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TPS7A74EVM-068: The module squeaks and whines

zhiyong chen
Prodigy 10 points
Part Number: TPS7A74EVM-068

Hello,

    The problem is that the module squeaks and whines when it works.Please help to analyze where the squeaks and whines come from.Thanks!

--chen

  • 0
    TI__Mastermind 33885 points

    Hi Chen,

    We have numerous copies of this EVM here and they do not make any squeaks or whines, or other audible noise. 

    1. Have you performed any rework to the EVM? 
    2. Under what conditions do you hear this noise?
    3. Can you provide an oscilloscope measurement of the voltages on IN, BIAS, EN, and OUT pins while the EVM is making this noise? 

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 10 points

     the voltages on IN：

     the voltages on OUT：

     the voltages on EN：

     the voltages on BIAS：

  • 0 in reply to zhiyong chen
    TI__Mastermind 33885 points

    Hi Chen,

    Can you place these measurements on the same oscilloscope plot?

    Can you zoom in to one of the sets of noise?  We need to see if we can identify what is happening first, noise on VIN or noise on VOUT.

    It looks like you have 5V on the input and 1V on the output - can you confirm? What is your load current during these tests?

    Can you try a different bench supply powering VIN and VBIAS?  The repetition rate of the dirty waveforms looks to be around 50-60 Hz, so perhaps the power supply has an issue.

    Thanks,

    Stephen