The LT1506 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.ApplicationsPortable ComputersBattery-Powered SystemsBattery ChargerDistributed Power