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Isolated 12-Port Power over Ethernet PSE Controller Chipset Eliminates Optos for Lowest Solution Cost

MILPITAS, CA – May 2, 2011 – Linear Technology Corporation introduces 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. 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 suitable 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, 14-bit per-port voltage and current readback, 8-bit programmable current limits and 7-bit 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.

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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. All chipsets are offered 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 LTC4270/71 chipset is priced starting at $12.00 each in 1,000 piece quantities and is now available in production quantities. 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. Please visit www.linear.com/product/LTC4270 for more product information.

Summary of Features: LTC4270/LTC4271 12 Independent PSE Channels Compliant with IEEE 802.3at Type 1 and 2 Chipset Provides Electrical Isolation     •Reduce BOM Cost     •Eliminates up to 6 High Speed      Opto-Couplers     •Eliminates Isolated 3.3V Power      Supply Low Power Dissipation     •0.25Ohm Sense Resistance Per      Channel Very High Reliability 4-Point PD Detection     •2-Point Forced Voltage     •2-Point Forced Current Temperature Monitoring VEE & VPORT Monitoring 1 Second Rolling IPORT Averaging 1MHz I²C Compatible Serial Control Interface Available In Three Power Grades     •A-Grade – LTPoE++ 35W to 90W     •B-Grade – PoE+ 25.5W     •C-Grade – PoE 13W Available in 52-Lead 7mm x 8mm (LTC4270) & 24-Lead 4mm x 4mm (LTC4271) QFN Packages

Transformer-Isolated 12-Port PSE Controllers Reduce Cost Click Photo for High-Res Image