RE: [IBIS-Users] Slew Rate Controlled I/O pad modeling

Every Model that I have seen where someone places a reactive load on the
driver as part of the model making process has created more problems than
they hoped to solve. Let the simulators correct for the load, make the
model with the standard 50 Ohm load.

Tom Dagostino
Teraspeed Consulting Group LLC
Device Modeling Division
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com <mailto:tom@teraspeed.com>

Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
http://www.teraspeed.com

-----Original Message-----
From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org]On Behalf Of John Phillippe
Sent: Tuesday, March 16, 2004 11:50 AM
To: ibis-users@server.eda.org
Subject: [IBIS-Users] Slew Rate Controlled I/O pad modeling

I've been trying to produce a half-way respectable IBIS model of a
slew-rate controlled output buffer. Attached is one of my models.
Basically I want to generate a buffer model that can be used to drive a
50pF load accurately in an IBIS simulator. My theory was that if I used
a 50pF test load for the V/T curve modeling, then the resulting IBIS
model would work at that specific load. Well after I simulated the IBIS
buffer driving a 50ohm, 1ns transmission line in series with a 50pF cap,
things still don't match. The rise-time of my ibis model is about twice
as fast as the rise time of my spice model. Is this as close as I can
get, or am I missing something? I tried increasing the rload from 50 to
100ohm then 200ohm, but that didn't help, and at 200ohms things got
worse. Any suggestions?

--
John Phillippe
SPS, 32 Bit Embedded Controller Division, IC Creation
Motorola      -  512-895-1835
Austin, TX    -  john.phillippe@motorola.com
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