[gta02-core] ECN0024 (GPS ground and layout)
alvieboy at alvie.com
Wed Oct 7 10:18:49 CEST 2009
Werner Almesberger wrote:
> I'm scratching my head at ECN0024 :) Alvaro, is there any part of
> it that's already covered by the schematics or is it all really
> just a reminder for things to do in the layout ?
That was mostly a reminder, but we should discuss that a bit more.
The GPS chip has two grounds, digital and RF. GTA02 does not distinguish between one and other, nor in schematics nor in layout.
Digital ground is very noisy. Also we need to avoid ground current to flow near the RF part. One idea is to have a separate ground for the RF part, and connect
it to digital ground at one point, forming some sort of ground peninsula, thus avoiding digital current flow to interfere with RF. We should also have these
ground planes (RF) filled with through-hole vias, to avoid EMI emission (and maybe mitigate interferences).
> Also in the latter case, it would be good to mention the key
> points of what should be changed/observed.
> - Werner
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