35W Power over Ethernet PD Controller Enables Emerging PoE+ Applications

Apr 9 2007 - MILPITAS, CA
  • Linear Technology Corporation introduces the LTC4264, a Power over Ethernet (PoE) interface controller for high-power Powered Device (PD) applications.  The LTC4264 allows users to develop power-hungry applications beyond the IEEE 802.3af-mandated 12.95W limit, while still maintaining backward compatibility. The LTC4264 can deliver up to 35W for 2-pair systems and as much as 70W for 4-pair systems. To control turn-on surge current in the system, the LTC4264 incorporates a precision dual current limiting circuit with an onboard power MOSFET and sense resistor to provide a complete inrush control circuit without additional external components. The LTC4264 is compatible with the most current decisions on the PoE+ (P802.at) committee.


    The precision dual level current limit enables legacy Power Sourcing Equipment (PSE) with limited current sourcing capability to power up the device while also allowing the device to draw full power from custom PSEs that exceed the limit of the existing standard. The LTC4264 is capable of handling 750mA with the lowest on-resistance (0.55 Ohm typ, 0.8 Ohm max) Hot Swap MOSFET on the market. The ultra-low FET on-resistance minimizes power wasted by device heating and improves overall efficiency. Additionally, the user has the option to disable the normal operating current limit and to increase the maximum current limit to approximately 1.4A.

    The LTC4264 features both active-high and active-low power good signaling for simplified interface to any DC/DC converter. The part includes an onboard 25Kohm signature resistor, precision undervoltage lockout (UVLO) and thermal overload protection. The signature resistor can be disabled so that the device is not recognized or powered by the PSE in order to provide a seamless interface for an external wall adapter or other auxiliary power options.

    The LTC4264 has the flexibility to support applications that meet the emerging IEEE 802.3at standard, as well as proprietary high power applications. Specified over the full commercial and industrial temperature range, the LTC4264 is offered in a thermally enhanced 12-pin 4mm x 3mm DFN package for superior high current performance. Pricing begins at $1.80 each for 1,000-piece quantities.

    Summary of Features: LTC4264

    • Complete High Power PD Interface Controller
    • IEEE 802.3af Compliant
    • Onboard 100V, 750mA Power MOSFET
    • Flexible Auxiliary Power Options
    • Precision Dual Current Limit with Disable
    • Complementary Power Good Outputs
    • Onboard 25K Signature Resistor with Disable
    • Undervoltage Lockout
    • Complete Thermal Overload Protection
    • Low Profile 12-pin, 4mm × 3mm DFN Package

    High Power PD Interface Controller with750mA Current Limit

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