SN74CB3Q3125: S-parameters

Danilo,

Unfortunately we don't have an s-parameter model for the SN74CB3Q3125. What's the application here? The On Capacitance is 8pF in the 3125 so it should be able to handle some higher speed applications but the load would really affect the bandwidth more truthfully. Do you have a frequency range in mind that they're working with?
There is an IBIS model for the SN74CB3Q3125 but IBIS models wouldn't represent this as well as using a spice model or modeling this with a circuit equivalence using the parasitic resistance and capacitances in SPICE or TINA. The signal paths aren't buffered input/outputs. They can be thought of as simple wire connections with parasitic associations. So something like the figure below to model the switch and see it's performance. 

Thanks,
Rami Mooti