LT1506

Features:

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


Application

Portable Computers
Battery-Powered Systems
Battery Charger
Distributed Power


Specifications

Input Voltage ..........................................................  16V
BOOST Pin Above Input Voltage.............................  15V
SHDN Pin Voltage.....................................................  7V
FB Pin Voltage (Adjustable Part)............................  3.5V
FB Pin Current (Adjustable Part)............................  1mA
Sense Voltage (Fixed 3.3V Part) ...............................  5V
SYNC Pin Voltage .....................................................  7V
Operating Junction Temperature Range
     LT1506C...............................................0°C to 125° C
     LT1506I...........................................  40°C to 125°C
Storage Temperature Range................  65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C


Description

The LT^(R) 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 tech- niques 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 utiliz-ing 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 20A. Synchronization allows an external logic level sig-nal to increase the internal oscillator from 580kHz to 1MHz.