DESCRIPTION
The LTC®3548-2 is a dual, constant frequency, synchronous step down DC/DC converter. Intended for low power applications, it operates from 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, allowing the use of tiny, low cost capacitors and inductors with a profile ≤1.2mm. For channel 1, the output voltage is fixed at 1.8V/800mA; for channel 2, the output voltage is adjustable from 0.6V to VIN. Internal synchronous 0.35Ω, 1.2A/0.7A power switches provide high efficiency without the need for external Schottky diodes.

FEATURES
■ High Efficiency: Up to 95%
■ 1.8V/800mA Fixed Output and 400mA Adjustable
   Output Voltage
■ Only 40µA Quiescent Current (Both Channels)
■ 2.25MHz Constant Frequency Operation
■ High Switch Current Limits: 1.2A and 0.7A
■ No Schottky Diodes Required
■ Low RDS(ON) Internal Switches: 0.35Ω
■ Current Mode Operation for Excellent Line
   and Load Transient Response
■ Short-Circuit Protected
■ Low Dropout Operation: 100% Duty Cycle
■ Ultralow Shutdown Current: IQ < 1µA
■ Power-On Reset Output
■ Externally Synchronizable Oscillator
■ Small Thermally Enhanced 3mm × 3mm DFN Package

APPLICATIONS
■ PDAs/Palmtop PCs
■ Digital Cameras
■ Cellular Phones
■ Portable Media Players
■ PC Cards
■ Wireless and DSL Modems