If you are trying to model static nonlinear elements, you can enter the dependency directly. However, if you trying to model a transfer function that varies with load current, I would try to model the RC elements directly instead of the resulting Laplace transfer function. I think it will be easier to make the RC elements depend on the desired variable.

Srikanthpam,

 One other approach you might want to try is building a more structural
model. An LDO is "beautiful" analog circuit. It looks very simple but the
behavior is very complex. For this class of  circuits it can be difficult to
create pure behavioral circuits since the behavior is "rich" . The other
issues is that the characteristics of interest for a designer are almost entirely
the complex behaviors that are hard to describe. Since the structural model
for an LDO is an op-amp with non-linear resistor in the feedback path, the
overhead of a structural model is minimal.

                                                                Best Regards,

                                                                   Sheldon

Hi Srikanth,

I really don´t know if my reply can help. Nevertheless, I attach a document with my LDO model together with simulation results (time domain). I have modelled the npn-transistor output current as a function of Vce and the opamp as a single pol device. The simulation shows the response to a step change of the reference voltage, of the input voltage  as well as of the load. The program I´ve used is VISSIM.