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TS3A226AE: Switch not working after splitting headset grounds
Part Number: TS3A226AE
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.
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In reply to Helen Sun:
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):
In reply to Ortal Koren:
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 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 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.
We connected the jack through ferrite beads to a b2b connector which is connected to our board:
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.
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