• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 30 subscribers
  • Views 634 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.

PCM1808: input needs biasing circuit?

[FAE] Andrew Wang
Genius 10685 points
Part Number: PCM1808


Hi Team,

From the PCM1808 datasheet, spec said max rating min input is -0.3V. But our reference circuit didn't show any biasing circuit, may I know why? 

Thanks.

Andrew

  • 0
    TI__Guru 57800 points

    Hi, Andrew,

    The PCM1808 has a DC common move voltage (Vref on the device) in the input pins, the decoupling cap on the inputs is used to isolate the DEC level from the input signal to the input pin. An input signal centered on ground level before the cap will be mounted on the common mode voltage at the input pin, that's where the absolute maximum values are measured.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    TI__Genius 10685 points

    Hi Diego,

    Thanks for feedback. I understand now.

    Do you know if  any page of PCM1808  datasheet  explain for the input stage has internal biasing, I couldn't find it. Or this is common sense for all our audio ADC input stage that we don't need any external biasing resistor but just an AC coupling cap.

    Thanks

    Andrew

  • 0 in reply to [FAE] Andrew Wang
    TI__Guru 57800 points

    Hi, Andrew,

    This is a common configuration for almost all our audio devices, you can typically find this explained in the ADC section (where available) of the datasheets.

    PCM1808 is a simple device which ADC does not have special features, hence the datasheet is kept simple. In general, the typical application section of our devices highlight the recommended circuit which can be used as reference.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer