Subject: Re: [IBIS-Users] IBIS problem
From: Kevin Fisher (kfisher@sisoft.com)
Date: Sun Sep 15 2002 - 07:28:57 PDT
Akhilesh,
For each VT curve entry in a model, the IBIS parser will take the
fixture circuit used for that VT curve and draw a load line representing
the circuit against the IV curves of the same process corner. The DC
endpoints found, which in your example were 2.30V and 3.30V, are
determined as the intersection of the load line with the pullup (+ power
clamp if I/O) and pulldown (+gnd clamp if I/O) IV curves. There are few
possible causes for this descrepency, however in my experience, the most
common reason was that the VT curves never reach the DC values. Either
the VT curves simulation was not run long enough, or the extraction of
the VT curves did not get the whole curve. I would first check the VT
curves and see if it looks like they've reached DC.
Hope this helps.
Kevin
--Kevin M. Fisher Consultant Signal Integrity Software Inc. 6 Clock Tower Place, Suite 250 Maynard, MA 01754 Phone: (978) 461-0449, ext 11 http://www.sisoft.com
akhilesh.chandra@st.com wrote:
>Hello, > I got one problem in my during ibischk > >ERROR - Model BD2TARDQP_TC_40: The [Rising Waveform] > with [R_fixture]=50 Ohms and [V_fixture]=3.3V > has TYP column DC endpoints of 2.44V and 3.30v, but > an equivalent load applied to the model's I-V tables yields > different voltages ( 2.30V and 3.30V) > > My cell's Rising Waveform have 2.44V & 3.30V dc end ponit but I am >unable to find out how IBISCHK got 2.30V & 3.30V DC end point. > > Can anyone tell me please how IBISCHK got DC endpoint. > >Regards >Akhilesh >|------------------------------------------------------------------ >|For help or to subscribe/unsubscribe, email majordomo@eda.org >|with just the appropriate command message(s) in the body: >| >| help >| subscribe ibis <optional e-mail address, if different> >| subscribe ibis-users <optional e-mail address, if different> >| unsubscribe ibis <optional e-mail address, if different> >| unsubscribe ibis-users <optional e-mail address, if different> >| >|or email a written request to ibis-request@eda.org. >| >|IBIS reflector archives exist under: >| >| http://www.eda.org/pub/ibis/email_archive/ Recent >| http://www.eda.org/pub/ibis/users_archive/ Recent >| http://www.eda.org/pub/ibis/email/ E-mail since 1993 > >
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