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TPA6139A2: TPA6139 pop noise issue on mute off

Gary Teng
Genius 5860 points
Part Number: TPA6139A2

Hi all,

 Please help to check the pop noise issue on TPA6139: we insert a audio jack and then unmute TPA6139 after 200ms.

1. When we unmute TPA6139 on customer's board, we'll get a negative waveform on audio out channel and we'll hear a pop noise.

2. At the same time, we see an signal shown on TPA6139's audio input side.

3. If I let amp's audio input as floating, there will not have negative signal on audio out and no pop noise is heard.

 Is there any suggestion for us to solve the pop noise issue? Like delay more time (500ms or more?)  or modify the capacitor or...? We've remove C476 and C581  and Cvss and Ccharge has the same 1uF capacitor.

Thanks for your kindly help.

Best regards,

Gary Teng

  • 0
    TI__Guru** 109825 points
    Hi Gary,

    The pop noise is caused by a transient at the input of TPA6139A2, as you've already identified.
    Increasing the wait time could be an option, considering the second oscilloscope capture it would take around 400mS for a safe/no-pop unmute.
    What is connected to the input of TPA6139A2? In the last picture I can see the device and the output connection, but not the input.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Genius 5860 points
    Hi Ivan,
    1. The input signal you see on fig. 2 is come from the process of headphone jack plug in automatically. The audio source of TPA6139 is audio codec in Displaylink's chip. In the condition, no matter there's sound send out from codec or not, there'll have a positive signal waveform in amp's input when headphone jack is pluged, and the negative waveform is shown at amp's output when we unmute amp. But, if I disconnect the connection between amp and codec, no abnormal signal will be found on headphone plug in process.
    2. I'll try to find TPA6139 evm to test the issue. But why TPA6139 has a negative -500mv pop when I un-mute it? How to eliminate it?

    Thanks for your response.

    Gary
  • 0 in reply to Gary Teng
    TI__Guru** 109825 points
    Gary,

    I tested the mute/un-mute on a TPA6139A2 evm board and it does not generate any transient signal.
    Did you had a chance to get an evm to test?

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Genius 5860 points
    Hi Ivan,
    I don't have TPA6139 EVM, but I test other TPA613x EVM and I don't hear pop noise. I've provided your comment to customer and wait if there have other question about it. Thanks for your kindly help.

    Best regards,

    Gary