8.4.18 Data and Error Logging to Flash Memory

The UCD90160 can log up to 18 faults and the number of device resets to flash memory. Peak voltage measurements are also stored for each rail. To reduce stress on the flash memory, a 30-second timer is started if a measured value exceeds the previously logged value. Only the highest value from the 30-second interval is written from RAM to flash.

Multiple faults can be stored in flash memory and can be accessed over PMBus to help debug power-supply bugs or failures. Each logged fault includes:

• Rail number
• Fault type
• Fault time since previous device reset
• Last measured rail voltage

The total number of device resets is also stored to flash memory. The value can be reset using PMBus.

There are three settings for handling the fault log once it reaches its maximum capacity. These settings allow to keep the latest faults by using a First In, First Out (FIFO) mode.

• FIFO log disabled - The first 18 faults will be logged. No additional faults will be logged until the fault log is cleared.
• FIFO log for all faults - The most recent 18 faults will be logged. Once 18 faults are logged, any additional faults will cause the oldest fault log entry to be lost.
• FIFO log for last half of faults - The first 9 faults will be logged. The most recent 9 faults will also be logged. In the FIFO portion of the log, once 9 faults are logged, any additional faults will cause the oldest fault entry to be lost.

With the brownout function enabled, the run-time clock value, peak monitor values, and faults are only logged to flash when a power-down is detected. The device run-time clock value is stored across resets or power cycles unless the brownout function is disabled, in which case the run-time clock is returned to zero after each reset.

It is also possible to update and calibrate the UCD90160 internal run-time clock via a PMBus host. For example, a host processor with a real-time clock could periodically update the UCD90160 run-time clock to a value that corresponds to the actual date and time. The host must translate the UCD90160 timer value back into the appropriate units, based on the usage scenario chosen. See the REAL_TIME_CLOCK command in the UCD90xxx Sequencer and System Health Controller PMBus Command Reference for more details.