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TPA3251： Sound is interrupted

user5886159
Prodigy 40 points
Part Number: TPA3251

A single-ended audio signal is made up of a reverse phase signal by a differential amplifier and input to input A and input B, respectively, to output audio signals.
The output signal is connected through the transformer through the decoupling capacitor to the speaker.

PVDD is supplying 24V.
If the capacity of the coupling capacitor is increased, the sound from the speaker is interrupted.
The moment the sound was interrupted, the FAULT signal fell to Low.
Does this mean that it is overcurrent?

  • 0
    TI__Mastermind 24835 points
    Hi Ozawa-san,
    Could you please share your SCH, it helps our debug work.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 40 points

    I attach SCH.　

  • 0 in reply to user5886159
    TI__Mastermind 27850 points

    Hi User5886159,

    This does sound like it could be an OC function, but the easiest what to tell is to look at the FAULT and CLIP_OTW pins, and their combination of stated at the fault will tell you why it faulted. Table 2 in section 9.3.1 of the datasheet shows the error codes. 

    It is also recommend that the C/D inputs be grounded through capacitors and the C/D outputs at least have the BST caps installed. You could also just use the device in PBTL mode using a pre filter PBTL setup.

    Justin

  • 0 in reply to Justin Bohr
    Prodigy 40 points

    Hi Justin,

    thank you for your answer.
    Short-circuit protection will work if the capacitor capacity is increased, does not it make it impossible to increase the sound pressure anymore with this circuit? Is the output limit?

    What should I do if I want a slightly higher output level from this input signal?

  • 0 in reply to user5886159
    TI__Mastermind 27850 points
    Hi,

    Are you talking about the sereies capacitor on the output? The size of this capacitor should only effect the high pass corner. If you are trying to output audio frequencies below the fc of the high pass then the size of the capacitor will affect the amplitude.

    What load and what frequency are you playing when the device shuts down?

    Justin
  • 0 in reply to Justin Bohr
    Prodigy 40 points
    Hi,

    It is voice guidance and alarm sound.
    We assume 40 Hz to 200 kHz.
    Through a transformer, we are thinking of speaker 1 W (10 kΩ) etc. connected in parallel and max load of 40 W.
    Since it is not enough for the desired sound pressure, we are considering sound pressure UP.


    Also, 21 pin was always Low output. Is there any cause? I think it is not overheated as it is just after startup.