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TPA3255: FAULT ERROR

eric li
Prodigy 175 points
Part Number: TPA3255

Tool/software:

Dear TI engineers,

The work mode is PBTL,and PVDD = 24V.

When i power on the PCBA,without any input signal,the FAULT pin of the TPA3255 is high level(3.3V),but when i add a sine signal(1kHz,) to the input pin of the tpa3255,even every small signal(100mV) the FAULT ERROR happens.In either situation,the CLIP_OTW pin is high level.

Attached is my circuit diagram. Could you please help me find out the possible causes and how to solve them?

  • 0
    TI__Genius 17960 points

    Hello,

    Thank you for reaching out! I am reviewing the schematic and will provide feedback tomorrow. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    TI__Genius 17960 points

    Hello,

    I recommend adding input capacitors in series with the input signal. Other than that the schematic looks okay. 

    Is there any signaling on the CLIP_OTW pin?
    If you stop supplying the input signal, does the fault clear?

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    Prodigy 175 points

     Hi Sydney,

    There is an 10uF input capacitor in series with the input signal.

    The signal on the CLIP_OTW pin is always high,about 3.3V.

    When the Fault happened,even if i stopped supplying the input signal,the fault did not clear until i reset the TPA3255.

  • 0 in reply to eric li
    TI__Genius 17960 points

    Hello,

    Given that you have to reset the device and CLIP_OTW is not triggering, it seems the device is trigger a current issue. What load are you using?

    Regards,
    Sydney Northcutt 

  • 0 in reply to Sydney Northcutt
    Prodigy 175 points

    Hi Sydney,

    Yes,i also think that the device is trigger a current issue.But my puzzle is even if i did not connect any load the issue is also triggered.And in most situation,the load is a 4 Ω speaker.When the issue was triggered,there was not any pwm wave bofore the LC filter.

  • 0 in reply to eric li
    TI__Genius 17960 points

    Hi Eric,

    Oh - this happens with no load as well. I wonder if you have some short on your board or a damaged component. Do you have various board you can try? Is this shown on all boards? You can also try swapping the IC. 

    Do your inductors have the proper current rating? 

    Can you also check the status of RESET to ensure it is not getting triggered mistakenly?

    Regards,
    Sydney Northcutt 

  • 0 in reply to Sydney Northcutt
    Prodigy 175 points

    Hi Sydney,

    Thanks for your reply.

    I changed the value of R36 and R52 to 0 Ω，and 3255 seemed to work. I could measure the PWM waveforms before the LC filters and the corresponding sine waveforms after the LC filters.But i do not understand why.And this is correct?Does the 3255 work well?

  • 0 in reply to eric li
    TI__Genius 17960 points

    Hello,

    I see, glad to heat the issue was resolved. In PBTL mode it is required that these pins are connected to ground. I believe without this direct connection the internal circuity was not properly setting to PBTL mode. 

    Regards,
    Sydney Northcutt