DESCRIPTION
The LT ®1506 is a 500kHz monolithic buck mode switching regulator functionally identical to the LT1374 but optimized for lower input voltage applications. It will operate over a 4V to 15V input range compared with 5.5V to 25V for the LT1374. A 4.5A switch is included on the die along with all the necessary oscillator, control and logic circuitry. High switching frequency allows a considerable reduction in the size of external components. The topology is current mode for fast transient response and good loop stability. Both fixed output voltage and adjustable parts are available.
A special high speed bipolar process and new design techniques achieve high efficiency at high switching frequency. Efficiency is maintained over a wide output current range by keeping quiescent supply current to 4mA and by utilizing a supply boost capacitor to saturate the power switch.
The LT1506 fits into standard 7-pin DD and fused lead SO-8 packages. Full cycle-by-cycle short-circuit protection and thermal shutdown are provided. Standard surface mount external parts are used, including the inductor and capacitors. There is the optional function of shutdown or synchronization. A shutdown signal reduces supply current to 20µA. Synchronization allows an external logic level signal to increase the internal oscillator from 580kHz to 1MHz.

FEATURES
■ Constant 500kHz Switching Frequency
■ Easily Synchronizable
■ Operates with Input as Low as 4V
■ Uses All Surface Mount Components
■ Inductor Size Reduced to 1.8µH
■ Saturating Switch Design: 0.07Ω
■ Shutdown Current: 20µA
■ Cycle-by-Cycle Current Limiting

APPLICATIONS
■ Portable Computers
■ Battery-Powered Systems
■ Battery Charger
■ Distributed Power