PCB grounding with mixed signals chips, talks about crosstalk.

3 posts in this topic

Just share documentation i found on this point.

Mixed signals:
- TUT5450.pdf
- june2001pcd_mixedsignal.pdf

Crosstalk explained;
- lccalc.pdf


AOUT_NG groug separation;


The famous 'Berlin Wall' on the SammichFM :D





Any other experience... Good or bad design, please 'cross'talk about it? :thumbsup:

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That first tutorial PDF was actually really helpful!


I've designed one set of mixed-signal boards, that for my ASIDITY project, to hold two SIDs (which are mixed-signal chips, of course) and a custom digitally-controlled feedback circuit. I was not able to determine whether there was significant noise getting from the digital signals to the analog side, because I always had my computer hooked up to the synth via USB, which connected the ground to that of my computer. My computer has a very noisy switching power supply, so the noise from that overpowered any noise from the SIDFB boards.


Speaking of my computer, my new computer has some sort of severe crosstalk issue: any sound coming out of any audio output jack, whether sharing a ground or not (e.g. headphones), is corrupted by an incredible amount of noise, as loud as the audio it's playing. It sounds like a data bus to the hard drive! So I've had to hook up my computer to my mixer via SPDIF/TOSlink optical and then have a converter to analog powered by a linear power supply that only shares a ground with the mixer. The ground is completely decoupled from that of the computer. Still working on how to record audio into the computer, currently working on a USB isolator that would allow data to flow between the computer and a cheap USB audio interface while keeping their grounds separated.

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