[IBIS-Users] Ramp vs. Rising/Falling waveforms, Cref missing ...

IBIS Users, 
I wondered if anyone could clarify for me the usage of Rload vs. Rref vs. 
Rfixture and similarly Cref vs. Cfixture.

I am using s2ibis3 and discovered that the Cref parameter specified in my 
.s2i file does not appear in my .ibs model file.  After looking at the 
netlists and reading the IBIS documentation, it appears Cref is not used 
for any simulations.  What is the purpose of Cref?  And why isn't it 
showing up in the .ibs file? 

Also, I read that C_comp is taken into account for the rising/falling V-T 
waveforms though I cannot find that paramater in any of the corresponding 
netlists.  How is C_comp used?

As for Rref vs. Rfixture, I thought I read somewhere that for best results 
Rref should match Rfixture.   Is that true?  In my model, I am using the 
keywords Rising/Falling Waveform.  I found that if I do not specify Rload 
even though I am not specifying the [Ramp] keyword, then 50ohms is used in 
one of the transient simulations despite Rref and Rfixture being set to 
500 ohms.  Should I be specifying the [Ramp] keyword along with the 
[Rising/Falling Waveform] keywords? If so, how do they work together?

- April

---------------------------------------------------
April Hachenburg
Core Technology Design Engineer
SMSC 

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