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TPS2384: failure with Fluke Linkrunner PoE tester

Part Number: TPS2384
Other Parts Discussed in Thread: TPS23861, TPS2388

Hello,

We've designed a board using the TPS2384 as a PSE for two ethernet ports on the device. The board is in production and I've been using the Fluke Linkrunner AT 2000 as a tester for in-process QC. The tester checks the following

  1. Class - asks for a specific class (can choose 0-4) and makes sure it's received
  2. Mode - checks which pairs power is present on
  3. Unloaded voltage - checks PoE voltage with no load applied
  4. Loaded voltage - checks PoE voltage with load applied (load is sized according to the class selected)

I have a handful of boards that fail on only one port (often multiple failure modes mentioned above). The same ports power other PDs fine (I have two different IP cameras - class 0 and class 2 - that have been working on failing ports for days).

Port Status Read 2, Register Select = 0101 reports "other fault (101)". PSE voltage is 53V as designed.

When I probe the N pin of a failing port I'm getting the following:

Discovery

Classification and power on

Then I see constant removal and application of power

I'm assuming the tester is just trying over and over again. The only consistent failure mode I've seen is the failing port unable to deliver as much power as the non-failing port. Failing ports won't give me more than 13W when testing class 4, but a good port provide the upto 20W (even though it's only a type 1 PSE).

Any ideas or debugging suggestions?

  • Hi Kashif,

    TPS2384 doesn't support type 2 class 4 and it is IEEE802.3af(15.4W) compliant PSE. The ICUT is set at 375mA and ILIM is set at 425mA. If you want your PSE system to be compliant to IEEE802.3at standard(30W), TPS23861(4 port, autonomous mode) or TPS2388(8 port, semi auto, host control required) would be best solutions for you. Thanks.

    Best regards,

    Penny

  • Thanks Penny.

    The design requirement was 802.3af, but our prod tech had the tester set to class 4 mistakenly.

    I adjusted the Fluke to test Class 0, 1, 2, and 3 - all fail. I get various failures (sometimes 0V unloaded and/or mode not recognized), but the power is always consistent at 13W. The scope captures are from testing with Class 3.

  • Thanks Penny.

    The design requirement was 802.3af, but our prod tech had the tester set to class 4 mistakenly.

    I adjusted the Fluke to test Class 0, 1, 2, and 3 - all fail. I get various failures (sometimes 0V unloaded and/or mode not recognized), but the power is always consistent at 13W. The scope captures are from testing with Class 3.
  • Hi Kashif,

    During unloaded testing, did you disconnect the PD from the PSE port or you just remove the load and still kept the PD connected to the port? What's the current going through the port during unloaded condition? Did you see any fault reported in register 0100? Did you use the device in auto mode? Thanks.

    Best regards,

    Penny

  • Kashif,

    I wanted to check in with this thread as we have not heard back from you in approximately 1 week. Please let us know if there is anything else we can do to assist...otherwise, we are going to assume this thread is resolved.

    Thank you for your interest in PoE products from TI,