
Simple Step-Up Voltage Regulator
Requires Few External Components
NPN Output Switches 3.0A, 65V(max)
Extended Input Voltage Range: 3.0V to 40V
Current Mode Operation for Improved
Transient Response, Line Regulation, and
Current Limiting
Soft Start Function Provides Controlled
Startup
52kHz Internal Oscillator
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
5-Pin TO-220 (Top View)
T Package
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
Also available in TO-263 Package (TD).
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