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TPS2384 can not find a valid PD

user4752259
Prodigy 30 points
Other Parts Discussed in Thread: TPS2384, TPS23861EVM-612

I used a TPS2384EVM as a PSE and a SI3402-B EVM as a PD.I put  the SI3402-B EVM into a temperature box .The temperature was set to 60℃ inside the box.The TPS2384EVM was outside the box,and the temperature is about 25℃.I connected TPS2384EVM with SI3402-B EVM through a 70-meter-long CAT6 cable. I set TPS2384 Pin ALTA/B=0,Pin MS =0.

After the SI3402-B EVM worked about 20 minutes,I plugged the cable into TPS2384EVM  again. But one of the four ports can not discovery SI3402-B EVM .And the waveform between P4 and N4 is as below.

As the picture shows,TPS2384 continues to cycle through the discovery process.

Then I set pin ALTA/B=1,the problem was gone.TPS2384 can work normally.

I set pin ALTA/B=0 again, the problem came back.Then,I gave a negtive pulse to pin PORB, TPS2384 began to reset.After that, it can work normally,and 48V voltage was powered on between pin P4 and pin N4.Then I replugged cable into Port4 again, it can not still power the SI3402-B EMV  .

Does anybody know the possible reason about this porblem?

  • 0
    TI__Genius 15685 points
    Hi,

    Did this issue happen only on port 4 or it had the same behavior on other ports? Did you use this PD boardwww.silabs.com/.../si3402b-evb.pdf

    Best regards,
    Penny
  • 0 in reply to Penny Xu
    Prodigy 30 points

    Hi Penny,
    Did this issue happen only on port 4 or it had the same behavior on other ports? ----It happened only on port 4.
    Did you use this PD boardwww.silabs.com/.../si3402b-evb.pdf-----Yes.

    SI3402-B EVM sch is as below,I increase the capacitance value of C18 from 0.1uF to 0.3uF.I put SI3402-B EVM in temperature box ,and set temperature to 60℃. I set  pin ALTA/B=0 on TPS2384 EVM.  There's no problem on port4 of TPS2384EVM .

    I compare the waveform between C18=0.1uF and C18=0.3uF. The rising egde is different.

    I soldered C18 off the SI3402-B EVM  ,and put SI3402-B EVM outside the temperature box. The temperature in the room was about 25℃.TPS2384 can still power SI3402-B EVM through port4 without C18.

    Do you know why the capacitance value of C18  influences TPS2384 when it discoverys PD in 60℃？

    I used BCM59101 , PD69104B1 and PD64004AH as PSE respectively. ALL of them can discovery SI3402-B EVM with C18=0.1uF in 60℃ .

  • 0 in reply to Penny Xu
    Prodigy 20 points
    1、This issue happen only on port 4；
    2、We use the PD that you said.
  • 0
    Prodigy 20 points
    1、This issue happen only on port 4；
    2、We use the PD as Penny says;
  • 0 in reply to Robin Jan
    TI__Genius 15685 points

    Hi Robin and user4122979,

    Here's my understanding of your situation. Please correct me if I am wrong.

    1. You have tried to connect the PD on other ports at 60℃, and it worked fine. The discovery issue only happened on port 4.
    2. At room temperature, the PD worked fine with both 0.1uF and 0.3uF.
    3. At 60℃, the port had discovery issue when the the PD input cap was 0.1uF(no issues with 0.3uF and no C18).

    I am curious why this issue only happened on port 4. If it is something related to the PSE, it should happen on all other ports. 

    If possible, I will set up something in lab and do some testing. Have you tried TPS23861EVM-612 which is our most popular PSE device.

    Best regards,

    Penny

  • 0 in reply to user4752259
    TI__Genius 15685 points
    Hi,

    Given the complexity of the situation, let's take the discussion offline and please contact me through email: p-xu@ti.com. Thanks.

    Best regards,
    Penny
  • 0 in reply to Penny Xu
    Prodigy 30 points

    Hi,

    OK.I'll send email to you .Thank you.