The LTC4263 is an autonomous single-channel PSE controller for use in IEEE 802.3af compliant Power over Ethernet systems. It includes an on-board power MOSFET, internal inrush, current limit, and short-circuit control, IEEE 802.3af compliant PD detection and classification circuitry, and selectable AC or DC disconnect sensing. On-board control algorithms provide complete IEEE 802.3af compliant operation without the need of a microcontroller. The LTC4263 simplifies PSE implementation, needing only a single 48V supply and a small number of passive support components.Programmable on-board power management circuitry permits multiple LTC4263s to allocate and share power in multi-port systems, allowing maximum utilization of the 48V power supply—all without the intervention of a host processor. The port current limit can be configured to automatically adjust to the detected PD class. Detection back-off timing is configurable for either Endpoint or Midspan operation. Built-in foldback and thermal protection provide comprehensive fault protection.An LED pin indicates the state of the port controlled by the LTC4263. When run from a single 48V supply, the LED pin can operate as a simple switching current source to reduce power dissipation in the LED drive circuitry.The LTC4263 is available in 14-pin 4mm × 3mm DFN and 14-pin SO packages.ApplicationsIEEE 802.3af Compliant Endpoint/Midspan PSEsSingle-Port or Multi-Port Power InjectorsPower ForwardersLow-Port Count PSEsEnvironment B PSEsStandalone PSEs