Hi: IO isolated from high speed region through ground moat is not a total solution. I mean layout control for IO signal and high speed signal is the key. Take care of high speed signal and make it's return loop as small as possible, such that IO signal/GND will capture less coupling from high speed signal. If you want implement GND moat on IO region, I think that 20 mils width is enough. Keep remember, GND moat isolation is not a catholicon! Jack W.C. Lin -----Original Message----- From: Johnston, Ross [mailto:RJ182000@xxxxxxxxxxxxxxxxxxxxxxxxx] Sent: Tuesday, August 06, 2002 10:58 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Ground plane split widths... Hi My design is basically a pc motherboard. I have isolated the I/O ground from the logic ground. Currently the ground plane split is 15 thou - I am contemplating increasing this width. Should the split be kept as small as possible? If so - why? If the ground split was too small, wouldn't noise be coupled across from each plane? What is the general consensus on this? CHEERS Ross Johnston Electronics Design Engineer, Core Electronics Group, Lifecycle GST, NCR FSG (Scotland) Ltd, Discovery Centre 2nd Floor West, 3 Fulton Road Dundee, Scotland DD2 4SW Tel: +44 (0)1382 592920 Direct Dial Fax: +44 (0)1382 591089 email: ross.johnston@xxxxxxxxxxxxxxxx ------------------------------------------------------------------ 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 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 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