Isolated 12-port PoE PSE controller eliminates optocouplers

Isolated 12-port PoE PSE controller eliminates optocouplers

The LTC4270/ LTC4271 isolated 12-port power source equipment (PSE) controller chipset is designed for use in IEEE 802.3at (PoE+) Type 1 and Type 2 compliant PoE systems. The transformer-isolated communication protocol replaces up to six optocouplers and an isolated 3.3-V supply. The devices provide 12 independent PSE channels for simpler, lower component count designs, reduced board space and lower solution costs. The LTC4271 provides a digital interface to the PSE host, while the LTC4270 provides the high-voltage Ethernet interface; the two ICs are then bridged by Ethernet transformers.

The isolated PSE controller chipset is suitable for PSE applications, including next generation switches, routers, hubs and midspans. It features 80-V port pins and lowest-in-industry power dissipation using low RDS(on) external MOSFETs and 250-mΩ sense resistors. Powered device (PD) discovery is accomplished using a proprietary dual-mode, four-point detection mechanism that ensures immunity from false PD detection. Power management includes prioritized fast shutdown, 14-bit per-port voltage and current readback, 8-bit programmable current limits, 7-bit programmable overload current limits, and field-upgradable firmware. A 1-MHz I2 C interface allows a host controller to digitally configure the IC or query port readings. The LTC4270 is available in three power grades to support up to 90-W PDs, 25.5-W PDs, and 13-W PDs. (From $12.00 ea/1,000 — available now.)

By Paul O’Shea

Linear Technology , Milpitas , CA
Sales Office 408-428-2050
www.linear.com