Roger Morella wrote:
>I recently had a discussion with an engineer friend regarding the best way
>to implement a TOP LAYER ground plane on a 2 layer board.
>


Roger,

There have been many past discussions about this on piclist, and
you might do a search in the archives to get some of those opinions.
Go here, and scroll to the search window on the bottom of the page:

http://www.infosite.com/~jkeyzer/piclist/
================


>As far as I can see, there are only 2 general ways to do it.
>1. Connect all ground pins directly to the ground plane, thereby reducing
>overall ground impedance.
>2. Use ground seperate traces for ground connections and connect the ground
>plane to the ground at one point (typically the main filter cap). thereby
>reducing potential ground interference.
>

I find these statements confusing, as they indicate there was no
consideration of analog vs digital gnd plane separation in your
talks with your engineer friend. ??????????????? [confusion]

I think most people believe that having gnd planes is better than
not having them, and that you want to keep analog and digital gnds
totally separate [both physically and electrically], except for a
1-pt connection.

During the most previous discussion of this, 1 - 2 months ago, there
was some question about whether the 1-pt connection should be made at
the power injection point, or under the A/D converter. I don't think
this was resolved very well.

best regards,
- dan michaels
www.oricomtech.com
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