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

May 2 2011 - MILPITAS, CA
  • 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.

    LTC4270-71 PR Image

    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 × 8mm QFN package, while the LTC4271 is in a 24-pin 4mm × 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 802.3 at 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
      • 0.25Ω 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 × 8mm (LTC4270) & 24-Lead 4mm × 4mm (LTC4271) QFN Packages

    Transformer-Isolated 12-Port PSE Controllers Reduce Cost

    LTC4270-71 PR Image
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