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TLV320AIC3110: small noise when connecting earphone but not heard when connecting speaker

Part Number: TLV320AIC3110

Hi,

my customer is using this device as below:

They use only SPRM and SPRP for both speaker and earphone.

When earphone is not connected, pin3/6 and pin4/5 are connected to one speaker.

When earphone connected, speaker is unconnected and pin3/6 connect to GND through left earphone, pin4/5 connect to GND through right earphone.

Now we can hear small noise when the volume is adjusted to maximum when no audio source input to I2S and earphone connected.

But this noise is absent when using a speaker, which I think is cancelled since it's differential signal on speaker.

1. What's the risk of connecting earphone to speaker output of the device (SPRM, SPRP)?

2. Is it possible that we remove the noise through software? How can we achieve it?

Since I'm not familiar with audio device, please tell me if any more information is needed to solve the noise problem.

  • Howard, 

    Your earphone connections are not correct. 

    first there will be a DC offset on the outputs of the speaker outputs,  so connecting the earphones to gnd this way will cause a DC current through the earphones, which will damage them. 

    second, the Amplifier is not designed to be used in a Single ended mode.  I can check with the design team if there would be concerns with this,  but there still wouldn't be a way to remove the pop from the DC offset in this mode. 

    I suggest using the headphone outputs on the AIC3110 (HPL and HPL)  These are designed for headphones.  Why not use them? you could even use the headphone detect functionality and assign the GPIO which you currently are not using as an Interrupt to the host processor. The Headphone outputs have built in pop suppression. note that these outputs should have a coupling capacitor on them too. 

    further comments on your schematic. 

    The SPLP and SPLM outputs should be left floating if not used. 

    best regards,

    -Steve Wilson 

  • Steve,

    we measured the output of SPRP and SPRM with no audio source input to I2S and got the waveform below:

    there is only DC spike at a very short time when power up or power down the driver through register writing (and there is POP), most of the time there is no DC offset, is the waveform normal?

    Is it possible to DE-POP this POP through software?

  • Howard, 

    Turn off your AC coupling on the probes.  what you are seeing is the DC bias of the outputs turning on.  but because you have AC coupling on,  it appears as a spike.

    best regards,

    -Steve Wilson