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TPA6211A1-Q1: Vo+ and Vo- waveforms are not synchronized during power-off

xiangsheng.du
Prodigy 20 points
Part Number: TPA6211A1-Q1
Other Parts Discussed in Thread: TPA6211A1

I designed this circuit according to the single-ended input circuit, as shown in the figure

When the chip is suddenly powered off, the waveforms measured by Vo+ and Vo- are as follows. When their voltage drops, they are not synchronized, which will cause abnormal sound. Is there any way to synchronize them without causing abnormal sound

  • 0
    TI__Guru* 95455 points

    Hi Xiangsheng,

    Can you test by AC coupling to GND pin IN- and repeating the power down? You may use C31 for this purpose.
    With this test I'm trying to identify if the difference at the outputs could be caused by mismatch at the input.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 20 points

    Hi Salazar

    Thank you very much for your reply.

    Here are the waveforms I measured, I measured the waveforms at both ends of C31 when it was power down, 

  • 0 in reply to xiangsheng.du
    TI__Guru* 95455 points

    Hi Xiangsheng,

    Thanks, but could you please use the scope to check Vo+ & Vo- while C31 is shorted to GND (at the input side) and all the previous circuitry is not used? (Make IN- similar to IN+)
    Basically, I want to check the performance when the inputs are both AC coupled to GND.

    You may also compare the waveform of C30 vs C31, the mismatch here would be the transient you see at the output. You may try changing some component values to make these waveforms match better or replace the components with lower tolerance ones. One more option is to connect the GND reference for the IN- components closer to the audio source.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 20 points

    Hi Salazar

    Yes, if C31 is shorted to GND, that is TP51 shorted to GND, The noise disappears, which means that the accuracy of the components is not related. Any good suggestions for this circuit.

    There should be no problem with my GND, and I connect TP50 to GND, there is still noise.

  • +1 in reply to xiangsheng.du
    TI__Guru* 95455 points

    Hi Xiangsheng,

    Thanks for checking the test with TP51 grounded.
    Based on the results it seems R32 and C33 somehow affect the performance? Could you please try by connecting C33 and R34 GND side closer to the audio source? What is sending the audio to TPA6211A1?

    Best regards,
    -Ivan Salazar
    Applications Engineer