Linear - High-efficiency LTPoE++ PD controllers integrate forward / fly-back controller (LT4276)

For applications that require output power from 2W to 90W, Linear Technology has introduced the LT4276 LTPoE ++, PoE + and PoE-Compatible Powered Device (PD) Interface Controller. The LT4276 integrates a PD controller and an isolated switching regulator controller, enabling synchronous operation in forward and flyback topologies with auxiliary power support. This integration simplifies front-end PD design by reducing component count and board space, allowing the LT4276A (LTPoE ++), LT4276B (PoE +), and LT4276C (PoE) to efficiently power PD loads using only one IC. Linear Technology's LTPoE ++ standard extends today ’s ultra-high-power applications (such as pico-cells) by extending the power budget to four new power levels (38.7W, 52.7W, 70W, and 90W) Base stations, signage and heated outdoor security cameras). Unlike traditional PD controllers with integrated power MOSFETs, the LT4276 controls an external MOSFET to greatly reduce the overall heat dissipation of the PD and maximize power efficiency, which is especially important at higher power levels. This novel approach allows the user to adjust the size of the MOSFET according to the specific heating and efficiency requirements of the application, and use MOSFETs as low as 30mΩ RDS (ON) when necessary. The nominal input voltage is 100V, which means that the LT4276 can easily survive and protect PDs from the most common Ethernet line surges. The LT4276 offers industrial and extended temperature grades, supporting operating temperature ranges of -40C to 85C and -40C to 125C, respectively, and is available in a small RoHS-compliant 28-lead 4mm x 5mm QFN package. The LT4276 can be mass produced, providing an upgrade path from Linear Technology's existing PD products (including the LT4275 LTPoE ++ PD controller) and seamlessly connecting to its latest PSE controllers, including single-port LTC4274, 4-port LTC4266 , 8-port LTC4290 / 71 chipset and 12-port LTC4270 / 71 chipset. The company states that the LT4276 can also be used with the LT4321 ideal diode bridge controller to maximize available power and reduce heat dissipation in the PD.