TLV320AIC3100: ESD protection on headphones and microphone

Sebastian Ciesluk80

Part Number: TLV320AIC3100

Tool/software:

Hello I am planning on adding ESD protection as per schematic attached. The TVS diodes SP1103C Little fuse are 1uA leakage and 130pF capacitance. I wonder if such parasitics will affect my circuit ( especially microphone input/ detection, where data sheet states input capacitance of 2pF) Does it matter if I add additional 150pF and 1uA to GND?

Also am I right assuming that in the places where I am connecting the TVSes teh signals are symmetrical below above gnd?( In other words I need to use bidirectional TVSes not to clip signals 1V below gnd)

5 months ago

0 Jeff McPherson 5 months ago

TI__Mastermind 40015 points

Hi Sebastian,

This looks fine to me. The headset detection circuits rely on DC impedance so the diodes should not interfere with the detection.

Also yes bidirectional would be required since on the headset side, the signal will be centered at 0V.

Best regards,
Jeff McPherson

0 Sebastian Ciesluk80 5 months ago in reply to Jeff McPherson

Expert 1071 points

Thanks Jeff, this is very helpful and resolves my question

0 Sebastian Ciesluk80 5 months ago in reply to Sebastian Ciesluk80

Expert 1071 points

Can I tag two more questions on this?

I have just measured signals on teh audio interface and the MIC1RP (pin14) pin surprised me . on the audio jack side (HPOUT0) the signal has DC level of 1.7V what i sfully expected. However on the other side of C128 ( so input to the codec) it has DC level of 1.28V . It looks like there is an internal DC bias from the codec in there . Is this expectd ?

2) If the internal bias is expected ( I assume so) i believe there will be also no isse tagging steering protection diodes on the mic input as well as on the headphones output (codec side , also dc biased) the blue elements on the schematic?

Thanks

0 Jeff McPherson 5 months ago in reply to Sebastian Ciesluk80

TI__Mastermind 40015 points

Hi Sebastian,

An internal bias is expected. The caps just help decouple whatever bias is only the signal from contending with the bias that the device is generating to properly balance the audio input range.

Placing ESD diodes where you have them in blue should not be a problem.

Best regards,
Jeff McPherson

0 Sebastian Ciesluk80 5 months ago in reply to Jeff McPherson

Expert 1071 points

Thnaks Jeff, good to hear that , all is clear.

Thank you very much for your help

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TLV320AIC3100: ESD protection on headphones and microphone