Si3402 PD Interface and Switching Regulator

The Si3402 is the industry’s most highly-integrated, IEEE 802.3 clause 33 compliant, PoE PD interface and pulse-width-modulated (PWM) switching regulator. By setting a new bar for device integration, lowest overall BOM cost, efficiency and reliability, the Si3402 enables designers to easily add PoE functionality to their Ethernet products. When connected in a PoE-enabled system, such as a wireless access point or VoIP phone, the Si3402 converts the high voltage (typically ±48 V) supplied over Ethernet copper UTP cabling into a regulated, low-voltage dc supply. In addition, the Si3402 combines all the required IEEE 802.3 clause 33 detection, classification and hot swap interfaces with a complete, high efficiency, PWM switching regulator, including programmable soft start.


  • Supports non-isolated and isolated switching topologies
  • Fully integrated high-voltage devices
  • Two complete diode bridges
  • Transient voltage suppressor
  • Switching regulator driver FET
  • Dual current-limited hot swap switch
  • Comprehensive protection circuitry
  • Transient over-voltage protection
  • Under voltage lockout
  • Thermal shutdown protection
  • Fold back current limiting
  • Low-EMI slew rate control



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Data Sheet (2)

User Guides (3)

Si3402 EVB User Guide
Si3402ISO EVB User Guide
Si3460-EVB User Guide

Application Notes (7)

White Papers (1)

Miscellaneous (2)

Si3402 Switcher Calculator
Si3402 UNH Reports

PCN (12)

Design Tools

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Schematics/Layout (2)

Product Matrix
Part NumberDatasheetTemperature RangeDescriptionPackage TypeMaximum Output Power

-40 to 85 °CPoE PD Interface with DCDC ConverterQFN2017 W


    • Complete IEEE 802.3af compliant PD interface, hot swap controller and efficient PWM switching regulator
    Compared to competing PD solutions, which typically require several external high-voltage discrete devices to complete a PD interface, the Si3402 uniquely integrates two full diode bridges, a transient voltage suppressor and a switching regulator driver FET on chip. Depending on the application’s power supply isolation requirements, the primary benefits of the Si3402 regulator's unmatched integration level are:
    • Elimination of four critical high-voltage BOM components: Two full diode bridges, a transient voltage suppressor and a switching regulator driver FET
    • Reduction in external BOM savings of at least $0.30 to $0.40 USD
    • Reduction of typical PCB layout footprints of 30%
    • Direct connection to RJ-45 jack for reduced EMI
    • Simplified design, PCB layout and validation processes
    Leveraging Silicon Labs' proven high-voltage design and manufacturing expertise, the Si3402 also enables enhanced PoE functionality, such as intelligent, system-level circuit protection and an early power loss indicator for reliable shut down of the PD when power is lost.


    Product Matrix





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