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PCM1863: PCM1863: Simultaneously stream digital audio from ADC channels

Nigel Taylor
Intellectual 345 points
Part Number: PCM1863

Good evening all,

I would like to understand if I only use two input channels of the PCM1863, 1 channel of each of the internal ADCs can I stream data from both ADC's at the same time via the I2S if not how can I do this connections are as follows:

  • 0
    TI__Guru 57800 points

    Hi, Nigel,

    You can stream the 2-channel data via I²S without any concerns. The PCM1863 has the option to mix the inputs as you need for each ADC. For this particular case, you need to select {VIN1P, VIN1M}[DIFF] as the source for ADC1L and {VIN3P, VIN3M}[DIFF] as the source for ADC1R using registers 6 and 7. The data from the ADCs will be streamed through the I²S DOUT output simultaneously.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Intellectual 345 points

    Hey Diego,

    Thanks for this one other question, we need the ability to apply single ended inputs so for instance if I ground the VINR2/VIN2M and VINR1/VIN2P I assume I can apply a single ended signal into VINL2/VINM and VINL1/VINP is my assumption correct ?

  • 0 in reply to Nigel Taylor
    Intellectual 345 points

    Apologies  missed of the schematic:

  • 0 in reply to Nigel Taylor
    TI__Guru 57800 points

    Hi, Nigel,


    The PCM1863 can be configured to support single-ended signals. Just as I mentioned before, you can select a single-ended signal for each ADC with Registers 6 and 7 (VINL1[SE] to ADC1L and VINR1[SE] to ADC1R). The schematic you sent should be updated as ADC1R only supports the VINRx inputs.

    It is not recommended to ground any input signal of the device, if unused, just leave them floating.

    There is a different configuration called pseudo-differential, where you can apply a single-ended signal to a device configured with differential input. This is achieved by connecting the audio signal to the positive input and AC-couple the negative input to GND with a cap with the same value as the one used in the positive input.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Intellectual 345 points

    Hi Diego,

    Thanks, do you have any links or implementations I can take a look at ? I need diff in, and single ended into the same ADC channel so sounds very interesting.

    Thanks

    -Nigel

  • 0 in reply to Nigel Taylor
    Intellectual 345 points

    Nigel Taylor said:

    Hi Diego,

    Thanks, do you have any links or implementations I can take a look at ? I need diff in, and single ended into the same ADC channel so sounds very interesting.

    Thanks

    -Nigel

    Hi Diego,

    Just had another thought with the circuit below would I be able to keep the diff input on VINL2/VIN1M, VINL1/VIN1P and VINR3/VIN3P, VINR4/VIN3M but if wanted SE use the VINL2/VIN1M for 1 channel and then use VINR3/VIN3P for 2nd channel SE ?

  • 0 in reply to Nigel Taylor
    Intellectual 345 points
    Hi Diego,

    Apologies circuit should have been below my last comment, not sure what happened, just to note I'm trying to finalise my design this weekend.

    Thanks
    Nigel
  • 0 in reply to Nigel Taylor
    TI__Guru 57800 points

    Hi, Nigel,

    Apart from the datasheet and PurePath Console GUI that is used to evaluate the EVM, we don't have more information about the input mixing capabilities of the device. 

    The PCM1863 can be configured to accept single-ended or differential inputs according to the setting on register 6 or 7. There should be no problem in using the described configuration as long as you change the corresponding register accordingly to the type of input used:

    • Differential inputs:
      • ADC1L: {VIN1P, VIN1M}[DIFF], Page 0: Register 6 = 0x10

      • ADC1R: {VIN3P, VIN3M}[DIFF], Page 0: Register 7 = 0x20
    • Single-Ended inputs:
      • ADC1L: VINL2[SE], Page 0: Register 6 = 0x02
      • ADC1R: VINR3[SE], Page 0: Register 7 = 0x04

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Intellectual 345 points
    Thanks Diego,

    I hope this helps other engineers!

    All the best

    -Nigel