Accurate and robust modeling of the characteristic I-V curve of a photovoltaic module is essential in many applications focused on forecasting and predicting photovoltaic (PV) performance. The single diode equivalent model has been used extensively for representing the working principles of solar cells. This work presents a simple methodology for solving the single diode equation from the manufacture's datasheet parameters, by combining the Lambert-W function and an iterative procedure on the ideality factor of the diode, which has a fast convergence and robustness. The model has been assessed by comparing with experimental I-V curves measured for different modules at indoor and outdoor conditions with good results. Sensitivity analysis has been also done to indicate the possible impact of the uncertainty of the initial parameters that input the model.