IMHO If a single series resistor is used, it MUST be as close as possible to the driver. After all, it is it plus the output impedance of the driver that terminates the line. Otherwise, there will be an impedance mismatch between in the line between the resistor and the driver. Then the branch MUST be very close to the receiver(s). Otherwise, there will be an impedance mismatch at the branch point that will reflect everywhere and won't be handled well by the series termination. In particular, if the branch is very close to the driver, then the reflection back from one branch will see the properly terminated driver in parallel with the other branch and proper termination of the first branch cannot result. Doug Brooks At 03:11 PM 4/12/2002 +0000, kevinlfitzgerald wrote: >Hi, > >I have a clock signal with a 1ns rise time which is distributed to 2 >parts. The 50 Ohm lines are matched length within +/-50 thou after >the branch. Our concern lies with the source termination. Should the >source termination be before the branch, or immediately after the >branch ? > >Any thoughts, > >Thanks, > >Kevin > > _____________________________________________________________________ UltraCAD Design, Inc. Celebrating 10 years of design excellence! www.ultracad.com ------------------------------------------------------------------ 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