Alternative Parts


Features and Benefits

  • Complete Power Interface Port for IEEE 802.3af® Powered Devices (PDs)
  • Onboard 100V, 400mA Power MOSFET
  • Precision Input Current Limit
  • Onboard 25k Signature Resistor
  • Programmable Classification Current (Class 0-4)
  • Undervoltage Lockout
  • Smart Thermal Protection
  • Power Good Signal
  • Available in 8-Pin SO and Low Profile (3mm × 3mm) DFN Packages

Product Details

The LTC4257 provides complete signature and power interface functions for a device operating in an IEEE 802.3af Power over Ethernet (PoE) system. The LTC4257 simplifies Powered Device (PD) design by incorporating the 25k signature resistor, the classification current source, input current limit with thermal foldback, undervoltage lockout and power good signaling, all in a single 8-pin package. By incorporating a high voltage power MOSFET onboard, the LTC4257 provides the system designer with reduced cost while also saving board space.

The LTC4257 can interface directly with a variety of ADI's DC/DC converter products to provide a cost effective power solution for IP phones, wireless access points and other PDs. Analog Devices also provides solutions for Power Sourcing Equipment (PSE) applications with quad network power controllers.

The LTC4257 is available in the 8-pin SO and low profile (3mm × 3mm) DFN packages.


  • IP Phone Power Management
  • Wireless Access Points
  • Telecom Power Control

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.

Tools & Simulations


LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.


Models for the following parts are available in LTspice:


Product Recommendations

LTC4257 Companion Parts

Recommended Related Parts

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

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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 Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

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