[SI-LIST] Re: AW: diff-pair via impedance
- From: "Lambert Simonovich" <bertsimonovich@xxxxxxxxxx>
- To: <Gert.Havermann@xxxxxxxxxxx>, <Dennis.Sipe@xxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 10 Jun 2014 09:59:04 -0400
Dennis,
I have a blog post on modeling differential via impedance that has the
equations you might find useful. It considers the effect of the antipad. At
the end of the post is a link to my web site for the white paper which has
more detail.
http://blog.lamsimenterprises.com/2011/03/14/the-poor-mans-pcb-via-modeling-
methodology/
BR/
-Bert
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Havermann, Gert
Sent: June-10-14 9:38 AM
To: Dennis.Sipe@xxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] AW: diff-pair via impedance
Try the twinax, or twisted Pair, or balanced pair cabling impedance formula
http://www.fccps.cz/download/adv/frr/RS485/RS485.html
But this can only be used as a very basic starting point for calculation. In
PCB, the return path within a via can dramatically change its performance,
thus I highly recommend to do 3D Simulations.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Sipe, Dennis (ES)
Gesendet: Dienstag, 10. Juni 2014 15:26
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] diff-pair via impedance
Hello all.
The equation for impedance calculation of a single via is the one for coax
cable.
I cannot find one for a diff-pair via; two vias within an oval anti-pad.
I could use HFSS to do the calculations, but a simple equation should fall
out from that.
Can anyone point to a reference? Google was not my friend today.
Thanks,
Dennis
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