I use to add the guard ring around clock signals until I attended a seminar
given by Lee Ritchey
who is very knowledgeable in this area. According to Lee, the only thing the
guard ring really does
is prevent you from routing to close to the clock line. You can remove it
just as long as you maintain
the same spacing as if the guard ring was still there . I have been doing it
here for some time now
and we have not seen any difference in the performance of our circuits.

Hope this helps.

John Bauer
IDEO Product Development



-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of Pat
Paulson
Sent: Friday, May 15, 1998 5:53 AM
To: [log in to unmask]
Subject: [DC] Clock lines...


First I want to say thanks for all the replies about BGA routing. I finally
decided against all pin escapes at the part. This makes life much easier.

Next question is concerning special considerations for clock signals and
EMI.  Some of the Engineers want a ground trace surrounding the clock lines
and others say it would be better to just leave the space around the clock
line that the guard band would normally take up. The clock speeds are 40
Mhz and below using 6/6 on the inners and 8/8 on the outers. One of the 2
clock routing layers is next to the ground plane and the other layer is
next to the power plane.

All info is greatly appreciated!

Pat Paulson
VTEL Corporation
[log in to unmask]

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