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TLV320ADC3101-Q1: Understanding Microphone Input

Heffalump
Prodigy 45 points
Part Number: TLV320ADC3101-Q1

I am confused by "Fig. 11 Typical Connections" from the TLV320ADC301-Q1 datasheet.  Why are IN2R(P) and IN3R(M) connected to the same microphone?  Same question obviously for the IN2L(P) and IN3L(M).  I see that both IN2L and IN2R are both labeled (P)... so maybe this is just a naming convention thing that's throwing me as I am expecting IN2(M) and IN2(P) to be connected across the same microphone.

Does this configuration get you stereo audio on IN2 as the L(P) and R(P) are connected to signal side from the microphones?

If I don't need stereo audio and just want to read in audio from 2 microphones, could I connect the microphone "across" IN2L(P) and IN2R(P)?

As the INXX(M) terminal is effectively connected to ground in both cases, this is a configuration using single-ended microphones, right?  However, the datasheet says that this part can handle 6 single-ended microphones... so it feels like each INXX channel could be used as a single-ended input and a single-ended configuration must look different.

As is probably apparent from my questions - I am pretty new to bringing in Microphone audio - so I'd appreciate one more assist: Your typical wired headset microphone (CTIA style), I am assuming that it's single-ended; however, I realize I could be wrong here.  Can someone confirm?

Thank you,

Heffalump

  • +1
    TI__Mastermind 22950 points

    Hi Heffalump,

    I apologize for any confusion here. There is a lot of muxing going on that allows various inputs to be connected in certain configurations. I have attached the input mux and mix scheme below that was taken from the data sheet. This shows you what inputs can go where and which inputs can be configured as a differential pair. 

    If you don't need stereo audio, you can connect a single microphone to any of the 6 inputs. If using a single-ended microphone, there is also no need to ground any minus pin as I believe the internal structure of the device connects the minus pin of the internal amp to the common mode. I hope this helps!

    Regards,

    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Prodigy 45 points

    Hi Aaron,

    I appreciate your reply as it addressed my main question.  Could you also speak to "hidden" question at the bottom of my last post where I asked about whether CTIA-plug-style headset microphones tend to be single-ended and not differential.  I believe they must be single-ended as there wouldn't seem to be any 'negative' of the microphone signal - only mic+ and ground, right?

    As an example: think Apple wired earbuds which have the microphone built in-line with the right earbud wire.  That's got to be single-ended, right?

  • +1 in reply to Heffalump
    TI__Mastermind 22950 points

    Hi Heffalump,

    Ahh my apologies, I missed that question! 

    I have only ever seen Stereo CTIA 3.5mm jacks with the rings assigned to Right, Left, MIC, and GND with the Left/Right and MIC channels being only (+). 

    Regards,

    Aaron Estrada