LTC4257-1

PRODUCTION

IEEE 802.3af PD Power over Ethernet Interface Controller with Dual Current Limit

Part Models: 8
1ku List Price: Starting From $1.29

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Overview

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

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

Part Models: 8
1ku List Price: Starting From $1.29

Documentation

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. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC4257CDD-1#PBF	8-Lead DFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257CDD-1#TRPBF	8-Lead DFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257CS8-1#PBF	8-Lead SOIC (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257CS8-1#TRPBF	8-Lead SOIC (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257IDD-1#PBF	8-Lead DFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257IDD-1#TRPBF	8-Lead DFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257IS8-1#PBF	8-Lead SOIC (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4257IS8-1#TRPBF	8-Lead SOIC (Narrow 0.15 Inch)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Dec 14, 2023 - 22_0255 Epoxy Change from Henkel 8290 to 8290A for 8-Lead SOIC Package (PCN part 2 of 2)
		PCN22_0255_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LTC4257CS8-1#PBF	PRODUCTION
LTC4257CS8-1#TRPBF	PRODUCTION
LTC4257IS8-1#PBF	PRODUCTION
LTC4257IS8-1#TRPBF	PRODUCTION
Jun 16, 2021 - 21_0026 Laser Top Mark for 8SOICN Assembled in ADPG, UTL and CRM
		PCN21_0026_Form Material_Report Delta Qualification Matrix
LTC4257CS8-1#PBF	PRODUCTION
LTC4257CS8-1#TRPBF	PRODUCTION
LTC4257IS8-1#PBF	PRODUCTION
LTC4257IS8-1#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

Parts	Product Life Cycle	Description
Circuit Monitors 1
LT2940	PRODUCTION	Power and Current Monitor
Power-over-Ethernet (PoE) Controllers 1
LT4275	PRODUCTION	LTPoE++/PoE+/PoE PD Controller

Tools & Simulations

LTspice 1

LTC4257-1 - Power-over-Ethernet (PoE) Interface Controllers

Models for the following parts are available in LTspice:

LTC4257
LTC4257-1

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.