Power over Ethernet controller for power-hungry applications

Linear Technology has introduced the LTC4279 single port PoEcontroller for PSE, delivering up to 123W of power over CAT-5e cable for power-hungry applications. Demand for higher power delivery comes from a widespread set of applications, including LTE picocell base stations, LED signage, security monitoring systems, home automation and machine vision systems. The highly versatile device delivers power to a wide variety of PDs. This includes all legacy (<13W), IEEE 802.3at Type 1 (13W) and Type 2 (25.5W) PDs, Linear’s proprietary LTPoE++ (up to 90W), and custom (<123W) PDs. Two-pair and four-pair output topologies are supported, as well as single-signature and dual-signature architectures. Resistor-adjustable power selection allows the device to be easily configured for multiple sockets, simplifying design and bill of materials. The device provides fully autonomous operation for a wide variety of PSE applications, including endpoints and midspan power injectors. A low power sense resistor and external MOSFET simplify thermal design; traditional PSEs utilize less robust MOSFETs with higher RDS(ON). PD discovery is accomplished using a high reliability four-point detection mechanism that ensures best-in-class immunity from false PD detection. The device provides a comprehensive set of PD classification mechanisms to enable wide system compatibility. Robustness is reinforced with classification-dependent current cutoff and limit thresholds, short-circuit protection and ±80V cable surge protection. The device is offered in the industrial temperature grade (–40C to 85C) and is available in RoHS-compliant 4mm x 5mm QFN-20 and SO-16 packages.