LT3781

LT3781 “Bootstrap” Start Dual Transistor Synchronous Forward Controller U U FEATURES s High Voltage Operation up to 72V s Synchronizable Operating Frequency and Output Switch Phase for Multiple Controller Systems s Synchronous Switch Output s Undervoltage Lockout Protection with 6V Hysteresis for Self-Biased Power s Fixed Frequency Operation to 350kHz s Local ±1% Voltage Reference s Input Overvoltage Protection s Low Start-Up Current s Programmable Start Inhibit for Power Supply Sequencing and Protection s Optocoupler Support s Soft-Start ControUl APPLICATIO S s Isolated Telecommunication Systems s Personal Computers and Peripherals s Distributed Power Step-Down Converters s Lead Acid Battery Backup Systems s Automotive and Heavy Equipment DESCRIPTIO The LT®3781 controller simplifies the design of high power synchronous dual transistor forward DC/DC converters. The part employs fixed frequency current mode control and supports both isolated and nonisolated topologies. The IC drives external N-channel power MOSFETs and operates with input voltages up to 72V. The LT3781 is ideal for output derived power schemes, through the use of a large undervoltage lockout hysteresis range. The part is also equipped with an 18V VCC shunt regulator, which prevents exceeding absolute maximum ratings while in trickle start applications. The LT3781’s operating frequency is programmable and can be synchronized up to 350kHz. Switch phase is also controlled during synchronized operation to accom...