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PCM1690: Master clock synchronization.

Part Number: PCM1690

Hi,

I have a quick question. I am working on a digital audio front end. I am using a DSP ADAU1701 in tandem with a DAC PCM1690. Do I have to synchronize the master clock between them (the SCKI pin on the DAC and MCLKI pin on the DSP), or can I just use crystal oscillators of the same frequency (like this one - SG7050CAN)?

Thanks!

  • Anton,

    The system clock (SCKI) has no relationship with any of the configuration interfaces (HW, SPI, or I2C) so from that perspective you would have no concerns about relative timing of the DSP clock to the PCM clock.

    From the I2S perspective, though, there is a relationship required between BCK, LRCK, and SCKI - the datasheet probably most specifically speaks to this on Page 26. Page 18 shows Table 2 which shows the options for relationship between system clock (SCKI) and the sampling frequency (LRCK) as 128fs, 192fs, 256fs, 384fs, 512fs, 768fs, and 1152fs. From there, there would be an implication as well on the BCK frequency based on the selected input data format as 16, 20, 24, or 32 bits - more details on those conditions are explained on Page 24.

    As long as these conditions can be met with the available clock dividers in the DSP while still meeting the timing requirements shown on Page 10, it does not matter where the clock sources are being provided from as there is not really a relative timing requirement concerning the exact clock edges - just the frequencies.