XS3868 / OVC3860 5sec idle noise. Help needed

[ESXi]

Hi,

I don't want to copy paste my problem.
http://www.diyaudio.com/forums/car-audio/310717-xs3868-ver-3-0-bluetooth-stereo-audio-noise-5-idle.html

This is the issue I have.
Here is a video of it :
https://youtu.be/9YBVj6Cl-cE

Here is the diagram (shown in the video on the prototype board)

I have tried to hook it up to another amp, same problem. I tried headphones and those work without the buzzing sound after 5 seconds! I don't understand why.. Soms people say it's a fault on the board (gnd and audio gnd being the same. I don't know. I used the diagram provided by the DS).

[danadak]

This is a longshot but datasheet does not show specifically a
system ground connection between car 12V chassis and the
bluetooth batteries common. So try it without a common
ground......Although chip does have a Li battery charging
capability, but in your schematic does not appear to be
connected.

Datasheet very poor on unterminated connections, like VPOW,
and a lot of others. Maybe their website has a FAQ section or
forum where you can post.


Regards, Dana.

[ESXi]

Hi Dana,

Thanks for your response. I have my OVC3860 powered by common and vbat pin. It is powered for testing now by USB 5 volt to a LM2596S buck convertor or DC DC step down set to 3.8volt.

With headphones (without amp) I never hear this noise. After 5 seconds when using headphones nothing can be heard in the headphones after 5 seconds idle. Not even a tiny little RF noise (which is normal). So I tried another small amp instead of the car amp I used in the video. And the result was the same.

Best regards,
ESXi

[ESXi]

It was a design fault.. 

I fixed the problem by adding a 4.7uF cap to pin 20 of the OVC3860 (VMID) to I believe pin 16 A0M (audio ground).

If I change 4.7uf to 100uf almost all of the HF crosstalk is filtered out but at the cost of the audio quality.. The pcb design still has some flaws. It has been improved over ver.2.0 but still.. Add a small wire to the antenna this will lower the noise as well. So far I'm happy now. For this price can't really complain, but the developer could improve software button debounce a bit. The board needed some tweaks but hey, it works and was only 2 dollars!