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TS3A227E: Detect headset removal through a permanently-connected TRRS extension without glitching audio

Batuhan Kaya
Prodigy 40 points

Part Number: TS3A227E

Hi all,

We have designed audio board using TS3A227E and we have a problem about the headset detection.

In our system a passive TRRS extension cable is permanently plugged into our jack, users plug/unplug the headset at the extension's far end. So a plug is always mechanically inserted — only the load at the far end changes. 

When the headset is removed from the far end, the mechanical insertion doesn't change, so AUTO_DET never re-runs and we cant detect the remove action, we have to unplug the extension cable. 

So can anyone give information about it or help?

 

Thanks and regards,

Batuhan

  • 0
    TI__Mastermind 27305 points

    Hello Batuhan,

    When you plug-in the extension cable the mux detects it and routes the signals accordingly.
    It will not detect a remove action as long as the extension cable is plugged in. 

    I am not sure how many muxes you are using in your system, but you should have another mux for the headset if you want two different detections.

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    Prodigy 40 points

    Hi Nir,

    Thanks for your reply. Yes I think the only solution is discrete muxes on each side but I can't change the system right now so do you have any alternative IC or circuit for this? Can you recommend app note or EVM for it?

    Regards,

    Batuhan

  • 0 in reply to Nir Gilgur
    Prodigy 40 points

    Hi Nir,

    I have one more question.

    With the manual polling method (triggering det_trigger via I2C), I can successfully detect headphone insertion and removal while the extension is connected.

    However, every time I trigger the det_trigger during the polling cycle, I hear a brief noise/hiccup in the audio output. Is this expected behavior, or is there a way to eliminate this?

    Regards,
    Batuhan

  • 0 in reply to Batuhan Kaya
    TI__Mastermind 27305 points

    Hello Batuhan,

    We don't really have an alternate part here to recommend. The only current solution is to add another one for the headset.
    We do have an EVM for the part you are using, you can find it here. 

    Yes, this is an expected behavior, but not ideal.
    You are hearing parasitic capacitance getting discharged. 
    You can eliminate it using a termination resistor to ground on the line, or use the TS3A226E instead. 

    It has reduction in click/pop noise feature due to its internal design.

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    Prodigy 40 points

    Hi Nir,

    Thank you for your suggestions. I can’t test the TS3A226E right now, but I can add the terminating resistors. Where exactly should I place the resistors, and what values do you recommend? Or can you share a schematic?

    Thanks and regards,

    Batuhan

  • +1 in reply to Batuhan Kaya
    TI__Mastermind 27305 points

    Hello Batuhan,

    The pull down resistors can be used on the audio output line, since that is where you hear the pop.
    We recommend 50ohms, but this is something you need to do trial and error.

    A strong pull will help with the reduction of pop noise, but might affect other aspects of your system.

    Thanks,

    Nir