Isolated Monolithic Flyback Regulator Eschews Optoisolator, Third Winding
The LT8302 monolithic flyback regulator developed by Linear Technology simplifies the design of isolated dc-dc converters: It samples the isolated output voltage directly from the primary-side flyback waveform, eliminating the need for an optoisolator or third winding for regulation. The device operates over a 2.8- to 42-V input voltage range. It incorporates a 3.6-A/65-V power switch, and delivers up to 15 W of output power. The LT8302 operates in boundary mode (a variable frequency current-mode control switching scheme), which usually results in ±5% regulation over the full line, load, and temperature range. With boundary mode, a smaller transformer can be used versus those employed in continuous conduction-mode designs. Two external resistor set the output voltage and transformer turns ratio. Other features include output short-circuit protection, 380-µA no-load quiescent current with output voltage in regulation, internal soft-start and compensation, and output-diode temperature compensation. It comes in a thermally enhanced SO-8 package. The LT8302 will find homes in various industrial, medical, datacom, military, and automotive applications.