Chipset pushes 12-port Power over Ethernet PSE up to 90W per channel

The original version of the Power- over-Ethernet (PoE) standard specifies 13W for each powered device (PD);  the latest version, IEEE 802.3at (PoE+),  increases the power to 25.5W. However, PoE PDs’ increasing number of features and new, industrial applications are driving the need for ever-increasing amounts of power.   For example, one such application is charging laptops: Power adapters for laptops can range from 60-90W. In addition, POE applications on the factory floor can require higher power to drive actuator and control devices. (PoE seems to be becoming a de facto standard for dc power distribution in microgrids, such as factory floors.)

Linear Technology has developed its own proprietary version, LTPoE++, that can power as much as 90W per port.  The “A” version of Linear Tech’s new LTC4270/LTC4271 chipset for power sourcing equipment (PSE) uses LTPoE++ to provide up to 90W of delivered power to as many as 12 LTPoE++ PDs.   LTPoE++ uses proprietary signaling methods to identify LTPoE++ PDs requiring more than the 25.5W limit of the PoE+ specification.  LTPoE++ is interoperable and backward compatible with IEEE PoE/PoE+ compliant devices, so LTPoE++, PoE+ and PoE devices can work together seamlessly.

The LTC4271 provides a digital interface to the PSE host, while the LTC4270 acts as a high-voltage Ethernet interface, delivering power to the 12 independent PoE ports.  A pair of low-cost Ethernet transformers bridge the two ICS, providing galvanic isolation, and replacing as many as six opto-couplers and eliminating the need for an isolated 3.3V supply.

The LTC4270 is available in three power grades: A-grade uses Linear’s LTPoE++ signaling to support up to 90W PDs, B-Grade uses PoE+ signaling to support up to 25.5W PDs, and C-grade uses PoE signaling to support up to 13W PDs.  The LTC4270 is in a RoHS-compliant 52-pin 7mm x 8mm QFN package, while the LTC4271 is in a 24-pin 4mm x 4mm QFN package.  The LTC4270/71 chipset is priced starting at $12.00 each in 1,000 piece quantities.