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TPS23881: Detection function issue

Jason Kuo
Prodigy 10 points
Part Number: TPS23881


We found that TPS23881 has an issue that cannot power on for the first time.
And we found TPS23881 kept repeating detection function while the issue occurred.

We also found that adjusting detection resistor can recreate this anomaly (described as follows).

With a detection resistor of 24.9k, the detection function can be completed normally.
When we slowly decrease the detection resistor, we observe some abnormal wave forms starting at 20.6k.
Further reduce the detection resistor, it recreates the behavior of repeating detection at low temperatures.

The allowable range for detection resistor specified in standard is 19k to 26.5kΩ.
It is our understanding that within this range,detection should be successful. We seek your assistance in clarifying this issue.
Thank you.

  • 0
    TI__Mastermind 37111 points

    Hi Jason,

    Thanks for reaching out.

    In the standard, the detection resistance at the PD PI and PSE PI are addressed in below. The Range of resistance on the PD side is 23.7k - 26.3k.

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Prodigy 10 points

    Thank for your response.
    We understand the range of detection resistance on PD side is 23.7k - 26.3kΩ.
    However, we are not using PD for testing.
    We adjust the detection resistor directly on the TPS23881 RJ45 port.
    In this case, what we should be looking at is the acceptance range on PSE side (19k - 26.5kΩ).

    Is the TPS23881 detection resistance acceptance range programmable?

  • 0 in reply to Jason Kuo
    TI__Mastermind 37111 points

    Hi Jason,

    Thanks for your clarification.

    Our PSE applications engineer Brandon will assist you on your questions.

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    TI__Genius 15295 points

    Hi Jason,

    The acceptable range is correct, can you confirm you are loading SRAM to TPS23881? The SRAM patches over bug fixes and includes bug fixes related to detection accuracy. I would expect abnormal behavior if SRAM is not being loaded correctly. Please see steps for loading SRAM.

    How to load SRAM.pdf

    It is also not a programmable feature from the PSE side. The PSE detection range is directly reflective of the standard and not something that can be changed. 

    Regards,

    Brandon