Access to PoE power w/ 802.3af adaptor board?

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Re: Access to PoE power w/ 802.3af adaptor board?

Post by Ohmware » Mon Feb 13, 2012 7:55 pm

Ah, got it! I like how this style of layout leaves relatively little copper to be removed. Does it have any advantages or disadvantages as far as circuit characteristics? I have read that in multilayer designs it's best practice to avoid routing any signals in a ground plane. And I have also read that you never want to have any areas of copper left "unconnected". So does Eagle insure the latter, or do you have to anticipate how the copper pours will fill areas when you're laying out the board?

I am thinking of trying to design a PoE adaptor around the TPS23756, which I was able to get samples of from TI.

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Re: Access to PoE power w/ 802.3af adaptor board?

Post by jonoxer » Mon Feb 13, 2012 11:33 pm

For a board like a regulator it's a good idea to have as much copper as possible connected to thermal ground, so having the polygon pour into all the available space is great.

You can tell Eagle whether you want it to pour copper into unconnected areas as well (called "orphans") by changing a setting on the polygon itself. If you use the "info" tool (or right-click the border of the polygon and select "properties") you'll see a dialog with options for the polygon. Down past half way is a checkbox called "orphans".

I tend to leave orphans turned on, but that's probably just a habit from years ago etching my own boards when the objective was to remove as little copper as possible so the chemicals would last longer.

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