Demonstration circuit 1803A is a monolithic high voltage isolated flyback converter featuring the LT3512. The demo circuit is designed for a 5V isolated output from an input voltage range of 36V to 75V. The maximum output current is 500mA. VIN can be lower if output current is less than 500mA. The circuit doesn’t require an opto-isolator due to the output voltage being sensed directly from the primary side transformer winding. A third winding is used to bias the LT3512 for highest efficiency.