[sdiy] PCB layout tips

[Theo]

I often do this, IMO it simply makes for the easiest layout.
However having a ground plane under your ICs may help prevent noise
problems.
Sometimes e.g. with higher resolution DACs having the ground plane under the
IC is often mandatory.
With double sided layouts my usual way is to have a ground plane under the
ICs on the component layer and the power lines on the solder side.

As for a do and don't list:
- Use a "star" ground layout as much as possible
  (in practice more likely a mix between "star" and "not star")
- Do not mix digihell and Analogue, especially the grounds.
- Keep they traces short.
- Use a star ground layout.
- Don't run stuff in parallel that could influence each other.
   (extreme example; a digital clock parallel to microphone signal)
- From about 20Mhz and up keep digital traces that belong together the same
lenkt,
  even if this means you have to make a silly to and fro pattern with one.
- Did I already mention to use a "star" ground layout?
- Use ground planes.
- Don't make "loops", traces should NEVER come full circle
  (ok there _are_ exceptions, but few and are _exceptions_)

Theo



From: Scott Juskiw <scott at tellun.com>


> In AN-15 (Electronotes), BH suggests putting +ve and -ve supply lines
> in two parallel rows underneath the chips. This sounds like a good
> idea to me. Yet when I look at PCBs of various modules (from people
> on this list no less), I never see this in practice. Is there some
> reason why this is in fact a really bad thing to do?
>
> Is there a PCB layout "do's and don'ts" list available? Would anyone
> care to share any layout tips for a newbie?