I want to use Filled Zone and Keepout Area to create a VCC donut, with another voltage zone inside the hole.
I usually start with a top fill for VCC and a bottom ground plane. I added a keepout zone to create the Hole for the Donut. Because it’s a Keepout Zone, I can’t put another Filled Zone in there.
In one application, I want to make a +12V zone inside a +5V zone. These are rails from an ATX power connector.
In another application, I need to isolate an analog AVCC zone, inside the top fill which is a digital VCC zone. (connected through a ferrite bead). The AVCC zone is for audio or video DACs. The video DACs have pixel clock up to 60MHz.
Is there a way to make a complex polygon Filled Zone, without using a Keepout Area?
The ideas I have so far are:
Forget the +12V filled zone from the ATX power connector, and just use fat +12V traces. The +12V rails are primarily for fans or lamps, so I thought I should keep them away from any 3V3 or 5V digital traces. There is a picture below.
Move the +12V or AVCC zones to the edge of the board, so I can draw simple polygons for each voltage zone.
So, is there is a general solution to the “Filled Donut Hole” problem?
Alternately, if you have an opinion, is a donut hole overkill here? I am one of those digital guys trying to get up to speed on the analog side.
I would appreciate any advice. (And now I’m thinking of going to Krispy Kreme.)