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TPA3110D2: White noise hiss

Xavier G.
Prodigy 10 points
Part Number: TPA3110D2

Greetings,

I made a board with the TPA3110D2, and it presents a high level of constant white noise hiss. If I short the input to GND, the noise disappears, but I'm not sure what to do to reduce the noise level. I've tried the board connecting it to a motherboard, and supplying it power from the same source. If the power comes from a different adapter than the motherboard, the noise is significantly reduced. The gain is set to 20dB

I also tried a board with the same IC that I bought on Ebay to compare its performance, and the noise level is quite lower, even if powered by the same source as the motherboard. This board had the power limiter set at half the VGDD, but I tried removing the power limit (connecting PLIMIT to GVDD) and the noise level is still lower than that of my board.

These are the schematics/PCB of my board. Is there anything on the input side that might be the cause of the poor performance?

bottom copper

Thank you kindly,

  • 0
    TI__Genius 13360 points

    Hi Xavier

    your pcb seems no big problem.

    but C5 and R4 change their position would be much better.

    about the noise, have you measured obvious noise at the output when no signal been inputted?

    btw, have you measure the avcc and other power supply, do they having any noise adhere in them?

    thanks.

    jesse

  • 0 in reply to Jesse Ji
    Prodigy 10 points

    Hello Jesse,

    Thanks a lot for your response.

    Regarding the C5 and R4 position, you mean to exchange their positions and have C5 be closer to the IC?

    As for the noise, if the input is floating there is stronger white noise. If I short the input to GND there is very little noise.

    I've captured the signals at VCC, AVCC and the input signal. The input noise is a lot higher when I supply the audio board with the same supply as the motherboard, but what I don't understand is why the eBay board does not have the same high noise under the same power/signal input circumstances.

    Best regards,

  • 0 in reply to Xavier G.
    TI__Mastermind 19330 points

    Hi,

    According to your description, the noise source is audio input and power supply.

    You can check FFT to find out noise frequency, then it is easy to find out noise source.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 10 points

    Hi Derek,

    I understand the problem is noise getting to the audio input, but I'm mostly concerned about the PCB design because I've tried other boards that, when supplied from the same means, do not present such high noise. So I was mostly looking for suggestions as to how to improve the routing / component placement on the PCB.

    From what I've been reading, I think I should set the PVCC traces in a star connection, and distance those traces from the input part of the IC (the noise in the input seems related to the 300kHz APA switching frequency). Also place smaller capacitors and closer to the amplifier.

    Thank you,

  • 0 in reply to Xavier G.
    TI__Mastermind 19330 points

    Hi,

    I do not think PCB has problem. the audio input trace is very short to connector. The noise mainly be related to audio source or power supply noise.

    Please double check.

  • 0 in reply to Yanming Gong
    Prodigy 10 points

    Hello,

    I only think there might be something wrong with my design because, when trying other boards with the same APA, the noise is much lower. If that wasn't the case I would just accept that the issue only lies in the power source / audio input line, but it seems like the design could be improved to lower the noise level.

    Thank you,

  • 0 in reply to Xavier G.
    TI__Mastermind 19330 points

    Hi

    I am sorry that I can not confirm the issue is related to audio source or cable. The PCB layout you shared seems have no problem.

    So you can check one by one, power supply, audio source, audio input cable.

    Regards,

    Derek