Independent of their individual topology and application, due to AC components in their lines switching controllers create conducted EMC interferences. Würth Elektronik MagI³C power modules are optimized for a low line-bound and radiated emission of interferences. Their residual ripple generally exhibits a negligibly low value, meaning that an output filter can be dispensed with in most applications. Since the input current at the step-down converter is pulsating, this may generate radio-frequency interferences in the application. Depending on the specific application, the hardware developer decides whether an input filter is necessary directly before the power module or in another position in the switch. This general Application Note describes the design process of input filters for Würth Elektronik MagI³C power modules and the measurement techniques that are used.