(ACTIVE) SIMPLE SWITCHER® 3.5V to 40V, 3A Low Component Count Step-Up Regulator


Functional diagram

Typical Performance


The LM1577/LM2577 are monolithic integrated circuits that provide all of the power and control functions for step-up (boost), flyback, and forward converter switching regulators. The device is available in three different output voltage versions: 12V, 15V, and adjustable.

Requiring a minimum number of external components, these regulators are cost effective, and simple to use. Listed in this data sheet are a family of standard inductors and flyback transformers designed to work with these switching regulators.

Included on the chip is a 3.0A NPN switch and its associated protection circuitry, consisting of current and thermal limiting, and undervoltage lockout. Other features include a 52 kHz fixed-frequency oscillator that requires no external components, a soft start mode to reduce in-rush current during start-up, and current mode control for improved rejection of input voltage and output load transients.


  • Requires Few External Components
  • NPN Output Switches 3.0A, can Stand off 65V
  • Wide Input Voltage Range: 3.5V to 40V
  • Current-mode Operation for Improved Transient Response, Line Regulation, and Current Limit
  • 52 kHz Internal Oscillator
  • Soft-start Function Reduces In-rush Current During Start-up
  • Output Switch Protected by Current Limit, Under-voltage Lockout, and Thermal Shutdown

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Vin (Min) (V) 3.5   
Vin (Max) (V) 40   
Vout (Min) (V) 1.23   
Vout (Max) (V) 15   
Switch Current Limit (Typ) (A) 3   
Regulated Outputs (#) 1   
Switching Frequency (Min) (kHz) 52   
Switching Frequency (Max) (kHz) 52   
Iq (Typ) (mA) 10   
Duty Cycle (Max) (%) 95   
Operating Temperature Range (C) -40 to 125   
Rating Catalog   
Package Group DDPAK/TO-263^TO-220   

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