Linear chip ups power level for PoE
Linear Technology has introduced power-over-Ethernet (PoE)-compliant interface controllers for higher power applications requiring up to 90W of delivered power.
As the PoE+ standard limits the maximum power delivery to 25.5W, which can be insufficient to power some mobile picocells and basestations, the controllers also support Linear’s own LTPoE++ technology which expands the power budget to four different power levels (38.7W, 52.7W, 70W and 90W).
The LTPoE++ technique uses a classification scheme that enables power sourcing equipment controllers and powered device controllers to communicate with one another while maintaining interoperability with IEEE standard equipment.
The LT4275A (LTPoE++), LT4275B (PoE+) and LT4275C (PoE) efficiently deliver power to PD loads using just one IC.
There is no integrated power mosfet to reduce heat dissipation and, according to the supplier, this will improve power efficiency, especially important at higher power levels.
“This novel allows users to size the mosfet to their application’s specific heating and efficiency requirements, enabling the use of low RDS(on) 30ohm mosfets if necessary,” said Linear.
The LT4275 recognises a PSE as either Type 1 hardware complying with the IEEE 802.3af 13W power level, Type 2 hardware, complying with IEEE 802.3at 25.5W power level or LTPoE++ hardware complying with 38.7W to 90W power levels, and passes power accordingly.
For efficient power allocation, PD users can configure a classification that represents the PD power usage. A 100V abs max rated input voltage means the LT4275 easily survives and protects PDs from the most common Ethernet line surges. A programmable auxiliary power pin with signature corrupt provides support down to 9V.
The LT4275 also includes a power good output, onboard signature resistor, undervoltage lockout and comprehensive thermal protection.
The LT4275 is offered in industrial and automotive grades, supporting operating temperature ranges from -40°C to 85°C and -40°C to 125°C, respectively, and is available in small RoHS-compliant 10-pin MSOP or 3mm x 3mm DFN packages.