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Does 4-pair PSE (two) work for 2-pair (PD)

veera venkateswara rao pusala
Intellectual 280 points

Hi,

     I am designing the 4-pair Mid-span, can you tell me what happens when we connect 2-pair PD to the 4-pair PSE? (Assume each PSE supports 40W, 2-pair PD requires 5oW)

Regards,

Venkat

  • 0
    TI__Mastermind 42795 points

    Standard compliant PD's are required to accept power from either of two pair sets (1/2,3/6 or 4/5, 7/8 pins of RJ45). A standard compliant PD OR's the bridge connection together for a single voltage feed to the PD controller. If the PSE DC voltage is applied to both pair sets, the PD diode bridges will rectify and OR the two pair set connections. Since the PSE source connections, forward drops of the diodes and resistances of the wires are not identical, there will be some current sharing mismatch (IE, one pair set may furnish more of the load current than the other pair set).