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UCD9090: Re-sequence does not work and stop

fei chen65
Prodigy 80 points
Part Number: UCD9090

Hi, 

I am using UCD9090 to design a power monitor system and I introduced a re-sequence for the system, but some time all the power rail got stuck and EN_control is low. Never go to high after re-sequencing stuck.

I am sure that all the rails are below Power_GOOD_OFF threshold. 

I have re-sequence for rail #7 (UV, shutdown rail 1 2 3 4 5 6 8) and rail #9 (OV, shutdown rail 1 2 3 4 5 6). Basically, UCD9090 has EN for rail# 1 2 3 4 5 6. But for monitor port is for rail# 1 2 3 4 5 6 7 8 9. rail #7 is 5.3V from POE, rail #8 is 48V from PoE. Rail #9 is a pulse for WDT, named Kill_all. 

So we are monitoring few rails that UCD9090 can not control. 

Do you have any idea why the re-sequence does not work in this case?

I attached the project, circuits schematic, and fault logs (it seems that when these faults (Rail #7 UV, Rail #9 OV) happen,  rail 1 2 3 4 5 6 was shutdown and never re-sequence )

PICO test.zip

  • 0
    TI__Guru 65860 points

    Hello

    Does Both UV of Rail 7 and OV of Rail 9 happen together?

    Let just take example of UV of Rail7 fault only.

    When Rail 7 has UV fault, UCD9090 shutdown rail 1-6 accordingly. my question is when Rail 7 was back to norminal value since this is rail not controlled by UCD.

    if rail 7 is back to normail value(above power_good) before rail 1-6 reach below POWER_GOOD_OFF. the resequenc will not happen. Could you please check this?

    As for the OV fault, since we do not control rail 9, when does rail 9 faull below power_good_off threshold?

    Regards

    Yihe

  • 0 in reply to yihe
    Prodigy 80 points
    Hi, yihe

    Thanks a lot for your reply.

    No, they would not happen together. Ok, let forget the rail 9 for this moment.

    Ok, I got you idea. We do not have control for Rail #7 (5.3V from PoE). Our idea is that when we this power low, we would like to do the power cycle (re-sequence).

    I did see the rail #7 UV for short period time, but I forget how long it would get back to normal, I would check it. Usually, how long power rail 1-6 reach below POWER_GOOD_OFF? any typical number? or totally dependent on our regulator design?
    or any idea how long would the EN pin go low?

    BR,

    Fei
  • 0 in reply to fei chen65
    Prodigy 80 points
    another short question. You mentioned that "if rail 7 is back to normail value(above power_good) before rail 1-6 reach below POWER_GOOD_OFF, re-sequence would not happen."

    If this is the case of what you mentioned (if rail 7 is back to normail value(above power_good) before rail 1-6 reach below POWER_GOOD_OFF), what is the next status for rail #1-6 in this case. Still keeping shutdown, or stop shutdown and get back to normal?

    BR,
    Fei
  • 0 in reply to fei chen65
    TI__Guru 65860 points
    Hi
    Based on your settings, rail 1-6 shall be donw whithin couple ms. if rail 7 indeed is back to normal before rail 1-6 are off, rail 1-6 will maintain off until the rail 7 is below power_good_off again to start the re-sequence.

    Could you set the Max Turn Off to 20ms for the rail 7? with this settings, 1-6 shall be resequenced even rail 7 is back in the middle of shutdown.
    regards
    Yihe
  • 0 in reply to yihe
    Prodigy 80 points

    thanks a lot. you reply kinds of solve our problem on this topics.

    Got some other issue regarding programming. created another post.

    BR,

    Fei