[SI-LIST] : RE: PCI crosstalk on Dual stripline

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From: Doug Hopperstad ([email protected])
Date: Tue Nov 21 2000 - 11:29:26 PST


Here is a question that should generate a lot of opinions: When routing PCI
devices, what rules or guidelines are used for parallel and tandem crosstalk
for the given stackup: (The board material is set for FR408 with a
dielectric constant of 3.8)

Dual stripline:
----------------------- Ground Plane (0.5 ounce)
 ------ ------- 5 mil trace layer (0.5 ounce)
 ------ ------- 5 mil trace layer (0.5 ounce)
---------------------- Ground Plane (0.5 ounce)

* The Plane-to-Layer spacing is 8 mils
* The Layer-to-Layer spacing is 10 mils
* The trace width is set for 5 mils (which will provide a 70 ohm trace
impedance)
* The trace-to-trace spacing is set for 5 mils (10 mil pitch)

The traces are routed orthogonal for the most part. The major problem is
that the routing out of the ASIC is hindering the orthogonal routing and
making the tandem crosstalk a big concern.

Doug Hopperstad
QLogic Corporation
[email protected]

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