The LT3574 from Linear Technology is an isolated monolithic flyback switching regulator that is said to simplify the design of low-power isolated DC/DC converters. No opto-isolator, third winding or signal transformer is required for feedback since the output voltage is sensed from the primary-side flyback signal. The LT3574 operates over a 3V to 40V input voltage range, has a 0.65A NPN power switch and can deliver up to 3W of output power. This makes it suitable for a variety of industrial, medical, telecom, datacom and automotive applications. The LT3574 operates in boundary mode, which is a variable frequency current mode control switching scheme, resulting in +/-5 per cent regulation over the full line, load and temperature range. Boundary mode also permits the use of a smaller transformer compared with equivalent continuous conduction mode designs. The output voltage is easily set by two external resistors and the transformers turns ratio. Several off-the-shelf transformers are identified in the data sheet that can be used for numerous applications. The high level of integration and use of boundary mode operation results in a simple, clean application solution to the traditionally tough problem of isolated power delivery. Additional features include an onboard low dropout regulator for IC power, programmable soft start, undervoltage lockout, adjustable current limit and output voltage temperature compensation. The LT3574 is available in a small MSOP-16 package and is offered in an extended and industrial operating junction temperature range at -40C to 125C.