[SI-LIST] Re: Common-mode return path for differential signals.

When routing 100-ohm differential nets is there advantage to keeping the =
two nets closely coupled other than for crosstalk issues? For current =
designs the space between the two nets is set for 1.5 times the width of =
the net. For a 8mil trace, the gap is 12mils (20mil pitch). If the =
differential pair needs to become uncoupled, the trace geometry is =
adjusted to maintain the proper impedance. Length matching maintained =
for the route to reduce unwanted common-mode currents due to length =
skew. All routing is done on balanced, striplines using ground reference =
planes only.=20

Some of the information I have read recently states to keep the =
differential pair tightly coupled while others state that there is no =
major advantage other than crosstalk. With the 12mil gap design, the =
nets are loosely coupled (8mil dielectric thickness) and has shown good =
results.=20

Any comments or feedback would be great,
Thanks,
Doug.
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: