Features and Benefits

  • Wide Input Supply Range: 3.7V to 30V
  • Preactive Mode:
    • No Pulse Transformer Required
    • DCM Operation at Light Load
  • SYNC Mode:
    • FCM or DCM Operation at Light Load
    • Achieves Highest Efficiency
  • 1.5% Feedback Voltage Reference
  • 10mA Opto-Coupler Driver
  • Output Power Good Indicator
  • Integrated Soft-Start Function

Product Details

The LT8311 is used on the secondary side of a forward converter to provide synchronous MOSFET control and output voltage feedback through an opto-coupler. The LT8311’s unique preactive mode allows control of the secondary-side MOSFETs without requiring a traditional pulse transformer for primary- to secondary-side communication. In preactive mode, the output inductor current operates in discontinuous conduction mode (DCM) at light load. If forced continuous mode (FCM) operation is desired at light load, the LT8311 can, alternatively, be used in SYNC mode, where a pulse transformer is required to send synchronous control signals from the primary-side IC to the LT8311.

The LT8311 offers a full featured opto-coupler controller, incorporating a 1.5% reference, a transconductance error amplifier and a 10mA opto-driver. Power good monitoring and output soft-start/overshoot control are also included. The LT8311 is available in a 16-lead FE package with pins removed for high voltage spacing requirements.


  • Offline and HV Car Battery Isolated Power Supplies
  • 48V Isolated Power Supplies
  • Industrial, Automotive and Military Systems

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (4)

Tools & Simulations


LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

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Models for the following parts are available in LTspice:


Design Resources

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PCN-PDN Information

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Evaluation Boards

Pricing displayed is based on 1-piece.

Up to two boards can be purchased through Analog.com. To order more than two, please purchase through one of our listed distributors.

Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.