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Fault pin protection of TAS5612LA

Jeffrey
Expert 1920 points
Other Parts Discussed in Thread: TAS5612LA

Dear all...

My customer designed TAS5612LA on their product and it is being produced at their factory.

But the field failure of this product was occurred on /FAULT pin of TAS5612LA. (total 2 times)

So FAR(Failure Analysis Request) of this case was requested to TI and got the result that the conclusion is EOS.

I think that /FAULT pin of TAS5612LA seems to be damaged by somthing such as ESD, surge and etc.

I want to know the protection solution (such as TVS diode or zener diode, etc) that can resolve this problem.

Is there any recommend solution for this case?

Please let me know that.

  • 0
    TI__Genius 9175 points
    Hello Jeffery,

    EOS on fault is interesting since this is an output pin with usually no connection to the outside world.
    In the customers system is Fault pin exposed to the user in any way?

    Has the customer tried to view the voltage waveform on fault when the amplifier is driven into a fault condition? I am wondering if some long trace inductance or other issue is causing voltage overshoot on this pin.

    In any case, yes a TVS diode can be used to clamp to voltage on the fault pin from rising to a dangerous level.

    Best Regards,
    Matt
  • 0 in reply to Matthew Beardsworth
    Expert 1920 points

    Hi Mattew

    In the customer system, Fault pin is connected to GPIO of MCU for monitoring of fault condition.

    The point is that fault is occurred even though it has not a fault conidtion such short circuits, overload and etc.

    Voltage waveform of Fault pin is low and is also low when Fault pin is disconnected to GPIO of MCU.

    Voltage waveforms of Fault pin are as follows.

    - When Fault pin is connected to GPIO of MCU

    - When Fault pin is disconnected to GPIO of  MUC

    - When TAS5612LA is replaced

    Is there any recommend solutions or ideas?

  • 0 in reply to Jeffrey
    TI__Genius 9175 points
    Hi Jeffery,

    To confirm, your are experiencing returns where the TAS5612LA fault pin is held low even with the MCU disconnected correct?
    At which point, the failure analysis indicated that the Fault pin was broken due to EOS correct?

    When the MCU checks the fault condition, why does it pull fault pin low as show in the first image?
    Fault should only be pulled low by the power amplifier when a fault occurs since it is an active drain output pin. The MCU should just read the logic level of the fault pin.

    Is your MCU driving current into the fault pin burning out the fault transistor?

    Best Regards,
    Matt
  • 0 in reply to Matthew Beardsworth
    Expert 1920 points
    Hi Matthew

    I have answered your questions.

    To confirm, your are experiencing returns where the TAS5612LA fault pin is held low even with the MCU disconnected correct?
    --> Yes, it is right
    At which point, the failure analysis indicated that the Fault pin was broken due to EOS correct?
    --> Yes, the conclusion of failure analysis is as follows.
    --> The unit failed due to the EOS damage observed. An over-voltage/over-current condition or event is the most likely cause of failure.

    When the MCU checks the fault condition, why does it pull fault pin low as show in the first image?
    --> The voltage level of fault pin is periodically repeated up and down, it seems to be affected by pull-up resistor or other causes.

    Is your MCU driving current into the fault pin burning out the fault transistor?
    --> It may be right but I think that driving current of MCU into the fault pin is very low and then can't burn out the fault transistor.

    Thanks.
  • 0 in reply to Jeffrey
    TI__Genius 9175 points

    Hi Jeffery,

    Thanks for the clarification.

    I just wanted to understand if there was something from an applications standpoint causing the EOS on FAULT.
    Keep in mind the pull-up resistor should be relatively large to avoid excess current into the FAULT pin when it is pulled low by the TAS5612LA. Maximum continuous current is 9mA but in practice this should be much less.

    I also recommend placing a resistor between the MCU GPIO and FAULT for the same reason.

    As mentioned before, a TVS diode will help clamp any voltage spikes on this pin as well.

    Best Regards,
    Matt

  • 0 in reply to Matthew Beardsworth
    Expert 1920 points
    Hi Matthew

    The pull-up resistor value of Fault pin is 4.7kohm.
    And a resistor(33ohm) between GPIO of MCU and Fault pin was already designed.
    As you told me, I'm going to verifiy whether a TVS diode can be resolved this problem or not.
    Is there any recommend TVS diode?

    Thanks for your response and help.