Subject: Re: ibischk3 problems
From: Bob Ross (bob_ross@mentorg.com)
Date: Thu Oct 18 2001 - 15:04:53 PDT
Brian:
The problem is in the [Pulldown Reference] line. I believe
you wanted it to be 0V.
You will still get some Errors and Warnings, for smaller
mismatches. One of the Warning messages has an incorrect
percentage calculation, and I believe that problem needs
to be filed as a BUG.
Bob Ross
Mentor Graphics
Brian Young wrote:
>
> Hello,
>
> I am getting errors from ibischk3, but I can't figure out what
> the problem is. The IBIS file was generated by a methodology in
> development, so there are lots of little problems. Right now,
> there are also big problems:
>
> IBISCHK3 V3.2.7
>
> Checking test.ibs for IBIS 2.1 Compatibility...
>
> ERROR - Model mod.A35_2.5V: The [Rising Waveform]
> with [R_fixture]=50 Ohms and [V_fixture]=2.5V
> has TYP column DC endpoints of 1.15V and 2.45v, but
> an equivalent load applied to the model's I-V tables yields
> different voltages ( 2.52V and 2.50V),
> a difference of 54.34% and 1.87%, respectively.
> ERROR - Model mod.A35_2.5V: The [Rising Waveform]
> with [R_fixture]=50 Ohms and [V_fixture]=0V
> has TYP column DC endpoints of 0.00V and 1.20v, but
> an equivalent load applied to the model's I-V tables yields
> different voltages ( 1.43V and 1.38V),
> a difference of 100.00% and 13.05%, respectively.
> ERROR - Model mod.A35_2.5V: The [Falling Waveform]
> with [R_fixture]=50 Ohms and [V_fixture]=2.5V
> has TYP column DC endpoints of 1.25V and 2.50v, but
> an equivalent load applied to the model's I-V tables yields
> different voltages ( 2.52V and 2.50V),
> a difference of 50.37% and 0.13%, respectively.
> ERROR - Model mod.A35_2.5V: The [Falling Waveform]
> with [R_fixture]=50 Ohms and [V_fixture]=0V
> has TYP column DC endpoints of 0.05V and 1.35v, but
> an equivalent load applied to the model's I-V tables yields
> different voltages ( 1.43V and 1.38V),
> a difference of 96.51% and 2.18%, respectively.
>
> Errors : 4
>
> File Failed
>
> Take for example the first error. Before the start of the rising edge,
> the NFET is holding the voltage low. I can find the holding low voltage
> by finding the point on the PULLDOWN IV curve where 2.5V=V+50*I. Using
> the IV curve entry 1.10 27.69m, I find the voltage to be 1.1V. From the
> [Rising Waveform], R_fixture = 50, V_fixture = 2.500 curve, I get the
> starting voltage as 1.15V. That looks like a match to me, but ibischk3
> comes up with an error and different numbers.
>
> Can someone ID the problem with these errors?
>
> Thanks,
> Brian
>
---> [Model] mod.A35_2.5V > Model_type I/O > Polarity Non-Inverting > Enable Active-High > Vinh = 1.23V > Vinl = 1.21V > Cref = 0 > Rref = 0 > Vref = 0 > C_comp 4p 3p 6p > [Temperature Range] 27 NA NA > [Pullup Reference] 2.5V NA NA > [Pulldown Reference] 2.5V NA NA > [Power Clamp Reference] 2.5V NA NA > [GND Clamp Reference] 0.0V NA NA >
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