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TPS2384: PoE Load Transient response on Startup

Sebastien Ricard
Prodigy 40 points
Part Number: TPS2384

Hello there,

I have the TPS2384 connected to four PoE loads and I am measuring the transient voltage response on boot up of my system and I am wondering if the PSE has a protection feature that connects the loads one after the other, or if they all are all connected at once. In other words, I want to answer my hypothesis that what I am measuring with the oscilloscope is in fact the response of one load and not all four.

In short: Does the TPS2384 connect all four loads at the same time, or one after the other on startup?

 


Thank you

Sébastien

  • 0
    TI__Genius 15685 points

    Hi Sébastien,

    In auto mode, if all four ports connect with four loads at the same time, TPS2384 only allows one port to enter classification and power on at the same time. In other words, four ports will be turned on separately. Please see session 9.4.2.2 of the datasheet. Thanks. 

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    Prodigy 40 points
    Right, thank you Penny.

    Sebastien
  • 0 in reply to Penny Xu
    Prodigy 40 points

    Right, thank you Penny. I guess I overlooked that part of the datasheet. I couldn't find it.

    What is strange however is that I see no sign of the other three ports connecting. The transient response appears to be independent of the number of PoE loads I connect. Here is a close up of the transient response when four loads are connected. Ch.1 is the DC measurement, Ch.2 is the AC measurement.

  • 0 in reply to Sebastien Ricard
    TI__Genius 15685 points
    Hi Sebastien,

    Did you mean you connected four PDs to the PSE port and didn't see other three ports doing detection and classification while one port is turning on? Did you use TPS2384 in auto mode and what kind of PD did you connect to the PSE port? Thanks.

    Best regards,
    Penny