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Original question:

TPS2384: TPS2384 ; PD Detection Function Test Result with Device for or not for PoE

TPS2384: TPS2384 ; PD Detection with SI3402

Joseph Ting
Prodigy 10 points
Part Number: TPS2384
Other Parts Discussed in Thread: TPS23861, TPS2388

Hi, 

 This is regarding TPS2384 detection problem with Si3402 at room temperature. I found few threads in forum with similar issue. 

TPS2384 fail to detect SI3402BISO-EVB module if the port capacitance is 0.22uF. I tried to reduce the capacitance and tested it again.

I found that the rise time of detection pulse will directly impact the detection of SI3402. It seem like the rise time need to be longer than 2.6 ms in order to detect SI3402.

Can I know what happened to TPS2384 that cause this issue and what is the recommended capacitance value to solve it? 

Link: 

https://e2e.ti.com/support/power_management/power_interface/f/204/t/532291?TPS2384-can-not-find-a-valid-PD

https://e2echina.ti.com/question_answer/analog/power_management/f/24/t/112946 

  • 0
    TI__Genius 15685 points
    Hi Joseph,

    The port capacitance of TPS2384 should be 220 nF – 470 nF. When you varies the port capacitance, did you change the port capacitance on the PSE side or PD side? TPS2384 requires minimum 220nF to ensure system stability. Thanks.

    Best regards,
    Penny
  • 0 in reply to Penny Xu
    Prodigy 10 points
    Hi Penny,

    I changed the port capacitance on PSE side. So, I should increase the port capacitance instead of decreasing. Do you have a specific capacitance value that will work with Si3402 evaluation module? Since this detection issue is a known issue , do you have recommended solution to solve it?
  • 0 in reply to Joseph Ting45
    TI__Expert 5615 points
    Joseph,

    In addition to Penny's continued technical support - working to get the TPS2384 performing as best as it can - I would like to suggest to consider moving to the TPS23861 or TPS2388 during your next design cycle.

    The TPS2384 is an older device...with the TPS23861 and TPS2388 both offering better technical support and design tools.

    Thank you for your interest in PoE products from Texas Instruments,
  • 0 in reply to Joseph Ting45
    TI__Genius 15685 points

    Hi Joseph,

    For the other TPS2384 detection issue, it only happens at high temperature on the customer side, however, we din't reproduce the issue on our bench. TPS2384EVM just worked fine with our customer's IP camera with SI3402 inside. What's your port cap on the PD side? Thanks.

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    TI__Expert 5615 points
    Joseph, It has been some time since we last heard from you.

    Is this matter resolved or do you require additional assistance? If we don't hear from you by the end of this week (9/14), I am going to assume this matter is closed.

    Thank you for your interest in PoE products from Texas Instruments,