Subject: Re: [IBIS-Users] IBIS Info.
From: Rickey Kingen (u1018@email.sps.mot.com)
Date: Thu Mar 14 2002 - 08:16:10 PST
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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