Re: Voltage ranges

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IBISers,

This is possibly a nit, but "span" indicates to met that it has to cover
_at least_ the stated range. Going beyond it is not precluded. Has anyone
checked out how the parser handles greater ranges?

Will Hobbs
Intel Corp.

Hi IBIS folks,

I had an AR to find out how SPICE people feel about the "100 point limit".
From the answers I received from three different SPICE simulation tool
vendors I concluded that there is no need to limit the data to 100 points.
That's all I want to say about this now, but we can discuss it in more detail
on the next Open Forum meeting.

Along the same lines, I would like to extend each I-V curve to cover the same
voltage span. Currently the GND clamp and POWER clamp curves are limited to
a smaller range than the pulldown and pullup curves. I see the need
for this when there is a weak pullup (or pulldown) "resistor" in a buffer or
receiver. The current understanding is that these kinds of "resistors" can
be put into the 0 to 5V range of the GND clamp curve. However, putting a
Vcc-relative pullup resistor into a ground relative GND clamp curve creates a
bunch of problems.

For this reason, it would be nice to be able to put the pullup "resistors"
into the POWER clamp curve, but it's voltage range - as defined in ver1.1
(and 2.0) - does not provide room for it. The logical step would be to
extend it's range to be the same as the GND clamp's range is. But then why
not just make all of the ranges the same for simplicity sake?

When I wrote about this before, some people responded that they view the
specified ranges as minimum required ranges and it did not matter if
I published wider ranges in my models. However, I looked up in the ver1.1
spec, and it says:

"Points for each curve must span the voltages listed below"

which means no more and no less. I am about to release a new set of models
in which I will most likely violate the spec. by using exdended voltage
ranges in some of the clamp curves. Since I do not want to get blamed for
changing my mind all the time, I would like to hear what you, IBIS people
think about releasing such models before I do so.

I must admit that I am not one of those Godly people who can see into the
future, so when I wrote ver1.1 I did not see this problem coming.

Sincerely

Arpad Muranyi
Intel Corporation

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Subject: Voltage ranges
To: ibis@vhdl.org
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From: Arpad Muranyi <Arpad_Muranyi@ccm.fm.intel.com>
Date: Thu, 18 Aug 94 11:21:32 PST
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