Simple Step-Up Voltage Regulator

•

Requires Few External Components

•

NPN Output Switches 3.0A, 65V(max)

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Extended Input Voltage Range: 3.0V to 40V

•

Current Mode Operation for Improved

Transient Response, Line Regulation, and

Current Limiting

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Soft Start Function Provides Controlled

Startup

•

52kHz Internal Oscillator

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Output Switch Protected by Current Limit,

Undervoltage Lockout and Thermal

Shutdown

•

Improved Replacement for LM2577-ADJ

Series

The UC2577-ADJ device provides all the active functions neces-

sary to implement step-up (boost), flyback, and forward converter

switching regulators. Requiring only a few components, these sim-

ple regulators efficiently provide up to 60V as a step-up regulator,

and even higher voltages as a flyback or forward converter regula-

tor.

The UC2577-ADJ features a wide input voltage range of 3.0V to

40V and an adjustable output voltage. An on-chip 3.0A NPN switch

is included with undervoltage lockout, thermal protection circuitry,

and current limiting, as well as soft start mode operation to reduce

current during startup. Other features include a 52kHz fixed fre-

quency on-chip oscillator with no external components and current

mode control for better line and load regulation.

A standard series of inductors and capacitors are available from

several manufacturers optimized for use with these regulators and

are listed in this data sheet.

UC2577-ADJ

3/97

FEATURES

DESCRIPTION

CONNECTION DIAGRAM

BLOCK DIAGRAM

UDG-94034

•

Simple Boost and Flyback Converters

•

SEPIC Topology Permits Input Voltage to

be Higher or Lower than Output Voltage

•

Transformer Coupled Forward Regulators

•

Multiple Output Designs

TYPICAL APPLICATIONS

5-Pin TO-220 (Top View)

Also available in TO-263 Package.