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TPS2553-1: vout discharge uncompleted issue

Henry Wang3
Genius 3345 points
Part Number: TPS2553-1

Hi Sir,

Please refer to the below scope waveform and the schematic.

When the system power-off, if the output cap(C431) does not fully discharged, the TPS2553-1 will go to Reverse-Voltage Protection mode and asserts the FAULT output (active-low). Is it right?

After the system power-off, my customer is doing the power reset and found the Fault pin still been asserted active-low.

They thinks the root cause since the Vin(3V2_PROJ) has not achieved 0V, or the EN pin has not less than 0.66V(EN pin VIL), so the TPS2553-1 power cycle or enable is toggled uncompleted. Is it right?

How to modify the schematic to fix the TPS2553-1 vout discharge uncompleted issue? please advise. Thanks!

  • +1
    TI__Genius 11155 points

    Hi Henry,

    I'm not entirely certain what might be happening.  Can you clarify a few things for me?

    Is ILLUM_INT related to TPS2553-1 FAULT signal in any way?

    Are ~FAULT1 and ~FAULT2 nets pulled up to 3.2 V?

    I agree the power reset may not be recognized.  One quick test that can be done is to manually pull EN low after 3V2_PROJ returns high.  You should be able to take a jumper wire and connect the IC pin or associated test point to GND on your board.  The short only needs to be made for a few ms and we should see 3V2_current_limited1 return to its high state once the short is removed.

    If the above test is successful, you could try adding a cap from LED_EN to GND.  This will ensure the input voltage clears UVLO before EN reaches logic high.

    Regards,
    Eric

  • 0 in reply to Eric Hartigan
    Genius 3345 points

    Hi Sir,

    The customer followed your comments to add a 10uF cap from LED_EN to GND, and fixed this issue.

    Thank you for your kind assistance.