Subject: [IBIS-Users] Validation of IBIS model
From: Anshuli Goel (anshuli@india.ti.com)
Date: Mon Jan 06 2003 - 00:10:36 PST
Hello Hazem
Thanx for pointing out these problems with the model . I have a few
questions though ?
1. Why the response at short and open load matching ? (Is it because
there I don't have any load resistance )
2. How do I change the step size of rising and falling waveforms in
s2ibis2 scripts ? (By default it is 0.2ns)
3. How do I take into account of the load which is capacitive in nature
( I had posted this question earlier on this reflector and I got the
answer from ("Mike LaBonte" <milabont@cisco.com>) that for this purpose
I should use the
R_f V_f V_f_min V_f_max L_f C_f R_d C_d L_d etc parameters for
that purpose)
4. I don't understand about the four waveforms that you have
referred. Can you point me out to some doc or some thing on that . How
does s2ibis2 generates these 4 waveforms or do I need to do smiulations
in spice and put the waveforms in IBIS. if I do that what is the syntax
in IBIS model for that ?
Regards
Anshuli
Hazem Hegazy wrote:
I'm not sure of the model quality because of the followings:
- The number of point in the rising and falling edges is
quit a few before it
reach steady state.
- There are Rising to gnd and Falling to VDD only V-T data,
I strongly recommend
to have the other two (Rising to VDD and Falling to ground).
- There is C_Fixture = 30p in the V-T data!! This is not
recommended while you
generate the IBIS model wave forms, Please regenerate the V-T
tables without these
capacitance.
- The C_comp value must be calculated and optimized in order
to get complete
overlay with SPICE.
I think that all of these might be the cause.
One more thing, I noticed also from the validation you sent in this mail
the SPICE
simulation reaches 2.7 as a steady state, while the IBIS simulation
reached 2.4 !!
BR,
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