Optocoupler-Less Flyback Regulator Delivers Up To 6 W

Linear Technology says its LT3801 monolithic flyback regulator simplifies isolated dc-dc converter design: By sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no opto-isolator or third winding for regulation. Input voltage ranges from 2.7 to 42 V. Coupled with a 1.2-A/65-W power switch and up to 6 W of output power, the device will find homes in industrial, medical, datacom, military, and automotive applications. Boundary-mode operation—a variable-frequency, current-mode control switching scheme—typically results in ±5% regulation over the full line, load, and temperature range. A single resistor and transformer turns ratio facilitate setting the output voltage. Other features include overload protection, 380-µA no-load quiescent current with the output voltage in regulation, internal soft-start, internal loop compensation, and output diode temperature compensation. The LT8301, which comes in a TSOT-23 package,  operates over a junction temperature range of ‒40 to 125°C (automotive- and military-grade versions operate from ‒40 to 150°C and ‒55 to 150°C, respectively).

LINEAR TECHNOLOGY CORP.