[SI-LIST] Re: Serpentine patterns for length matching

Hello, Jim,

I tried a simple test case (10 parallel traces serpentined together, older
5V I/O), with a trace center-to-center spacing/width of 4.  Even at a slow
edge rate, there was about a 10% change in flight time caused by crosstalk.
Simulation experiments showed that the change increases as the edge rate
increases.

If your edge rates are fast (and aren't they all these days), you might want
to have your layout simulated.

Lynne


"IBIS training when you need it, where you need it."

Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@xxxxxxxxxxxxxx


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of otter30@xxxxxxxxxxxxx
Sent: Thursday, October 23, 2008 8:22 AM
To: SI-List
Subject: [SI-LIST] Serpentine patterns for length matching

Hello,
Does anyone know of general guidelines for the serpentine patterns used to
match net lengths?

We have a board with lots of diff pairs, and our board designer made the
serpentines very tight. The separation between the adjacent bends of a pair
is the same as the spacing of the traces in the pairs themselves. This seems
to imply imedance variations if the trace widths don't change in the bends.

Any insights would be greatly appreciated, Jim  


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