Lee, The capacitor used for AC coupling on the signal path, should be able work just as good if it were placed on the return path as a decoupling capacitor for that signal. Each signal trace will of course need a dedicated capacitor to avoid additional crosstalk. Thanks, Vinu Lee Ritchey wrote: > 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 > > > > ------------------------------------------------------------------ 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