JAJSH44C April 2011 – March 2019 UCD90120A
In addition to the turn-on and turn-off sequencing options, the time between when a rail is enabled and when the monitored rail voltage must reach its power-good-on setting can be configured using max turn-on (TON_MAX_FAULT_LIMIT). Max turn-on can be set in 1-ms increments. A value of 0 ms means that there is no limit and the device can try to turn on the output voltage indefinitely.
Rails can be configured to turn off immediately or to sequence-off according to rail and GPI dependencies, and user-defined delay times. A sequenced shutdown is configured by selecting the appropriate rail and GPI dependencies, and turn-off delay (TOFF_DELAY) times for each rail. The turn-off delay times begin when the PMBUS_CNTRL pin is deasserted, when the PMBus OPERATION command is used to give a soft-stop command, or when a fault occurs on a rail that has other rails set as fault-shutdown slaves.
Shutdowns on one rail can initiate shutdowns of other rails or controllers. In systems with multiple UCD90120As, it is possible for each controller to be both a master and a slave to another controller.