This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • TI Thinks Resolved

TS3A226AE: Pressing on earphone buttons makes noises in the earphones

Prodigy 80 points

Replies: 9

Views: 468

Part Number: TS3A226AE

Hello

We are using TS3A226E in our design for detecting MIC and GND, and we supply the audio jack with bias voltage of 2V using a codec.

For some reason the press of buttons on the earphones is audible in the earphones (we hear clicks) and when we test with a scope we see that instead of the MIC line connecting to GND, we can see a square waveform (like CLK) as long as a button is pressed.

Also when we short the SLEEVE and RING2 inputs of the TS3A226E  we also see the square wave.

Is that a normal response? Is it possible to use TS3A226E with earphones that have buttons? We know it does not have press detection, but we plan on doing the detection with a processor.

Thank you

Ortal

  • Hi Ortal,
    To better understand your issue, could you please help with the below:

    1) What is the click like? Please share the sqaure waveform scopeshot you mentioned that was captured during the click.

    2) What are the conditions when the click was heard( you mentioned pressing button and shorting SLEEVE/RING2?)

    3) What are the system conditions during the click ? Do you have a schematic?

    Thank you,
    Helen
  • In reply to Helen Sun:

    Hi, 

    The click sounds on the earphones, as I said, when we pressed any one of the buttons of the headset andwe we shorted the inputs SLEEVE and RING2.

    We can see it on a resistor we placed between MICP output pin and the BIAS pin of the codec, marked in a black arrow is where we measured:

    Here is the schematic of the TS3A226 and the sensing of the audio jack:

    Here is the scope measurement of the point marked with the black arrow (sorry for the poor quality):

    Thank you,

    Ortal

  • In reply to Ortal Koren:

    Hi Ortal,

    What is connected to your Ring2 and Sleeve pin? could you share the audio jack portion of schematics?( see below example)

    When the below transiant occured( in red below), did you press the button( short Sleeve and Ring2 together) and release it, or did you continue to hold the button?

    A possible theory is that since Sleeve and Ring 2 is shorted together, and the selection of S1 from control logic, FET1 may be off and FET2 may be on( or vise versa) and MIC may be shorted to ground. 

    Thank you,

    Helen

  • In reply to Helen Sun:

    Hi,

    Thank you for the quick response,

    We get the clicks and the transient response when we press and release. When we hold the button, we get the cyclic response I attached in the previous scope graph.

    The audio jack is connected through TVS diodes and beads and caps using as EMI filters:

    If your theory is correct, is it possible to use TS3A226 with a headset with buttons?

    Thank you

    Ortal

  • In reply to Ortal Koren:

    Hi Ortal,

    Thank you for your reply. I am actually wanting to find out what is the headset portion schematics/detection scheme look like, which is the below portion highlighted in red.

     

    Thank you,

    Helen

  • In reply to Helen Sun:

    Hi Helen,

    We connected the jack through ferrite beads to a b2b connector which is connected to our board:

    Thank you,

    Ortal

  • In reply to Ortal Koren:

    HI Ortal,

    Thanks for the reply. your headphone set should be configured as below with R1( Left speaker), R2( Right speaker) and R3( microphone). What are the value of R1,R2,R3?

    What seems to be happening is when you press the button the transient is within the range that you could hear the click. The frequency normal human ear can hear is 20~20k Hz and if the click is happening within this range then the noise could be heard. 

    Ways around this is to add in low pass filter circuit to filter out the click. Another method is to add a second switch to first press the button, let the click noise happen, then connect the headphone through the second switch. 

    Thank you,

    Helen

  • In reply to Helen Sun:

    Hi,

    Thanks for your response.

    The values of R1, R2 and R3 are 35 ohm, 35 ohm and 15K ohm respectively.

    I still don't understand the explanation you suggested.
    If it is supposed to be a transient response why is it repeating as long as the button is pressed, as can be seen in the scope images?
    Also, since only R3 is supposed to change during button press, why does the button press transient affect the Left Speaker and Right Speaker, if they are not supposedly affected by the press?

    Thank you,
    Ortal
  • In reply to Ortal Koren:

    Hi Ortal,
    I had sent you a private message on E2E, please check.
    Thank you!
    Helen

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.