A follow up to my question below. Has anyone created simulations that show the change ins signal ball performance as a function of the distance from signal ball to the return path ball on the package? If so, how did you create your models? Thanks again, Steve Waldstein swldstn@xxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of swldstn@xxxxxxxxxxxx Sent: Wednesday, October 22, 2003 9:14 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] SI impact on BGA Ball placement and pwr/gnd ratios To all, I am looking for any rules of thumb other component designers are using for placing your external BGA balls for signals along with power and ground. In general we were using the rules that a signals must be no farther than 2 away from a VSS if the signals are < 100MHz and neighboring a VSS if they are faster 100MHz or faster. I'm not sure how to increasing the frequency up to 400 - 533 MHz should be handled. I should also note I am concerned with single ended interfaces like DDR-1 and DDR-II, PCI, AGP, Processor front side buses, GMII, etc. For differential signals we have different constraints. We have not been too concerned with VCC ball placement but currently I am thinking VCC balls ( which are not always the same number as VSS balls) should be next to a VSS to reduce noise coupling to signals. My thinking is that this will allow a place for mutual inductance to terminate that is not a signal. Is this a valid assumption? Any rules people have and are willing to share would be appreciated. Steve Waldstein swldstn@xxxxxxxxxxxx ------------------------------------------------------------------ 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