This is one of the big pitfalls of partial inductance models: they're only valid if hooked up properly in SPICE (since they rely on SPICE to make sure that all the loops are closed). It's really easy to have a node 0 sneak in where it's not expected. You're lucky if it fails to converge in that case; it could easily converge and give you a bogus answer. The fact that the partial inductance models isolate large portions of your circuit from node 0 makes convergence much more difficult for SPICE, it seems, even when used properly. Ever since I've given up partial inductance models in favor of loop inductance models, I've been much happier. :-) --=20 Michael Tsuk Compaq AlphaServer Platform Group (508) 467-4621 -----Original Message----- From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx] Sent: Wednesday, September 26, 2001 2:31 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Convergence problems with Hspice Good point Scott. I remember a case many years ago ( before I understood the folly in such endeavors) where I created a huge=20 PEEC model of a power plane (with tens of thousands of mutually=20 coupled inductors) where I just couldn't get the simulation to converge. Found a single node (out of thousands and thousands) in the model subcircuit that was shorted to ground. Turns out that the error message emitted by Hspice (version 95 or 96 I think) were worse than useless in that they were misleading. -Ray >One more possibility: > >Sometimes convergence problems will occur when >Ansoft package models do not have the correct connections >made to power and ground. > >Be sure that power and ground pass through the model >and have different names on the die side of the model. >Many people mistakenly (or inadvertently) tie both the >die side and the pin side of the model to ground. This can >cause all sorts of convergence problems due to the shorted >loop. > > >regards, > >scott ------------------------------------------------------------------ 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: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: =20 http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ 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: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://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