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PCM1865: TDM vs I2S Level Differences

Colin R.
Intellectual 475 points
Part Number: PCM1865
Other Parts Discussed in Thread: PCM1864

Hello,

I'm trying to use the PCM1865 in TDM mode, but am seeing a 6dB level difference between Channels 1/2 (the pair that is ~6dB down) vs Channels 3/4. I compared TDM vs I2S mode (using the DOUT2 on a GPIO) and the problem is only in TDM mode. Perhaps I'm missing 2 bits in TDM for the first two channels? No storage scope here at the moment to check that, but want to make sure it's not a known TDM issue. Attached images below.

I2S with 2 Serial Data Lines (looks OK):

TDM shows first channel about 6dB down:

  • 0
    TI__Guru 57800 points

    Hi, Colin,

    This is not an expected behavior, the data output from the PCM1865 should not have any difference in the signal level (unless it is configured by user) regardless the format used. Can you please check if the receiver processor format is properly configured to match the PCM1864 output data?. One thing to check as well is the offset configuration in the PCM1865 and see if it is matching the expected processor format.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer