Fwd: Re[2]: Non-Monotonic Drivers

-- [ From: Ron Christopher * EMC.Ver #2.10P ] --

Forwarding to the reflector.

Ron Christopher
------- FORWARD, Original message follows -------

> Date: Wednesday, 23-Aug-95 03:43 PM
>
> From: Arpad Muranyi \ Internet:
> (arpad_muranyi@ccm.fm.intel.com)
> To: Ron Christopher \ PRODIGY: (EGJJ77A)
>
> Subject: Re[2]: Non-Monotonic Drivers
>
> Text item:
>
> John,
>
> Thanks again for your reply. I have mixed feelings about what to say
now.
>
> 1) This kind of a behavior is most likely caused by a feedback
circuit in
> the buffer. It is true, IBIS currently does not have provisions to
> describe buffers with feedback. However, we had discussions on this
> subject in the open forum meetings before, and we could pick it up
again
> if there is a real need for modeling such buffers in IBIS.
>
> 2) On the other hand, I am not sure if IBIS is to blame for the
situation
> that you described, that simulators alter the curve this and that
way. I
> imagined how I would use this data in my HSPICE behavioral (=IBIS)
> models. I am using piecewise linear (PWL) sources for the I-V
curves.
> If I make the voltage values the independent variable, and current
the
> dependent variable, it will work no problem, because each voltage
value
> is assigned only one current value. (It doesn't matter whether the
> current values are repeated). If I turned it around, however, to
have
> current values as the independent variable and voltage the dependent
one,
> it would not work, because the simulator would have to pick between
two
> or more voltages for one current value. What I am trying to say
here is
> that this kind of a curve should work, as far as IBIS is concerned
(as it
> does in my HSPICE behavioral models). It depends on what the
simulator
> tool does with it.
>
> Arpad
>
=======================================================================
==
> ====
> Arpad,
>
> Each point on the curve is what you would get if you put a battery DC
> voltage at the output of the driver and measured the current through
the
> pad with all other operating conditions constant. The curves were
> generated with multiple DC analysis using ASX(the IBM SPICE program).
I do
> not think IBIS can handle this today. Specifically, simulation
programs
> will try to alter the DC curves, and there is nothing that tells them
how
> to do this(I believe the correct thing to do would be to not alter
the
> curve).
>
> Thanks,
> John
>
>
***********************************************************************
> John Brennan Internal: jbrennan@btv
> IBM Microelectronics Internet:
jbrennan@vnet.ibm.com
> G77V/862-1 Tel: 802-769-6982 (Tie-Line:
446)
> Burlington, VT Fax: 802-769-5882 (Tie-Line:
446)
>
***********************************************************************
>
> Text item:
>
> John,
>
> Thanks for the graphical response to my question. This is the kind
> of response
> I really wanted to get. I have a question, though. Is this I-V
curve a
> function of the voltage on the output pin, or time. I mean, is
> "translating
> between two Vgs curves" done with a feedback circuit by monitoring
the
> output
> voltage, or is it a function of time as slew rate controlled devices
> usually do
> it?
>
> If the answer is time, IBIS can definitely do it, but if it is
voltage (as
> in feedback), IBIS would not be able to help you at this time.
However,
> the open forum committee did consider this issue in meetings before,
and I
> don't think that it would be impossible to incorporate features that
can
> model it.
>
> Arpad
>
=======================================================================
==
> =====
>
> Arpad,
>
> The drivers Ron refers to have the following IV curve shape...
>
> Ids * *
> * *
> * *
> * *
> * ****************
> *
> *
> *
> * Vds
>
>
> Instead of the normal transistor curve shape like...
>
> Ids * ***********************
> *
> *
> *
> *
> *
> *
> *
> * Vds
>
>
> The top curve comes about because we are manipulating the gate
voltage to
> control di/dt noise in the maximum Vds region of the large output
device.
> Essentially we are translating between two Vgs curves for the output
> transistor. Hence the non-monotonicity is real and not noise related.
> Clamp diodes would add another bend in the curve and create 3 current
> values for 1 voltage value.
>
> The simulation tools we looked at would "correct" the data by making
the
> top curve look like the bottom. We saw some extreme differences in
> benchmark nets after this manipulation from the full transistor
> simulation. Since there is no standard on how to "correct" the above
> curve, we would not know how various simulation vendors would treat
the
> model.
>
> The above and the time schedule of IBIS 2.1 and CMOS 4 makes
supporting
> the IBIS modeling strategy unattractive for our CMOS 4 products.
>
> Thanks,
> John Brennan
>
>
***********************************************************************
> John Brennan Internal: jbrennan@btv
> IBM Microelectronics Internet:
jbrennan@vnet.ibm.com
> G77V/862-1 Tel: 802-769-6982 (Tie-Line:
446)
> Burlington, VT Fax: 802-769-5882 (Tie-Line:
446)
>
***********************************************************************
>
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> From: "John Brennan" <jbrennan@VNET.IBM.COM>
> Date: Tue, 22 Aug 1995 13:34:03 -0400
> Subject: Non-Monotonic Drivers
> To: EGJJ77A@prodigy.com, arpad_muranyi@ccm.fm.intel.com, jonp@qdt.com
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> From: "John Brennan" <jbrennan@VNET.IBM.COM>
> Date: Wed, 23 Aug 1995 09:01:18 -0400
> In-Reply-To: Your message of Tue, 22 Aug 1995 15:47:55 PST.
> <950822154755_9@ccm.fm.intel.com>
> Subject: Re: Non-Monotonic Drivers
> Cc: jbrennan@VNET.IBM.COM, EGJJ77A@prodigy.com, jonp@qdt.com,
> Will_Hobbs@ccm2.jf.intel.com
> To: Arpad Muranyi <Arpad_Muranyi@ccm.fm.intel.com>
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Received on Thu Aug 31 08:58:13 1995