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TPS2373: Design confuse

Sara Jia
Expert 2975 points
Part Number: TPS2373
Other Parts Discussed in Thread: TIDA-050023, TPS2121

Hi team,

We use TPS2373-3 plus LM5151-Q1 as poe application.

The output power of tida-050023 demo can be 12V 3.7a with POE, and 12V 4.25a with adapter power supply. Can Poe input be more than 4A?

2: What is the MOS tube here in demo? There is no welding on the demo board

3: Can the accessory transformer be used as Poe transformer of tps2373-3?

4: As shown below:


I use the 12 adapter to do the oring through the diode and Poe 12V output. Can I ask if there is any good solution? Is the adapter 12V preferred power supply? Plug in 12V adapter and switch to 12V adapter power supply


5: About the MPS function of tps2373-3, if I plug in the 12V adapter, it is powered by the 12V adapter, but PD is still connected with PSE. Once the 12V adapter is unplugged, it will switch to Poe for power supply. PD will not do classification, detection and power supply again with PSE, but supply power to the load immediately, so that the load will not be restarted due to power failure during switching.

6. Poe and 12V adapter are used for oring, and general Schottky diode is used for oring. Due to the large current, the power consumption on the diode is also large. What's the better plan and cost if the ideal diode is used?

G24102CE SPEC .pdf

  • 0
    TI__Mastermind 41760 points

    Hi Sara,

    1. The standard only allows 51W at the PoE PD front end (RJ45) this means, to be compliant, the output power when poe is connected must be 51Wxefficiency. This reduces the output current availability to ~3.8A. This is to be compliant, if non compliant, yes you can go to 4A. However, the diode may get hot.

    2. Looking at the BOM in the TIDA-050023 webpage, the primary FET is FDMS86252.

    3. Sorry im not too sure what this means. Please clarify. I believe you are asking if you can have an alternative power transform? If so, yes, however, it should similar spec as the one used in the reference design.

    4. Yes this is common practice. To prioritize the adapter, the adapter voltage should be higher than 12V PoE voltage.

    5. The autoMPS function allows the PSE to maintain power to the PD so that you don't have to redo detection and class. Then you would surely have to start converter when adapter is removed.

    6. I recommend using TPS2121 which is an integrated PMUX that can handle this current and voltage and has smooth transition between both inputs.