LTC4279 - Single Port PoE/PoE+/ LTPoE++ PSE Controller


  • Compliant with IEEE 802.3at Type 1 and 2
  • Supports LTPoE++® Up to 90W
  • Supports Dual-Signature PDs
  • Fully Autonomous Operation without Microcontroller
  • Very Low Power Dissipation
    – 0.1Ω Sense Resistance
    – Low RDS(ON) External MOSFET
  • Very High Reliability 4-Point PD Detection
    – 2-Point Forced Voltage and Forced Current
  • Robust Short-Circuit Protection
  • Cable Surge Protected ±80V OUT pin
  • Classification Dependent ICUT and ILIM Current Thresholds
  • Supports 2-Pair and 4-Pair Output Power
  • UltraPWR Mode Supports Custom PDs up to 123W
  • Pin-Selectable Detection Backoff Timer for Midspans
  • Pin Programmable Legacy PD Detection
  • Pin Programmable Maximum Power Mode
  • Status LED Pin
  • Available in 20-Pin QFN and 16-Pin SO Packages

Typical Application

LTC4279 Typical Application
LTC4279 Typical Application


The LTC®4279 is an autonomous single port power sourcing equipment (PSE) controller designed for use in IEEE 802.3at Type 1, Type 2 and LTPoE++ compliant Power over Ethernet (PoE) systems. The LTC4279 provides fully autonomous IEEE 802.3 and LTPoE++ compliant operation without a microcontroller. The LTC4279 simplifies PSE implementation, requiring only a single supply and a small number of passive support components.

The LTC4279 delivers lowest-in-industry heat dissipation by utilizing a low-RDS(ON) external MOSFET and a 0.1Ω sense resistor, eliminating the need for expensive heat sinks and increasing efficiency.

PD discovery uses a proprietary dual-mode 4-point detection mechanism ensuring excellent immunity from false PD detection. Midspan PSEs are supported with physical layer classification and a 2.5 second backoff timer.

Legacy and custom PDs are supported with pin-selectable LEGACY and UltraPWR modes. LEGACY mode detects and powers pre-IEEE specification PDs. UltraPWR mode aggressively turns on and powers custom PDs requiring high inrush and/or operational currents.


For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LTC4279IS#PBF SO-16 S I 05-08-1610 (S16) Yes
LTC4279IS#TRPBF SO-16 S I 05-08-1610 (S16) Yes
LTC4279IUFD#PBF 4x5 QFN-20 UFD I 05-08-1711 Yes
LTC4279IUFD#TRPBF 4x5 QFN-20 UFD I 05-08-1711 Yes

LTC4279 Package Drawing
LTC4279 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LTC4279IS#PBF SO-16 I $4.93 $3.45 Yes
LTC4279IS#TRPBF SO-16 I $4.99 $3.51 Yes
LTC4279IUFD#PBF 4x5 QFN-20 I $4.93 $3.45 Yes
LTC4279IUFD#TRPBF 4x5 QFN-20 I $4.99 $3.51 Yes
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC2541A LTC4279 Demo Board | Single Port PoE/PoE+/LTPoE++ PSE Controller (Up to 123W) $150.00
DC2579A LTC4279 Demo Board | Single Port UltraPWR PSE Controller (123W) $200.00
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Click here to view our complete list of demo boards


  • PoE PSE Endpoints (Switch/Router)
  • PoE Midspan Power Injectors
  • Power Forwarders
  • Femto Cells
  • Security Systems

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Design Tools

Linear Technology provides a variety of custom design simulation tools and device models to allow even novice designers to quickly and easily evaluate circuits using high performance switching regulators, amplifiers, data converters, filters and more. Please visit our Design Tools page to view and download:

  • LTspice - A powerful SPICE simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators
  • LTpowerCAD - A complete power supply selection, synthesis and design tool
  • LTpowerPlay - A development environment supporting Linear Technology's Digital Power System Management (PSM) products
  • PScope & QuikEval - USB-based product demonstration and data acquisition system for use with our ADCs, DACs, and more
  • Linduino - Arduino compatible system for developing and distributing firmware libraries and example code
  • LinearLab Tools - A collection of Matlab and Python programs that provide direct access to Linear Technology’s data converter evaluation boards
  • And More!

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