Date: 13/12/2008

IEEE 802.3af/802.3at compliant PoE interface controller PD applications

The new LTC4265, IEEE 802.3at/ IEEE 802.3af/ compliant High Power Powered Device (PD) Controller from Linear Technology is suitable for applications needing up to 25.5W of power. The LTC4265 comes with 2-Event Classification Recognition that is backward compatible with IEEE 802.3af.
The applications catered are video teleconferencing stations, RFID readers, pan-tilt-zoom security cameras and longer-range wireless access points. The LTC4265 recognizes the PSE as either Type-1 hardware complying with the IEEE 802.3af power levels or Type-2 hardware complying with IEEE 802.3at 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 802.3at power. This new classification mechanism ensures interoperability between Type 1 and Type 2 devices.

The other key features are,

1. For efficient power allocation, users can configure a classification load current that represents the PD power classification.
2. A shutdown pin with signature corrupt provides flexible auxiliary support.
3. 100V MOSFET isolates the controller and external DC/DC converter during detection and classification, while providing 100mA of inrush current limiting for smooth power-up transitions.
4. The LTC4265 also includes complementary power good outputs, an on-board signature resistor, undervoltage/overvoltage lockout and comprehensive thermal protection.

The LTC4265 is offered in commercial and industrial versions, supporting operating temperature ranges from 0°C to 70°C and -40°C to 85°C respectively.
Package: 4mm x 3mm DFN-12 package.
Price: Each at $1.40 each in 1,000 K pieces
Availability: Available now in production quantities.

The LTC4265 provides an upgrade path from Linear's existing PD products, including the IEEE 802.3af pin-compatible LTC4264.
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