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TLV320AIC3254: Does headset detection work for headphones without a microphone?

Scott Brenneman
Genius 3295 points
Part Number: TLV320AIC3254

Does headset detection require that the headset include a microphone?  We're not using one; we are going to have headphones only, no microphone.

I'm hoping for a quick yes/no answer -- I realize that I could dig deeply into the app note on headset detection, but if there's no point in doing so, I'd rather save the time!

Thanks,

Scott

  • 0
    TI__Expert 6440 points

    Hi Scott,

    We will confirm with our expert and get back to you on this.

    Best Regards.

  • 0 in reply to Diljith
    Genius 3295 points

    Great!  This is very urgent, so hopefully this can happen today.

    Thanks,

    Scott

  • 0 in reply to Scott Brenneman
    TI__Expert 6440 points

    Hi Scott,

    Yes, the device is capable of detecting headphones only. A microphone does not need to be a part of the accessory for the detection .

    Best Regards.

  • 0 in reply to Diljith
    Genius 3295 points

    I'm unclear how to connect the circuitry.  I understand that MICBIAS provides a voltage which feeds an internal divider, and that the comparators look at the voltage coming back on SCLK/MFP3.  However, as I look at the schematic (Figure 2-58) in the 'AIC3254 datasheet, I have a couple of questions.

    1.  How do we determine the value for the MICBIAS resistor?

    2.  The Sleeve pin of our headphone jack is tied to ground, as is typical.  This would mean that SCLK/MFP3 is always grounded, whether or not headphones are plugged in.  The only way detection would work is if somehow the headphones grounded SCLK when they were plugged in, and let it float otherwise, but I don't see how to make that happen.  Do you have a suggestion for this?

    Thanks,
    Scott

  • 0 in reply to Scott Brenneman
    TI__Expert 6440 points

    Hi Scott,

    I am not very familiar with the detection scheme. Our expert will be back from travel next week and I will get these question clarified by early next week.

    Best Regards.

  • 0 in reply to Diljith
    Genius 3295 points

    Okay, we will make do in the meantime.  We look forward to hearing the followup next week!

    Thanks,

    Scott

  • 0 in reply to Diljith
    Genius 3295 points

    Has there been any progress on this?

    Thanks,

    Scott

  • 0 in reply to Scott Brenneman
    TI__Expert 6440 points

    Hi Scott,

    Apologies for the delay. Please refer to the connection diagram in the EVM user guide. For headset detection, the recommendation is to set the jumpers as follows:

    1. W1: 2-3
    2. Remove W2, W3, W4, W6, W7, W9, W10, W11, W12
    3. Insert W5
    4. W14: 2-3

    Our suggestions are with respect to these connections (i.e. with the jumper settings as mentioned).

    The EVM uses a 2.2K ohm between the MICBIAS and MICDET pin. Using a four-conductor audio jack (i.e. 1:Sleeve, 2/3: HPL/R, 4: Mic), inserting a headphone results in a short between 4 and 1 and this enables the device to detect the insertion of a stereo headphone. So in a four-connector jack, the MICDET signal is to be connected to terminal 4 of the jack. Terminal 1 (the sleeve) is to be grounded, which is what you are already doing. However, if you are using a three-terminal jack (1: Sleeve, 2/3: HPL/R), MICDET can be connected to HPL and with this configuration of the device, inserting a headphone results in a “stereo + cellular” headset detection. The headset detection de-bounce time may need to be adjusted  to prevent false insertion/removal.

    What connector where you considering using for the jack? Please let us know if you are consider some other connector for the jack or if you have questions regarding this information.

    Best Regards.

  • 0 in reply to Diljith
    Genius 3295 points

    Hi Diljith,

    Thank you for this info.  We had to get the board out for fab, so I took my best shot, not sure if it will work or not.  We are using a three-conductor jack, so I arbitrarily chose HPR for detection, not HPL.  I can send you the schematic page, but I don't want to post it publicly.  How can I send it privately?

    Regards,

    Scott

  • 0 in reply to Scott Brenneman
    TI__Expert 6440 points

    Hi Scott,

    I have sent a request to connect privately on E2E. Please accept it to send me the schematic..

    Best Regards.