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PCM1801: antialiasing filter

Part Number: PCM1801

Hi Team,

I have two questions about PCM1801.

#1: figure 20 shows up to 10MHz but what is the filter curve from 10MHz to 1000MHz?

is it ok to think that curve just follows -20dB/decay like below?

#2: does antialiasing filter frequency response has dependency on fs and SYSCLK or 150kHz stop-band is fixed frequency regardless of fs and SYSCLK?

Regards,

Kai

  • Hi Kai,

    The Antialiasing filter should be a simple RC circuit with a -20dB/decade rolloff. It's safe to assume the -20dB/decade rolloff on the data sheet extends from 10 MHz to 1000 MHz on the same trend. 

    Because the antialiasing filter is analog, it should have no dependency on fs or SYSCLK.

    Regards,

    Jeff

  • Hi Jeff,

    I have one more question.

    When customer does EMC test, it looks 590kHz band noise affects PCM1801 converting result.

    Do you have anything idea of this 590kHz noise for PCM1801?

    If you have any workaround, could you let me know?

    Regards,

    Kai

  • Hi Kai,

    Can you clarify your test conditions? Is there a schematic? I would need to know things like clock frequencies, input/output frequencies and what the test set up is. Is the 590kHz being projected onto the device? Or is the device radiating 590kHz noise?

    Regards,

    Jeff