LTC2978A Datasheet, PDF (55/80 Pages) Linear Technology – 8-Channel PMBus Power System Manager Featuring Accurate Output Voltage Measurement

LTC2978A
PMBus Command Description
All MFR_SPARE registers may be stored and recalled from EEPROM using the STORE_USER_ALL and RESTORE_
USER_ALL commands.
MFR_VOUT_MIN
This command returns the minimum ADC measured value of the channel’s output voltage. This register is
reset to 0xFFFF (7.999) when the LTC2978A emerges from power-on reset or when a CLEAR_FAULTS com-
mand is executed. When odd channels are configured to measure current, this command is not supported.
Updates are disabled when undervoltage detection is disabled, such as when Margin Low (Ignore Faults and
Warnings) is enabled.
MFR_VOUT_MIN Data Contents
BIT(S)
SYMBOL
OPERATION
b[15:0]
Mfr_vout_min The data uses the L16 format.
Units: V.
MFR_VIN_MIN
This command returns the minimum ADC measured value of the input voltage. This register is reset to 0x7BFF
(approximately 2²⁵) when the LTC2978A emerges from power-on reset or when a CLEAR_FAULTS command is ex-
ecuted. Updates are disabled when unit is off for insufficient input voltage.
MFR_VIN_MIN Data Contents
BIT(S) SYMBOL
OPERATION
b[15:0] Mfr_vin_min The data uses the L11 format.
Units: V.
MFR_TEMPERATURE_MIN
This command returns the minimum ADC measured value of junction temperature in °C as determined by the LTC2978A’s
internal temperature sensor. This register is reset to 0x7BFF (approximately 2²⁵) when the LTC2978A emerges from
power-on reset or when a CLEAR_FAULTS command is executed.
MFR_TEMPERATURE_MIN Data Contents
BIT(S) SYMBOL
OPERATION
b[15:0] Mfr_temperature_min The data uses the L11 format.
Units: °C.
Fault Log Operation
A conceptual diagram of the fault log is shown in Figure 13. The fault log provides black box capability to the LTC2978A.
During normal operation, the contents of the status registers, the output voltage/current readings, temperature readings
as well as peak and min values of these quantities are stored in a continuously updated buffer in RAM. You can think
of the operation as being similar to a strip chart recorder. When a fault occurs, the contents are written into EEPROM
for nonvolatile storage. The EEPROM fault log is then locked. The part can be powered down with the fault log being
available for reading at a later time.
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