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TPA3244: TPA3244 Signal Clipping detection functionality

Zhonghui Xu
Expert 5445 points
Part Number: TPA3244

Hi team,

I am designing an amplifier that uses the TPA3244 in its power stage in BTL mode, with one channel configured for use with a woofer and one channel for a tweeter. When using the amplifier at high volume, with bass heavy tracks, the woofer seems to "lose control" and the cone starts to flap. I investigated many possible causes (the power supply is a 250W Meanwell SMPS), but on checking the CLIP/OTW signal, the problem seems to happen when the signal goes low. Could you please explain what exactly happens to the output signal when the clipping detection circuitry intervenes? I should be able to use this amplifier even at 1-2% clipping, but the way the woofer loses control makes me worry that it could be damaged with extended use, apart from the fact that the music sound quality becomes too poor for good listening at these high volumes.

Thank you. 

Best regards,

  • 0
    TI__Mastermind 24920 points

    Hi Zhonghui,

    You are saying that the woofer behaves unexpectedly at 1-2% clipping levels? You are correct that far too low for that to be happening. Have you tried running the device through a resistive load and checking the signal to see if it's seeing the same issues? 

     I recommend reading section 9.4.1.2 Signal Clipping and Pulse Injector of the datasheet for a detailed explanation of how the device handles clipping. 

    Best Regards, 

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    TI__Expert 5445 points

    Hi Robert,

    Apologies for my late reply and thanks for your feedback.

    To be honest, I have read the datasheet again and I still haveb't really understood exactly what happens in the moments that CLIP/OTW kicks in. Does something actually happen to the audio signal (which is what I understood), or does the CLIP/OTW signal just go low and that's it (see attached image of the CLIP/OTW signal)? Apart form the woofer losing control, we notics that the sound becomes harder and less pleasant to listen to in those moments.

    Thanks again

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Mastermind 24920 points

    Hi Zhonghui,

    The CLIP_OTW pin is just a warning pin. It doesn't change how the device behaves, it simply reports when a CLIP or OTW even is occurring.

    What is the speakers impedance? What is the power rating? Does this issue occur at only specific frequencies or across the entire audio band? 

    Best Regards,

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    TI__Expert 5445 points

    Hi Robert,

    sorry for the belated reply. Your answer was satisfactory, I just needed to understand if anything happened to the signal in case of active clipping. I'm attacking the problem from a different angle so we can consider the case as closed.

    Thanks so much for your time and assistance.

  • 0 in reply to Zhonghui Xu
    TI__Mastermind 24920 points

    Hi Zhonghui,

    Thank you for letting us know! I'm glad to have been able to help assist you. 

    Best Regards,

    Robert Clifton