Steve, Do you mean by PP preperg? If so, that would infer what is often called broadside coupling or one over the top of the other. If that is what you mean by this, it's about the worst way there is to route a diff pair and I would never want to do that. It is really a tough one to get right. Lee W. Ritchey Speeding Edge P. O. Box 2194 Glen Ellen, CA 95442 Phone- 707-568-3983 FAX- 707-568-3504 I just used the energy it took to be angry to write some blues. Count Basie > [Original Message] > From: steve weir <weirsi@xxxxxxxxxx> > To: <leeritchey@xxxxxxxxxxxxx>; Ravindra Johari <Ravindra.Johari@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Date: 12/22/2005 6:38:13 PM > Subject: Re: [SI-LIST] Re: XAUI > > Lee, I agree that loosely coupled usually brings fewer issues to deal with > than tightly coupled, making it a safer default recommendation. For > loosely coupled, I would avoid broadside coupling including tandems, > particularly across PP. If B/S coupled across PP, the registration, and > therefore coupling can vary quite a bit, especially for narrow traces. If > the PP is thin, it just makes it worse. > > Steve. > At 02:17 PM 12/22/2005 -0800, Lee Ritchey wrote: > >Actually, neither. Coupling doesn't have any benefit. If you can spread > >the traces out so there is no coupling, you've got the best geometry. Real > >world, you can't do this and route a PCB, so route side by side with as > >much separation as your topology will allow. Then adjust trace widths to > >give you 100 ohm diff impedance. > > > >Lee W. Ritchey > >Speeding Edge > >P. O. Box 2194 > >Glen Ellen, CA 95442 > >Phone- 707-568-3983 > >FAX- 707-568-3504 > > > >I just used the energy it took to be angry to write some blues. > >Count Basie > > > > > > > [Original Message] > > > From: Ravindra Johari <Ravindra.Johari@xxxxxxxxxxxxxxxxxx> > > > To: <si-list@xxxxxxxxxxxxx> > > > Date: 12/22/2005 11:19:44 AM > > > Subject: [SI-LIST] XAUI > > > > > > > > > Hello Gurus!! > > > > > > > > > > > > Which is a better coupling for running a differential pair at XAUI Speeds > > > i.e at 3 Gbps.. > > > > > > > > > > > > Is it Edge coupled stripline or Broadside coupled stripline.. > > > > > > What kind of constraints can I face with these? > > > > > > > > > > > > Thanks! > > > > > > Ravi > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------ > > > 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 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: > > > //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 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: > > //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 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: //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