Re: [IBIS-Users] How Ramp data is processed ?

Itzik:

I agree with Arpad. The only non-theoretcal (and mostly
incorrect) reason is to assume that one transistor is
turning on at the same rate that the other is turning off.
However, without any additional data, there was no basis
for making any other assumption such as formulating a
more complicated equation relationship.

The second approach is a rather crytic idea. The rising
waveform Ramp is specified with an Rload connected to
ground. The idea is to ASSUME that a same-shape
(but with different voltage swings) Ramp waveform
is obtained by attaching the Rload to the Vcc rail.
Then this data provides the two waveform data needed to
find both multipliers in the equation below. This
algorithm can also be used for single rising waveform
based models to copy the same waveform shape, as a
first order assumption. An extension of this approach
is to time-scale the Ramp (or rising waveform) for the
Rload to Vcc case since that waveform typically switches
faster. The falling edge Ramp (or single waveform) would
be handled in a similar manner.

The B-element has time scaling tuning elements
for the user to specific the turn-off table switching
speed faster than the turn-on table switching speed.
I do not know if the transitions are time-scaled directly
or if other internal assumptions are mede.

In all cases, we are making some assumptions without
supporting data. There is also some danger in introducing
errors, such as incorrect relative time shifts. The best
approach still is to supply two waveforms and to use this
information directly.

Bob

Muranyi, Arpad wrote:
> Itzik,
>
> There is no theoretical explanation for that assumption.
> It is an arbitrary assumption with no scientific backing
> so it really has nothing to do with reality. It is just
> convenient, and it does give you a waveform.
>
> Arpad
> =========================================================
>
> ------------------------------------------------------------------------
> From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
> Behalf Of Itzik Peleg
> Sent: Tuesday, June 15, 2004 10:14 PM
> To: Bob Ross
> Cc: ibis-users@eda.org
> Subject: Re: [IBIS-Users] How Ramp data is processed ?
>
> Hello Bob
>
> Thanks for your answer.
>
> Is there any theoretical explanation why we can assume that W(t)pu =
> 1-W(t)pd ?
> As for the second approach I didn't understood it. please apply more
> details.
>
> Thanks
>
> Itzik
>
> Bob Ross wrote:
>
>> Hello Itzik:
>>
>> One approach is simply to assume a relationship such as
>>
>> W(t)pu = 1-W(t)pd
>>
>> Another approach is to the same R_load to the other rail
>> and to assume an amplitude adjusted and time scaled V(t)
>> for that rail.
>>
>> Both approaches are assumptions and may still not
>> produce results that correlate with the source data.
>>
>> Bob
>>
>> Itzik Peleg wrote:
>>
>>> Hello IBIS Users
>>>
>>> When only ramp data exist in the model.
>>> As far as I understand the ramp rate is used to calculate the two
>>> weight functions (one of the pull down and one for the pull up) that
>>> describe this transition (high to low or low to high).
>>>
>>>
>>> >From Ramp we got the V(t) that describe the transition (linear curve).
>>> The resistor load is also known R_load.
>>> We also got the I(V) curves for pullup and pulldown (I will mark this
>>> function as I(V)pu and I(V)pd).
>>> I will mark the weight function as W(t)pu for pullup and W(t)pd.
>>> Then we can write this equation for the transition:
>>>
>>> V(t) = R_load* (I(V)pu * W(t)pu - I(V)pd * W(t)pd)
>>>
>>> In order to get the W(t)pu and W(t)pd we need one more equation.
>>> What I am missing here ?
>>> Can anyone point me to a relevant paper on this subject ?
>>>
>>> --
>>> Regards
>>>
>>> Itzik Peleg Board Technology Group
>>>
>>> Marvell Semiconductor Israel Ltd
>>> 6 Ha'mada St. Industrial Area
>>> P.O.Box 692 Yokneam 20692 ISRAEL
>>> Email - itzik.peleg@il.marvell.com
>>> Tel - +972 4 9091192 Cell - +972 54 4452482
>>> Fax - +972 4 9091501
>>> WWW Page: http://www.marvell.com
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>>> If you have received this communication in error, please notify us
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>>>
>>
>
> --
> Regards
>
> Itzik Peleg
> Board Technology Group
>
> Marvell Semiconductor Israel Ltd
> 6 Ha'mada St. Industrial Area
> P.O.Box 692 Yokneam 20692 ISRAEL
> Email - itzik.peleg@il.marvell.com
> Tel - +972 4 9091192
> Cell - +972 54 4452482
> Fax - +972 4 9091501
> WWW Page: http://www.marvell.com
> ========================================================================
> This message may contain confidential, proprietary or legally privileged
> information. The information is intended only for the use of the
> individual or entity named above. If the reader of this message is not
> the intended recipient, you are hereby notified that any dissemination,
> distribution or copying of this communication is strictly prohibited.
> If you have received this communication in error, please notify us
> immediately by telephone, or by e-mail and delete the message from
> your computer.
>
> Thank you!
> ========================================================================

-- 
Bob Ross
Teraspeed Consulting Group LLC     Teraspeed Labs
121 North River Drive              13610 SW Harness Lane
Narragansett, RI 02882             Beaverton, OR 97008
503-750-6481                       503-430-1065
http://www.teraspeed.com           503-246-8048 Direct
bob@teraspeed.com
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