Re: gEDA-user: pcb, howto partition power planes?

[Larry Doolittle <ldoolitt@xxxxxxxxxxxxxxx>]

DJ -

On Tue, Oct 28, 2008 at 12:49:51PM -0700, Larry Doolittle wrote:
> Your board looks decent.  What kind of voltage resolution are you
> looking for (e.g., what IC are Uxx0)?

I see now, ADE7753ARSZ, $3.834 in 25's at DigiKey.  16-bit Sigma-Delta
under the hood.  Good luck with that.

> The first thing that leaps
> out at me is the large loop for power supply filtering on those
> chips (both AGND to AVdd, and DGND to DVdd).  Oh, and do you really
> want REF filtered to digital ground?

No, you don't.

> If you have noise troubles with that layout, I can offer suggestions
> to improve it.  Hint: it will involve more closely approximating a
> real ground plane over the whole board.

I guess your layout will need at least one more rev before you
can get to the noise limit of that chip.  OTOH, maybe that isn't
the goal.

I do really like the idea behind that board!  I have a Kill-A-Watt
at home.  It's really handy, but a real multi-channel power datalogger
would be even better.  I thought about building one myself many years
ago, but never got the traditional Round Tuit.  Don't let my snarky
comments about grounds keep you from building yours.

   - Larry


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