DESCRIPTION
The LTC®1773 is a current mode synchronous buck regulator controller that drives external complementary power MOSFETs using a fixed frequency architecture. The operating supply range is from 2.65V to 8.5V, making it suitable for 1- or 2-cell lithium-ion battery powered applications. Burst Mode® operation provides high efficiency at low load currents. 100% duty cycle provides low dropout operation which extends operating time in battery-operated systems.

FEATURES
■ High Efficiency: Up to 95%
■ Constant Frequency 550kHz Operation
■ VIN from 2.65V to 8.5V
■ VOUT from 0.8V to VIN
■ OPTI-LOOP® Compensation Minimizes COUT
■ Synchronizable up to 750kHz
■ Selectable Burst Mode Operation
■ Low Quiescent Current: 80µA
■ Low Dropout Operation: 100% Duty Cycle
■ Secondary Winding Regulation
■ Soft-Start
■ Current Mode Operation for Excellent Line and Load Transient Response
■ Low Shutdown IQ = 10µA
■ ±1.5% Reference Accuracy
■ Precision 2.5V Undervoltage Lockout
■ Available in 10-Lead MSOP

APPLICATIONS
■ Cellular Telephones
■ RF PA Supplies
■ Portable Instruments
■ Wireless MODEMS
■ Distributed Power Systems
■ Notebook and Palm Top Computers, PDAs
■ Single and Dual Cell Lithium-Ion Powered Devices