LM5027

LM5027 Voltage Mode Active Clamp Controller www.DataSheet4U.com August 18, 2009 LM5027 Voltage Mode Active Clamp Controller General Description The LM5027 pulse-width modulation (PWM) controller contains all of the features necessary to implement power converters utilizing the Active Clamp / Reset technique. With the active clamp technique, higher efficiencies and greater power densities can be realized compared to conventional catch winding or RDC clamp / reset techniques. Three control outputs are provided: the main power switch control (OUTA), the active clamp switch control (OUTB), and secondary side synchronous rectifier control (OUTSR). The timing between the control outputs is adjustable with external resistors that program internal precision timers. This controller is designed for high-speed operation including an oscillator frequency range up to 1 MHz and total PWM propagation delays less than 50 ns. The LM5027 includes a high-voltage startup regulator with a maximum input voltage rating of 105V. Additional features include Line Under Voltage Lockout (UVLO), separate softstart of main and synchronous rectifier outputs, a timer for hiccup mode current limiting, a precision reference, and thermal shutdown. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Voltage-Mode control Line feed-forward PWM ramp Internal 105V rated start-up bias regulator Programmable line Under-Voltage Lockout (UVLO) with adjustable hysteresis Versatile dual mode over-current protection Programmable volt...