Re: [SI-LIST] : Transient impedance

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From: sweir (weirsp@a.crl.com)
Date: Tue Nov 16 1999 - 21:20:27 PST


Sandy,

Thanks. I guess we will look forward to Feb. with great anticipation.

Regards,

Steve.
At 03:01 PM 11/16/99 -0800, you wrote:
> > Can you point to any existing papers on linearized output impedance, and
> > any ASIC mfgs currently offering this? Thanks.
> >
> > Regards,
> >
> > Steve.
>
>Two references that touch on it are:
>Gunning, "A CMOS Low Voltage Swing Transmission Line Transceiver". ISSCC 92
>and
>Horel & Lauterbach, "UltraSPARC-III: Designing third generation 64-bit
>Performance" IEEE Micro May/Jun 99
>I do not know of any asic support for this.
>
>Bob Perlman wrote:
> > A nice pedestal right in the transition region that lasts
> > perhaps as long as the risetime/falltime? Yecch!
>
>The situation you described would lead to a short pedestal with a duration
>about equal to the non overlap time of the drivers.
>
>The problem I saw was when you have multiple drivers on a bus
>running with fast turnaround times. You must control all spurious reflections.
>If there is energy coming into the driver from the transmission line you
>do not want to reflect it, this will degrade your noise margin.
>The more the driver looks like a fixed impedance
>connected to a time dependent voltage source the quicker you will
>be able to damp out reflections on the bus.
>
>Charles Hill gave a good example of this.
>"Maintaining (a constant) source impedance therefore a high return loss"
>is exactly the right thing to do. Sai will show a great method for
>implementing this
>in February.
>
>Sandy Taylor
>CMOS Solutions
>
>
>
>
>
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