• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 30 subscribers
  • Views 417 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM1861: differential input - missing n or p channel doesn't make a difference

rifo
Expert 1105 points
Part Number: PCM1861

Hello,

For a test equipment, I am using a PCM1861 in differential input mode.The card that is under test outputs a sinus wave. I then use PCM1861 to convert it into I2S stream and take a 256 point FFT

Sometimes, the cards that I am testing  have the P or N line of the differential line missing (due to problems happening in auto assembly) PCM1861 still outputs a valid I2S stream and the FFT of the incoming stream produces correct results.

Is this normal behaviour of PCM1861? Is there a way to detect this anomaly?

thanks a lot for your help

rifo

  • 0
    TI__Guru 57800 points

    Hi, Rifo,

    This can be considered a correct behavior, when differential mode is used, what changes in the device is the internal Full-scale reference (from 2.1Vrms to 4.2Vrms; that is 2.1 VRMS per pin, out of phase) and interconnection to the ADCs. The PCM1861 will take the content of either positive and negative inputs in case one of them is missing and process it internally, the only side effect would be that the expected level will be attenuated by half, as result of the missing input leg.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 1105 points

    Hello Diego,

    Thanks. Then I guess I will have to check the magnitude of the FFT and see whether the level is attenuated by half or not.

    rifo