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LT1950

Single Switch PWM Controller with Auxiliary Boost Converter

Linear Technology 

FEATURES

■ 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 SSUOP Package

APPLICATIO S

■ Telecom Power Supplies

■ Automotive Power Supplies

■ Portable Electronic Equipment

■ Isolated and Nonisolated DC/DC Converters

LT1950

Single Switch PWM

Controller with Auxiliary

Boost Converter

DESCRIPTIO

The LT®1950 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 appli-

cations. 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 shut-

down. The LT1950 is available in a small 16-Pin SSOP

package.

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATIO

36V to 72V DC to 26V/5A (Single Switch) Forward Converter

2.5V

0.1µF

249k

4.99k

SLOPE

VIN

VREF

VIN2

BOOST VSEC

ROSC

SHDN

LT1950

BLANK GATE

SYNC

GND

ISENSE

PGND

FB

COMP

10VBIAS

VIN

MBRB20200 47µH

470k

1µF 18k

PA0581

Si7450

47µF

0.015Ω

4.7k

0.022µF 100k

1950 TA01a

VOUT

26V

5A

Efficiency vs Load Current

95

VIN = 36V

90

VIN = 48V

VIN = 72V

85

80

75

70

0.5

1.5 2.5 3.5 4.5 5.5

LOAD CURRENT (A)

1950 TA01b 1950fa

1

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