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PCM1840: Harmonic Noise

Kuramochi Tadahiko
Guru 28715 points
Part Number: PCM1840

Hi,

My customer is considering using PCM1840 and concerns about harmonic noise.

Regarding the following figure 9,  the harmonic noise of the power line(50Hz) is observed on only Channel-2.

1. Why is the harmonic noise amount different between each channel?

2. Is this harmonic noise caused by internal PGA?

3. Do you have the data that how much is the dispersion of the harmonic noise?

Best Regards,

Kuramochi

  • 0
    TI__Mastermind 23050 points

    Hi Kuramochi-san,

    Noise is a random phenomena, so the spikes that you see are going to be different for each channel and different each time you measure an FFT unless there is a true idle tone present in the device, but this would not be considered noise. I don't think this is actually 50Hz noise, but it is possible a small amount of this could make it through the device when tested with a source that is powered by a 50Hz line. If this is an idle channel tone though then even still the level is so low that it will not be heard in an application.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Guru 28715 points

    Zak-san,

    Thank you for your support.

    Is this peak noise caused by PCM1840?

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Mastermind 23050 points

    Hi Kuramochi-san,

    I am not aware of any idle tones on channel 2 of PCM1840. This could possibly have been some very low level line noise from the test equipment used.

    Best,

    Zak