[SI-LIST] Re: power plane spacing

  • From: Ritchey Lee <leeritchey@xxxxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Wed, 11 Jul 2001 14:50:18 -0700

The small spacing has nothing to do with EMI.  It has to do with creating a
large value, high performance capacitor to supply switching currents.

Lee

DORIN OPREA 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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