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PCM6260-Q1: PCM6260-Q1:

shan sara
Prodigy 40 points
Part Number: PCM6260-Q1

Tool/software:

Dear TI Team

Below schematic mark green need to realize in our design！

Could you please help confirm whether PCM6260 could realize？

Based on my analysis, it is necessary to provide bias voltage to MIC(MIC impedance is 3.3k)  while also using AC coupling for audio analysis.

Could PCM6260 realize this function?

Another question is that why AC coupling still require bias voltage. What’s the function of the MICBIAS?

From my understand, the bias voltage is not the mic working voltage .

Does it support providing bias voltage to mic so that AC coupling cannot be achieved？

  • 0
    TI__Mastermind 46425 points

    Hi Shan,

    1) Any of our ADCs can realize the design. The schematic shown is just a microphone pre-amp circuit.

    2) Your understanding is correct, the mic needs a supply voltage and the PCM6260 requires an external bias. These are different requirements. You can combine these two by DC coupling the microphone to the ADC.

    3) AC coupling still requires the bias voltage because the ADC does not generate its own bias. Most of our ADCs generate their own internal bias, and MICBIAS is used to supply the microphone power. However for this family of devices PCM6xx0 as well as TAC54xx and TAC53xx, there is no internal bias, so it must applied externally, most commonly by MICBIAS.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 40 points

    Hello Jeff

    Thanks for your Reply!

    From my shown schematic. I understand that this is the AC coupling design!

    Whether I could understand that when need PCM6260 to supply bias voltage to external MIC, PCM6260 only can use DC coupling design?

  • 0 in reply to shan sara
    TI__Mastermind 46425 points

    Hi Shan,

    You are correct, if MICBIAS is to supply external bias voltage to MIC, DC coupling is required.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 40 points

    Hello Jeff

    IN DC coupling application, could you share me how to choose the bias resistor? 

  • 0 in reply to shan sara
    TI__Mastermind 27280 points

    Hi Shan, 

    For a single-ended ECM microphone connection the typical pull-up resistor value is the output impedance of the microphone. Based on your current schematic, the impedance of the microphone is 680Ohms

    This is expanded on further in section 8.3.3 of the datasheet.

  • 0 in reply to Daveon Douglas
    Prodigy 40 points

    Hello Daveon

    From datasheet ，I know that for a single-ended input, the external bias resistor is recommend to be same as the microphone impedance.

    so Is the bias impedance  based on the microphone impedance? When the microphone impedance is 2k, the DC coupling application should choose the 2k?

  • 0 in reply to shan sara
    TI__Mastermind 27280 points

    Yes that's correct for a single-ended configuration

    For differential, half the mic impedance would be referenced to MICBIAS (IN1P) and half the impedance reference to ground (IN1M)