LM1577

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...