[IBIS-Users] IBIS question on C_comp

Hello,

I have some questions about C_Comp parameter in IBIS models. I am trying 
to resolve some issues for IBIS models of high frequency differential 
output buffers.
I am trying to compare my SPICE model transient simulations with the 
IBIS model I generated for a differential output buffer. At low 
frequencies (eg ~ 100MHz), the SPICE and IBIS model output simulation 
waveforms correlate closely. But at higher frequencies (>400MHz), the 
SPICE and IBIS model simulations don't match as well. I am trying to see 
if the mismatch is due to the C_comp parameter, or if this is just a 
limitation of IBIS models not being able to capture high frequency effects.

1. How IBIS simulators use the C_comp parameter during simulations?
2. Don't the V-T tables and ramp information already take into account 
the effect of C_comp?
3. What does the C_comp parameter exactly represent?
-should it include die routes, pad capacitance, etc?
4. How should it be measured?
5. Should C_comp be measured in a special manner for differential 
buffers like LVDS buffers?

I would appreciate your response.

Thank you,
-Chitiz Mathema
Cypress Semiconductor




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