The LTC4291 includes a digital interface to the PSE host, while the LTC4292 implements the high voltage Ethernet power interface. The two ICs intercommunicate using an inexpensive Ethernet transformer.
The transformer-isolated communication protocol replaces up to six expensive opto-couplers and a complex isolated 3.3V supply used in traditional designs, resulting in significant BOM cost savings and a more robust and easy to manufacture design.
The LTC4291/LTC4292 chipset operates seamlessly with compliant 802.3bt PD controllers, the LT4294 or LT4295, forming complete end-to-end PoE++, PoE+ and PoE solutions. Up to 71.3W of power can be delivered to single-signature or dual-signature PDs. Users will appreciate the robustness of the 80V pins.
PD discovery is accomplished using a multipoint voltage and current detection mechanism, ensuring the best immunity from false PD detection. Advanced power management includes Autoclass support, prioritised fast shutdown, 14-bit per-port power and current readback, 8-bit programmable power limits and 7-bit programmable overload current limits.
Systems can be updated with field-upgradable firmware. A 1MHz I2C interface allows a host controller to digitally configure the chipset or query port status. Power management “C” demonstration libraries are also available to reduce NRE and improve time to market.
The LTC4291/LTC4292 chipset is offered in the industrial temperature range. The LTC4291 digital controller is in a RoHS-compliant 24-pin 4x4mm QFN package, while the LTC4292 analogue controller is in a 40-pin 6x6mm QFN package. The LTC4291/LTC4292 is Analog Devices’ first 802.3bt PSE controller and provides an upgrade path from the popular LTC4266 4-port 802.3at PSE controller.