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

From: Muniswara Reddy Vorugu <Muniswarareddy.Vorugu_at_.....>
Date: Mon Aug 18 2008 - 20:58:11 PDT
Hi Chetana, 

Slide-20 of the presentation in the link can help you, in correcting
IV-VT mismatch.

http://www.eda.org/ibis/summits/jan02/bell1.pdf

 

This presentation discusses some more common errors and warnings.

 

Thanks,

Muniswar

 

________________________________

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of
Chetana Raghuwanshi
Sent: Monday, August 18, 2008 7:21 PM
To: Sudarshan H N
Cc: ibis@eda.org; ibis-users@eda.org; owner-ibis-users@eda.org
Subject: Re: [IBIS-Users] Re: [IBIS] Different PMOS and NMOS driver
impedence

 

Hi Sudarshan,

You are right. My concern is IV VT mismatch error.
How would it disappear by increasing the simulation time ?

Best Regards
Chetana

--------------------------------------------------------
Chetana Raghuwanshi
CTO / Process & Library Technology
NXP Semiconductors India
NXP Block C, 4th Floor
MFAR Manyata Tech Park
Nagavara, Bangalore-560045
Tel : +91 80 4024 7072
--------------------------------------------------------
 "Sudarshan H N" <hn.sudarshan@gmail.com>



"Sudarshan H N" <hn.sudarshan@gmail.com> 
Sent by: 

owner-ibis-users@server.eda.org 

2008-08-18 06:43 PM

 

To

 
"Chetana Raghuwanshi" <chetana.raghuwanshi@nxp.com>



cc


ibis-users@server.eda.org, ibis@server.eda.org



Subject


[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 <mailto: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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Received on Mon Aug 18 20:59:21 2008

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