MPM3683-7 calcul RCS

How to calculate RCS current limit.
You will find attached an Excel file, the application of the formulas do not give the right result
For Vin=12V Vout=5V Ilim=8A RCS=249K I find -414915 ???

See calculation below.
The formula does not seem to me to be exact

Can you give us the simulation model *.lb of the MPM3683-7?
It is not in design tools simulation model