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PCM1804: BCK Rates

Ken Patterson37
Prodigy 30 points
Part Number: PCM1804


I am unclear about how to set the BCK rate for the PCM1804.  I will be configured in slave mode, I2S format, using an fs of 192kHz with a system clock of 24.576MHz.  According to table 2 in the datasheet I will need to set the over sampling rate to Quad rate (x32 fs) which would be 6.144MHz since the system clock will be running at 128fs.  However the table in figure 38 states the maximum BCK period is 1/(48fs) which is 9.216MHz.  This would indicate that I can't use 6.144MHz as the BCK rate.  Any clarification would be appreciated.

Thanks,

Ken

  • 0
    TI__Expert 5645 points

    Hi Ken,

    Welcome to e2e Forum.

    As far as the PCM1804 configuration goes, I do see that the outlined BCK requirements to be in the range of 1/(64 fs) and 1/(48 fs) will result in the device not working when configured to operate in Quad rate at 192kHz. I also see that the EVM for the device does not allow configuring the device for quad-rate@192kHz either. We do allow 64*fs when operating at 192kHz.

    I'll run some tests here and will confirm if one of the table is inaccurate in the DS. Thanks.


    Best regards,
    Ravi

  • 0 in reply to Ravi Patil
    TI__Expert 5645 points

    Hi Ken

    First off, Sorry for taking a bit longer as I had to make sure I run a few tests on EVM as the design team that worked on this part is no longer with the team. 

    I did look at the EVM and based on my testing, the BCK requirement does apply for the part to be functional (9.216MHz to 12.288MHz). As a result, we may not be able to configure the quad-rate oversampling. The max sampling rate at quad-rate is 96kHz.

    We are looking at the design database and make sure of few more things before we revise the DS. We do apologize for this inaccuracy and we will make sure we strive to fix this as soon as we figure out the design details for this part.

    Thanks.


    Best regards,
    Ravi

  • 0 in reply to Ravi Patil
    Prodigy 30 points

    Hi Ravi,

    Is there a way to use the 192kHz sampling rate?  I do have some control over my BCK and SCK rates.

    Thanks,

    Ken

  • 0 in reply to Ken Patterson37
    TI__Guru 57800 points

    Hi, Ken,

    Sorry for the delay, my colleague Ravi has been out these days and will return next week.

    From what I can see, it seems 192KHz in I²S mode may be possible only with a BCLK is 64×Fs and SCK is 128×Fs combination for quad mode, but I don't have an EVM to try it. If it does not work, it is likely that 192KHz sampling rate is possible only in DSD mode. I I would recommend to wait for my colleague Ravi to see what are the findings on the device database.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Intellectual 575 points

    Hello

    Any news about topic?

    If there are any issues with BCK rates, when PCM1804 datasheet will be revised?

    -- Regards,

    Victor