Isolated Monolithic Flyback Regulator Simplifies Design & Eliminates Optocoupler

Aug 2 2010 - MILPITAS, CA
  • Linear Technology Corporation announces the LT3575, an isolated monolithic flyback switching regulator that significantly simplifies the design of an isolated DC/DC converter. No opto-isolator, third winding or signal transformer are required for feedback since the output voltage is sensed from the primary-side flyback signal. The LT3575 operates over a 3V to 40V input voltage range, has a 2.5A power switch and delivers up to 14 Watts of output power, making it well suited for a wide variety of industrial, medical, telecom, datacom and automotive applications.

    The LT3575 operates in boundary mode, which is a variable frequency current-mode control switching scheme, typically resulting in ±5% regulation over the full line, load and temperature range. Boundary mode also permits the use of a smaller transformer compared to equivalent continuous conduction-mode designs. The output voltage is easily set by two external resistors and the transformer turns ratio. Several off-the-shelf transformers, identified in the data sheet, can be used for numerous applications. The high level of integration and the 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 on-board low dropout regulator for IC power, programmable soft-start, undervoltage lockout, adjustable current limit and output voltage temperature compensation.

    The LT3575 is available in a small thermally enhanced TSSOP-16 package and is offered in an extended and industrial operating junction temperature range from –40°C to 125°C. Pricing starts at $3.50 each in 1000-piece quantities. For more information, visit

    Summary of Features: LT3575

    • VIN Range from 3V to 40V
    • Onboard 2.5A, 60V Integrated Power Switch
    • No Transformer, Third Winding or Opto-Isolator Required for Feedback
    • Current-Mode Control
    • Boundary-Mode Operation
    • VOUT Set with Two External Resistors
    • Off-the-Shelf Transformers
    • Programmable Soft-Start
    • Programmable Undervoltage Lockout
    • Output Voltage Temperature Compensation
    • Adjustable Current Limit

    Isolated Monolithic Flyback Converter


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