Datasheet

X =
1
m
(Y x 10
-R
- b)
LM5066
SNVS655G –JUNE 2011–REVISED FEBRUARY 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 40, 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 40. 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:
(37)
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 41. Telemetry and Warning Conversion Coefficients
Commands Condition Format Number of m b R Units
Data Bytes
READ_VIN, READ_AVG_VIN DIRECT 2 4587 -1200 -2 V
VIN_OV_WARN_LIMIT
VIN_UV_WARN_LIMIT
READ_VOUT, READ_AVG_VOUT DIRECT 2 4587 -2400 -2 V
VOUT_UV_WARN_LIMIT
READ_VAUX DIRECT 2 13793 0 -1 V
(1)
READ_IIN, READ_AVG_IIN CL = VDD DIRECT 2 10753 -1200 -2 A
MFR_IIN_OC_WARN_LIMIT
(1)
READ_IN, READ_AVG_IN CL = GND DIRECT 2 5405 -600 -2 A
MFR_IIN_OC_WARN_LIMIT
(1)
READ_PIN, READ_AVG_PIN, CL = VDD DIRECT 2 1204 -6000 -3 W
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
(1)
READ_PIN, READ_AVG_PIN, CL = GND DIRECT 2 605 -8000 -3 W
READ_PIN_PEAK
MFR_PIN_OP_WARN_LIMIT
READ_TEMPERATURE_1 DIRECT 2 16000 0 -3 °C
OT_WARN_LIMIT
OT_FAULT_LIMIT
(1) The coefficients relating to current/power measurements and warning thresholds shown are normalized to a sense resistor (R
S
) value of
1mΩ. In general, the current/power coefficients can be calculated using the relationships shown in Table 42.
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