[SI-LIST] Re: Can I get this from an IBIS model?

Don't forget to count in the clamp tables (and the IV tables of
the [Submodel] sections).

More and more of the new high speed buffers have on-die
terminations, which usually are described in the one or the
other clamp tables.

Arpad Muranyi
Intel Corporation
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

-----Original Message-----
From: Dunbar, Tony [mailto:tony_dunbar@xxxxxxxxxxx]
Sent: Sunday, September 29, 2002 4:02 PM
To: 'SI-List'
Subject: [SI-LIST] Re: Can I get this from an IBIS model?



Doug,

The [Pullup] and [Pulldown] tables are, effectively, impedance tables, =
since
they are constructed as instantaneous voltage-current points. For a =
brief
period of time at the start of a transition from one state to the other,
both the pullup and pulldown tables are contributing to the overall =
current
at the IBIS model pin. However, if this is ignored the impedance of the
buffer while driving the line to the high state can be determined from =
the
pullup table and the impedance to drive the line to the low state can be
determined from the pulldown table. Through the transition, the
instantaneous impdedance will, most likely, be found to be not constant, =
as
you might expect.

Regards,
Tony

-----Original Message-----
From: Doug Brooks [mailto:doug@xxxxxxxxxx]
Sent: Saturday, September 28, 2002 12:06 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Can I get this from an IBIS model?



Suppose I have an IBIS model, but not the physical part. Is there a way =
I=20
can determine the output impedance of the device (and if different, the=20
output impedance for each digital state) from the IBIS model itself?

I know I can build a simulation and solve for the output impedance that=20
way, but can I get it from the IBIS model itself without going through =
the=20
simulation step? . And if so, where in a model do I look?

Thanks for any help.

Doug Brooks

_________________________________________________________________________=
___
___
UltraCAD Design announces availability of its new book "Signal Integrity =

Issues in PCB Design"
Details at  www.ultracad.com


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