LTC4257-1 Datasheet | Linear Technology

IEEE 802.3af PD Power over Ethernet Interface Controller with Dual Current Limit Features - plete Power Interface Port for IEEE 802®.3af Powered Devices (PDs) - Onboard 100V, 400m A 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 × 3mm) DFN Packages U APPLICATIO S - IP Phone Power Management - Wireless Access Points - Tele Power Control DESCRIPTIO The LTC®4257-1 provides plete signature and power interface functions for a device operating in an IEEE 802.3af Power over Ethernet (Po E) 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 patibility 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 Linear Technology DC/DC converter products to provide a cost effective power solution for IP phones, wireless access points and other PDs. Linear Technology 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 × 3mm) DFN packages. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO Powered Device (PD) - 48V FROM POWER...