A simple and straightforward method to estimate the maximal instantaneous voltage peak during switching operations in resonant structures is presented. It is based on the time-domain analysis of an elementary RLC circuit as a model for such systems. For short pulses, a very simple relation is obtained, independent of the pulse shape. For slow excitations, the noise amplitude is safely estimated solely by the slew rate. Pulses with arbitrary length and shape are approximately treated by a trapezoid with effective width and rise time, for which an accurate solution is derived. The approach is extended to current pulse trains. Several validation examples demonstrate the applicability and versatility of the developed estimation formulas.Index Terms-Impulse response, power bus, power distribution networks (PDN), pulse trains, switching voltage.