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TPS65950: Why is a capacitor to GND recommended in unused mic inputs?

Scott Brenneman
Genius 3265 points
Part Number: TPS65950

We are not using any analog audio inputs in our TPS65950-based design; we're only taking in I2S data and using the headset amplifier output.  The schematic checklist says to leave unused inputs such as microphone inputs "floating" but recommends a capacitor to ground on each.  Given that we aren't using these, what does the capacitor do for us?  We're trying to save space, cost and trace routing area, so we'd rather leave off the capacitors.

Thanks,

Scott

  • 0
    TI__Mastermind 30260 points

    Scott,

    I assigned this post to the expert on the TPS65950 device, but please allow until Monday for a response.

  • 0 in reply to Brian Berner
    TI__Genius 12735 points

    Hi Scott,

    After reviewing the schematic checklist, my interpretation of those lines are if the mic inputs are enabled in the device but you are not using the output of the microphones then you should connect a capacitor to the input and short it to ground. This would prevent the microphones from picking up any noise and causing issues with your system.

    If the mics are disabled in the device then you should be able to leave the inputs floating. If you do leave the inputs floating and you have any issues with noise injection, I would try adding the capacitor to see if that fixes the issue.

    Best regards,

    Layne J

  • 0 in reply to Layne J
    Genius 3265 points

    That makes sense -- thank you for confirming!

    Scott