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PCM1808 Channel Separation

Sadanori Kato
Guru 36510 points
Other Parts Discussed in Thread: PCM1808, PCM5152

Hi,

The noise appeared to the output of the right channel when the audio signal which is over 0dbFS was input to the left channel(VinL) with the non-signal right channel(VinR).
The channel separation is mentioned on page 3 of the data sheet as below.
Could you please give us your advice whether this result is specifications ?

Best regards,
Kato

  • 0
    TI__Mastermind 27900 points
    Hi Kato,

    How much noise are you seeing on the right channel, could you send me some measurements? If you have an AP there is a channel separation measurement, have you run this test?

    Justin
  • 0 in reply to Justin Bohr
    Guru 36510 points

    Hi Justin-san,

    Thank you for your reply.
    I don't have any more detailed information since I have not obtained the evaluation result from our customer.
    So, have you received a similar inquiry?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 27900 points
    HI Kato-san,

    There have been only a couple inquiries I know of in the past year or two, so this is not a common problem we have seen from customers. There will be some noise transfer but the data sheet specifies a channel separation of about 90 dB or better as you posted before. I will try and run a quick test on the EVM, is the customer running this test on an EVM or their own board? Is this noise audible?

    Justin
  • 0 in reply to Justin Bohr
    Guru 36510 points

    Hi Justin-san,

    Thank you for your reply.
    I have evaluated the channel separation by using PCM1808 + PCM5152 as below.
    Could you please give us your advice about this issue ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 27900 points
    Hi Kato-san,

    As you can see in your scope captures, the worst noise on the left channel is generated when the right channel is saturated at its peak. I believe this is because when saturating the input, the entire analog input circuitry will be affected by the saturation's effect on the analog supply. If the analog supply is manipulated this will have an effect on both both channels, since they both run on the analog supply. To solve this I would suggest adjusting the input circuitry so that clipping does not occur.

    Justin
  • 0 in reply to Justin Bohr
    Guru 36510 points

    Hi Justin-san,

    Thank you for your advice.
    I have also been thinking the same thing as you.
    So, I will inform our customer of your information since I understood it.

    Best regards,
    Kato