DESCRIPTION
The LT®3573 is a monolithic switching regulator specifically designed for the isolated flyback topology. No third winding or optoisolator is required for regulation. The part senses the isolated output voltage directly from the primary side flyback waveform. A 1.25A, 60V NPN power switch is integrated along with all control logic into a 16- lead MSOP package.

FEATURES
■ 3V to 40V Input Voltage Range
■ 1.25A, 60V Integrated NPN Power Switch
■ Boundary Mode Operation
■ No Transformer Third Winding or
   Optoisolator Required for Regulation
■ Improved Primary-Side Winding Feedback
   Load Regulation
■ VOUT Set with Two External Resistors
■ BIAS Pin for Internal Bias Supply and Power
   NPN Driver
■ Programmable Soft-Start
■ Programmable Power Switch Current Limit
■ Thermally Enhanced 16-Lead MSOP

APPLICATIONS
■ Industrial, Automotive, Medical
■ Low Power PoE