LTC1149-3.3 Datasheet

• Operation to 48V Input Voltage
• Ultrahigh Efficiency: Up to 95%
• Current Mode Operation for Excellent Line and Load Transient Response
• High Efficiency Maintained over Wide Current Range
• Logic-Controlled Micropower Shutdown
• Short-Circuit Protection
• Very Low Dropout Operation: 100% Duty Cycle
• Synchronous FET Switching for High Efficiency
• Adaptive Nonoverlap Gate Drives
• Available in 16-Pin Narrow SO Package

• Notebook and Palmtop Computers
• Portable Instruments
• Battery-Operated Digital Devices
• Industrial Power Distribution
• Avionics Systems
• Telecom Power Supplies

The LTC1149-3.3 is a family of synchronous step down switching regulator controllers featuring automatic Burst Mode^™ operation to maintain high efficiencies at low output currents. These devices drive external complementary power MOSFETs at switching frequencies up to 250kHz using a constant off-time current-mode architecture.

Special onboard regulation and level-shift circuitry allow operation at input voltages from dropout to 48V (60V absolute max). The constant off-time architecture maintains constant ripple current in the inductor, easing the design of wide input range converters. Current mode operation provides excellent line and load transient response. The operating current level is user-programmable via an external current sense resistor.

The LTC1149-3.3 incorporates automatic power saving Burst Modeoperation when load currents drop below the level required for continuous operation. Standby power is reduced to only about 8mW at VI_N = 12V. In shutdown, both MOSFETs are turned off.