DESCRIPTION

The LTC®1772B is a constant frequency current mode step-down DC/DC controller providing excellent AC and DC load and line regulation. The device incorporates an accurate undervoltage lockout feature that shuts down the LTC1772B when the input voltage falls below 2.0V.

The LTC1772B provides a ±2.5% output voltage accuracy and consumes only 270µA of quiescent current. In shutdown, the device draws a mere 8µA.

To further maximize the life of a battery source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High constant operating frequency of 550kHz allows the use of a small external inductor.

FEATURES

■ Burst ModeTM Operation Disabled for Lower Output Ripple at Light Loads

■ High Efficiency: Up to 94%

■ High Output Currents Easily Achieved

■ Wide VIN Range: 2.5V to 9.8V

■ Constant Frequency 550kHz Operation

■ Low Dropout: 100% Duty Cycle

■ Output Voltage down to 0.8V

■ Current Mode Operation for Excellent Line and Load Transient Response

■ Shutdown Mode Draws Only 8µA Supply Current

■ Tiny 6-Lead SOT-23 Package

APPLICATIONS

■ One or Two Lithium-Ion-Powered Applications

■ Cellular Telephones

■ Wireless Devices

■ Portable Computers

■ Distributed 3.3V, 2.5V or 1.8V Power Systems