LM1577/LM2577 Series SIMPLE SWITCHER Step-Up Voltage Regulator
June 1999
LM1577/LM2577 Series SIMPLE SWITCHER ® Step-U...
LM1577/LM2577 Series SIMPLE SWITCHER Step-Up Voltage
Regulator
June 1999
LM1577/LM2577 Series SIMPLE SWITCHER ® Step-Up Voltage
Regulator
General Description
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.
Features
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 n 52 kHz internal oscillator n Soft-start function reduces in-rush current during start-up n Output switch protected by current limit, under-voltage lockout, and thermal shutdown n n n n
Typical Applicat...