Hi,
I'm using a UCD90120A to sequence and monitor 8 on-board voltage supplies and I have 2 questions about the operation under fault conditrions.
Q1. The 8 supplies are enabled and monitored individually and this works OK. However, I can't get the OV/ UV faults to perform the shutdown response I'm after (i.e. the faulty supply enable line is disabled).
In the Fault Responses and Limits tab, I've set Vout Over and Under Voltage set to "Shut down with delay" and "do not restart". I would therefore expect the fault to be detected, and the supply will be shut down.
To simulate a fault, I've changed the expected Vout value on one rail, and this update is then written to the hardware (which is my actual board rather than an eval card).
I enable the UCD90120A start-up (which is controlled via a GPI) which sequences the supplies. The supply I've altered measures the same as it did (which is correct), but it should now be considered as out of spec and turned off. However, it stays on. Can you advise what I might be doing wrong?
Q2. In addition, the UCD90120A monitors 3 external supplies. There are no enables associated with these (and they're set to Auto On/ Off), and the 90120A starts monitoring these when the 3V3 (i.e V33A, V33D, V33DIO) powers up. If any of these are out of spec, I want the enables for the 8 other rails to be switched off. Can this be done? I don't even seem to be generate a UV or OV fault on these 3 supplies, even though this appears to be possible. It seems that using one rail status to control a different rail enable might only be possible if supply which has the status is also switched off. However, in my design the UCD90120A does not control these 3 supplies, it only monitors them. Can you advise please?
For information, I'm using Fusion Version 1.8.284 on Windows 7 to interface with the UCD90120A on the PMBus.
Thanks
Stuart
