RE: [SI-LIST] : RF & Digital

[email protected]
Wed, 11 Aug 1999 16:29:57 -0400

yes indeed, and avoid all those problems introduced by breaks or moats or
islands , etc...
Tho' there are them that will invoke the current spreading argument...

Bill Owsley, EMC Engineer
EMC Design - Do It First... Do It Last... But It must be Done...

"THOMPSON, Martin" <[email protected]> on 08/11/99 12:22:00 PM

Please respond to [email protected]

To: "'[email protected]%internet'" <[email protected]>
cc:
Subject: RE: [SI-LIST] : RF & Digital

Would routing carefully not steer the ground.power currents as effectively?

Martin Thompson.
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-----Original Message-----
From: Mark Sauerwald [SMTP:[email protected]]
Sent: Wednesday, August 11, 1999 4:25 PM
To: si-list
Subject: Re: [SI-LIST] : RF & Digital

Lum

In addition to the stack up changes that have been mentioned, I would cut
isolation rings in the ground and power planes to separate the RF and Digital
sections of the board. Noise induced in the ground plane in one part of the
circuit can capacitively couple into components in the RF section if you are
not careful. By cutting a slot in the plane, you can steer ground and power
currents around the more sensitive portions of your circuit. Another thing
that will help isolate the digital signals from the RF is to use small-swing
differential logic levels, such as LVDS, rather than fast CMOS wherever
possible.

Mark Sauerwald
National Semiconductor

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