RE: [SI-LIST] : RE: 100 ohm differential Vs 150 ohm

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From: Ronald E. Nikel (renikel@tricn.com)
Date: Thu Jan 25 2001 - 10:40:23 PST


Doug,

I actually have alot of experience with this question. The basic reason I
have used 150 ohm differential in the past is that cabled interconnect that
meets this impedance profile has much lower loss. This allows the user to
transmitt at higher frequencies across longer distances before loss kills
the signal. There was alot of good work done in this area by Gore and
Amphenol in support of the HIPPI-6400 project (ANSI T-11). For more
traditional PCB environments it is very difficult to acheive 150 ohm
differential and still have thin boards that are highly routable, thus 100
ohm differential is much prefered in PC board environments and as it turns
out the loss difference between 100 and 150 in PCB materials is not really
different.

So you should look at your application and its interconnect environment and
cost target before deciding one over the other.

Ron.

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Doug Hopperstad
Sent: Thursday, January 25, 2001 10:14 AM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : RE: 100 ohm differential Vs 150 ohm

Can someone give me some feedback on using 100 Vs 150 differentials? Is
there a reason that one would choose the 100 over the 150 in a design.

Doug Hopperstad
Qlogic

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