[gta02-core] PMU schematics

Werner Almesberger werner at openmoko.org
Thu Jun 18 23:33:40 CEST 2009

?lvaro Lopes wrote:
> PMU schematic is progressing well, it's about 70% complete I'd say.

Wow, that's great !

> But some problems. We seem to miss some symbols, like the power button
> (is it same as aux button?),


> battery connector. Maybe others.

I see that you found that one already :-)

> And sheet is quite small. I tried to make things as compact as possible,
> but without compromising readability. Still it is very hard to place
> everything in there.

My goal with using A4 was to make sure the schematics aren't
difficult to print or read, with the assumption that most people
who print them will use A4 or letter paper. This is based on the
experience with Openmoko's schematics that were always difficult
to handle.

I gave the PMU schematics a try and I'm confident I'll have no
trouble with the A4 version even well beyond reaching retirement
age :) I found the PMU zoomed from A3 to A4 still very readable.
The Openmoko PMU is about borderline readable in A4.

Looking at the schematics on the screen (1680x1050), A4 is
excellent, A3 is borderline (the aliasing effects show), and
Openmoko's is unreadable without 125-150% zoom.

So I'm fine with going to A3.

> So please take a look and give me your feedback.

Looks very good. The spacing is adequate to set things apart
properly and to give room for labeling. Three problems:

- we have an inconsistency with some of the font sizes. E.g.,
  the inductor uses 50 mil text and the test point even only 40
  mil, where 60 mil are used for resistors and the like.

- all the VAA power nodes are still considered to be the same,
  despite having different labels.

  I can see that this may actually be useful in some strange
  situations, so I wouldn't consider it a bug, rather a
  dangerous feature.

  Seems that we'll need a separate symbol for each power net.

- ERC will gleefully point out that SYS1 and SYS2 are in
  conflict with each other, both being Power Out. Duh. I've
  asked for advice on kicad-users.

For component references, I would suggest the following scheme:

- use Openmoko's numbers, so that we can use a single name to
  refer to the component

- if we remove a component, we should try not to reuse the

- if we add a new component, it gets a new unique reference

Then there are a few small simplifications we can make. But
let's talk about them when you're done with the PMU.

- Werner

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