Subject: RE: [IBIS-Users] IBIS Info.
From: Peters, Stephen (stephen.peters@intel.com)
Date: Thu Mar 14 2002 - 08:39:12 PST
Hi Rick:
That is one way of doing it. An easier method (easier in that you don't
have to edit the actual netlist) would be to:
a) set the output in the logical low then do the I-V sweep
b) tri-state the output then do another I-V sweep
c) subtract the two curves,
The result will be I-V data for the [Pulldown] table. Of course, this
assumes that the output is tri-stateable... but if it isn't, then seperate
clamp tables are not required in the first place.
Regards,
Stephen Peters
Intel Corp.
-----Original Message-----
From: Rickey Kingen [mailto:u1018@email.sps.mot.com]
Sent: Thursday, March 14, 2002 8:16 AM
To: Ingraham, Andrew
Cc: whiz kid; ibis-users@server.eda.org
Subject: Re: [IBIS-Users] IBIS Info.
Andy,
When you say the pulldown curve gives the I/V characteristics when the
output is in the low state, but with Clamps subtracted; do you mean that
the physical clamping circuit should be removed from the spice netlist
when performing the S2IBIS2 generation?
Rick
"Ingraham, Andrew" wrote:
>
> > Pullup/Pulldown curves: Does the Pullup VI curve give
> > the voltage and current charecteristics when the
> > buffer is in logic high state or does it give the VI
> > char. when transitioning to the logic high from a
> > logic low and vice versa with Pulldown.
>
> The Pulldown curve gives the I/V characteristics when the output is in the
low state, but with Clamps subtracted. Pulldown + Clamps = the total output
I/V characteristics while in the low state.
>
> Likewise for Pullup.
>
> When switching from one state to the other, the simulator has to figure
out how to transition from one I/V curve to the other; i.e., from 100%
Pulldown and 0% Pullup, to 0% Pulldown and 100% Pullup. Without V/T data,
the exact nature of that transition is a somewhat arbitrary guess, although
the speed of transition depends on the Ramp rate. With V/T data, the
simulator can adjust the exact transition in accordance with the V/T data.
>
> Regards,
> Andy
>
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