The LM3485 is a high efficiency PFET switching regulator controller that a system designer can use to quickly and easily develop a small, low cost, switching buck regulator for a wide range of applications. The use of a hysteretic control scheme provides for simple design without any control loop stability concerns using a wide variety of external components. The PFET architecture also allows for low component count as well as ultra-low dropout operation. Another benefit is high efficiency operation at light loads without an increase in output ripple. Current limit protection circuit is provided by measuring the voltage across the PFET's RDSON thus eliminating a costly sense resistor. The current limit can be adjusted allowing for designs at various output currents and costs.