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PCM5100A: PCM5100A POP nosie on power on

kerr chang
Genius 4075 points
Part Number: PCM5100A

Hi Team

          I have pop noise in PCM5100A. When Power on the line out have Pop. 

The output cap use 2200pf have pop noise , if we change cap to 0.47uF, look like pop sound resolved. Can we use 0.47uF on output for PCM5100A?

  • 0
    TI__Guru 53633 points
    Hi Kerr Chang,

    The RC filter on the output of the PCM510xA is designed to reduce out of band noise. The RC filter created by the 5.1kΩ and 2.2nF components has a cutoff frequency (fC) of about 14kHz. If you change the capacitor to 470nF you will have a fC of about 70Hz, which will filter nearly all of the audible range. You could experiment with other capacitor values to find a compromise between the pop noise and the fC.

    In addition, you could consider using an external mute device to keep the output grounded until the PCM is fully powered on. The pop noise is due to the device calibrating it's offset at startup. This cannot be disabled.

    Thanks,
    Paul
  • 0 in reply to Paul_Frost
    Genius 4075 points
    Hi Paul
    I will try to use 1.6uF and 5.1k , The FC will be 20hz , IF I did not have cap , Pop will happen on power on.
    I have try to keep mute and power up , the Pop have -40db. Is PCM5100A have pop issue ?
  • 0 in reply to kerr chang
    TI__Guru 53633 points
    Hi Kerr Chang,

    The pop you are hearing is the device calibrating the offset to bring the center (common mode) voltage as close to 0V. This is usually only audible on systems with high analog gain. I recommend you look at an analog mute topology to prevent any transients on the output during power up or auto mute.

    Thanks,
    Paul