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.