Istvan, I think your comments apply to serdes signals routed as stripline traces that are referenced to both a power plane and a ground plane. If the traces are routed referencing only ground planes and these ground planes also serve as power return, I think the serdes signals will be unaffected. Do you agree? Thanks, Vinu istvan novak wrote: > Hi Joe, > > There are the following generic guidelines that come to my mind, not > knowing the > details of the system: > - if the 60A power rail serves also as reference for SerDes lines, it > has to be quited sufficiently > for that purpose, which means that you need to design that rail as a > high-speed power rail. > This is especially true if you also need to carry reference clock or > sensitive low-level analog > signals around the backplane. > - if you have switching regulators connected to this rail (most probably > you have), either > feeding this rail with raw power or taking this voltage to generate > local sypply voltages, > you want to check very carefully for high-frequency ringing generated by > the converters. > Today the ringing can be anywhere in the 50-500MHz frequency range; if > they spread > freely on the power rail, it will reduce your SerDes margin. > Unfortunately the ringing > is not limited by converter specifications (in other words there is no > spec item for the > potential high-frequency ringing). > - as others pointed out, you dont need to worry about saturation of > copper, unless you > have local features increasing the current density too much. Make sure > you use the > largest area that you can afford and many vias for connecting the > high-current inputs > and outputs. > > Regards, > > Istvan Novak > SUN Microsystems > > Joe Paul M wrote: > > >> I have a midplane carrying 60Amps of current and Same GND plane is used >> as reference for multiple of 6.6 Ghz serdes lines , PCI-e lines and GE lines >> Is there anything similar to 'saturation' in Inductors applicable to GND >> plane? >> ( Due to saturation of flux in the flux carrying medium , beyond a >> certain amount of DC current inductors saturate and wont act as >> inductors for any AC superimposed on the DC. ) >> Will cross talk increase due to the absence of mutual inductance between >> signals and gnd plane ? >> Is there anything else that can go wrong due to this DC , AC current >> mixing in planes ?? >> >> >> >> >> >> >> >> >> >> > > ------------------------------------------------------------------ > 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