LTM4686BIVPBF datasheet(121/130 Pages) AD

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LTM4686B

121

Rev. 0

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APPENDIX C: PMBUS COMMAND DETAILS

RESTORE_USER_ALL

The RESTORE_USER_ALL command provides an alternate means by which the user can perform a MFR_RESET of

the LTM4686B.

This write-only command has no data bytes.

MFR_COMPARE_USER_ALL

The MFR_COMPARE_USER_ALL command instructs the PMBus device to compare current command contents with

what is stored in nonvolatile memory. If the compare operation detects differences, a CML bit 0 fault will be generated.

MFR_COMPARE_USER_ALL commands are disabled if the die exceeds 130°C and are not re-enabled until the die

temperature drops below 125°C.

This write-only command has no data bytes.

Fault Log Operation

A conceptual diagram of the fault log is shown in Figure 61. The fault log provides telemetry recording capability to

the LTM4686B. 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.

4686B F61

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

•

Figure 61. Fault Log Conceptual Diagram

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