The LTC4274A from Analog Devices is a Power Sourcing Equipment Controller that has been designed for use in IEEE 802.3at Type 1 and Type 2 (high power)-compliant power-over-ethernet (PoE) systems. It requires an input voltage of 3 - 4.3 V and delivers an output power of 90 W. This controller uses low-resistance external MOSFETs and 250 milli-ohms sense resistors to ensure low power dissipation, especially at higher current levels. It includes 14-bit current monitoring ADCs, a DAC-programmable current limit, and a versatile quick port shut-down function. It uses proprietary detection/classification scheme that allows mutual identification between the LTPoE++ controller and LTPoE++ PD, and subsequent powering of the PD.

This controller IC also incorporates a unique dual-mode 4-point detection mechanism for power delivery (PD) discovery, which ensures strong immunity against false PD detection. The controller features a high-speed 1 MHz I2C serial interface for control and a midspan backoff timer. It is available in a surface-mount package that measures 5 x 7 mm and is ideal for PoE PSE switches and routers and PoE PSE midspans applications.