DESCRIPTION
The LTC®3549 is a high efficiency, monolithic synchronous buck regulator using a constant-frequency, current mode architecture. The output voltage is adjusted via an external resistor divider.

FEATURES
■ 1.6V to 5.5V Input Voltage Range
■ Internal Soft-Start
■ Low Ripple Burst Mode® Operation
   Output Ripple: <20mVP-P
   IQ: 50µA
■ 2.25MHz Constant-Frequency Operation
■ High Effi ciency: Up to 93%
■ 250mA Output Current (VIN = 1.8V, VOUT = 1.2V)
■ 450mA Peak Inductor Current
■ No Schottky Diode Required
■ Low Dropout Operation: 100% Duty Cycle
■ 0.611V Reference Voltage
■ Stable with Ceramic Capacitors
■ Shutdown Mode Draws <1µA Supply Current
■ Current Mode Operation for Excellent Line and Load
   Transient Response
■ Overtemperature Protection
■ Available in a Low Profi le (0.75mm) 6-Lead
   (2mm x 3mm) DFN Package

APPLICATIONS
■ 2 AA-Cell Applications
■ Cellular Phones
■ Digital Cameras
■ MP3 Players