Datasheet

X =
1
m
(Y x 10
-R
- b)
LM25066I, LM25066IA
SNVS824C –JUNE 2012–REVISED MARCH 2013 www.ti.com
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 43, 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 43. 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:
(38)
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 44. Current, Power and Warning Conversion Coefficients (R
S
in mΩ)
Commands Condition Format Number of m b R Unit
Data Bytes
READ_VIN, READ_AVG_VIN DIRECT 2 22070 -1800 -2 V
VIN_OV_WARN_LIMIT
VIN_UV_WARN_LIMIT
READ_VOUT, READ_AVG_VOUT DIRECT 2 22070 -1800 -2 V
VOUT_UV_WARN_LIMIT
READ_VAUX DIRECT 2 3546 -3 0 V
READ_IIN, READ_AVG_IIN CL = GND DIRECT 2 13661 x R
S
-5200 -2 A
MFR_IIN_OC_WARN_LIMIT
READ_IIN, READ_AVG_IIN CL = VDD DIRECT 2 6854 x R
S
-3100 -2 A
MFR_IIN_OC_WARN_LIMIT
READ_PIN, READ_AVG_PIN, CL = GND DIRECT 2 736 x R
S
-3300 -2 W
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
READ_PIN, READ_AVG_PIN, CL = VDD DIRECT 2 369 x R
S
-1900 -2 W
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
READ_TEMPERATURE_1 DIRECT 2 16000 0 -3 °C
OT_WARN_LIMIT
OT_FAULT_LIMIT
READ_PIN, READ_AVG_PIN, CL = VDD DIRECT 2 369 x R
S
-1900 -2 W
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
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