Subject: Re: [IBIS-Users] Question about warning message
From: Fred Balistreri (fred@apsimtech.com)
Date: Mon Nov 18 2002 - 13:08:58 PST
The reason IBIS models go from -Vcc to 2Vcc is because that is what it
says in the spec. The following is a direct quote from the spec,
immediately
following the section that describes the testing voltage range:
"These voltage ranges must be spanned by the IBIS data. Data derived
from
lab measurements may not be able to span these ranges as such and so may
need to be extrapolated to cover the full range. This data must not be
left for the simulator to provide."
If we don't want people to follow the spec then I would argue that the
spec needs modification. More importantly because of the spec ibis tools
all
conform to the voltage testing as prescribed, included s2ibis which a
lot
of people use. So I don't think the statement about people blindly
following
the voltage requirement is true. It may be more of the case that
historically
this is what we have done, which can be traced back to where it all
started,
the specification itself.
Best Regards,
"Flora, Matthew" wrote:
>
> Hi All,
>
> The non-monotonic warnings are generated by the IBIS Golden Parser because it is
> not summing the I-V table together before checking for monotonicity. I believe
> there is a pending bug (71) fix to the IBIS Golden Parser which will sum the
> tables before the monotonicity check.
> http://www.vhdl.org/pub/ibis/bugs/ibischk/bug71
>
> It has been argued that the extreme currents are acceptable because a part
> pushed to those extremes may actually give extreme current in the instant before
> it melts. I believe this is because people are blindly following the -VCC to
> 2VCC voltage range recommendation for I-V tables and so are trying to come up
> with currents well outside of the normal operating region for some parts. I
> don't know if the IBIS spec actually say it, but I believe the intention is that
> the I-V tables should include all of the voltages where "interesting" things
> happen. If the part was never designed to handle voltages out at -VCC or 2VCC,
> then the tables need not include such voltages. I believe this was more common
> when more people were doing bench measurements to make the tables and they
> limited the voltage range to actual voltages that got close to melt down, but
> not beyond.
>
> Just my two pence,
> Matthew Flora
>
> > -----Original Message-----
> > From: Angulo, John
> > Sent: Monday, November 18, 2002 10:28 AM
> > To: 'ibis-users@eda.org'
> > Subject: RE: [IBIS-Users] Question about warning message
> >
> >
> > The following is posted on behalf of Tom Dagostino at
> > Teraspeed Consulting Group. Please send any private replies
> > to tom@teraspeed.com only.
> >
> > ----------------------------------------------------------------
> >
> > I'll disagree on this. The extreme currents are likely OK but the
> > non-monotonic warnings may cause the simulations to not
> > converge properly or
> > in some simulators cause the model not to load at all. If
> > the sum of the IV
> > curves do not have monotonic issues you are OK. If the sum
> > of the curves do
> > have monotonic issues I would investigate before I would say it is OK.
> >
> > Tom Dagostino
> >
> > Device Modeling Division
> >
> > Teraspeed Consulting Group LLC
> >
> > 2926 SE Yamhill St.
> >
> > Portland, OR 97214
> >
> > (503) 430-1065
> >
> > tom@teraspeed.com
> >
> > http://www.teraspeed.com
> >
> > -----Original Message-----
> > From: owner-ibis-users@server.eda.org
> > [mailto:owner-ibis-users@server.eda.org]On Behalf Of
> > Abdulrahman A. Rafiq
> > Sent: Friday, November 15, 2002 11:32 PM
> > To: Eric Hsu; ibis-users@server.eda.org
> > Subject: Re: [IBIS-Users] Question about warning message
> >
> >
> > Eric,
> >
> > The warning message of "non-monotonic" is perfectly
> > acceptable and can be
> > ignored. As for the warning message of extrreme currents
> > present, it also is
> > acceptable. In fact if you open the .ibs file and comment our all the
> > extreme +ve and -ve currents in the I-V tables and then rerun
> > ibischks, this
> > warning message will not show up.
> >
> > In short you needn't worry too much about these warnings.
> >
> > Hope this helps.
> >
> > Regards,
> >
> > Abdulrahman Rafiq
> >
> > Eric Hsu <ehsu@netlogicmicro.com> wrote:
> >
> > Hi All,
> >
> > When running ibischk3 to check ver2.1 model, if there are warning
> > messages complaining about "non-monotonic"and "extreme
> > currents present"
> > around hundred amp level, is it possible and acceptible?
> >
> > Thanks
> >
> > ~eric
> >
> >
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> > <DIV><SPAN class=3D434591623-16112002><FONT face=3DArial
> > color=3D#0000ff =
> > size=3D2>I'll=20
> > disagree on this. The extreme currents are likely OK but the =
> > non-monotonic=20
> > warnings may cause the simulations to not converge properly
> > or in some=20
> > simulators cause the model not to load at all. If the
> > sum of the =
> > IV curves=20
> > do not have monotonic issues you are OK. If the sum of
> > the curves =
> > do have=20
> > monotonic issues I would investigate before I would say it is
> > OK. =20
> > </FONT></SPAN></DIV>
> > <DIV> </DIV>
> > <DIV class=3DSection1>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Tom Dagostino</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Device Modeling =
> > Division</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Teraspeed
> > Consulting Group =
> >
> > LLC</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">2926 SE Yamhill =
> > St.</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Portland, OR =
> > 97214</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">(503)
> > 430-1065</SPAN></P>
> > <P style=3D"MARGIN: 0in 0in 0pt"><SPAN=20
> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
> > Arial">tom@teraspeed.com</SPAN></P>
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> > style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
> > Arial">http://www.teraspeed.com></P></DIV>
> > <BLOCKQUOTE>
> > <DIV class=3DOutlookMessageHeader dir=3Dltr align=3Dleft><FONT =
> > face=3DTahoma=20
> > size=3D2>-----Original Message-----<BR><B>From:</B>=20
> > owner-ibis-users@server.eda.org =
> > [mailto:owner-ibis-users@server.eda.org]<B>On=20
> > Behalf Of </B>Abdulrahman A. Rafiq<BR><B>Sent:</B> Friday,
> > November =
> > 15, 2002=20
> > 11:32 PM<BR><B>To:</B> Eric Hsu; =
> > ibis-users@server.eda.org<BR><B>Subject:</B>=20
> > Re: [IBIS-Users] Question about warning message<BR><BR></FONT></DIV>
> > <P>Eric,=20
> > <P>The warning message of "non-monotonic" is perfectly
> > acceptable and =
> > can be=20
> > ignored. As for the warning message of extrreme currents
> > present, it =
> > also is=20
> > acceptable. In fact if you open the .ibs file and comment
> > our all the =
> > extreme=20
> > +ve and -ve currents in the I-V tables and then rerun
> > ibischks, this =
> > warning=20
> > message will not show up.=20
> > <P>In short you needn't worry too much about these warnings.=20
> > <P>Hope this helps.=20
> > <P>Regards,=20
> > <P>Abdulrahman Rafiq=20
> > <P> <B><I>Eric Hsu
> > <ehsu@netlogicmicro.com></I></B> wrote:=20
> > <BLOCKQUOTE=20
> > style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
> > #1010ff 2px =
> > solid">Hi=20
> > All,<BR><BR>When running ibischk3 to check ver2.1 model,
> > if there =
> > are=20
> > warning<BR>messages complaining about "non-monotonic"and
> > "extreme =
> > currents=20
> > present"<BR>around hundred amp level, is it possible and=20
> > =
> > acceptible?<BR><BR>Thanks<BR><BR>~eric<BR><BR>|---------------
> > -----------=
> > ----------------------------------------<BR>|For=20
> > help or to subscribe/unsubscribe, email
> > majordomo@eda.org<BR>|with =
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> > 1993</BLOCKQUOTE><BR><BR>************************************<
> > BR>ABDULRAH=
> > MAN=20
> > AK RAFIQ<BR>Scientific Engineering Consultants,
> > Inc<BR>Phone: (805)=20
> > 708-1976<BR>Email: arafiqsi@yahoo.com <BR>URL: =
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-- Fred Balistreri fred@apsimtech.comhttp://www.apsimtech.com |------------------------------------------------------------------ |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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