In mobile platforms, RF interference issues caused by the switched-mode power supply (SMPS) ringing noise often arise in the on-the-go mode and the charging mode of the interface power management integrated circuits. In this paper, we introduce the modeling method for the SMPS ringing noise in the conventional two-level dc-dc converters and then, based on the modeling insight from the two-level dc-dc converter, we investigate and validate the modeling of the SMPS ringing noise in the three-level buck converters, which are newly adopted SMPSs for fast charging in mobile devices. To reduce such noise, we propose the novel SMPS noise-managing methodologies that handle the printed-circuit-board-level design optimization in mobile devices.