FEATURES
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LTC4278 IEEE 802.3at PD with Synchronous No-Opto Flyback Controller and 12V Aux Support DESCRIPTION
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 specically 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 classications as dened by the IEEE, thereby allowing the use in a wide range of product congurations. The LTC4278 synchronous, current mode, yback controller generates multiple supply rails in a single conversion step providing for the highest system efciency 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.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5841643.
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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 Efciency >92% – 88% Efciency Including Diode Bridge and Hot Swap FET Superior EMI Performance Robust 100V 0.7Ω (Typ) Integrated Hot Swap MOSFET IEEE 802.3at 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

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