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TPA2028D1: Loud POP Noise on startup

RedWine++
Prodigy 115 points
Part Number: TPA2028D1

Hello all,

I am currently using the TPA2028D1 in my application / custom prototype PCB and are pretty satisfied with the control as well as the output. The amplifier is directly powered through an attached 3.7V 1S LiPo-Battery.

Unfortunately I have one issue with the device that I can not solve:

When powering up the TPA2028D1 in one of the following ways:

  • provide VDD to the EN PIN (3.3V from the MPU I am using) OR
  • writing 1 to the EN bit to activate the amplifier channel OR
  • enabling the amplifier by using software shutdown

I can hear a loud, very noticeable POP noise on the speaker (8Ohm, 2W, 40mm) before any audio output appears. The noise is available over all gain levels (in different intensity for sure). What I have tried to overcome this issue:

  1. small delay (10ms) after startup allowing the TPA2028D1 to startup properly (datasheet recommends 5ms)
  2. fully mute all input until the TPA2028D1 is fully there 
  3. make sure to have proper connection also of the passive components used 
  4. checked the size of input capacitors (1uF/10V -> Murata GCM155C71A105KE38D)
  5. added a 100ms silence to the beginning of the audio track  
  6. tested with AGC on/off
  7. set agcCompressionRation 1:1 (off)
  8. set outputlimiter to minimum value before enabling the amplifier channel
  9. set fixed gain to lowest possible value before startup

The only way to lower the (noticeable) noise is when I delay the start of the amplifier by >150ms after the audio codec is already providing sound to the input. I have attached the noise (recorded with my phone so sorry for the low quality) as well as the schematics to give you an idea. As my application will include the playback of a lot of very short sounds I was hoping to turn the amp off when not needed. With this noise appearing it is not possible to use this amplifier for the mentioned purpose.

Can anyone point me in the right direction on how to fix this issue or can tell me what I am doing wrong?

Thank you for any hint. 

Happy holidays...

B

 

  • 0
    TI__Prodigy 640 points

    Dear customer,

    from your wav file, I can see there is a signal around 3kHz~4kHz  and last for around 5 cycles. this is not a typical pop noise . 

    can you help to get the electrical output signal to check whether it is a real pop noise? (maybe you can use audio precision(AP) to record the electrical signal at the output).

    two more suggested test to check the noise:

    1 bypass the input cap ( C23/C24 in your schematic)

    2 change the value of C23/C24. (maybe 4.7u just for test)

    Br,

    Wenbin

  • 0 in reply to Wenbin Li1
    Prodigy 115 points

    Hi Wenbin,

    thank you for your response. Unfortunately I don´t have all of my equipment with me during holidays but will perform the mentioned test with the input caps (bypass and replacement) in the first week of January when I am back at the workbench. In the meantime I will try to record the signal on the output. The moment I will have any information I will let you know.

    I was assuming that this noise is a "Pop"-noise as it is directly related to the startup of the amplifier (and only appears on startup). 

    Will keep you posted on any progress. Again - thank you for looking into it!

    Have a great holiday season.

    Best

     

  • 0 in reply to Wenbin Li1
    Prodigy 115 points

    Hi Wenbin,

    sorry for the late response on this matter. I have just tested your suggestions:

    1 - bypass the input caps - no change

    2 - change input caps to 4.7u - no change

    2b: leave the input caps out (no connection between vs1053 and tpa2028d1) - amp stays absolutely quiet on startup.

    Will now continue to search for the issue on the vs1053 side as the amp seems to be fine.

    Attached some more sound samples just fyi.

    I believe this topic can be closed.

    Thank you for your help.

    Best,

    B.

  • 0 in reply to Wenbin Li1
    Prodigy 115 points

    Hi Wenbin,

    sorry for the late response on this matter. I have just tested your suggestions:

    1 - bypass the input caps - no change

    2 - change input caps to 4.7u - no change

    2b: leave the input caps out (no connection between vs1053 and tpa2028d1) - amp stays absolutely quiet on startup.

    Will now continue to search for the issue on the vs1053 side as the amp seems to be fine.

    I believe this topic can be closed.

    Thank you for your help.

    Best,

    B.

  • 0 in reply to RedWine++
    TI__Prodigy 640 points

    Dear customer,

    as you request, I will close this issue now.

    if you have further questions, please submit another ticket. thanks.

    Br,

    Wenbin