Electronics > Beginners
Creating controller for LED display, help / review needed
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Lt_Flash:
You can have a look at my project here:

https://workspace.circuitmaker.com/Projects/Details/LtFlash/Sandwich-Battery-Charger

There is a release documentation down below so you can see schematic and PCB but here's an example of bypass caps ties directly to ground plane on one side and to power polygon on another, capacitors C3, C4, C5, C6 and C7.

And pretty much any device on this PCB that requires ground connection is directly attached to the top ground plane, which is very useful, you don't need to think about best ground trace layouts and connection is rock-solid.
muktupavels:

--- Quote from: Lt_Flash on May 03, 2018, 06:54:10 pm ---In your case you can just put traces up and down from the cap, not sideways, as you did.

--- End quote ---

Not sure if I understood this part... :( Anyway, I tried to redo power traces. Should I try to keep traces on top or it is better to route at least some power traces on bottom side?

Also your linked images shows something very similar how I have placed capacitors so I don't get what is wrong with them. :( Or was it because of power traces?
Lt_Flash:
The power looks very good now. In regards to bypass caps - I meant it has to be like C15 on your PCB, with a single shortest possible track to power and to ground and as close as possible to MCU pins. C7 and C17, for example, are not optimal because their ground traces are bent. With C7 - why did you put that trace sideways anyway? There's plenty of space to put it directly below the cap! That's why I posted this picture, for example:


--- End quote ---


Also, if you'd have a GND plane on top layer - you wouldn't need vias to the back of your board. For bypass caps one of the links I showed before says 'Preferably there should be no vias for bypass caps and they should be located on the same side of the board where IC is'. Of course, on these low frequencies it would work anyway, but you've asked about good design. As to my opinion - GND planes on both sides are good, they're shielding your board, providing easy connections - you don't need vias or traces, they act as heatsinks and so on. The less vias you have - the better, ideal design would use just a single side of your board.
Lt_Flash:
Also, you can replace all the power traces past voltage regulator with a big power polygon. Any CAD would just make cutouts in that polygon for traces and you just need to rearrange them so they don't break the polygon, or make the polygon not square, but with many points. Again - that's better because it won't act as an antenna picking up EMIs and impedance would be much lower. And on top of that polygon just draw a square one covering the whole top side of the board for GND. That would actually simplify your design even more. But, of course, that's up to you :) Just my opinion.
muktupavels:

--- Quote from: Lt_Flash on May 05, 2018, 08:38:59 pm ---Also, if you'd have a GND plane on top layer - you wouldn't need vias to the back of your board. For bypass caps one of the links I showed before says 'Preferably there should be no vias for bypass caps and they should be located on the same side of the board where IC is'.

--- End quote ---

Ok, removed vias and put also gnd plane on top layer. Is that really better? Now GND plane under atxmega chip is almost completely separated from remaining gnd plane on top... Also I think I read that traces should first connect to capacitor and then to pins, but now gnd first connects to pins and only then to capacitor (C7, C16).
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