Computer Controls

Si3406x - PoE+ Powered Device ICs with PD Interface and Switching Regulator

The Si3406x family of PoE+ Powered Devices ICs are the industry’s most highly-integrated, IEEE 802.3at Type 2-compliant, PoE PD interface and pulse-width-modulated (PWM) switching regulator ICs.

A Si3406x IC converts the high voltage (typically >48 V) supplied over Ethernet copper UTP cabling into a regulated, low-voltage dc supply. The Si3406x products combine all the required IEEE 802.3at Type 2 detection, classification and hot swap interfaces with a complete, high efficiency, PWM switching regulator.

Silicon Labs’ Si3406x family of devices provide high voltage discrete devices onto the PD chip, PoE+ power capability, flexible power conversion topology options with up to 90% efficiency, robust sleep/wake/LED support modes, and superior EMI performance aiding customers in creating cost-effective, high power, highly efficiency, and fast time to market PoE PD-powered solutions

Si3406x: Functional Diagram


Key Features:

  • Type 1 (PoE) or Type 2 (PoE+) power
  • Full IEEE 802.3at compliance
  • Synchronous secondary FET driver
  • Current mode dc-dc converter
  • Tunable switching frequency
  • Auxiliary transformer winding support
  • Auxiliary wall adapter support (12 V to 57 V)
  • Internal hotswap and switching FET bypass support
  • Automated maintain-power-signature (MPS) support
  • Sleep mode augmented with wake pin, mode control, and LED driver
  • 120 V Absolute Max voltage performance
  • Extended –40 to +85 °C temperature
  • Compact ROHS-compliant 5 mm x 5 mm QFN Package


  • Voice over IP telephones
  • Wireless access points
  • Security and surveillance IP cameras
  • Lighting luminaires
  • Point-of-sale terminals
  • Internet appliances
  • Network devices

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