Abstract

As power supply efficiency becomes more important, faster switching speeds are necessary to reduce efficiency losses. However, as switching speeds are increased, there are trade-offs that must be considered, such as significant overshoot, ringing voltage on the switch node, and electromagnetic interference (EMI). The magnitude of the ringing is a function of the switching speed of the high-side NFET and the parasitic inductance in the layout and device package. There are several methods to reduce the ringing to keep the MOSFET switches within the safe operating region and the EMI noise so caused, such as a boot resistor, a high-side gate resistor, or an RC snubber.

This application note highlights design consideration when using a boot resistor to control switch-node ringing and optimize EMI.