cheap/chinese LPSU's - minefield?

[marce]

WIth digital power delivery systems there is a lot more than just the main power supply, though that is important, what is more important is the care laying out the circuitry with the local decoupling, point of load power. Get that wrong and no front end is going to help, you will get increased noise, especially simultaneous switching noise and more ground bounce.

Here is a PDF from a course on PDS, SIV and EMC that I did in Germany a few years ago. It will hopefully give you and others a bit more understanding of the noise mechanisms at play and issues on solving them as well as how to design a PDS. Its got pictures which I always fine easier than words to get to grips with all this stuff, picturing the wave fields round signals shows how interaction happens, magnetic its just basic Maxwell. Sorry it is a bit software orientated but it does have relevant info. Did a week of this in a heatwave in Munich!!! Staying awake was an issue in the afternoon after a large lunch and wine! The cafeteria had beer and wine on offer as well as amazing food.

02_PIA_Architecture.pdf

[marce]

I posted it because we often talk about noise, so its nice to see how its created and how it couples. High speed digital not so bad, all the microwave stuff that;s appearing is a different ball game all together, for the high end stuff your looking at 2mm+ wall thickness for shielding...

As things get faster the noise margin decreases, the positive from this is motherboards have to have a better PDS and less noise just to operate, unlike the old clunky PC;s of yesteryear that could tolerate crappy SMPS's.