[SI-LIST] : PCB impedance variation v.s. layout pattern

Allen Wang (Allen_Wang@asus.com.tw)
Fri, 27 Aug 1999 10:17:20 -0700

Dear all:

We are designing a Rambus related product which requires the PCB to
maintain
28 Ohm +/- 10% trace impedance.
However, what we have found that a straight line trace will get a higher
impedance (through TDR, 1 Ohm or more) than
a trace with many turns on it. We know a turn on the trace will change
the
impedance. However, is it the root cause
that make our trace impedance not consistent?

Two traces are on the same layer, with the same trace width.


+---------------------------------------------------------------------------
------------------------------------+
Straight line

+-----------+ +------+ +---- \\\\ -----+
+------------------------+
| | | | | |
| | | | | |
+-----+ +----+ +---+
line with turns

Allen

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****