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Original question:

PCM6260-Q1: Schematic review

PCM6260-Q1: Single Ended Microphone Expected DC Bias?

Steven Perry
Prodigy 10 points
Part Number: PCM6260-Q1

Tool/software:

I have a design where the DC bias of the signal from the microphone is 1.25V. The ADC is reading this DC level at -5 dBFS. The internal MicBias is turned off, and I am not seeing any other details in the datasheet that would lead me to set up the signal differently. What is the expected DC Bias that the ADC is expecting to detect the largest signal possible?

Here is my electret microphone schematic:

The signal goes from here into channels 5P and 6P with 5N/6N connected to ground:

Thank you,

Steven

  • 0
    TI__Mastermind 27220 points

    Hi Steven,

    PCM6260 high swing mode supports 10Vrms (14Vp) differential, 5Vrms (7Vp) single-ended and you would ideally set the DC bias or voltage common mode to the middle of this input swing, at roughly 7V.

    For a single-ended ECM microphone, ensure you set CHx_CFG register correctly. Since the output signal is reading -6dBFS, this is signaling that the ADC is receiving half the desired input signal amplitude. This could be due to the registers being configured for differential mode rather than single-ended. 

    What is the current signal level swing provided?