Subject: Re: Warning Message (ibischk3 V3.2.x)
From: Mike LaBonte (mike@labonte.com)
Date: Thu Jan 31 2002 - 20:22:36 PST
Yes the ESD diode, or whatever circuit is used for over-voltage
protection. It may be fair to propose having ibischk allow
clamp currents to not quite reach zero, since real circuits
show zero current only if:
- you use insensitive measuring equipment
- you simulate using approximate models
- there is no power supplied
If you are an IC vendor, it may be helpful to take advantage of
the Free Model Review Service described at
http://www.eigroup.org/ibis/support.htm
The reviewers may be able to give information on how well the
various IBIS simulators will tolerate clamp curves that do not
reach zero current.
Mike LaBonte
akimoto@lsi.nec.co.jp wrote:
>
> Hello,
>
> What is "diode"?
>
> Is it only "ESD diode"?
> Or, does it include the leak current at Hi-Z state of
> P-ch transistor?
>
> If the first case, we can not separate only this effect
> from the measurement curve.
> If the last case, how did you decide the limitation value
> as like 1uA?
>
> I cannot understand what does this WARNING warn to us.
> Can I ignore this WARNING?
>
> Best regards,
> Akimoto
>
> >It is expected that clamps behave like diodes, and conduct no
> >current within some voltage range. A diode certainly conducts
> >no current with zero volts across it. If a clamp curve shows
> >current flow with zero volts across it, there may have been an
> >error separating the clamp curve from the output curves. It is
> >common to force the 0V currents to 0mA.
> >
> >Or, there may be a terminator resistor that someone has chosen
> >to add into the wrong clamp curve. I think it is customary to
> >add resistors to the curve of the same rail they are attached to.
> >
> >Mike LaBonte
> >
> >Takanobu Ura wrote:
> >>
> >> Dear all.
> >>
> >> I have a question.
> >> What dose the following warning mean?
> >>
> >> WARNING -
> >> Model xxx: POWER Clamp : Typical value never becomes zero
> >>
> >> The below is PowerClamp infomation.
> >>
> >> [Power Clamp]
> >> 0 4.957u 5.049u 4.825u
> >> -76m 5.07u 5.376u 4.918u
> >> -152m 5.348u 6.904u 5.053u
> >> -227m 7.611u 15.19u 6.135u
> >>
> >> Is there somthing wrong with the PowerClamp?
> >>
> >> Best Regards.
> >> T.Ura
> >
> ------------------------------------------------------
> Akimoto Tetsuya
> Design systems Grp. System LSI Design Engineering Div.
> NEC Electron Devices, NEC Corporation
> Email:akimoto@lsi.nec.co.jp Phone:044-435-1511
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