SLVUCU5 December 2025 UCD91160 , UCD91320
The Fault Response bytes (the first eight bytes) are formatted as shown in Table 26-23.
| Bits | Description | Value | Meaning |
|---|---|---|---|
| 7 | Operation | n/a | When this bit is set to one, the device shuts down (disables the output) and responds according to the retry setting in bits [3:0]. The function associated with the following Glitch Filter bit, can delay or prevent the shutdown. |
| When set to zero, the PMBus device continues operation without interruption. | |||
| 6 | Glitch Filter | n/a | When this bit is set to one, the device continues operation for a delay time specified by the “Maximum glitch time for voltage faults” or the “Maximum glitch time for non-voltage faults” byte. If the fault condition is removed during the delay time, the timer resets, and the fault is ignored. If the fault condition is present for longer than the delay time, the device responds to the fault as programmed in the Retry Setting (bits[3:0]). |
| 5 | Soft Stop | n/a | If this bit is set to 1, the rail comes to a soft stop (using TOFF_DELAY). If it is set to 0, the rail shuts down immediately. |
| 4 | Re-sequence | n/a | When this bit is set to 1 and the retries have been exhausted, the rail and its Fault Slaves are shutdown in a manner based on the Soft Stop bit. All of those rails are resequenced after a delay time defined by the “Time between Resequences” byte in the MISC_CONFIG command (see Section 26.42) |
| 3:0 | Retry Setting | 0000 | A 0 value for the Retry Setting means that the device does not attempt to restart the rail. The rail remains off until a turn-off and then turn-on command (by OPERATION command or CONTROL pin or Pin-Selected State) are received. |
| 0001–1110 | The device attempts to restart the rail for the number of times set by these bits. The minimum number is 1 and the maximum number is 14 when the soft stop bit is not set. When the soft stop bit is enabled, one less retry will be attempted. If the rail fails to restart successfully within the allowed number of retries, the device disables the rail and remains off unless Resequence bit is set. The rail can be also turned back on according to the conditions described in Section 10.7 of PMBus specification. The time between the start of each restart attempt is set by the ”Time between retries” byte. | ||
| Note: This retry count is reset whenever the rail stays in regulation for a TON_MAX_FAULT_LIMIT amount of time without having a glitch. (If TON_MAX_FAULT_LIMIT is set to 0, 4 seconds are used for the time.) Glitches on faults where the Operation bit is set to zero are ignored. | |||
| 1111 | The device attempts to restart the rail continuously, without limitation, until it is commanded OFF (by the CONTROL pin or OPERATION command or both), bias power is removed, or another fault condition causes the rail to shut down. |