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PSE PoE reduces board space, cuts costs

Posted: 04 May 2011 ?? ?Print Version ?Bookmark and Share

Keywords:chipset? Ethernet? power? current?

Linear Technology Corp. has introduced the LTC4270/LTC4271 isolated 12-port Power Source Equipment (PSE) controller chipset designed for use in IEEE 802.3at (PoE+) Type 1 and Type 2 compliant Power over Ethernet (PoE) systems. The LTC4270/71 provides 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 inexpensive Ethernet transformers. It is said that 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 cost savings and a more robust and manufacturable design.

The LTC4270/LTC4271 is compatible for a wide variety of PSE applications, including next generation switches, routers, hubs and midspans. Users will appreciate the robustness provided by 80V port pins and low power dissipation, making thermal design easier than designing with PSEs that integrate more fragile normally higher RDS(ON) MOSFETs. Powered Device discovery is accomplished using a proprietary dual-mode, four point detection mechanism that ensures the best immunity from false PD detection. Advanced power management includes prioritized fast shutdown, 14bit per-port voltage and current readback, 8bit programmable current limits and 7bit programmable overload current limits and field-upgradeable firmware. A 1MHz I2C interface allows a host controller to digitally configure the IC or query port readings. "C" libraries are available to reduce engineering costs and improve time to market.

The LTC4270 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. All chipsets are presented in industrial temperature grades. 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/LTC4271 is backward compatible with the LTC4266 4-port PoE+ PSE controller and LTC4274 single-port PoE+ PSE controller, supported by Linear's extensive technical experience in PoE circuit design, ensuring a smooth transition to the new PoE+ standard or higher power levels.

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