[SI-LIST] Re: Questions on GND Ref Plane and Diff pair coupling
- From: Ravinder.Ajmani@xxxxxxxxxxxxxx
- To: shemshak <shemshak1@xxxxxxxxx>
- Date: Tue, 18 Mar 2008 13:17:39 -0700
Hi Shemshak,
The coupling between the two lines is much smaller than the coupling each
line has with the adjacent plane. Hence any discontinuity in the return
plane will affect signal propagation. Absence of a ground plane will also
result in higher crosstalk.
If you are not short on routing space then loosely coupled traces are
better than the tightly coupled. In such a configuration you need not
route traces next to each other, and it is easier to maintain equal length
around vias etc.
Regards, Ravinder
Server PCB Development
Hitachi Global Storage Technologies
Email: Ravinder.Ajmani@xxxxxxxxxxxxxx
shemshak <shemshak1@xxxxxxxxx>
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[SI-LIST] Questions on GND Ref Plane and Diff pair coupling
Hi all,
I have two questions which I really appreciate your feedback on them.
1) If we have differentail pairs which they can reference to each other
(one signal and the other as the return path), then do still need to have
GND plane adjacent to these signals for the return path? I think the
answer is yes, we need GND plane, but why?
2) When do we use loosly coupled vs tightly coupled differential pairs?
When would be better to use one over the other.
thanks,
Shemshak
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