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PCM1804-Q1: Modulator clock range

David Sandler
Intellectual 1910 points

Part Number: PCM1804-Q1
Other Parts Discussed in Thread: PCM1804

Hi,

We are evaluating the PCM1804 for use in a new product. I would like to use the modulator only mode (DSD) for a range of sampling rates. The datasheet indicates that DSD mode runs at a 44.1kHz(fs) sample rate. Can I vary the System Clock (SCKI) to increase or decrease the modulator clock rate (64xfs) for any frequency within the 8.192MHz to 36.864MHz range listed on page 4 of the datasheet? Will the modulator scale with the clock?

Also, does TI provide components that just contain 24-bit delta-sigma modulators?

Thanks,

David

  • 0
    TI__Guru 57800 points

    Hi, David,

    Unfortunately, the DSD mode operation for this device is fixed at 44.1KHz sampling rate only. The spec form datasheet page 4 corresponds to all the possible SCKI clock ranges across the different operation modes.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 130 points
    Diego,

    Thanks for the quick response. Sorry I didn't get back to you earlier. David had submitted my question to you while I went through the process of getting set up on the TI E2E Community.

    It is unfortunate that the PCM1804 only runs at 44.1kHz in DSD mode. Could I ask two follow up questions:
    1) Could you explain a bit more about how the modulator will run at 44.1kHz even if the sampling frequency clock is not at 44.1kHz. On page 18 of the datasheet Table 3 provides correlations between the system clock frequency and sampling frequency. In each case it shows that the modulator will run at some multiple of the sampling frequency for various sampling frequencies. Isn't the modulator using a 64*fs clock to derive the modulator rate in DSD mode? What will happen if a use a sampling clock that is not 44.1kHz, but is within the range of sampling frequencies provided on page 4 and page 5?
    2) Does TI provide components that just contain 24-bit delta-sigma modulators or other ADCs which support modulator output for various sampling rates?

    Mike