The TPSM831D31 provides a "black box" feature to aid in system-level debugging. According to the PMBus specification, status bits are latched whenever the condition causing them occurs, regardless of whether or not other status bits are already set. This, however, makes it difficult for the system designer to understand which fault condition occurred first, in the case that one fault condition causes others to trigger. The MFR_SPECIFIC_08 command provides a "snapshot" of the first faults to occur chronologically, for each channel, which may be stored to NVM, for future debugging. Only the most catastrophic fault conditions are logged, such as the over-voltage fault, over-current fault, and power stage failure. The black box command may also be reset, or cleared by writing 00h to the register, and storing to NVM if the NVM value must also be cleared.

Resetting the Black Box Record

Resetting the record allows the user to determine which faults occur first, after the register is cleared. To clear the record, write 00h to MFR_SPECIFIC_08, and issue STORE_DEFAULT_ALL.

Triggering Black Box Recording

Black box recording is always active, whether or not the TPSM831D31 is converting power. Note however many of the critical faults summarized in MFR_SPECIFIC_08 are only possible to trigger during power conversion. Whenever any of the following catastrophic faults occur, the MFR_SPECIFIC_08 register will be updated according to the register description below, but only if the black box record has been cleared since the last catastrophic faults occurred. Faults logged include:

• Overvoltage Fault (Device was Converting Power)
• Overvoltage Fault (Device was not Converting Power)
• Input Overcurrent Fault
• Output Overcurrent Fault
• Power Stage Fault
• Input Over-Power Fault

Retrieving the Black Box Record

Reading the MFR_SPECIFIC_08 returns the current value of the Black Box record. If the register reads 00h, no catastrophic faults have occurred since the record was last cleared. If any value other than 00h is stored in the register, then de-code the value according to the register description below. In order to read-back the black box record following a power-down, the STORE_DEFAULT_ALL command must be issued, to store the contents of the black box record to NVM.