High power controller

Linear Technology has introduced the LTC4265, an 802.3af/802.3at-compliant Power over Ethernet interface controller for high-power powered device (PD) applications needing up to 25.5 W. A new IEEE 802.3at definition, also known as the PoE+ standard, has expanded the power budget and improves the classification mechanism used by power sourcing equipment and PDs to identify each other.

The device is an IEEE 802.3at high-power interface controller with 2-Event Classification Recognition that is backward-compatible with IEEE 802.3af and unlocks the next level of potential for PoE applications.

The controller caters to a new breed of high-performance devices, using the new PoE+ standard, including video teleconferencing stations, RFID readers, pan-tilt-zoom security cameras and longer range wireless access points.

The device recognises the PSE as either Type-1 hardware complying with the IEEE 803.2af power levels or Type-2 hardware complying with IEEE 802.3 at power levels, allocating power accordingly.

2-Event hardware classification allows Type-2 PSEs to identify connection to an 802.3at-compliant PD and provides a signal to the PD that is able to source the higher power levels associated with 802.4at power.

This latest classification ensures interoperability between Type 1 and Type 2 devices.

The controller also features a slew of conventional PoE features. For efficient power allocation, users can configure a classification load current that represents the PD power classification.

A shutdown pin with signature corrupt provides flexible auxiliary set-up. A rugged 100 V MOSFET isolates the controller and external DC/DC converter during detection and classification, while providing 100 mA of inrush current limiting for smooth power-up transitions.

The device also includes complementary power good outputs, an onboard signature resistor, undervoltage/overvoltage lockout and comprehensive thermal protection.