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On a 4 layer stackup with signals routed on top/bottom; 2nd layer VCC powerplane; 3rd layer GND powerplane.

How should the VCC powerplane be layed out? Should it be surrounded with a few mm of GND pour like a moat(GND) surrounding an island(VCC)? I would like to stitch gnd vias all around the board so it seems the VCC layer may need some gnd aorund the edges.

Thanks, I am an amateur at layout and trying to do best emi/rf practices. Note; the board has a GSM module on it but most digital signals do not exceed 2Mhz. There are some analog audio signals and I going to trying to keep that gnd isolated.

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  • \$\begingroup\$ My quick advice would be don't bother isolating the ground planes if you're a first timer. Concentrate on proper part placement and routing. \$\endgroup\$ – scld Feb 20 '15 at 20:45
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Don't worry about trying to make the power plane fit your ground plane. That is: don't try to fashion the moat / island combination that you are talking about.

Your CAD package will allow clearance in the power plane when you place your vias. You can do a complete stitch of ground-plane vias all around the perimeter of the board and the Vdd plane will have clearance holes in the power plane from those vias. You specify how much clearance you provide in the design rules for your board.

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