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TLV320AIC3007: [High priority] How to turn off an unused microphone correctly?

Andrey Yurlov
Prodigy 10 points
Part Number: TLV320AIC3007

Hello Anybody,

I have board based SoC realtek and codec TLV320AIC3007IRSBR which connected via I2S bus to SoC. 3 microphones are connected to codec - LINE2LP+LINE2LM, LINE1LP+LINE1LM, LINE1RM+LINE1RM and all are configured so that its are "not connected to the left ADC PGA". The PGA is configured for maximum gain volume, the ADC is in the "Left ADC channel is powered up" state, and the "1st order HP filter" and "AGC" are disabled.

However, if you shout loudly into the microphone, the voice will leak through the preamp, which should not have sent a signal to the PGA and then to the ADC. Only the Left ADC is used.

Is it possible to make it so that with 3 microphones connected, the signal would be taken from only one? How is it that the path from the microphone is "not connected" to the PGA, but is still connected?

Values of registers:
register 12 = 0x0F
register 15 = 0x7F
register 16 = 0x80
register 17 = 0xFF
register 18 = 0xFF
register 19 = 0xFС
register 20 = 0xF8
register 21 = 0xF8
register 22 = 0xF8
register 23 = 0x78
register 24 = 0x78

Previously, we used a different codec realtek alc5633q and it did not have the problems I described.

Thanks,

Andrey

  • 0
    TI__Mastermind 22950 points

    Hi Andrey,

    There may be some cross talk making it's way to the PGA and since it is configured for max gain, it may be just enough to be heard. If you are disconnecting the microphone inputs, why leave the PGA gain set to max? Is it possible to mute the PGA?

    Regards,

    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Prodigy 10 points

    Hi Aaron,

    This is just an example, which shows that even when we disable all of the MICs in codec registers, they still makes sound. In real case we are going to use only 1 of those MICs connected, and all other disconnected. Of course, we need to have an ability to change MICs at any time.
    So the main problem is that when we use MIC1 (let it be LINE1LP+LINE1LM) and disconnect all other MICs, we still can hear sound from MIC2 and MIC3.
    If we mute PGA, then all of the MICs will be silenced, but we need only 2 out of 3 to be silenced.
    You mentioned about cross talk. If that so, it means we can't avoid this situation? Cause the amplifier, which is being interfered, are based inside the codec, so we don't have anything to do with it.

    Andrey

  • 0 in reply to Andrey Yurlov
    TI__Mastermind 22950 points

    Hi Andrey,

    Understood. I feel like this may be a crosstalk issue. Our device specs crosstalk to typically be around -75dB.This -75dB spec assumes a 1kHz -2dBFs sine wave input and 0dB PGA gain. Is it possible to test the crosstalk in the device between the MIC1L and MIC1R channels? I have also added the specs from the other channels below:

    MIC2L to MIC2R has better separation. Is it possible to use the MIC2RP/M, MIC2LP/M and MIC1LP/M channels with the connected mic on MIC2RP/M?

    For the PGA gain setting, what level is the incoming mic signal? The device supports an analog full scale input of up to .707Vrms or 2Vpp. Are you needing the full PGA gain for your mic signal? Might it be possible to lower the PGA gain?

    Regards,

    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Prodigy 10 points

    Hello Aaron,

    Our problem was solved when we lowered the PGA gain. Thanks

    Andrey