RE: [SI-LIST] : Physcially-small far-end LVDS terminations?

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From: Tom Dagostino (tom_dagostino@mentorg.com)
Date: Fri Dec 17 1999 - 10:57:15 PST


How are you terminating the lines then?

Tom Dagostino

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Jim Freeman
Sent: Thursday, December 16, 1999 1:33 PM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Physcially-small far-end LVDS terminations?

Hi Eric,
    Another answer would be to ensure that the differential impedance of the
board between the differential pairs is 100 ohms. Then you wouldn't need the
resistors. I have performed Hspice sims on this and it works fine if the
stackup/trace spacing is correct.

Jim Freeman

Eric Goodill wrote:

> Hi,
>
> I want to use the typical LVDS termination where you have two 50-ohm
resistors in series placed between the two lines of the LVDS diff. pair and
also have a cap at the junction of the resistors to ground. I have a
jillion LVDS pairs to terminate at a high-pin-count ASIC, and I'm looking to
squeeze more terminations per square inch. (There's no hope of putting the
terminations inside the ASIC at this point.) I'm hoping some company makes
a single three-pin part the has those two resistors and a cap even if not
specifically for termination use.
>
> How about any other ideas for even higher density?
>
> Regards, Eric
> --
> Eric Goodill
> Siara Systems, ericg@siara.com
>
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