1 Features

1• Qualified for Automotive Parts

• AEC-Q100 Qualified With the Following Results:

– Device Temperature Grade 1: –40°C to 125°C

Ambient Operating Temperature Range

– Device HBM ESD Classification Level 2

– Device CDM ESD Classification Level C5

• Easy-to-Use Control Methodology

• No Control Loop Compensation Required

• Wide 4.5-V to 35-V Input Range

• 1.239 V to VIN Adjustable Output Range

• High Efficiency: 93%

• ±1.3% (±2% Over Temperature) Internal

Reference

• 100% Duty Cycle Operation

• Maximum Operation Frequency > 1 MHz

• Current Limit Protection

• Dedicated Enable Pin (on if Unconnected)

• Shutdown Mode Draws Only 7-μA Supply Current

• 8-Pin VSSOP Package

2 Applications

• Set-Top Boxes

• DSL or Cable Modems

• PC/IA

• Auto PCs

• TFT Monitors

• Battery-Powered Portable Applications

• Distributed Power Systems

• Always-On Power

• High-Power LED Drivers

• Automotive

3 Description

The LM3489 device is a high-efficiency PFET

switching regulator controller that can be used to

quickly and easily develop a small, cost-effective,

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 ultra-low dropout,

100% duty cycle operation. Another benefit is high

efficiency operation at light loads without an increase

in output ripple. A dedicated enable pin provides a

shutdown mode drawing only 7 μA. Leaving the

enable pin unconnected defaults to on.

Current limit protection can be implemented by

measuring the voltage across the PFET’s RDS(ON),

thus eliminating the need for a sense resistor. A

sense resistor may be used to improve current limit

accuracy if desired. The cycle-by-cycle current limit

can be adjusted with a single resistor, ensuring safe

operation over a range of output currents.