TI LM25056A

LM25056A
System Power Measurement IC with PMBus™
General Description
Features
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 real-time 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.
■ Input voltage range: 3V to 17V
■ I2C/SMBus™ interface with PMBus compliant command
PMBus is a trademark of SMIF, Inc. SMBus is a trademark of Intel Corp.
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
LLP-24 package
Applications
■ Server backplane systems
■ Base station power distribution systems
■ Subsystem power measurement
Typical Application Schematic
30180001
© 2012 Texas Instruments Incorporated
301800 SNVS785
www.ti.com
LM25056A System Power Measurement IC with PMBus™
January 16, 2011
LM25056A
Connection Diagram
Solder exposed pad to ground.
30180002
Top View
LLP-24
Ordering Information
Order Number
Package Type
Package Drawing
Supplied As
LM25056APSQ
LLP-24
SQA24B
1,000 units in tape and reel
LM25056APSQE
LLP-24
SQA24B
250 units in tape and reel
LM25056APSQX
LLP-24
SQA24B
4,500 units in tape and reel
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LM25056A
Pin Descriptions
Pin
No.
Name
Description
Applications Information
PAD
Exposed
Pad
Exposed pad of LLP
package
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 (-)
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-.
No internal electrical connections. Solder to the ground plane to reduce thermal
resistance.
Negative IIN sense amplifer input. The voltage across the current sense resistor (RS) is
measured from VS+ to this pin.
10
NC
No Connect
11
VIN
Positive supply input
12
ENABLE
Enable
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.
13
VAUX
Auxiliary voltage input
Auxiliary pin allows voltage telemetry from an external source. Full scale input of 1.2V
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.
Not bonded to die. Can be connected to the ground plane.
16
NC
No Connect
17
AGND
Analog ground
Not bonded to die. Can be connected to the ground plane.
A small 0.1 µF ceramic bypass capacitor close to this pin is recommended. VIN is
measured from this pin.
Connect analog ground to digital ground and then to a quiet system ground. Be sure to
avoid high current return ground lines.
18
NC
No Connect
19
DGND
Digital ground
Not bonded to die. Can be connected to the ground plane.
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
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.
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LM25056A
Storage Temperature
Junction Temperature
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the Texas Instruments Sales Office/
Distributors for availability and specifications.
VIN, VS-, VS+ to AGND/DGND
SCL, SDA, SMBA, ADR0, ADR1, ADR2,
VDD, VAUX, DIODE, ENABLE to
AGND/DGND
VS+ to VSESD Rating (Note 2)
Human Body Model
-65°C to +150°C
+150°C
Operating Ratings
-0.3V to 24V
VIN, VS-, VS+ voltage
3V to 17V
VDD
3V to 5.5V
Junction Temperature
-0.3V to 6V
-0.3V to +0.3V
2kV
-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 guaranteed 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 (Note 3) and (Note 4).
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 input bias current
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
293
µV
25.13
V
VAUXFSR
VAUX input full scale range (ADC native
range)
VAUXLSB
VAUX input LSB
VINFSR
Supply voltage measurement full scale For calculation only, observe maximum
range
voltage ratings.
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
+1.5
%
PERR
Input power measurement error
GAIN = 0, VIN = 12V, VSENSE = 25 mV
-3
+3
%
PERR
Input power measurement error
GAIN = 1, VIN = 12V, VSENSE = 55 mV
VINERR
Input voltage measurement error
VIN = 12V, +10°C to +85C
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6.14
4
mV
1
%
2
-1.0
%
+1.0
%
VINERR
Parameter
Conditions
Min.
Typ.
Max.
Units
Input voltage measurement error
VIN = 12V
-1.5
+1.5
%
VAUXERR
Auxiliary measurement error
VAUX = 1V, +10°C to +85C
-1.5
+1.5
%
VAUXERR
Auxiliary measurement error
VAUX = 1V
-2.5
+2.5
%
Remote Diode Temperature Sensor
TACC
Temperature accuracy using local diode
3
Remote diode resolution
IDIODE
External diode current source
°C
9
High Level
240
Low Level
9.2
Diode Current
Ratio
bits
µA
325
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
ENABLE = 5V
ENABLE pin pullup current
mV
mA
1
2.8
µA
Note 1: 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, but do not guarantee specific performance limits. For guaranteed specifications and conditions see the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 3: Current out of a pin is indicated as a negative value.
Note 4: All limits are guaranteed. All electrical characteristics having room temperature limits are tested during production at TA = +25°C. All bold limits are
guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
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LM25056A
Symbol
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 (μA)
CURRENT (mA)
1.7
1.6
1.5
1.4
1.3
1.2
-40 -20
10
12V
8
5V
6
3V
3V
4
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
30180071
30180079
VS+ Pin Input Bias Current (Enabled)
VS- Pin Input Bias Current (Enabled)
12
25
CURRENT (μA)
CURRENT (μA)
24
11
10
23
22
21
9
20
-40 -20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
-40 -20
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
30180076
30180075
POR Threshold
ENABLE Threshold
2.50
1.30
2.46
2.40
1.25
Rising
VOLTAGE (V)
VOLTAGE (V)
LM25056A
Typical Performance Characteristics
2.35
2.30
2.25
Falling
1.15
Falling
1.10
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
2.20
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
301800a13
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Rising
1.20
301800a14
6
LM25056A
VREF Voltage
VDD Voltage
3.73
2.840
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)
30180072
30180089
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)
30180080
30180081
IIN Error, GAIN=0, VSENSE=25mV
PIN Error, GAIN=0, VIN=12V, VSENSE=25mV
0.8
0.4
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)
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
30180073
30180074
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LM25056A
PIN Error, GAIN=1, VIN=12V, VSENSE=55mV
0.4
0.8
0.3
0.6
0.2
0.4
0.1
0.2
PIN ERROR (%)
IIN ERROR (%)
IIN Error, GAIN=1, VSENSE=55mV
0.0
-0.1
-0.2
-0.3
-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)
-40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
30180077
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0.0
30180078
8
LM25056A
Block Diagram
30180010
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.
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 1.
30180017
FIGURE 1. ENABLE Control
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LM25056A
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.
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 sub-regulator. 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 sub-regulator requires a ceramic bypass capacitance of 1 µF or greater
to be placed as close to VDD as the PCB layout allows.
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
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10
LM25056A
Application Section
30180001
FIGURE 2. Typical Application Circuit
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 3, 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.
DESIGN-IN PROCEDURE
(Refer to Figure 2 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:
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
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LM25056A
30180019
FIGURE 3. Sense Resistor Connections
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 3.
- 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.
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-, and VIN
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12
The device features an SMBus interface that allows the use
of PMBus commands to set warn levels, error masks, and get
TABLE 1. Supported PMBus Commands
Number
Default
Of Data
Value
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
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
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
13
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LM25056A
telemetry on VIN, VAUX, IIN, PIN, and temperature. The supported PMBus commands are shown in Table 1.
PMBus Command Support
LM25056A
Number
Default
Of Data
Value
Bytes
Code
Name
Function
R/W
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
R
2
0080h
E1h
MFR_SPECIFIC_17
Manufacturer-specific parallel of the STATUS_WORD
MFR_DIAGNOSTIC_WORD_READ to convey all FAULT/WARN data in a single transaction.
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
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14
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)
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 4. OT_WARN_LIMIT Register
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.
Meaning
Default
0h –
0FFEh
Overtemperature Fault Threshold
Value
0960h
0FFFh
Overtemperature Fault detection
disabled
n/a
Default
Overtemperature Warn Threshold
Value
07D0h
0FFFh
Overtemperature Warn detection
disabled
n/a
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.
TABLE 3. OT_FAULT_LIMIT Register
Value
Meaning
0h –
0FFEh
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 2. CAPABILITY Register
Value
Value
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.
TABLE 6. VIN_UV_WARN_LIMIT Register
Value
Meaning
1h – VIN Undervoltage Warning detection
0FFFh
threshold
0000h
15
VIN Undervoltage Warning disabled
Default
0000h
(disabled)
n/a
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LM25056A
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.
STANDARD PMBus Commands
LM25056A
Bus read byte protocol. To clear bits in this register, the
underlying fault should be cleared and a CLEAR_FAULTS
command issued.
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 PM-
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
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.
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
TABLE 8. STATUS_WORD Definitions
Bit
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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16
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
mand 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.
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 com-
TABLE 10. STATUS_TEMPERATURE Definitions
Bit
Name
Meaning
Default
7
6
OT FAULT
An overtemperature fault has occurred
0
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
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.
STATUS_CML (7Eh)
The STATUS_CML is a standard PMBus command that returns the value of a number of flags related to communication
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
17
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LM25056A
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.
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
LM25056A
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.
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 15. MFR_ID Register
TABLE 12. STATUS_MFR_SPECIFIC Definitions
Byte
Name
0
Number of bytes
Value
03h
MFR ID-1
4Eh ‘N’
Bit
Meaning
Default
1
7
Not supported
0
2
MFR ID-2
53h ‘S’
3
MFR ID-3
43h ‘C’
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
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.
TABLE 16. MFR_MODEL Register
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
Meaning
Default
Measured value for TEMPERATURE
0000h
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Value
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
TABLE 17. MFR_REVISION Register
TABLE 14. READ_TEMPERATURE_1 Register
0h –
0FFFh
Name
0
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.
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.
Value
Byte
18
Byte
Name
0
Number of bytes
Value
02h
1
MFR ID-1
41h ‘A’
2
MFR ID-2
41h ‘A’
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.
Meaning
Default
0h –
0FFFh
Measured value for AUX input
0000h
Default
0h –
0FFFh
Measured value for input current
sense voltage
0000h
0h –
0FFEh
Value for input over current warn limit
0FFFh
0FFFh
Input over current warning disabled
n/a
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 Coefficients Table.
TABLE 19. MFR_READ_IIN Register
Meaning
Default
TABLE 22. MFR_PIN_OP_WARN_LIMIT Register
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.
Value
Meaning
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 18. MFR_READ_VAUX Register
Value
Value
TABLE 23. MFR_READ_PIN_PEAK Register
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.
Meaning
Default
0h –
0FFFh
Value for input current x input voltage
0000h
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.
TABLE 20. MFR_READ_PIN Register
Value
Value
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.
19
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LM25056A
TABLE 21. MFR_IIN_OC_WARN_LIMIT Register
Manufacturer Specific PMBus
Commands
LM25056A
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
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 guarantees that the VIN, VAUX, IIN and PIN measurements are all
time-aligned 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.
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
4
Meaning
TABLE 26. MFR_BLOCK_READ Register Format
Reserved, always
set to 0
Current sense gain
3
Reserved, always
set to 0
2
Reserved, always
set to 0
1
Reserved, always
set to 0
0
Software reset
GAIN = 0, Low setting
(30mV)
GAIN = 1, High setting
(60mV)
(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:
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
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Byte Count (always 12)
Y = (X(N) + X(N-1) + ... + X(0)) / N
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
20
cients shown in the Telemetry and Warning Conversion
Coefficients Table.
TABLE 27. MFR_SAMPLES_FOR_AVERAGE
TABLE 30. MFR_READ_AVG_VAUX Register
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
Value
0h – Average of measured values for current
0FFFh
sense voltage
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
1011
2048
2048
1100
4096
4096
TABLE 28. MFR_SAMPLES_FOR_AVG Register
Meaning
Default
0h –
0Ch
Exponent for number of samples to
average over
00h
Meaning
Default
Average of measured values for input
voltage
0000h
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.
TABLE 29. MFR_READ_AVG_VIN Register
0h –
0FFFh
0000h
TABLE 32. MFR_READ_AVG_PIN Register
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.
Value
Default
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.
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.
Value
Meaning
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 coeffi-
21
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LM25056A
(in this example, 4096) to be taken before the new average is
ready.
LM25056A
TABLE 33. MFR_DIAGNOSTIC_WORD_READ Format
Bit
Name
Meaning
Default
15
Reserved
14
MFR_IIN_OC_WARN or
MFR_PIN_OP_WARN
Input Overcurrent or Overpower Warning
0
0
13
VIN_UV_WARN
Input Undervoltage Warning
0
12
VIN_OV_WARN
Input Overvoltage Warning
0
11
Reserved
10
OT_WARN
Overtemperature Warning
0
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
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.
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 guarantees 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 35. VAUX_OV_WARN_LIMIT Register
(1 byte)
DIAGNOSTIC WORD
(1 word)
AVG_IIN
(1 word)
AVG_VAUX
(1 word)
AVG_VIN
(1 word)
AVG_PIN
(1 word)
TEMPERATURE
Default
0h –
0FFEh
VAUX Overvoltage Warning
detection threshold
0FFFh
(disabled)
n/a
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
(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
www.ti.com
Meaning
0FFFh VAUX Overvoltage Warning disabled
TABLE 34. MFR_AVG_BLOCK_READ Register Format
Byte Count (always 12)
Value
22
Value
Meaning
Default
1h –
0FFFh
VAUX Undervoltage Warning
detection threshold
0000h
(disabled)
0000h
VAUX Undervoltage Warning
disabled
n/a
FIGURE 4. Command/Register and Alert Flow Diagram
301800a2
LM25056A
23
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LM25056A
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.
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
TABLE 37. Telemetry and Warning Word Format
Byte
B7
B6
B5
B4
B3
B2
B1
B0
1
Bit_7
Bit_6
Bit_5
Bit_4
Bit_3
Bit_2
Bit_1
Bit_0
2
0
0
0
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.
TABLE 38. Telemetry and Warning Conversion Coefficients
Commands
Condition
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
*MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 0
DIRECT
2
13797
-1833
-2
A
*MFR_READ_IIN,
MFR_IIN_OC_WARN_LIMIT,
MFR_READ_AVG_IIN ,
GAIN = 1
DIRECT
2
6726
-537
-2
A
*MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 0
DIRECT
2
5501
-2908
-3
W
*MFR_READ_PIN,
MFR_PIN_OP_WARN_LIMIT,
MFR_READ_PIN_PEAK,
MFR_READ_AVG_PIN
GAIN = 1
DIRECT
2
26882
-5646
-4
W
DIRECT
2
1580
-14500
-2
°C
READ_TEMPERATURE_1,
OT_FAULT_LIMIT, OT_WARN_LIMIT
* 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.
www.ti.com
24
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.
efficients 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.
Reading Current
The current register actually displays a value equivalent to a
voltage across the user specified sense resistor, RS. The coStep
Example
1. Determine full scale current and shunt value based on 29.68 Example: Application with 250 µΩ shunt.
mV across shunt at full scale.Use either:
or:
2. Determine m':
3. Determine exponent R necessary to set m' to integer value m: Select R to provide integer value of m:
R = -2
m = 3450
4. Final values
R = -2
b=0
25
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LM25056A
TABLE 39. Current and Power Telemetry and Warning Conversion Coefficients (RS in mΩ)
LM25056A
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.
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.
Step
Example
1. Determine m' based on full scale analog input and full scale
digital range:
2. Determine exponent R necessary to set m' to integer value m Select R to provide 5 digit accuracy for the integer value of m
with desired accuracy:
(which would be 16295 in this example):
R = -2
m = 16295
3. Final values
R = -2
b =0
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.
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:
Step
Example
1. Determine full scale power from known full scale of input
current and input voltage
Example: Application with 250 µΩ shunt.
2. Determine m':
3. Optional: Determine exponent R necessary to set m' to integer Select R (in this case selected to provide 4 digit accuracy for the
value m with desired accuracy:
integer value of m):
R = -4
m = 13728
4. Final values
R = -4
b=0
www.ti.com
26
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.
5.
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
The above procedure can be repeated to determine the coefficients of any telemetry channel simply by substituting
measured current for some other parameter (e.g., power,
voltage, etc.).
Writing Telemetry Data
TABLE 40. Measurements for linear fit determination of
current coefficients:
Measured voltage Measured Current
across
(A)
RS (V)
3.
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"
READ_AVG_IIN
(integer value)
0.005
1
672
0.01
2
1362
0.02
4
2743
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.
Once the ‘R’ coefficient has been determined, the ‘b’
coefficient is found by multiplying the y-intercept by
10-R. In this case the value of b = -185.
Calculated Current Coefficients:
m = 6904
b = -185
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 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
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:
MFR_READ_AVG_IN value = slope x (Measured
Current) + (y-intercept)
slope = 690.4
y-intercept = -18.5
27
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LM25056A
4.
Determining Telemetry Coefficients
Empirically with Linear Fit
LM25056A
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):
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
TABLE 41. Device Addressing
www.ti.com
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
28
LM25056A
SMBus Communications Timing
Requirements
301800a1
FIGURE 5. SMBus Timing Diagram
TABLE 42. SMBus Timing Definition
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
(Note 5)
tLOW
Clock low period
1.5
µs
tHIGH
Clock high period
0.6
µs
(Note 6)
tLOW:SEXT
Cumulative clock low extend time (slave device)
25
ms
(Note 7)
tLOW:MEXT
Cumulative low extend time (master device)
10
ms
(Note 8)
tF
Clock or Data Fall Time
20
300
ns
(Note 8)
tR
Clock or Data Rise Time
20
300
ns
(Note 9)
Note 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).
Note 6: tHIGH MAX provides a simple method for devices to detect bus idle conditions.
Note 7: 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.
Note 8: 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-toack, or ack-to-stop.
Note 9: Rise and fall time is defined as follows:
• tR = ( VILMAX – 0.15) to (VIHMIN + 0.15)
• tF = 0.9 VDD to (VILMAX – 0.15)
29
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LM25056A
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 6
depicts a schematic version of this flow.
SMBA Response
The SMBA effectively has two masks:
1. The Alert Mask Register at D8h, and
2. The ARA Automatic Mask.
The ARA Automatic Mask is a mask that is set in response to
a successful ARA read. An ARA read operation returns the
PMBus&trade; 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
301800a0
FIGURE 6. Typical Flow Schematic for SMBA Fault
www.ti.com
30
LM25056A
Physical Dimensions inches (millimeters) unless otherwise noted
NS Package Number SQA24B
31
www.ti.com
LM25056A System Power Measurement IC with PMBus™
Notes
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