This document is about L6566B multi-mode controller. It features selectable multi-mode operation, on-board high-voltage start-up, advanced light load management, low quiescent current, adaptive undervoltage lockout, line feedforward for constant power capability vs mains voltage, pulse-by-pulse overcurrent protection, transformer saturation detection, programmable frequency modulation for EMI reduction, overvoltage protection, brownout protection, and -600/+800 mA totem pole gate driver.