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.ApplicationsIP Phone Power ManagementWireless Access PointsTelecom Power Control