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PSE controller chipset offers 12 independent channels

Posted: 06 May 2011     Print Version  Bookmark and Share

Keywords:chipset  Ethernet  power  current 

Linear Technology Corp. debuts the LTC4270/ LTC4271 isolated 12-port Power Source Equipment (PSE) controller chipset aimed at use in IEEE 802.3at (PoE+) Type 1 and Type 2 compliant Power over Ethernet (PoE) systems.

The LTC4270/71 offers 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 lowest-in-industry power dissipation, making thermal design significantly easier than designing with PSEs that integrate more fragile normally higher RDS(ON) MOSFETs.

Powered Device (PD) 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++ signalling to support up to 90W PDs, B-Grade uses PoE+ signalling to support up to 25.5W PDs, and C-grade uses PoE signalling 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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