Analog Devices LTC1773 Product Info

• High Efficiency: Up to 95%
• Constant Frequency 550kHz Operation
• V_IN from 2.65V to 8.5V
• V_OUT from 0.8V to V_IN
• OPTI-LOOP^® Compensation Minimizes C_OUT
• 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 Quiescent Current: 80µA
• Low Shutdown I_Q = 10µA
• ±1.5% Reference Accuracy
• Precision 2.5V Undervoltage Lockout
• Available in 10-Lead MSOP

The LTC1773 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.

The operating frequency is internally set at 550kHz, allowing the use of small surface mount inductors. For switching-noise sensitive applications, it can be synchronized up to 750kHz. Peak current limit is user programmable with an external high side sense resistor. A SYNC/FCB control pin guarantees regulation of secondary windings regardless of load on the main output by forcing continuous operation. Burst Mode operation is inhibited during synchronization or when the SYNC/FCB pin is pulled low to reduce noise and RF interference. Soft-start is provided by an external capacitor.

Synchronous rectification increases efficiency and eliminates the need for a Schottky diode, saving components and board space. The LTC1773 comes in a 10-lead MSOP package.

Applications

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