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PCM5100A: Generating SCLK from BCLK using internal PLL when fs = 8 kHz

Jay Coggin
Prodigy 180 points
Part Number: PCM5100A

Hi,

We would like to use the PCM5100A in a design, but we need the DAC to support 8 kHz sample rates with a simple 3-wire i2s interface (using the internal PLL to generate SCLK from BCLK). Our BCLK runs at 64*fs, but I am worried by Table 11 from the data sheet:

Is this saying there is no way use BCLK to generate SCLK in an 8 kHz application? If so, I'm wondering will it work but with decreased jitter performance, or will it just not work at all? If it's the former, we may evaluate if it's acceptable for our application.

Thanks in advance for any insight.

-Jay

  • 0
    Prodigy 180 points

    Bump. We need to answer this before we proceed with design, if anyone can confirm whether PCM5100A can be used at a sample rate of 8kHz in 3-wire i2s mode, it'd be greatly appreciated!

  • 0 in reply to Jay Coggin
    TI__Guru 52663 points

    Hi Jay,

    I have tested the PCM5100a the device does work with a 8kHz input.  In addition my colleague has done this test as well:

    I am also seeking some input from the design team, but I think you should be able to begin your evaluation.

    Thanks!

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 180 points
    Thanks for the reply, that clears it up and is good to know! Maybe the datasheet shouldn't list dashes for those fields, but possibly have a footnote about jitter performance.
  • 0 in reply to Jay Coggin
    TI__Guru 52663 points

    Hi Jay,

    After speaking with my design team I received some additional understanding of the configuration.  The PLL has a minimum input frequency of 1MHz, which cannot be achieved with 8kHz fS.  The DAC tries to auto detect the BCK frequency, so in the case of 8kHz the device will likely configure the clocks for minimum BCK rate supported, 1.024MHz.  As the clock is actually only half the speed, most of the functions of the device will be running at half the desired rate.  As such the performance of the device cannot be guaranteed, but you might have reasonable functionality.  Officially we do not support 8kHz, so the specifications are not guaranteed in you application.

    Thanks,

    Paul