necessary in systems where m is required to be an integer (for example, where m may be stored
in a register in an integrated circuit). In those cases, R only needs to be large enough to yield the desired
accuracy.
(3)
Table 38. Telemetry and Warning Conversion Coefficients
Commands
Format
Number of
Data Bytes
m
b
R
Units
READ_VIN, MFR_READ_AVG_VIN,
VIN_OV_WARN_LIMIT
VIN_UV_WARN_LIMIT
DIRECT
2
16296
1343
-2
V
MFR_READ_VAUX, MFR_READ_AVG_VAUX,
MFR_VAUX_OV_WARN_LIMIT
MFR_VAUX_UV_WARN_LIMIT
DIRECT
2
3416
-4
0
V
(1)
26
Condition
(1)
MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 0
DIRECT
2
13797
-1833
-2
A
(1)
MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 1
DIRECT
2
6726
-537
-2
A
(1)
MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 0
DIRECT
2
5501
-2908
-3
W
(1)
MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 1
DIRECT
2
26882
-5646
-4
W
* The coefficients relating to current/power measurements and warning thresholds shown in Table 38 are normalized to a sense resistor
(RS) value of 1mΩ. In general, the current/power coefficients can be calculated using the relationships shown in Table 39.
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Table 38. Telemetry and Warning Conversion Coefficients (continued)
Commands
Condition
READ_TEMPERATURE_1,
OT_FAULT_LIMIT, OT_WARN_LIMIT
Format
Number of
Data Bytes
m
b
R
Units
DIRECT
2
1580
-14500
-2
°C
Table 39. Current and Power Telemetry and Warning Conversion Coefficients (RS in mΩ)
Commands
Condition
Format
Number of
Data Bytes
m
b
R
Units
*MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 0
DIRECT
2
13797 x RS
-1833
-2
A
*MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 1
DIRECT
2
6726 x RS
-537
-2
A
*MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 0
DIRECT
2
5501 x RS
-2908
-3
W
*MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 1
DIRECT
2
26882 x RS
-5646
-4
W
Care must be taken to adjust the exponent coefficient, R, such that the values of m and b remain within the
range of -32768 to +32767. For example, if a 5 mΩ sense resistor is used, the correct coefficients for the
MFR_READ_IIN command with GAIN = 0 would be m = 3363, b = -537, R = -1.
A Note on the "b" Coefficient
Since b coefficients represent offset, for simplification b is set to zero in the following discussions.
Reading Current
The current register actually displays a value equivalent to a voltage across the user specified sense resistor, RS.
The coefficients enable the data output to be converted to amps. The values shown in the example are based on
having the device programmed for a 30 mV current sense range (GAIN = 0). In the 30 mV range, the LSB value
is 7.25 µV and the full scale range is 29.68 mV. In the 60 mV current sense range (GAIN = 1), the LSB value is
14.87 µV and the full scale range in 60.88 mV.
Step
Example
1. Determine full scale current and shunt value based on 29.68 mV
across shunt at full scale.Use either:
Example: Application with 250 µΩ shunt.
(5)
(4)
or:
2. Determine m':
(7)
(6)
3. Determine exponent R necessary to set m' to integer value m:
Select R to provide integer value of m:
(8)
(9)
R = -2
m = 3450
4. Final values
R = -2
b=0
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Reading Input Voltage
Coefficients for VIN are consistent between read telemetry measurements (e.g., READ_VIN, READ_AVG_VIN)
and warning thresholds (e.g., VIN_OV_WARN_LIMIT, VIN_UV_WARN_LIMIT). Input voltage values are
read/written in Direct format with 12-bit resolution and a 6.14 mV LSB. An example of calculating the PMBus
coefficients for input voltage is shown below. Reading the auxiliary voltage (e.g. MFR_READ_VAUX,
MFR_READ_AVG_VAUX) and setting the warning threshold (e.g. MFR_VAUX_UV_WARN_LIMIT) is done in
similar manner with different coefficients provided in Table 38.
Step
Example
1. Determine m' based on full scale analog input and full scale digital
range:
(11)
(10)
2. Determine exponent R necessary to set m' to integer value m with Select R to provide 5 digit accuracy for the integer value of m (which
desired accuracy:
would be 16295 in this example):
(12)
(13)
R = -2
m = 16295
3. Final values
R = -2
b =0
Reading Power
The power calculation of the LM25056A is a relative power calculation meaning that full scale of the power
register corresponds to simultaneous full scale values in the current register and voltage register such that the
power register has the following relationship based on decimal equivalents of the register contents:
PIN =
IIN x VIN
4095
(14)
For this reason power coefficients will also vary depending on the shunt value and must be calculated for each
application. The power LSB will vary depending on shunt value according to 374 mW/RS for the GAIN=1 range or
182 mW/RS for the GAIN=0 range.
Step
Example
1. Determine full scale power from known full scale of input current
and input voltage
Example: Application with 250 µΩ shunt.
(16)
(15)
2. Determine m':
(18)
(17)
3. Optional: Determine exponent R necessary to set m' to integer
value m with desired accuracy:
Select R (in this case selected to provide 4 digit accuracy for the
integer value of m):
(19)
(20)
R = -4
m = 13728
4. Final values
R = -4
b=0
28
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Determining Telemetry Coefficients Empirically with Linear Fit
The coefficients for telemetry measurements and warning thresholds presented in Table 38 are adequate for the
majority of applications. Current and power coefficients must be calculated per application as they are dependent
on the value of the sense resistor, RS, used. Table 39 provides the equations necessary for calculating the
current and power coefficients for the general case. The small signal nature of the current measurement make it
and the power measurement more susceptible to PCB parasitics than other telemetry channels. This may cause
slight variations in the optimum coefficients (m, b, R) for converting from Direct format digital values to real-world
values (e.g., amps and watts). The optimum coefficients can be determined empirically for a specific application
and PCB layout using two or more measurements of the telemetry channel of interest. The current coefficients
can be determined using the following method:
1. While the LM25056A is in normal operation measure the voltage across the sense resistor using kelvined
test points and a high accuracy DVM while controlling the load current. Record the integer value returned by
the MFR_READ_AVG_IIN command (with the MFR_SAMPLES_FOR_AVG set to a value greater than 0) for
two or more voltages across the sense resistor. For best results, the individual MFR_READ_AVG_IIN
measurements should span nearly the full scale range of the current (For example, voltage across RS of 5mV
and 20mV).
2. Convert the measured voltages to currents by dividing them by the value of RS. For best accuracy the value
of RS should be measured. Table 40 assumes a sense resistor value of 5 mΩ.
Table 40. Measurements for linear fit determination of current coefficients:
Measured voltage across
RS (V)
Measured Current (A)
READ_AVG_IIN
(integer value)
0.005
1
672
0.01
2
1362
0.02
4
2743
3. Using the spreadsheet or math program of your choice determine the slope and the y-intercept of the
returned by the MFR_READ_AVG_IIN command values versus the measured current. For the data shown in
Table 39:
(a) MFR_READ_AVG_IN value = slope x (Measured Current) + (y-intercept)
(b) slope = 690.4
(c) y-intercept = -18.5
4. To determine the ‘m’ coefficient, simply shift the decimal point of the calculated slope to arrive at at integer
with a suitable number of significant digits for accuracy (typically 4) while staying with the range of -32768 to
+32767. This shift in the decimal point equates to the ‘R’ coefficient. For the slope value shown above, the
decimal point would be shifted to the right once hence R = -1.
5. Once the ‘R’ coefficient has been determined, the ‘b’ coefficient is found by multiplying the y-intercept by 10R
. In this case the value of b = -185.
(a) Calculated Current Coefficients:
(b) m = 6904
(c) b = -185
(d) R = -1
Where:
•
•
•
•
•
X: the calculated "real world" value (volts, amps, watts, temperature)
m: the slope coefficient, is the two byte, two's complement integer
Y: a two byte two's complement integer received from device
b: the offset, a two byte, two's complement integer
R: the exponent, a one byte two's complement integer
(21)
Step 5 can be repeated to determine the coefficients of any telemetry channel simply by substituting measured
current for some other parameter (e.g., power, voltage, etc.).
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Writing Telemetry Data
There are several locations that will require writing data if their optional usage is desired. Use the same
coefficients previously calculated for your application, and apply them using this method as prescribed by the
PMBus™ revision section 7.2.2 "Sending a Value"
where
•
•
•
•
•
X: the calculated "real world" value (volts, amps, watts, temperature)
m: the slope coefficient, is the two byte, two's complement integer
Y: a two byte two's complement integer to send to the device
b: the offset, a two byte, two's complement integer
R: the exponent, a one byte two's complement integer
(22)
PMBus Address Lines (ADR0, ADR1, ADR2)
The three address lines are to be set high (connect to VDD), low (connect to GND), or open to select one of 27
addresses for communicating with the LM25056A. These lines are read after the ENABLE pin is returned high,
and the VDD and VREF are out of a POR condition. Table 41 depicts 7-bit addresses (eighth bit is read/write
bit):
Table 41. Device Addressing
30
ADR2
ADR1
ADR0
Decoded Address
Z
Z
Z
40h
Z
Z
0
41h
Z
Z
1
42h
Z
0
Z
43h
Z
0
0
44h
Z
0
1
45h
Z
1
Z
46h
Z
1
0
47h
Z
1
1
10h
0
Z
Z
11h
0
Z
0
12h
0
Z
1
13h
0
0
Z
14h
0
0
0
15h
0
0
1
16h
0
1
Z
17h
0
1
0
50h
0
1
1
51h
1
Z
Z
52h
1
Z
0
53h
1
Z
1
54h
1
0
Z
55h
1
0
0
56h
1
0
1
57h
1
1
Z
58h
1
1
0
59h
1
1
1
5Ah
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Product Folder Links: LM25056A
LM25056A
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SNVS785A – JANUARY 2011 – REVISED APRIL 2013
SMBus Communications Timing Requirements
tR
SCL
tF
tLOW
VIH
VIL
tHIGH
tHD;DAT
tHD;STA
tSU;STA
tSU;STO
tSU;DAT
SDA
VIH
VIL
tBUF
P
S
S
P
Figure 19. SMBus Timing Diagram
Table 42. SMBus Timing Definition
(1)
(2)
(3)
(4)
(5)
(6)
Symbol
Parameter
Limits
Units
Min
Max
fSMB
SMBus Operating Frequency
10
400
tBUF
Bus free time between Stop and Start Condition
1.3
µs
tHD:STA
Hold time after (Repeated) Start Condition. After this
period, the first clock is generated.
0.6
µs
tSU:STA
Repeated Start Condition setup time
0.6
µs
tSU:STO
Stop Condition setup time
0.6
µs
tHD:DAT
Data hold time
300
ns
tSU:DAT
Data setup time
100
tTIMEOUT
Clock low time-out
25
Comments
kHz
ns
35
ms
See (1)
tLOW
Clock low period
1.5
µs
tHIGH
Clock high period
0.6
µs
See (2)
tLOW:SEXT
Cumulative clock low extend time (slave device)
25
ms
See (3)
tLOW:MEXT
Cumulative low extend time (master device)
10
ms
See (4)
tF
Clock or Data Fall Time
20
300
ns
See (4) (5)
tR
Clock or Data Rise Time
20
300
ns
See (6) (5)
Devices participating in a transfer will timeout when any clock low exceeds the value of tTIMEOUT,MIN of 25 ms. Devices that have
detected a timeout condition must reset the communication no later than tTIMEOUT,MAX of 35 ms. The maximum value must be adhered
to by both a master and a slave as it incorporates the cumulative stretch limit for both a master (10ms) and a slave (25ms).
tHIGH MAX provides a simple method for devices to detect bus idle conditions.
tLOW:SEXT is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start to the stop. If a
slave exceeds this time, it is expected to release both its clock and data lines and reset itself.
tLOW:MEXT is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as defined from
start-to-ack, ack-to-ack, or ack-to-stop.
Fall time is defined as:
tF = 0.9 VDD to (VILMAX – 0.15)
Rise time is defined as: tR = ( VILMAX – 0.15) to (VIHMIN + 0.15)
SMBA Response
The SMBA effectively has two masks:
1. The Alert Mask Register at D8h, and
2. The ARA Automatic Mask.
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LM25056A
SNVS785A – JANUARY 2011 – REVISED APRIL 2013
www.ti.com
The ARA Automatic Mask is a mask that is set in response to a successful ARA read. An ARA read operation
returns the PMBus™ address of the lowest addressed part on the bus that has its SMBA asserted. A successful
ARA read means that THIS part was the one that returned its address. When a part responds to the ARA read, it
releases the SMBA signal. When the last part on the bus that has an SMBA set has successfully reported its
address, the SMBA signal will de-assert.
The way that the LM25056A releases the SMBA signal is by setting the ARA Automatic mask bit for all fault
conditions present at the time of the ARA read. All status registers will still show the fault condition, but it will not
generate and SMBA on that fault again until the ARA Automatic mask is cleared by the host issuing a Clear Fault
command to this part. This should be done as a routine part of servicing an SMBA condition on a part, even if the
ARA read is not done. Figure 20 depicts a schematic version of this flow.
From other
fault inputs
SMBAlert
Fault Condition
Alert Mask D8h
From PMBus
Set
ARA Operation Flag Succeeded
ARA Auto Mask
Clear
Clear Fault Command Received
Figure 20. Typical Flow Schematic for SMBA Fault
32
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LM25056A
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SNVS785A – JANUARY 2011 – REVISED APRIL 2013
REVISION HISTORY
Changes from Original (April 2013) to Revision A
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 32
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33
PACKAGE OPTION ADDENDUM
www.ti.com
27-Jun-2016
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM25056APSQ/NOPB
ACTIVE
WQFN
NHZ
24
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
L25056A
LM25056APSQE/NOPB
ACTIVE
WQFN
NHZ
24
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
L25056A
LM25056APSQX/NOPB
ACTIVE
WQFN
NHZ
24
4500
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 125
L25056A
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
27-Jun-2016
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
20-Sep-2016
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
LM25056APSQ/NOPB
WQFN
NHZ
24
LM25056APSQE/NOPB
WQFN
NHZ
LM25056APSQX/NOPB
WQFN
NHZ
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1000
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
24
250
178.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
24
4500
330.0
12.4
4.3
5.3
1.3
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
20-Sep-2016
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM25056APSQ/NOPB
WQFN
NHZ
24
1000
210.0
185.0
35.0
LM25056APSQE/NOPB
WQFN
NHZ
24
250
210.0
185.0
35.0
LM25056APSQX/NOPB
WQFN
NHZ
24
4500
367.0
367.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
NHZ0024B
SQA24B (Rev A)
www.ti.com
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