TPA6132A2EVM2: POP noise and current noise

Hi Marc,

What event triggers the pop noise? Also what do you mean by current noise?

Thank you,
Jeff McPherson

Hi Jeff,

A popping noise may occur when turning on an LED. This can cause interference in the speaker path. 

Would you have the suggest how to reduce the pop noise?

Thanks,

Jamie

Hi Jamie,

Is the device operating OK if you remove this additional LED control circuitry? This is essentially shorting the output of the amplifier to VDD, which in turn will change the charge/discharge sequence of the AC coupling capacitor at the output this will most likely cause pop noise.

Best regards,
-Ivan Salazar
Applicaitons Engineer

Hi Ivan,

Yes, removing the LED control circuit works fine. We have tried to add a capacitor to the output, although there is no more noise, there is still pop sound and signal quality drops.
Is there any suggestion for this requirement?

Thanks,
Kuntin

Hi Kuntin,

I'll check if any ideas come to keep the LED functionality, but please keep in mind that this is not an issue with TPA6132A2 and it's not something TI has to resolve.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

I understand, thank you for your help. Also, could you please help explain the reason for the distortion caused by adding DC at the output through a diagram? 

Thanks,
Kuntin

Hi Kuntin,

I don't really know what kind of distortion is this, do you have any waveforms we can check? Perhaps this is an oscillation due to the R and C in the circuit?

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

Some test results for your reference.

Thanks,
Kuntin

test_result.pdf

Hi Kuntin,

Thanks for the detailed information, did option on page 3 suffice the requirements?

Best regards,
-Ivan Salazar
Applications Engineer

No, the options on page 3 do not meet the requirements. The reason is that while it functions normally before loading the DC, after loading the DC, it exhibits the abnormal behavior described on page 4.

Hi Kuntin,

I understand, pages 1 and 3 show the performance before each implementation and then 2 and 4 show after each case.
The purpose of the LED is to sync the brightness with the audio content? Perhaps you have to take the signal into a high input impedance buffer and then apply the DC.

Best regards,
-Ivan Salazar
Applications Engineer