[SI-LIST] Re: power plane spacing
- From: "S. Weir" <weirsp@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 11 Jul 2001 11:52:32 -0700
Dorin, I assume that you are worried about the lateral spacing between the
split plane sections. I have never heard of anyone worrying about edge to
edge coupling between digital supplies. The plane to plane coupling of
each to the ground plane will swamp out the meager coupling along the
edges. So, excessive spacing like 50 mils doesn't seem to offer benefit,
unless you have a very sensitive plane section for say low-level analog.
Regards,
Steve.
At 02:23 PM 7/11/01 -0400, you wrote:
>Hi everyone,
>
>In high speed design we often use the split planes on a power layer. The
>spacing between the digital planes is correlated with the distance
>between the power layer to the ground layer. In general we have 50 mil
>spacing. It just happen to run into a different opinion which recommends
>a very small spacing due to the slot antenna effect (the gap between the
>planes) that allows the eddy currents to radiate. A small spacing may
>couple noise into the low power supply (1.5V or 1.8V).
>How critical is this radiation effect versus noise coupling between the
>two power distribution systems ?
>What is the practice out there ?
>
>Thanks very much for you guys always being there,
>Dorin
>
>
>
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