Datasheet

LTC2977
67
2977fa
For more information www.linear.com/LTC2977
Response When Part Is Busy
The part will indicate it is busy accessing the EEPROM by the following mechanism:
1) Clearing Mfr_common_busyb of the MFR_COMMON register. This byte can always be read and will never NACK a
byte read request even if the part is busy.
2) NACKing commands other than MFR_COMMON.
MFR_EE Erase and Write Programming Time
The program time per word is typically 0.17ms and will require spacing the I
2
C/SMBus writes at greater than 0.17ms
to guarantee the write has completed. The Mfr_ee_erase command takes approximately 400ms. We recommend using
MFR_COMMON for handshaking.
FAULT LOG OPERATION
A conceptual diagram of the fault log is shown in Figure 14. The fault log provides black box capability to the LTC2977.
During normal operation the contents of the status registers, the output voltage 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 available
for reading at a later time.
MFR_FAULT_LOG_STORE
This command allows the user to transfer data from the RAM buffer to EEPROM.
MFR_FAULT_LOG_RESTORE
This command allows the user to transfer a copy of the fault-log data from the EEPROM to the RAM buffer. After a
restore the RAM buffer is locked until a successful MFR_FAULT_LOG read or MFR_FAULT_LOG_CLEAR.
PMBus COMMAND DESCRIPTION