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TPA3221: A continuous pause phenomenon in TPA3221

Wenting Wu
Intellectual 2375 points
Part Number: TPA3221


Hello sir,

 A continuous pause phenomenon is found by using TPA3221 BTL 2* 75w@4r when setting up to the maximum volume and playing large dynamic music with only one channel connecting to a speaker, and the other channel is empty ( if two channels are connected to speakers, there will not be a pause.)

TPA3221 is supplied by 27.5V, input about RMS≈ 0.5V, PK≈ 2.2V, observing that  PWM duty cycle with oscilloscope sometimes close to 100%. In this case, the problem can be solved if TPA3221 i's supplied voltage is boosted to 32.5V and  the maximum PWM duty cycle  will be reduced to about 90%.

May I ask whether other D-class amplifiers have the same output pause phenomenon when input is overloading? Why the phenomenon is caused? Is it because of TPA3221 has different internal protection mechanism to be triggered? besides the method of using boost to promote VCC, are there some other methods?

Many thanks for your reply！

  • 0
    TI__Mastermind 19080 points

    Hi Wenting,

    How long is the "pause" lasts? And does "if two channels are connected to speakers, there will not be a pause" means it works in PBTL mode?

    Can you double check the inductor used has adequate saturation current? If possible, please measure the inductor current when it having a pause.

    Thanks!

    Regards,

    Hao

  • 0 in reply to Sam(MPAA) Zhang
    TI__Intellectual 2375 points

    Hello Hao,

    • How long the pause lasts?

    only 50ms around only continue happening in Music peak value.

    • When both channels are connected with TPA3221, does TPA3221 work under PBTL mode?

    Yes, 2*BTL

    • Advice to check the current of inductor when PAUSE happening.

    there is not a lot possibility for the inductor becoming saturation.Because in this logistic, when Load becomes large, the inductor will return back from saturation status to normal status.

  • 0 in reply to Wenting Wu
    TI__Mastermind 19080 points

    Hi Wenting,

    What's the capacitance of the BST cap? Could you try 33nF or 100nF?

    The behavior in your description looks like some protection with auto recovery. As the pause is relatively long (~50ms), it's more likely to be the Over Temperature Protection. The device only support 100W on each channel. For 75W*2, please use PBTL mode.

    Thanks!

    Regards,

    Hao