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TPS23751: Relation of PoE standard and inlush current

Satoshi
Guru 19485 points
Part Number: TPS23751
Other Parts Discussed in Thread: PMP11254,

Please let me confirm about my understand is correct or not for PoE standard.

Information of PoE standard is attached below, is this mean ① and ② correct?

①Over current

　When overload current (Icut) continue to flow on the time of Overload time limit (Tcut, 50ms~75ms), PSE will be off the power source.

②Short condition

   When short current (Ilim) continue to flow on the time of Short circuit time limit (Tlim, 10ms~ at Type-2), PSE will be off the power source.

Customer is evaluating TPS23751 based on PMP11254 and below condition (No load).

 ・Connect LAN to PSE ⇒ After PSE sequence, supply PSE to VDD(52V) ⇒ VDD supply to VC ⇒ When TPS23751 startup, inlush  is occur  

Customer want to confirm below inlush is keep the rule of PoE standard or not.

Best regards,

Satoshi

  • 0
    TI__Genius 9230 points
    HI Satoshi,

    For 1 & 2, you are correct. These are the time limits for when the PSE needs to respond to a short circuit or overcurrent event.

    TPS23751 inrush complies with the PoE standard by limiting the current to 140mA, well below the 13W limit during inrush & compatible with all compliant PSEs. Additionally, it will stay in inrush for 80ms to make sure the inrush time duration more than satisifies the 75ms mentioned in the standard.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer