DESCRIPTION
The LTC®1148 series is a family of synchronous stepdown switching regulator controllers featuring automatic Burst ModeTM 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 providing constant ripple current in the inductor.
The operating current level is user-programmable via an external current sense resistor. Wide input supply range allows operation from 3.5V* to 18V (20V maximum). Constant off-time architecture provides low dropout regulation limited by only the RDS(ON) of the external MOSFET and resistance of the inductor and current sense resistor.
The LTC1148 series combines synchronous switching for maximum efficiency at high currents with an automatic low current operating mode, called Burst Modeoperation, which reduces switching losses. Standby power is reduced to only 2mW at VIN = 10V (at IOUT = 0). Load currents in Burst Mode operation are typically 0mA to 300mA.
For operation up to 48V input, see the LTC1149 and LTC1159 data sheets and Application Note 54.

FEATURES
■ Ultrahigh Efficiency: Over 95% Possible
■ Current-Mode Operation for Excellent Line and Load Transient Response
■ High Efficiency Maintained Over Three Decades of Output Current
■ Low 160µA Standby Current at Light Loads
■ Logic Controlled Micropower Shutdown: IQ < 20µA
■ Wide VIN Range: 3.5V* to 20V
■ Short-Circuit Protection
■ Very Low Dropout Operation: 100% Duty Cycle
■ Synchronous FET Switching for High Efficiency
■ Adaptive Nonoverlap Gate Drives
■ Output Can Be Externally Held High in Shutdown
■ Available in 14-Pin Narrow SO Package

APPLICATIONS
■ Notebook and Palmtop Computers
■ Portable Instruments
■ Battery-Operated Digital Devices
■ Cellular Telephones
■ DC Power Distribution Systems
■ GPS Systems