UCD90320
ZHCSFI3B –AUGUST 2016–REVISED MAY 2019
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When a rail receives a turn-ON or turn-OFF command as defined in On/Off Config , it checks its dependency
conditions. When all dependencies are fulfilled, the rail then waits for a Turn ON Delay time or a Turn OFF Delay
time, and then asserts or de-asserts the EN pin.
The device fulfills a Rail Sequence On Dependency status when the rail is in Power Good status. The device
fulfills a Rail Sequence Off Dependency status when the rail is in Not Power Good status. The device fulfills a
GPI Sequence On Dependency status when the GPI pin is asserted. The device fulfills a GPI Sequence Off
Dependency status when the GPI pin is de-asserted. The device fulfills a GPO Sequence On Dependency status
when the logical sate of the GPO is TRUE. The device fulfills a GPO Sequence Off Dependency status when the
logic state of the GPO is FALSE.
After the EN pin of a rail is asserted, if the rail voltage does not rise above Power Good On threshold within the
Maximum Turn-ON time, a Time On Max fault occurs. Similarly, after the EN pin of a rail is de-asserted, if the rail
voltage does not fall below 12.5% nominal output voltage within Maximum Turn-OFF time, a Time Off Max
warning occurs.
Each rail can include a Fault Shutdown Slaves function. When a rail shuts down as a result of a fault, the
associated slave rails also shut down. The device continues to monitor delays and dependencies of the slave
rails during the shutdown process. Fault Shutdown Slaves cannot cascade. In other words, if a rail that is acting
as a slave shuts down, the associated slave rails does not shut down.
Each rail can set Sequencing On/Off Timeout periods. The timeout periods begin to increment when a rail
receives a turn-ON or a turn-OFF command as defined in On/Off Config . When the Sequencing On/Off Timeout
period elapsed, the rail executes one of 3 actions including:
•
•
•
Wait Indefinitely
Enable or Disable Rail
Re-sequence (Sequencing On only)
Re-sequence is a series of actions that shuts down a rail and the Fault Shutdown Slaves, and then re-enables
the rails according to sequence-on delay times and dependencies. The re-sequencing parameters can be
configured in the Other Config tab, as shown in Figure 14.
Figure 14. Re-Sequencing Options (Global Configuration ► Misc Config)
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