Fast frequency domain models are presented allowing prediction of conducted EMI levels generated by a smart High-Side Switch on Printed Circuit Board in a typical automotive lighting application. The influence of design parameters such as switching speed, wiring length and decoupling capacitors can be evaluated without having to perform a Fast Fourier Transform (FFT). Thanks to the high execution speed of these models, insight in a particular design layout can be gained. Moreover, the design can be optimized by performing simulations under various conditions.