1 Features

? Easy-to-Use Control Methodology

? No Control-Loop Compensation Required

? 4.5-V to 35-V Wide Input Range

? 1.242-V to VIN Adjustable Output Range

? High Efficiency 93%

? ±1.3% (±2% Over Temp) Internal Reference

? 100% Duty Cycle

? Maximum Operating Frequency > 1 MHz

? Current Limit Protection

2 Applications

? Set-Top Box

? DSL or Cable Modem

? PC/IA

? Auto PC

? TFT Monitor

? Battery-Powered Portable Applications

? Distributed Power Systems

? Always On Power

3 Description

The LM3485 is a high-efficiency PFET switching

regulator controller that can be used to quickly and easily develop a small, low-cost, switching buck

regulator for a wide range of applications. The

hysteretic control architecture 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 ultralow dropout, 100% duty cycle

operation. Another benefit is high efficiency operation

at light loads without an increase in output ripple.

Current limit protection is provided by measuring the

voltage across the RDS(ON) of the PFET, thus

eliminating the need for a sense resistor. The cycle-

by-cycle current limit can be adjusted with a single

resistor, ensuring safe operation over a range of

output currents.