The FAN5099 combines a high-efficiency pulse-width modulated (PWM) controller and an LDO (low drop out) linear regulator controller. The PWM controller is designed to operate over a wide frequency range (50kHz to 600kHz) to accommodate a variety of applications. Synchronous rectification provides high efficiency over a wide range of load currents. Efficiency is further enhanced by using the low-side MOSFET's RDS(ON) to sense current. In addition, the capability to operate at low switching frequencies provides opportunities to boost power supply efficiency by reducing switching losses and gain cost savings using low-cost materials, such as powdered iron cores, on the output inductor.