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'[OT]: Ground Plane Debate'
2001\06\19@105339 by Roger Morella

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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.

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.

And of course, a third approach is to use some combination of the 2.

The questions we have are:
1. What is peferable for high speed (> 10MHz in this case) digital
circuitry? Any difference for lower speeds ( 4MHz and below)
2. What is preferable for analog circuitry?
3. What are the pros and cons of each?

Roger

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2001\06\19@113019 by Dan Michaels

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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
http://www.oricomtech.com
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