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PCM6240-Q1: MIC bias's inquiry

Lee, Sam
Expert 6025 points
Part Number: PCM6240-Q1

Hello team,

 

Can I ask about MIC bias in PCM6240-Q1?

  

I'm not familiar with MIC application, but my understanding is that MIC bias should be applied before AC coupling cap to power MIC. Is it correct?

                 

However, PCM6240-Q1 datasheet recommends MIC bias between AC coupling cap and input pins (INxP/M) as below. In that case, doesn’t the microphone need a bias before AC coupling cap?

       

 

Thanks,

Sam Lee

  • 0
    TI__Genius 10305 points

    Hey Sam, 

    The MICBIAS provides a DC signal and that offsets the MIC signal into the ADC's input range. Generally, capacitors block DC signals in very short amounts of time hence applying the MICBIAS after the coupling capacitor receives an AC signal (in this case, the mic signal) and not before is more reasonable. I hope this clarifies your question. 

    Regards,

    Ore. 

  • 0 in reply to Ore Ogundana
    TI__Expert 6025 points

    Hi Ore,

     

    Thank you for clarifying it. I'd like to double check it.

    Based on your comment, it sounds like MIC doesn't need a DC bias before AC coupling cap. Is that right? Can MIC work without a DC bias?

     

    Thanks,

    Sam Lee

  • +1 in reply to Lee, Sam
    TI__Genius 10305 points

    Hi Sam Lee,

    Yes, the mic doesn't need a DC bias before the AC coupling capacitors. However, the microphone you use would need to be biased to power on the MIC. Once you power your mic, the mic signal would need a MICBIAS to DC offset the signal into the ADC's input range. This application of the MICBIAS with AC coupled capacitors is correct.

    .

    If you are using this application, the datasheet provides a calculator to figure out your R0 values:

     I hope this helps.

    Regards, 

    Ore.

  • 0 in reply to Ore Ogundana
    TI__Expert 6025 points

    Hi Ore,

     

    Thank you for your reply.

     

    Best Regards,

    Sam Lee