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TLV320AIC3204 Headset Detect

Chris Davies
Prodigy 60 points

How does the headset detect function work? Enabling this function seems to change the voltage on the Mic Bias pin, thereby upsetting another internal microphone feed from this pin? When a headset is connected the Mic Bias voltage is correct, but when not connected it seems to rise to LDO input volts. Any clues?

Many thanks

Chris Davies

  • 0
    TI__Mastermind 46195 points

    Hi Chris,

    This is a very good question.

    When a headset is inserted (and headset detection is enabled), the voltage at MICDET will fall below a certain threshold (derived from MICBIAS) due to voltage a drop between MICBIAS and external resistor. This will register as a detection and the MICBIAS will be sourced by the programmed value (e.g. 1.25V, 1.7V, supply, etc..). 

    When a headset is removed and headset detection is enabled, the MICDET voltage will be rise to MICBIAS voltage since there is no microphone load between that particular resistor (typically 2.2kohm is used between MICBIAS and MICDET) and ground.

    In the case that no headset is detected, the MICBIAS circuit will go to a low power mode where it is switched to LDOin supply at periodic times to verify if a headset has been inserted.

    In case that a secondary on-board microphone that requires MICBIAS is used (when using headset detection feature for an external mic), then the MICBIAS pin should not be used for the on-board mic. If headset detection is not used, then multiple microphones can be connected to MICBIAS.

    We do offer several audio codecs with MICBIAS pins specifically designed for the previously mentioned scenario. For example, the TLV320AIC36 has an EXT_MICBIAS and an INT_MICBIAS pin. The EXT_MICBIAS pin is used by the headset detection circuit while INT_MICBIAS can be used for any on-board mic. Another alternative is to use a clean supply and noise resistant microphone circuit.

    Regards,

    J-