Electronics > Microcontrollers

PCB design question (crystal end ATmega)

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tiger80:
Hello everyone  :)
Ok so I have finished laying out a board. I have an ATMega128A running with a 14,7456MHz crystal. The board has two layers and I have chosen the top layer and bottom layer as the ground plane (GND).
Following design guidelines, I have kept the trace length between the crystal and the AVR minimal. Take a look at the layout and suggest any improvements if you can and also be sure to point out the faults.
Sorry for my bad English  ;)

PCB.Wiz:
I'm not sure a HC-49S-SMD is the cheapest/smallest anymore in 2024.
Of course, if you have shiploads in stock, use them up  8)

pcprogrammer:
You can clean it up by putting the two capacitors on the same y location and ground them on opposite sides. Then the trace from the crystal won't pass underneath the capacitor and takes less space. I also don't think you need to block out the ground plane underneath the crystal.

Another issue with SMD and a top ground plane might be with reflow based soldering where the heat dissipation for the pads of a component differs. Tombstone effect may happen. Not a problem when hand soldering.

tiger80:
I will solder the PCB by hand.
I changed the crystal and the arrangement of the capacitors.
Can capacitors C5 and C8 be arranged this way?
Where to place the ground grommets at the bottom?

pcprogrammer:
Looks better, but why the blocking of the ground plane? I don't think it will add to much capacitance with the crystal traces fully surrounded by the ground.

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