From: Alan Pearce <kiwiantipodean@googlemail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Sun, 13 Sep 2020 04:50:11 -0700
Subject: Re: [EE] Four Layer Routing Strategy
Thread-Topic: [EE] Four Layer Routing Strategy
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> Ok, sounds like keeping the inner layers as ground and 3.3V separately
> will be the best. No problems there.

That is the 'normal' way to do it. And using manhattan routing gives
you a good starting point. Once you have the board routed you can look
to see where the routing can be tweaked to minimise vias.

> One thing about planes though, I once read an article about being
> careful using planes, that essentially small ground loops could form
> in them.

Opinion on this has gone back and forth like a leaf in the wind, but
one of the most authoritative texts I have seen was an appnote or
article from ADI which advocated having one complete ground plane with
minimal distinction between digital and analogue ground. It doesn't
mean you could mix the digital and analogue parts willy nilly, some
care is still needed with relative parts placement.

On Sun, 13 Sep 2020 at 02:57, Josh Koffman <joshybear@gmail.com> wrote:
>
> Thank you all for the advice!
>
> Ok, sounds like keeping the inner layers as ground and 3.3V separately
> will be the best. No problems there.
>
> One thing about planes though, I once read an article about being
> careful using planes, that essentially small ground loops could form
> in them. Since then I've always had my planes as a separate net (ie
> not ground), and I connected them to the ground traces strategically.
> Each area of pour had only one connection to ground.
>
> Should I be using the pours a bit more liberally and letting them join
> all the pins on that actual net? That's easily done (actually easier
> than the way I have been doing it). I'd add thermals in to try to help
> make it easier to solder.
>
> The board service I've been using lately doesn't allow for
> blind/buried vias without a hefty upcharge. I am definitely not at
> that level, that's for sure!
>
> Thank you!
>
> Josh
> --
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