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Dead bug is not dead - yet

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PekkaNF:
Little tweaks, had problem with ringing. Turned out to be insufficient decoupling and the IC GND-pin had weak ground.

I asked help from one forum and got a link to this excelent paper
https://www.murata.com/~/media/webrenewal/support/library/catalog/products/emc/emifil/c39e.ashx
Unfortunately it gets pretty advanced after a easy start.

This is where I start: Power Supply Noise Reduction - An introduction into the basics of power supply noise reduction using supply bypassing and decoupling.
http://designers-guide.org/Design/bypassing.pdf

I had some serious ringing on the output, I could see the effect on the board IC supply pins. Tried adding more bypass capacitors and the result would change, but not improve. Changed the PSU from 5V SMPSU to linear supply and it did nothing, but I could estimate how pow hungry the circuit was.

After some more measurement I finally figured that the decoupling was a problem. Needed thigter routing for power wires (specially the IC GND pin had a large swing) and some more decoupling. Maybe if it were build with SMD:s and had a proper decoupling capacitor near IC, there were not problem at all.

It is funny how much stuff I studied (formally and hobby) is coming back, some of that looks familiar and much is new to me.

Pekka

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