LTC3882-1
101
Rev A
PMBus COMMAND DETAILS
(Fault Response and Communication)
MFR_FAULT_LOG
The MFR_FAULT_LOG command allows the contents of the fault log to be read. This log is created with a
MFR_FAULT_LOG_STORE command or at the first fault occurrence after a CLEAR_FAULTS or MFR_FAULT_LOG_CLEAR
command. If a fault occurs within the first second after applying power, some earlier pages in the log may not contain
valid data.
This read-only command uses block protocol with 147 bytes of data requiring an estimated data transfer time of 3.4ms
at 400kHz. The t
TIMEOUT
parameter is extended when this command is executed and a fault log is present.
Fault Log Operation
A conceptual diagram of the fault log is shown in Figure 53. The fault log provides telemetry recording capability to
the LTC3882-1. During normal operation the contents of the status registers, the output voltage readings, temperature
readings as well as peak values of these quantities are stored in a continuously updated buffer in RAM. The operation
is 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 available for reading at a later
time. As a consequence of adding ECC, the area in the EEPROM available for fault log is reduced. When reading the
fault log from RAM all 6 events of cyclical data remain. However, when the fault log is read from EEPROM (after a
reset), the last 2 events are lost. The read length of 147 bytes remains the same, but the fifth and sixth events are a
repeat of the fourth event.
38821 F53
TIME OF FAULT
TRANSFER TO
EEPROM AND
LOCK
AFTER FAULT
READ FROM
EEPROM AND
LOCK BUFFER
ADC READINGS
CONTINUOUSLY
FILL BUFFER
RAM BYTES
EEPROM BYTES
8
•
•
•
•
•
•
Figure 53. Fault Log Conceptual Diagram
MFR_FAULT_LOG_CLEAR
The MFR_FAULT_LOG_CLEAR command erases all stored fault log values. After a clear is issued, up to 8ms may be
required to clear related bit 3 in STATUS_MFR_SPECIFIC.
This write-only command has no data bytes.
