The LTC3765 is a start-up controller and gate driver for use in a self-starting secondary-side control forward converter. When combined with the LTC3766 secondary-side synchronous forward controller, a complete isolated power supply is created using a minimum of discrete parts. A proprietary scheme is used to multiplex gate drive signals and bias power across the isolation barrier through a small pulse transformer. A precision undervoltage lockout circuit and linear regulator controller ensure a quick and well-controlled start-up. The LTC3766 has been designed to simplify the design of active clamp forward converters. Working in concert with the LTC3765, the LTC3766 forms a robust, self-starting converter that eliminates the need for the separate bias regulator that is commonly used in secondary-side control applications. A precision current-limit coupled with clean start-up into a pre-biased load make the LTC3766 an excellent choice for high-power battery charger applications. The LTC3766 provides extensive remote sensing and output protection features, while Direct Flux Limit guarantees no transformer saturation without compromising transient response.