[SI-LIST] analog and digital partitioning
- From: Gene Glick <gglick@xxxxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 21 Jun 2010 11:20:04 -0400
hi all,
I am struggling with some partitioning decisions, maybe you can help.
This card has an analog section (audio), digital (uP running around 200
MHz, SDRAM, etc.), mixed (ADC, DAC). For the most part, the analog and
digital sections are completely separate. The mixed signal devices
straddle the partition. Some digital signals pass over the boundary,
but are psuedo-static control lines. One clock signal (1 MHz) also
crosses the boundary.
Creating a single-point connection between analog area and digital area
is very unlikely given the topology. I wanted to moat around the analog
sections, but effectively will wind up with slots in the ground plane.
So the question is, how bad is it to have slots in the ground plane? Are
slots acceptable if no return currents or eddies flow around them?
Somehow, I don't believe it possible to be 100% certain of this.
An alternative, is to have one solid ground plane, keeping the signals
routed such that no return currents flow where they should not. But I
am concerned with keeping the audio noise floor at a very low level.
thanks
gene
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