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LM4990: Please help us with the review of the LM4990LD/NOPB audio amplifier design.

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Replies: 5

Views: 66

Part Number: LM4990

Hey,

I have installed the Audio amplifier and sound should be considerably low.

 I  have used CDS-25148-L100 sa speaker.

 please do needful to improve the audio quality

  • Hi, Sujitha,

    Could you provide your circuit schematic, please? This would give us a better approach to this issue.

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.

  • In reply to Sujitha S:

    Hi, Sujitha,

    Thank you for sharing the schematic circuit. In order to improve the signal quality, I would recommend few things:

    - Ensure that VDD is completely stable, adding 0.1uF and 10uF capacitors will ensure that the ripple is reduced. Since this kind of devices is directly related to the VDD activity, the high ripple content may affect the output signal.

    - Connect the thermal pad to GND, it is not internally connected.

    - If an audio converter is being connected to the amplifier input, I would suggest to use an out-of-band filter ( https://www.ti.com/lit/an/slaa313a/slaa313a.pdf ). Otherwise, there's risk to amplify out-of-band content.

    I hope this works for you. Please let me know if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.

  • In reply to Luis Fernando Rodriguez S.:

    where do i suppose to install 0.1uf and 10uf capacitors.

    could you please give us more clarification of out of band filter in this scenario 

  • In reply to Sujitha S:

    Hi, Sujitha,

    Sorry, I missed your response. Were you able to get better audio quality?

    Regarding the 0.1uF and 10uF capacitors, I was referring to connect them to VDD pin. They should be placed as close as possible to the device for better noise reduction.

    Best regards,
    Luis Fernando Rodríguez S.

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