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 V_IN 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 R_DS(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.

1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application Circuit