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.