Features and Benefits

  • 25.5W IEEE 802.3at Compliant (Type 2) PD
  • 10V to 57V Auxiliary Power Input
  • Shutdown Pin for Flexible Auxiliary Power Support
  • Integrated State-of-the-Art No-Opto Synchronous Flyback Controller
    • – Isolated Power Supply Efficiency >92%
    • – 88% Efficiency Including Diode Bridge and Hot Swap FET
  • Superior EMI Performance
  • Robust 100V 0.7Ω (Typ) Integrated Hot Swap MOSFET
  • IEEE 802.3 at High Power Available Indicator
  • Integrated Signature Resistor and Programmable Class Current
  • Undervoltage, Overvoltage and Thermal Protection
  • Short-Circuit Protection with Auto-Restart
  • Programmable Soft-Start and Switching Frequency
  • Complementary Power Good Indicators
  • Thermally Enhanced 7mm × 4mm DFN Package

Product Details

The LTC4278 is an integrated Powered Device (PD) controller and switching regulator intended for high power IEEE 802.3at and 802.3af applications. With a wide input voltage range, the LTC4278 is specifically designed to support PD applications that include a low-voltage auxiliary power input such as a 12V wall adaptor. The inclusion of a shutdown pin provides simple implementation of both PoE and auxiliary dominate applications. In addition, the LTC4278 supports both 1-event and 2-event classifications as defined by the IEEE, thereby allowing the use in a wide range of product configurations.

The LTC4278 synchronous, current mode, flyback controller generates multiple supply rails in a single conversion step providing for the highest system efficiency while maintaining tight regulation across all outputs. The LTC4278 includes Linear Technology’s patented No-Opto feedback topology to provide full IEEE 802.3 isolation without the need of an opto-isolator circuit. A true soft-start function allows graceful ramp-up of all output voltages.

The LTC4278 is available in a space saving 32-pin DFN package.


  • VoIP Phones with Advanced Display Options
  • Dual-Radio Wireless Access Points
  • PTZ Security Cameras
  • RFID Readers
  • Industrial Controls

Product Lifecycle icon-recommended Recommended for New Designs

This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.

Evaluation Kits (1)

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Product Recommendations

LTC4278 Companion Parts

Recommended Related Parts

Design Resources

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Evaluation Boards

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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.