RE: [SI-LIST] : Match of differential pairs

About this list Date view Thread view Subject view Author view

From: Moran, Brian P (brian.p.moran@intel.com)
Date: Wed May 10 2000 - 08:22:46 PDT


Martyn,

I don't have any data on matching lengths, but I thought I would mention the
option of broadside coupled differential pairs. If you define the stack and
trace widths correctly you can get much better characteristics and routing
density by routing differential signals an adjacent stripline layers as
opposed to side by side. In this way you can match lengths exactly and you
avoid layer to layer coupling where you don't want it. It sometimes
requires low dielectric laminate usless your going for low differential
impedance.

Brian P. Moran
Intel Corporation, FM6-45
1900 Praire City Road
Folsom, CA 95630
brian.p.moran@intel.com
(916) 356-1912

-----Original Message-----
From: Martyn Gaudion [mailto:Martyn@gaudionm.freeserve.co.uk]
Sent: Tuesday, May 09, 2000 3:47 PM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : Match of differential pairs

Hi everyone,

Can anyone help on the following subject? My customers
are in the PCB manufacturing industry and are increasingly
called to build differential striplines, however on fine line
boards it is very hard to make an exact match of the signal
pair.

This obviously has effects on cmrr, emc etc, but I cannot find
any documents that define how much mismatch is acceptable on
a differential pair.

National have a good app note on LVDS for example but when
matching is discussed it simply says good match is necessary.

This was easy on 7 or 8 mil line width, much less so at 3 to 4 mil.

Look forward to your input

Kind regards
Martyn Gaudion
martyn.gaudion@polar.co.uk
www.polarinst.com

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Wed Nov 22 2000 - 10:50:15 PST