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