Overview

Features and Benefits

  • Complete Power Interface Port for IEEE 802®.3af  Powered Devices (PDs)
  • Onboard 100V, 400mA Power MOSFET
  • Precision Dual Level Current Limit
  • Onboard 25k Signature Resistor with Disable
  • Programmable Classification Current (Class 0-4)
  • Undervoltage Lockout
  • Thermal Overload Protection
  • Power Good Signal
  • Available in 8-Pin SO and Low Profile (3mm x 3mm) DFN Packages

Product Details

The LTC4257-1 provides complete signature and power interface functions for a device operating in an IEEE 802.3af Power over Ethernet (PoE) system. The LTC4257-1 simplifies Powered Device (PD) design by incorporating the 25k signature resistor, classification current source, input current limit, undervoltage lockout, thermal overload protection, signature disable and power good signalling, all in a single 8-pin package. The LTC4257-1 includes a precision, dual level current limit circuit. This allows it to charge large load capacitors and interface with legacy Power over Ethernet systems while maintaining compatibility with the current IEEE 802.3af specification. By incorporating a high voltage power MOSFET onboard, the LTC4257-1 provides the system designer with reduced cost while also saving board space.

The LTC4257-1 can interface directly with a variety of ADI DC/DC converter products to provide a cost effective power solution for IP phones, wireless access points and other PDs. Analog Devices also provides network power controllers for Power Sourcing Equipment (PSE) applications.

The LTC4257-1 is available in the 8-pin SO and low profile (3mm x 3mm) DFN packages.

Applications

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

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

Tools & Simulations

LTspice

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.

LTspice

Models for the following parts are available in LTspice:

LTC4257
LTC4257-1

Product Recommendations

LTC4257-1 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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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.