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PCM4222: Master Clock (MCKI) Minimum Frequency

Michael Etheredge
Prodigy 130 points

Part Number: PCM4222

I am using the PCM4222 in DSD mode.  The minimum frequency is listed as 2.048MHz in the datasheet.  I've been using it with an MCKI of around 1.6MHz without and it seems to be preforming well.  Is there a lower bound for the MCKI where the performance will drop off? 

  • 0
    TI__Guru 57800 points

    Hi, Michael,

    Sorry for the delay, my colleague is looking into this question and will get back to you as soon as possible.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 130 points
    Thanks for looking into this Diego. I'm awaiting your reply.
  • 0 in reply to Michael Etheredge
    TI__Expert 5645 points
    Hi Micheal,
    Apologize for the delay as I had to check for the details on design/test side of things to better answer the question about using the device outside the spec...

    I do want to check few things about the use case -
    1) Is the device used in normal mode?
    a. The datasheet states that the MCLK needs to be 256*fs for normal mode. The OSR when used in this mode is 128. If you go lower than 2.048MHz , then the OSR would be lower and you will start seeing a noise degradation.

    The test program currently is configured to evaluate the performance up to min spec and we cannot guarantee performance of the device to meet the spec if we run below min freq...

    Best regards,
    Ravi
  • 0 in reply to Ravi Patil
    Prodigy 130 points

    Ravi,

    Thanks for the reply.  I really appreciate being able to speak with the engineers who are designing the components.  It is a great service.

    1)  I will be using the device in DSD or MBM mode.  I believe that Normal mode pertains to the PCM Sampling Mode (along with Double speed and Quad speed modes).  In the DSD and MBM mode the oversampling rate is not dependent on these choices.  In DSD or MBM modes I believe the delta-sigma modulator oversampling rate is fixed and fDSD or fMOD are based solely on the MCKI input clock frequency.  If I drop the MCKI clock below 2.048MHz the delta-sigma modulator would continue to operate and would continue to have the same OSR.  In DSD and MBM mode there is effectively no fs. 

    So to clarify my question, "Is there an MCKI frequency at which the delta-sigma modulator performance degrades for the DSD or MBM modes?"

    Thanks for your time.

    Mike