Capable of exceeding 25.5W as specified in the 2009 IEEE 802.3 at standard

Linear Technology Korea (CEO Hong Sa-kwak) announced the release of an IEEE 802.3bt PD (powered device) interface controller (product name: LT4295) for applications requiring a maximum power supply of 71W.

IEEE 802.3bt, the next-generation Power over Ethernet (PoE) standard, is characterized by its ability to handle power exceeding 25.5W as defined by the 2009 IEEE 802.3 at standard. Linear Technology has introduced the industry's first next-generation IEEE compliant product.

The new standard known as PoE++ or 4PPoE allows for increased power budgets, enabling new applications and features, while simultaneously supporting 10 Gigabit Ethernet (10GBASE-T) and maintaining backward compatibility using older IEEE equipment. The LT4295 is IEEE 802.3bt (Draft 2.0) compatible and supports new features including all additional PD classes (5, 6, 7, 8), additional PD types (Type 3, Type 4), and 5 event classifications.

The LT4295, a single-signature 802.3bt PD controller, includes an isolated switching regulator controller, supports auxiliary power input, and can operate in a synchronous flyback topology that does not require high-efficiency forward and optocouplers. By reducing the number of components and board space with such a high level of integration, it further simplifies the front-end PD design and enables efficient power supply to the PD load using a single LT4295 IC.

Unlike conventional PD controllers that integrate power MOSFETs, the LT4295 controls an external MOSFET to reduce overall PD power consumption and maximize power efficiency. This is a particularly important feature when dealing with high power levels, such as 802.3bt. The external MOSFET architecture allows for MOSFET sizing to meet the user's application requirements. Standard LT4295-based designs typically use a 30mΩ RDS(ON).

The LT4295 is available in industrial and automotive grades, operating over temperature ranges of –40°C to 85°C and –40°C to 125°C, respectively. The LT4295 starts at $2.75 per unit for 1,000 units, and bulk orders are available. The LT4295 is designed to be used as an upgrade for Linear Technology's existing PoE+PD controllers, such as the LT4276 or LT4275. To maximize available power and reduce power consumption at the PD, the LT4321 Ideal Diode Bridge Controller should be used.