August 28, 2012 – Linear Technology Korea (CEO Hong Sa-gwak) announced the launch of the LTPoE++™, PoE+, and PoE compatible PD (powered device) interface controller (product name: LT4275) for applications requiring maximum power supply of up to 90W. In the case of PoE+, the maximum PD power supply is limited to 25.5W, which is insufficient for powering new types of applications requiring high power consumption, such as picocells, base stations, signage, and outdoor cameras with built-in heaters. Linear Technology's LTPoE++ standard meets market demands by extending the power budget to four different power levels (38.7W, 52.7W, 70W, 90W), thereby enabling high-power LTPoE++ systems. The LTPoE++ standard features a classification scheme that allows LTPoE++ power sourcing equipment (PSE) controllers and LTPoE++ PD controllers to communicate reliably with each other while maintaining interoperability with IEEE standard equipment. The LT4275A (LTPoE++), LT4275B (PoE+), and LT4275C (PoE) use only a single IC to efficiently deliver power to PD loads.
Unlike conventional PD controllers with integrated power MOSFETs, the LT4275 controls external MOSFETs, dramatically reducing overall PD thermal losses and maximizing power efficiency. This feature is important at higher power levels. In this manner, users can size the MOSFET according to the specific requirements related to thermal and efficiency characteristics of the application. If necessary, a low RDS(ON) 30mOhm MOSFET can be used.
The LT4275 recognizes the PSE as Type 1 hardware compliant with IEEE 802.3af 13W power level and Type 2 hardware compliant with IEEE 802.3at 25.5W power level, or recognizes the PSE as LTPoE++ hardware compliant with 38.7W to 90W power levels, and accordingly allows power to pass through. For efficient power allocation, PD users can be configured with a classification indicating PD power consumption. The fact that the maximum rated absolute input voltage is 100V means that the LT4275 protects the PD from failure even in most common Ethernet line surges. The programmable auxiliary power pin features a signature corrupt function, providing support for descent to 9V. The LT4275 also includes power good output, onboard signature register, low voltage lockout, and comprehensive thermal protection features.
The LT4275 is offered in industrial and automotive grades, supporting operating temperatures ranging from -40°C to 85°C and -40°C to 125°C respectively. The product is supplied in a small 10-pin MSOP or 3mm x 3mm DFN package compliant with RoHS specifications. The LT4275 is priced at $1.45 per unit based on a quantity of 1,000 units and is supplied in volume. The LT4275 provides an upgrade path through existing PD products including Linear Technology's LTC4265 PoE+ PD controller, and is fully compatible with Linear Technology's latest PSE controllers, including the single-port LTC4274, 4-port LTC4266, and 12-port LTC4270/71 chipsets. For more information, refer to www.linear.com/LTPoE++.


Photo caption: 70W PoE (Power over Ethernet) PD Interface Controller

Product Features: LT4275

• IEEE 802.3af/at & LTPoE++ PD (Powered Device) Controller
• LTPoE++ supporting maximum 90W power level
• LT4275A supporting all of the following standards
o LTPoE++ 38.7W, 52.7W, 70W & 90W
o IEEE 802.3at 25.5W compatible
o IEEE 802.3af maximum 13W compatible
• LT4275B is IEEE 802.3at/af compatible
• LT4275C is IEEE 802.3af compatible
• 100V absolute maximum input voltage
• Integrated signature register
• External Hot Swap™ N-channel MOSFET for minimum power consumption & maximum system efficiency
• Auxiliary power supply programmable as low as 9V
• Supplied in 10-pin MSOP & 3mm x 3mm DFN package