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I can't clear TON_MAX_FAULT on UCD90120A

Douglas Peale
Intellectual 420 points

I have logic based on the TON_MAX_FAULT of 4 power supply rails that drives an LED (Pin35 GPIO 18).

Once a TON_MAX_FAULT occurs, the LED lights up, but it can never be turned off until the IC is reset.

When the TON fault occurs, the Fusion Digital Power Designer software correctly shows the error state, and when I clear faults, the software claims there are no faults, but the LED remains lit. I use the TON_MAX_FAULT for other logic as well, but the LED is the most obvious example of this bug

Attached is the design file:

6138.Labyrinth 54d.xml

  • 0
    Intellectual 420 points

    The only work around I have found so far for this bug is to send the I2C reset command to the IC to reset the IC.

    Be nice if I could get an actual response from TI about this.

    I tried e-mailing support, but all I got was a note saying support was now being handled by these forums and to post here.

  • 0
    TI__Genius 9320 points

    Please check the GPO Logic by reading the GPO_CONFIG for that pin. If TON_MAX_FAULT condition is clear (not by CLEAR_FAULTS command), the pin should be de-assert

  • 0 in reply to Anne Ngo77
    Intellectual 420 points

    8270.Labyrinth 53d Rev B.xml

    With the attached file, on the demo board

    switch to monitor mode

    Set the Control Line to high

    set operation to "on"

    Note that you get a turn on timeout error

    Note that GPIO18 LED illuminates

    set operation to "off"

    clear faults

    Note that the sofware no-longer claims "turn on timeout"

    note that GPIO18 LED remains illuminated.

    While reproducing this error, I noticed that the logic for GPIO18 is on the TON_MAX_FAULT signal instead of the TON_MAX_FAULT_LATCH signal. Changing this should fix my issue, but the question remains: Why does turning off the power supply and clearing faults not clear TON_MAX_FAULT?

  • 0 in reply to Douglas Peale
    TI__Genius 9320 points

    Please refer to UCD90XX PMBus Command Reference, section 9.39.16 (GPO_CONFIG / Status Type): For TON_MAX_FAULT, TOFF_MAX_WARN, SEQ_ON_TIMEOUT statuses, rail is required to turn off, then turn on before they are clear. You turn the rail off, but have not turn it on yet. If rail is turned on within the ton_max_fault_limit time, this bit will be clear.

  • 0 in reply to Anne Ngo77
    Intellectual 420 points

    Ok, I'll mark this as closed.