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TLV320AIC3100: how to automatically switch between internal / external microphone when either is present?

AnBer
Mastermind 30210 points
Part Number: TLV320AIC3100
Other Parts Discussed in Thread: TS3A225E, TLV320AIC3007

Team,

Could you please help with the below?

We would like to have an internal microphone combine with headphone with external microphone.
The goal is to use the interne microphone when no headphone (or no headphone with no micro) and switch to the external microphone when we have a headphone.
So far we used the TI TLV320AIC3100 combined with TS3A225E.
It seems doable but I cannot find all the info to do it easily.

Do we have any examples (schematics, app note) about this?
Are there any system level consideration to take into account for such requirements?

If it is not possible do we have any other pointers or other devices that would be easier to use for such scenario?

Thanks in advance,

Anthony

  • 0
    TI__Mastermind 30220 points

    Anthony,

    The headset detect internal to the AIC3100 can do this, it would not be automatic, but it wouldn't require an external device.  There would need to be a host processor polling the status of register 67,  which would tell it if there was a headset, stereo headphones, or no detect.   alternately there are programmable interrupt pins that could be used to alert the host processor that there is a headset detection event.  

    The customer could use different inputs for each mic, and turn those inputs on/off depending on the status of the registers.

    Take a look at section 7.3.10.5 in the datasheet,  you can also take a look at this application note for some insight into the headset detect.  it is for the AIC33 and AIC310x devices,  but the headset detection is not too dissimilar.

    I hope this helps you,  let me know if this isn't quite what you're looking for.  

    best regards, 

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    TI__Mastermind 30210 points

    Hi Steve,

    Thanks for the answer.

    In fact the is an on-board MIC that is always present and a MIC on the headset that need to be detected if present.
    This means that some sort of MUX is needed to switch from the on-board MIC to the Headset MIC.
    The AIC3100 does not seem to have an on-chip analog mux for the MIC input.
    What external MUX would you advise to use? Any schematics/design guide available for this?

    Are there some CODECs comparable to AIC3100 with an on-chip MUX for the MIC (ie 2 analog MIC inputs that can be switched depending on the detection results)?

    Thanks in advance,
    Anthony

  • 0 in reply to AnBer
    TI__Mastermind 30220 points
    are you using a differential microphone configuration? I suppose that my suggestion assumed that you were using Single ended.
    if you are using a single ended configuration there is no mux required. you just turn off one input and turn on another.
    however, if you need a differential configuration on your mic, there is only one differential input, and in that case you would require some kind of external mux. although, if the internal mic is differential, but the external is single ended, (or vice vesra) this would still work.

    If this doesn't quite work for you, you could look at the TLV320AIC3007, orAIC3107. These devices also have Class D amplifiers built in, but have more inputs, the class D amplifier is a close match at 8 ohms, but these do not go down to 4 ohm as the AIC3100 does.

    best regards,
    -Steve Wilson
  • 0
    Prodigy 70 points

    KDSG151108Q-IP8.pdfKDSG1511006Q-09P.PDFHi Steve,

    I’m a little bit lost… May I ask you to review schematic in attachment and check if it’s ok. Also any comment is welcome.

    Such as you will see, an external headphone is foreseen and internally we have a speaker + microphone. Can you review the schematic.. I have more than one question mark.

    I add also two datasheets. Can you advise which one does better suite according your chip?

    Regards

  • 0 in reply to MBa
    TI__Mastermind 30220 points
    Hi Michel,

    Is this in regards to microphone switching on the AIC3100? if not please start a new thread.

    best regards,
    -Steve
  • 0
    Prodigy 70 points


    I steve,

    Yes it is..

    Something’s get wrong with the uploads.. I send these back

    Please see the pdf

    Schema_to_review.pdf

    and the two datasheets

    KDSG151108Q-IP8.pdf

    KDSG1511006Q-09P.pdf

    Regards








    Schema_to_review.pdf1464.KDSG1511006Q-09P.PDF7433.KDSG151108Q-IP8.pdf5657.Schema_to_review.pdf

  • 0 in reply to MBa
    TI__Mastermind 30220 points

    I'm not sure why you don't want to use the on board headset detect. You can detect when headphones with a microphone are inserted, and you can turn off the internal mic and turn on the external mic.  Why bother with the extra chip?   

    best regards, 

    -Steve

  • 0
    Prodigy 70 points
    Hi Steve,
    I will summarise goal we want to achieve.
    If no headset is present we want to use internal speaker and microphone.
    If a headset is detected we will use it. Also we need to be able to support TRS (combined with internal microphone) and TRRS (in both configurations).
    I don’t know how to do this. Reason why I asked you to review the schematic. I’m quite sure a better solution exists. If so, please tell me (by mean of a full schematic) and I will implement it as such.
    Regards
  • 0 in reply to MBa
    TI__Mastermind 30220 points

    Did you look at the application report I attached above?  I've attached it again for reference.  This application report contains schematics for implementing capacitor coupled headphone/headset support. 

    In your solution,  how does the TLV320AIC3100 know to turn off the internal mic?  or the internal speaker. 

    The headset detect, shown in the application report,  has separate detection for stereo headphones, and headsets.  that way if headphones are connected, you can leave the internal mic on.  or if a headset is connected, the internal mic can be shut off.  

  • 0 in reply to Steve-Wilson
    Prodigy 70 points
    Hi Steve
    Yes I did and it was not clear for me… Ok I will do it back... I will send you another schematic to review… Unfortunately we are taking the long way… A correction of provided schematic had let to close the ticket… I have the feeling we are turning around…
    About your question regarding the internal mic, I’m asking support to check such issues… So please provide advice…
    Regards
  • 0 in reply to MBa
    TI__Mastermind 30220 points

    If you are using Capacitor coupled headphones,  this is the setup.  Internally to the AIC3100 there are registers that have the headphone detect status. to avoid constant polling,  you can set the GPIO pin to be an interrupt to the CPU,  the interupt would trigger when a change of state was taking place.  

    So if your device was using an internal microphone on MIC1LP, and a external headset jack with an external mic connected to Mic1RP was inserted,   there would be an interrupt,  the CPU would poll the headphone detect registers, determine which kind of external headphone/headset was detected,  in this case we have a pair of stereo headphones with a microphone. So the CPU would turn off MIC1LP,  and turn on MIC1RP.  it would also make sense to turn off the internal speaker and turn on the headphone amplifier. 

    is this making sense?

    -Steve

  • 0 in reply to Steve-Wilson
    Prodigy 70 points

    Hi Steve,

    Thanks for info and support. Please find in attachment schematic such has it has been implemented (I hope I took in account all yours remarks)

    It should be able to

    • Detect the headset insertion

    • Support internal and external (meaning ‘headset’), speaker and microphone

    • Support of TRS and both TRRS configs

    Regards

    Michel

     

    052-120020.pdf

  • 0 in reply to MBa
    TI__Mastermind 30220 points
    Michel,

    It looks good to me, this will allow you to test both the internal headphone/headset detect, and the external.

    Because you are using the capacitively coupled headphone outs, it will not be able to tell if the headphones are mono or stereo. so keep that in mind. The headphones have Short circuit detect, but if i recall correctly it only tells you there is a short on the headphones, it doesn't tell you left or right. you could place 16 ohm resistors in series with the headphone outputs, and this would make sure that even when the output was shorted to gnd at the jack, that the headphone amplifier would not enter into protect. Or you could set the protect mode to limit the current.

    This is only really an issue if you anticipate a mono headset being used.

    best regards,
    -Steve Wilson