[SI-LIST] Re: IBIS Model error
- From: Vadim Heyfitch <htc2rl@xxxxxxxxx>
- To: kimgh@xxxxxxxxxxx, chris.mcgrath@xxxxxxxx
- Date: Mon, 17 Nov 2003 10:28:07 -0800 (PST)
This thread reminds me of another thread - "[OT]
Offshore engineering" - that recently developed on the
list. It's almost amuzing how seven people
instantaneously jumped to the opportunity "to educate
their own replacement" in Bangalore-52. Judging by his
question, Mr. Suresh K. is one of those SI-novices who
"is on the list to pick your brains". Don't expect him
to hire you as a consultant to fix his IBIS
model...... Even if he's impressed with your deep
knowledge and understanding of IBIS, he would not have
$$$ to pay for your services :-)
-Vadim
--- Kim Helliwell <kimgh@xxxxxxxxxxx> wrote:
> It seems probable that the typ, min, max order was
> swizzled by the model creator. I've seen cases where
> the model creator thought the order was "max, typ,
> min"
> or "min, typ, max"
>
> Are other curves apparently swizzled as well?
>
> You probably should contact the supplier of the
> model
> to clarify this (I bet you already are doing that,
> though).
>
> Another possibility is that the curves are so close
> together
> that they cross at some point. But your evidence (a
> clear
> difference in sim results) suggests that this is not
> the case
> here.
>
> Kim
>
>
> On Nov 17, 2003, at 8:29 AM, Chris McGrath wrote:
>
> > Speaking of IBIS model problems...
> >
> > I have a model that has a couple of odd parameters
> that are
> > inconsistent
> > with all other models we have used.
> >
> > First, in the VI curve, the falling edge "maximum"
> is between the
> > "typical" and "minimum" curves.
> >
> > Second, dV/dt_r and dV/dt_f do not increase from
> minimimum to typical
> > to
> > maximum.
> >
> > In both cases when firing these drivers into test
> loads (PCI-X), they
> > do
> > not follow the expected trend where the "maximum"
> settings show the
> > fastest rise/fall time and the "minimum" settings
> show the slowest
> > rise/fall times.
> >
> > This operations seems very odd, but given my
> limited experience with
> > dissecting IBIS models I'm open to suggestions on
> why this component
> > behaves the way it does.
> >
> > Thanks,
> > Chris
> >
> >
> >
> >> -----Original Message-----
> >> From: Ingraham, Andrew
> [mailto:a.ingraham@xxxxxxxx]=20
> >> Sent: Monday, November 17, 2003 9:38 AM
> >> To: si-list@xxxxxxxxxxxxx
> >> Subject: [SI-LIST] Re: IBIS Model error
> >> =20
> >> =20
> >> Suresh,
> >> =20
> >> All these errors point to an incorrect IBIS
> model. Contact=20
> >> IDT and ask them to fix it.
> >> =20
> >> The IBIS checker in the simulator tries to verify
> that the=20
> >> waveform data is consistent with the I-V tables.
> Ohm's law=20
> >> and the I-V tables should tell you the
> steady-state (initial=20
> >> and final) voltages, which ought to closely match
> those in=20
> >> the waveform tables. In this model, they do not
> come close.
> >> =20
> >> The I-V data doesn't seem to be pulling the
> output down. =20
> >> Even when driving a 50 ohm load resistor to 1.5V,
> the LOW=20
> >> state is 2.13V. Something is seriously wrong
> here.
> >> =20
> >> Regards,
> >> Andy
> >> =20
> >> =20
> >> ...
> >>> ERROR- Model IOPAD2546Z: The [Rising Waveform]
> >>> with [R_fixture]=3D50 Ohms and
> [V_fixture]=3D1.5V
> >>> has TYP column DC endpoints of 0.50V and
> 2.21v, but
> >>> an equivalent load applied to the model's I-V
> tables yields=20
> >> different=20
> >>> voltages ( 2.13V and 2.69V), a difference of
> 288.80% and 84.70%,=20
> >>> respectively.
> >> ...
> >> =20
> >> =20
> >>
>
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> >
> Kim Helliwell
> kimgh@xxxxxxx
> Homepage: http://homepage.mac.com/kimgh
>
>
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