[SI-LIST] : re: Split Plane

About this list Date view Thread view Subject view Author view

From: Barry Ma (barry_ma@altavista.com)
Date: Fri May 19 2000 - 17:26:58 PDT


Brad,

Here is my two cents worth:
Did you consider exchanging 7 and 8 for more capacitance between 5V and gnd planes? Suppose you have 10 mil or less plane spacing. I understand that you want to use a gnd plane as return plane for signals on layer 9. But itís OK to use 3.3V plane as return plane. The plane cap would work well to let return signals go from 3.3V plane back to gnd pins on layer 9.

Itís also OK using part of 5V plane as additional 3V area. Youíd better stitch up the gap.

Regards,
Barry Ma
bma@ANRITSU.com
-------------
From: "Brad Crowell" <crowell@amirix.com>, on 5/19/00 2:04 PM:

I have been lurking in the shadows of the SI list for some time now, but
have come across a situation that I could use some advice on:

I am working on a board design that is using the following stackup:

1 - SIGNAL
2 - GROUND
3 - SIGNAL
4 - SIGNAL
5 - GROUND
6 - 5V PLANE
7 - 3.3V PLANE
8 - GROUND
9 - SIGNAL
10- SIGNAL
11- GROUND
12- SIGNAL

My problem is that we are running out of routing resources. Thus,
it has been suggested that a few traces could be routed on layer 6,
the 5v plane. The intent would be to route some traces for the 3.3v
devices which are located away from the 5v devices on the board. This
would reduce the effect of any splits in the plane. Also, since there
is a ground plane available as a reference for every signal layer,
a split in a supply plane shouldn't have much effect, if any. I am
inclined to think, with my limited SI experience, that this should
be ok, but would appreciate comments from some of the experts.

Thanks,
Brad
***************************************
Brad Crowell
Hardware Designer
AMIRIX Systems
***************************************

_______________________________________________________________________

Why pay when you don't have to? Get AltaVista Free Internet Access now!
http://jump.altavista.com/freeaccess4.go

_______________________________________________________________________

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Wed Nov 22 2000 - 10:50:25 PST