FW: [SI-LIST] : RE: IBIS model question

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From: L· (John@quantatw.com)
Date: Tue Jan 16 2001 - 23:43:30 PST


Scott,
Is it necessary to be 50 ohms?
Shall rfixture be the same as the resistor in test load, used for generating
AC timing spec?

Best Regards,

John Lin
Senior SI Engineer, Server Team, ARD4
Quanta Computer Inc.,Taiwan, R.O.C.
Email: John@quantatw.com
Tel: 886+3+3979000 ext. 5183

-----Original Message-----
From: Scott McMorrow [mailto:scott@vasthorizons.com]
Sent: Wednesday, January 17, 2001 2:36 PM
To: Doug Hopperstad
Cc: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : RE: IBIS model question

Doug,

The model is incorrectly extracted. The rfixture should have
been 50 ohms.

scott

Doug Hopperstad wrote:

> I have a question regarding the IBIS model format. Within the model there
> R_Fixture. I understand that the R_fixture was used to create the rise and
> fall time charts. My question is the value of the resistor. Is there a
> relationship of the resistor to a load resistor that would be used in the
> lab? The information below came from a SSTL-2 output model.
>
> Vref = 1.250V
> Rref = 0.125k
> Cref = 10pF
> Vmeas = 1.250V
>
> [Rising Waveform]
> R_fixture = 0.125k
> V_fixture = 1.250
> V_fixture_min = 1.250
> V_fixture_max = 1.250
>
> R_load = 0.125k
>
> How come the resistor value does not reflect a more typical 50 ohm
> application?
>
> Doug Hopperstad
>
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--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

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