500kHz Monolithic Buck Mode Switching Regulator

The LT1507 is a 500kHz monolithic buck mode switching regulator, functionally identical to the LT1375 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 LT1375. A 1.5A 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 (3.3V) and adjustable parts are available.

A special high speed bipolar process and new design techniques allow this regulator to achieve high efficiency at a 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 allow the NPN power switch to saturate. A shutdown signal will reduce supply current to 20µA.

The LT1507 can be externally synchronized from 570kHz to 1MHz with logic level inputs.The LT1507 fits into standard 8-pin SO and PDIP packages. Temperature rise is kept to a minimum by the high efficiency design. Full cycle-by-cycle short-circuit protection and thermal shutdown are provided. Standard surface mount external parts are used including the inductor and capacitors.

Applications

* Portable Computers

* Battery-Powered Systems

* Battery Charger

* Distributed Power

* Constant 500kHz Switching Frequency

* Uses All Surface Mount Components

* Operates with Inputs as Low as 4V

* Saturated Switch Design (0.3Ω)

* Cycle-by-Cycle Current Limiting

* Easily Synchronizable

* Inductor Size as Low as 2µH

* Shutdown Current: 20µA