Single Switch PWM Controller with Auxiliary Boost Converter

The LT1950 is a wide input range, forward, boost, flyback and SEPIC controller that drives an N-channel power MOSFET with few external components required.

A resistor programmable duty cycle clamp can be used to generate a volt-second clamp for forward converter applications. An internal boost switcher is available for creating a separate supply for the output gate driver, allowing 10V gate drive from input voltages as low as 3V. The LT1950’s operating frequency can be set with an external resistor over a 100kHz to 500kHz range and a SYNC pin allows the part to be synchronized to an external clock. Additional programmability exists for leading edge blanking and slope compensation.

A fast current sense comparator achieves 60ns current sense delay and the error amplifier is a true voltage mode error amplifier, allowing a wide range of compensation networks. An accurate shutdown pin with programmable hysteresis is available for undervoltage lockout and shutdown. The LT1950 is available in a small 16-Pin SSOP package.

Applications

* Telecom Power Supplies

* Automotive Power Supplies

* Portable Electronic Equipment

* Isolated and Nonisolated DC/DC Converters

* Wide Input Range: 3V to 25V

* Programmable Volt-Second Clamp

* Output Power Levels from 25W to 500W

* Auxiliary Boost Converter Provides 10V Gate Drive from VIN as Low as 3V

* Programmable Operating Frequency (100kHz to 500kHz) with One External Resistor

* Programmable Slope Compensation

* Programmable Leading Edge Blanking

* ±2% Internal 1.23V Reference

* Accurate Shutdown Pin Threshold with Programmable Hysteresis

* 60ns Current Sense Delay

* 2.5V Auxiliary Reference Output

* Synchronizable to an External Clock up to 1.5 • fOSC

* Current Mode Control

* Small 16-Pin SSOP Package