Michael, There are no capacitors that work at 3.125 Gb/S for decoupling. The way to provide this path is by placing the planes close to each other. I use 3 mils all of the time for this purpose. Works greast! Lee Ritchey Speeding Edge > [Original Message] > From: Michael Rose <mrose@xxxxxxxxxxxx> > To: SI-List <si-list@xxxxxxxxxxxxx> > Date: 9/15/2008 10:01:17 AM > Subject: [SI-LIST] plane-to-plane decoupling > > I looking for some suggestions regarding decoupling between co-planar > plane splits. I'm working on a backplane with a number of 3.125Gbps diff > pairs. I've specified a dual stripline stackup assigned as follows: > > 1 - P > 2 - G > 3 - S > 4 - S > 5 - P > 6 - G > and so on > > Some diff pairs on L4 will cross power plane splits (actual different > power sources and loads) and I wanted to provide an effective AC path > for any common-mode return currents. I was thinking about placing some > nearby decoupling caps from plane-to-plane across the split. Do you > think it would be better to decouple from plane-to-ground on both sides > to steer the current through the L6 ground layer? L5 and L6 are already > coupled through the inter-plane capacitance (they're about 4mils apart). > Which will provide a lower inductance path? > > Mike > ------------------------------------------------------------------ > 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: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //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 > ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //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