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TPS2373: Maximum and minimum power at PD

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: TPS2373

Dear Team,

I am not sure why the TPS2373 datasheet mention the maximum power at class 8 is 71W and minimum is 62W.

In my opinion, the maximum should be 90W as below and minimum power 71W

If yes, the datasheet is wrong?

What is the column of 62W for? 

BR

Kevin

  • 0
    TI__Mastermind 21320 points

    Hey Kevin,

    So the maximum and minimum values in the datasheet correlate to the PD class range. 

    Something important to note is there is an inherent power loss on the Ethernet cable between the PSE and PD. The IEEE802.3 standards specify these power levels for 100m of cable, so there is a standard resistance. Because of this resistance, there is a power loss over the wires. So 90W at the PSE output is 71.3W at the PD input. 

    So Class 8, the PSE range is 75W-90W on the PSE, or 62W-71.3W at the PD. Therefore, for a PD to be classified as Class 8, the max output power must be >62W at a minimum. Does that make sense? 

    I agree the Minimum power at PD column is not the clearest. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments