Linear supports IEEE 802.3at PoE+ standard
Launch of Switch-Integrated High-Power PD Controller


July 1, 2009 -- Linear Technology Korea (CEO Hong Sa-kwak, www.linear.com) announced the release of three PoE+ (Power over Ethernet) supported interface controllers with built-in switching regulators (product names: LTC4269-1, LTC4269-2, LTC4278) targeting high-power PD (powered device) applications of up to 25.5W or higher. The new IEEE 802.3at resolution, also known as the PoE+ standard, simultaneously expands the power budget and improves the classification mechanism used for Power Sourcing Equipment (PSE) and PDs, each of which can be identified.

The LTC4269 and LTC4278 support 2-event classification and are backward compatible with IEEE 802.3af devices, opening them to next-generation PoE applications. These devices integrate both PD controllers and either a synchronous flyback controller (LTC4269-1 and LTC4278) or a synchronous forward controller (LTC4269-2) for an integrated IEEE 802.3at PD control solution.

LTC4269 and LTC4278 can be used in new types of applications utilizing the new PoE+ standard, including video conferencing stations, RFID readers, pan-tilt-zoom security cameras, and long-range wireless access points. LTC4269 and LTC4278 are Type 1 hardware that distinguishes between PSE and PD and complies with IEEE 802.3af power levels, and also Type 2 hardware that distinguishes between PSE and PD and complies with IEEE 802.3at power levels, and distributes power accordingly.

2-event hardware classification enables a Type 2 PSE to verify a connection to a Type 2 PD and send a signal to the PD to source higher power levels associated with 802.3at power. This new classification mechanism ensures interoperability between Type 1 and Type 2 devices.

The LTC4269 and LTC4278 provide significant functional enhancements to existing PoE capabilities. For efficient power allocation, users can configure a classification load current to indicate the PD power classification. A shutdown pin with a signature corrupt function provides flexible auxiliary power supply support. Robust 100V Hot Swap™ MOSFETs provide 100mA of inrush current for smooth power-up transitions with PSE, isolating the PoE interface controller and DC/DC converter during the detection and classification phases.

The LTC4269 and LTC4278 also include complementary Power Good outputs, onboard signature resistors, low-voltage lockout, softstart ramping, and comprehensive thermal protection. The LTC4269-1 and LTC4278 integrate synchronous flyback controllers utilizing Linear's patented No-Opto feedback no-pology, providing complete IEEE 802.3 isolation. Additionally, the LTC4278 accepts 10V to 57V auxiliary power, offering the best power sourcing options.

The TC4269-2 incorporates a synchronous forward reverberation controller boasting an efficiency of over 94%. All versions are available in commercial and industrial grades, supporting operating temperature ranges of 0°C to 70°C and -40°C to 85°C, respectively, and are available in a compact RoHS-compliant 7mm x 4mm 32-pin DFN package.

The LTC4269-1 is supplied at $2.40 per unit in 1,000-unit quantities, while the LTC4269-2 and LTC4278 are supplied at $2.60 per unit in 1,000-unit quantities. The LTC4269 and LTC4278 provide an upgrade path for Linear's existing PD products, including the IEEE 802.3af pin-compatible LTC4268-1, and ensure a seamless transition to the new PoE+ standard with the support of Linear's skilled technical experts in PoE circuit design.

◇ Product Features: LTC4269 and LTC4278

• Perfect 25.5W power interface port for IEEE 802.3at PD (powered device)
• PoE+ 2-event classification with PSE indicator bit
• Programmable shunt current for 802.3at (Class 4) & 802.3af (Class 0-3) PDs
• Highly integrated synchronous no-opto flyback controller (LTC4269-1 & LTC4278) or synchronous forward controller (LTC4269-2)