[IBIS-Users] Re: [IBIS] Different PMOS and NMOS driver impedence

Hello Chetana,

You can use any of the 2 values for Rfixture to generate Vt curves. There is
no rule that , your Rfixture should match to the PMOS or NMOS driver
resistance. But you should always use one value to generate the one set of
rising and falling waveforms(experts, correct me if i am wrong). If you are
seeing any errors with respect to IV and Vt curve mismatch , just simulate
for more time so that it will reach the saturation.

Regards
Sudarshan

On Mon, Aug 18, 2008 at 6:37 PM, Chetana Raghuwanshi <
chetana.raghuwanshi@nxp.com> wrote:

> Hello Experts,
>
> One of my IO cell has a buffer with different PMOS and NMOS impedences.
> PMOS impedence is approx 200 Ohms and that for NMOS is 96 Ohms.
> In this case what should be the value of Rfixture for calculating IV VT
> curves ?
> Would it be Rfixture1 for calculating pull down and falling waveforms and
> Rfixture2 for calculating pull up and rising waveforms ?
> If I do rise/pullup and fall/pulldown simulations with different Rfixture
> values, is it acceptable ?
>
> Best Regards
> Chetana
>
>
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