It is a fact that real-silicon drivers of these signals r injecting common-mode propagation, therefore, the GND stitching becomes a critical & integral part for the modes of propagation along w the diff-modes of propagation. Hany Fahmy Intelligent Solutions BVBA hanymhfahmy@xxxxxxxxxxxxxxxxxxx http://www.intelligentsolutionsbvba.com/ http://www.linkedin.com/pub/hany-fahmy/66/852/b11 Phone: +32471650724 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Istvan Nagy Sent: Saturday, September 6, 2014 10:52 PM To: leeritchey@xxxxxxxxxxxxx; lee.home.61@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: One stitching via or more vias is better for 25Gbps application??? Lee, Did you do simulations both with/without stitching vias? Also try the simulation on a diffpair that previously (before arriving to the via) got some skew/imbalance. I don't know but suspect that the skewed diffpair will get more mode transformation if the return paths are not good. To be tested with simulation. It was a lot of work for us to set the signal via to gnd via distance to minimize reflections. Now with no gnd via, the signalvia to gnd via distance depends on the surrounding elements in the pcb layout. How about via impedance and reflections? Without the stitching vias, the signal via impedance will be as much as "who knows". Regards, Istvan Nagy -----Original Message----- From: Lee Sent: Saturday, September 06, 2014 12:17 PM To: lee.home.61@xxxxxxxxx ; si-list@xxxxxxxxxxxxx Cc: lee.home.61@xxxxxxxxx Subject: [SI-LIST] Re: One stitching via or more vias is better for 25Gbps application??? No stitching vias are needed. Where did this idea get started? -----Original Message----- From: Leeyuyun Sent: Saturday, September 06, 2014 4:25 AM To: si-list@xxxxxxxxxxxxx Cc: lee.home.61@xxxxxxxxx Subject: [SI-LIST] One stitching via or more vias is better for 25Gbps application??? Hi, all I am doing 100Gbps (4x25Gps) product now How do we put stitching vias when high speed signal change the layer? This is a differential pair, which has P and N Someone told me that one stitching vias is better because P and N share the common return Someone told me that more stitching vias is better because loop inductance could be reduced more I am confused which one is better? Can anyone help me? Thanks, Lee------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2014.0.4765 / Virus Database: 4015/8162 - Release Date: 09/05/14 ------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu