Crosstalk can dramatically affect the impedance of a trace.=20 Under certain conditions the impedance will INCREASE and under other conditions the impedance will DECREASE from the desired value. I'd be interested in the cross section details.=20 Best Regards Charles Grasso Senior Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Pager/Short Message: 3032042974@xxxxxxxx Email: charles.grasso@xxxxxxxxxxxx; Email Alternate: chasgrasso@xxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of aminotg@xxxxxxx Sent: Tuesday, January 17, 2006 8:13 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Series termination greater than the characteristic impedance? Hi All, I was wondering if there is ever a case where a series termination should be higher than the characteristic impedance of a trace?=20 We had an SI analisys performed on our DDR2 interface and the conclusion was to change the series terminations of our data bus to 60ohms. The characteristic impedance of the traces on our board is 50ohms.=20 I always thought that a series termination was added to match the driver to the characteristic impedance of the trace, now I am confused, because the analysis on our board doesn't agree with this thinking. Kindest Regards, Gilles =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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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