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TPS2372: Solution suggestions

ajayt
Genius 9555 points
Part Number: TPS2372
Other Parts Discussed in Thread: TPS23880, UCC2809-2

Hi Team,

we want to have hogh-power (802.3bt) input and output capability. The output is on 2 ports. Input on a single port. Gigabit throughout. Basically a 3 port gigabit switch. I saw there are a few devices available so any pointers in what would be a good, easy to design and cost effective solution. Internally we'd probably need some voltage regulation from the input PoE voltage (57V) down to something a bit more useful - 3.3V maybe. Don't expect power requirements locally to be more than 1A at 3.3V.

  • 0
    TI__Genius 9230 points
    Hi Ajayt,

    Are you looking for an isolated or non-isolated solution for the 3.3V converter?

    How much power are you sourcing for the 2 downstream ports? What PoE types are the two downstream PD devices?

    Thanks,
    Tom
  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points

    Hi Ajayt,

    Apologies for deleting your reply. Here it is quoted:

    "We want to make this effectively a full PSE/PD implementation. So the single port input acts as the PD and both the other ports are PSE, to power further devices/switches, and all at 802.3bt level of compatibility if possible. Looked as though we could use the TPS23880 to drive the 2 PSE ports and something like the TPS2373-4 or TPS2372-4 for the input PD port."

    I have attached a 3.3V 1.5A flyback design (PMP4782) that would be a good fit for your system.

    At 1A load, the efficiency is ~78%, so it'll use ~4.2W. Let's say you 71W available at the PD input, so you will have ~66.8W left to send downstream.

    The maximum amount of power you will be  class 6 (60W) one port 1 & class 1 (4W) on port 2.

    As you suggest, TPS2880 would be an ideal choice for this application.

    For the PD input, TPS2372-4 would be a sufficient since UCC2809-2 already has an integrated startup, so the advanced startup feature from TPS2373-4 would not be necessary.

    Thanks,

    Tom

    PMP4782_RevA_Test Data.doc

    PMP4782_RevA_SCH.pdf

    1033.PMP4782_RevA_SCH.pdf