[SI-LIST] : differential pairs

Joachim Mueller ([email protected])
Wed, 17 Sep 1997 15:43:43 -0400 (EDT)

Hi,
I would like to get some opinions on how to layout differential pairs for
high speed (1 Gbit/s) data signals. I am not quite sure if it is preferable
to use broad side or edge side coupled differential pairs?

For data signals at that speed loss effects needs to be considered too. What
is a minimum trace width to avoid significant skin effect losses?

edge side coupled: broad side coupled:

----------------------- -------------------------

--- --- ---

---------------------- ---

-------------------------

Advantages for the broad side coupled pairs:
============================================

Transmission line delay deviations between both lines can be controlled better
with a broad side coupled pair.

I assume that the broad side coupled pair is also a better field guide because
the field lines are more straight and better contained between the conductive
bodies as it is the case for the edge side coupled pair.

Advantages for the edge side coupled pairs:
===========================================

The differential impedance of the edge side coupled pair can be designed
independend from the characteristic impedance of the cross section.

The distance between two traces might can be controlled more accurate than
the thickness of the core material?

All comments are appreciated

Joachim

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