Isolated Monolithic Flyback Simplifies Design & Eliminates Optocoupler

Nov 11 2008 - MILPITAS, CA
  • Linear Technology Corporation announces the LT3573, an isolated monolithic flyback switching regulator with an integrated 1.25A NPN power switch. The LT3573 significantly simplifies the design of a flyback converter since it does not require a third winding or optoisolator and can sense the output voltage directly from the primary side flyback waveform. The LT3573 operates over an input voltage range of 3V to 40V at output power levels up to 7 watts, and can be used in a wide variety of industrial, medical, datacom and automotive applications requiring isolated power, including marine electronics, low power PoE and VoIP telephone interfaces.

    The LT3573 operates in Boundary Mode, which is a variable frequency current mode switching scheme, resulting in a total regulation band of ±3% over a wide input voltage range and output load current in a typical application. Boundary mode operation also permits the use of a smaller transformer when compared to equivalent continuous conduction mode designs. The output voltage is easily set by two external resistors.

    The LT3573 has additional features that include an on board LDO for 3rd winding powering, programmable soft start, undervoltage lockout, adjustable current limit and output voltage temperature compensation.

    Summary of Features: LT3573

    • VIN Range from 3V to 40V
    • On-Board 1.25A, 60V Integrated NPN Power Switch
    • No Transformer, Third Winding or Optoisolator Required for Feedback
    • Current Mode Control
    • Boundary Mode Operation
    • VOUT Set with Two External Resistors
    • Programmable Soft-Start
    • Programmable Under Voltage Lockout
    • Output Voltage Temperature Compensation
    • Adjustable Current Limit

    Isolated Monolithic Flyback Converter


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