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TPS2372: How to Change Class resistor at the PD

xiang tao
Prodigy 100 points
Part Number: TPS2372

Hi, PoE Masters:

Q1: Is there any method to change the class resistor by an MCU? I want to change the class on the CLSA and CLAB pin of TPS2372 flexbilely.

Q2: If a type1 PSE connected to a type 4 PD which requests up to71W power, how does the PSE power the PD?

Q3: If a type 4 PSE(90W available) connected to a type 4 PD which only requests up to 3.84W(class=1), how many class events occur during phyiscal classification?

Q4: If a type 4 PSE(90W available) connected to a type 4 PD which only requests up to 3.84W(class=1), after power on, if PD draws more than 3.84W, like 71W, does PSE still matain power?

  • +1
    TI__Mastermind 37031 points

    Hi Xiang,

    Q1. You can use LLDP to do this. 

    Q2. Usually the PSE will do Type-1 negotiation.

    Q3. It usually depends on the PD's classification resistor. If the resistor is set as Class-1 then only 1 event; if the resistor is Class-8, then 5 event. TPS2372 can do auto class.

    Q4. If PD class set Class-1 but exceed the power, PSE may trigger overpower protection to turn off the port. 

    Best regards,

    Diang