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TPS23881EVM-008: Hardware design problem

Lin GarHao
Prodigy 50 points
Part Number: TPS23881EVM-008


Hi team,

In this EVM I have some questions as below：

1. Is there any recommended Transformer? Your company's BOM recommends JK0-0229NL (RJ-45 Jack). I already selected the RJ-45 Jack, so we hope to use the Transformer alone.

2. Each channel’s current resistor is recommended to be 0.2Ω. 1%, 0.25-W. Can it be replaced with 0.27Ω. 1%, 0.25-W?

3. Following question 2, what should I pay attention to if I do not use the resistance value (0.2Ω) recommended by EVM?

  • 0
    TI__Genius 15745 points

    Hi Lin,

    1. The data transformer will be based on two factors. The data speed on the PHY and the rating for PoE capability. The transformer should be rated to support PoE power up to 100W .

    2. I would not recommend changing the current sense resistor to be .27Ω as the PSE FW is programmed for a .20Ω resistor and may cause issues with sensing accuracy.

    3. If you do not use .20Ω you will need to monitor classification results to ensure the proper connection is being made. Since classification is dependent on the current measurement during classification cycles, if the sensing circuit is off, this may lead to improper classification since the FW will see a different current compared to the current actualy flowing through the sense resistor. Again, to avoid all these issues, I would only recommend using .20Ω sense resistor.

    Regards,

    Brandon