The LTC4279 is an autonomous single port power sourcing equipment (PSE) controller designed for use in IEEE 802.3at Type 1, Type 2 and LTPoE++ compliant Power over Ethernet (PoE) systems. The LTC4279 provides fully autonomous IEEE 802.3 and LTPoE++ compliant operation without a microcontroller. The LTC4279 simplifies PSE implementation, requiring only a single supply and a small number of passive support components.The LTC4279 delivers lowest-in-industry heat dissipation by utilizing a low-RDS(ON)external MOSFET and a 0.1Ω sense resistor, eliminating the need for expensive heat sinks and increasing efficiency.PD discovery uses a proprietary dual-mode 4-point detection mechanism ensuring excellent immunity from false PD detection. Midspan PSEs are supported with physical layer classification and a 2.5 second backoff timer.Legacy and custom PDs are supported with pin-selectable LEGACY and UltraPWR modes. LEGACY mode detects and powers pre-IEEE specification PDs. UltraPWR mode aggressively turns on and powers custom PDs requiring high inrush and/or operational currents.ApplicationsPoE PSE Endpoints (Switch/Router)PoE Midspan Power InjectorsPower ForwardersFemto CellsSecurity Systems