DESCRIPTION
The LT®1952/LT1952-1 are current mode PWM controllers optimized to control the forward converter topology, using one primary MOSFET. The LT1952/LT1952-1 provide synchronous rectifi er control, resulting in extremely high efficiency. A programmable Volt-Second clamp provides a safeguard for transformer reset that prevents saturation. This allows a single MOSFET on the primary side to reliably run at greater than 50% duty cycle for high MOSFET, transformer and rectifier utilization. The devices include soft-start for controlled exit from shutdown and undervoltage lockout. A precision 107mV current limit threshold, independent of duty cycle, combines with softstart to provide hiccup short-circuit protection.

FEATURES
■ Synchronous Rectifi er Control for High Effi ciency
■ Programmable Volt-Second Clamp
■ Output Power Levels from 25W to 500W
■ Low Current Start-Up
   (LT1952: 460μA; VIN On/Off = 14.25V/8.75V)
   (LT1952-1: 400μA; VIN On/Off = 7.75V/6.5V)
■ True PWM Soft-Start
■ Low Stress Short-Circuit Protection
■ Precision 107mV Current Limit Threshold
■ Adjustable Delay for Synchronous Timing
■ Accurate Shutdown Threshold with Programmable Hysteresis
■ Programmable Slope Compensation
■ Programmable Leading Edge Blanking
■ Programmable Frequency (100kHz to 500kHz)
■ Synchronizable to an External Clock up to 1.5 • fOSC
■ Internal 1.23V Reference
■ 2.5V External Reference
■ Current Mode Control
■ Small 16-Pin SSOP Package

APPLICATIONS
■ Telecommunications Power Supplies
■ Industrial and Distributed Power
■ Isolated and Non Isolated DC/DC Converters