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MSP430F5234: System will Power Off After Taking Off One PSU with 1500+ PoE Load

Cheng Shian Yan
Prodigy 121 points
Part Number: MSP430F5234
Other Parts Discussed in Thread: TPS23881

Hi,

We found an POE issue from the customer. Please help check the following description and help advise next action. Additionally, please let us know if you submit a ticket to TI E2E forum. Thanks.

Our system include MSP430F5234IRGZR with 12 PSE controllers(TPS23881). In our system, we specified two POE budget based on PSU status. When 2 PSUs are plugged, the total POE budget can reach 1800W. When only one PSU is available, the POE budget falls to 780W. Additionally, all ports are set to the same priority. I’ve attached the configuration file for your reference.

We aimed to observe the system would be stable after unplugging one PSU. We did two experiments below and found two different results. However, we found an issue in Test Case#2. This issue is more likely to reproduce with 90W per port and total consumption over 1565+W. We also tried two types of load cases: 48 ports with 30W and 25 ports with 60W. In both cases, we could not reproduce this issue.

 

Test configuration

  • 48Port PoE Switch
  • Total two PSUs present in the system. Each PSU is available to supply 1200W
  • POE
    • MCU: MSP430F5234IRGZR
    • PSE: 12x TPS23881
    • Poe Firmware Version:1.54.23.224
    • 90W per port, the maximum system POE load is limited to 1800W)
    • All ports are set to high-priority

 

Test Case#1

Test procedure:

  1. When the system is with 2 PSUs present, the total POE is around 1400-1500W. We tried to load two cases: 48 ports with 30W and 25 ports with 60W.
  2. Unplug PSU2, the system turn off partial POE ports to limit the total POE within 780W.
  3. Re-plug PSU2. The total POE load are back to 1400W-1500W in 1 minutes.

 

 

Test Case#2

Test procedure:

  1. When the system is with 2 PSUs present, the total POE is around 1500W. The maximum port load is 90-92W
  2. Unplug PSU2, the system did not turn off partial POE load as Test Case#1. Therefore, we observed the system off because the PSU1 is OCP.

 

We found an issue when most of ports are with 90W POE load.

 

Interface   Status    State             Max-Power(W)   Power-consumption(W)   Priority   Class   Error
------------------------------------------------------------------------------------------------------------
port1       Enabled   Delivering Power  24.46          91.40                  Low        8
port2       Enabled   Delivering Power  24.46          90.90                  Low        8
port3       Enabled   Delivering Power  24.46          90.50                  Low        8
port4       Enabled   Delivering Power  24.46          91.20                  Low        8
port5       Enabled   Delivering Power  24.46          90.90                  Low        8
port6       Enabled   Delivering Power  24.46          90.80                  Low        8
port7       Enabled   Delivering Power  24.46          90.80                  Low        8
port8       Enabled   Delivering Power  24.46          91.10                  Low        8
port9       Enabled   Delivering Power  24.46          92.40                  Low        8
port10      Enabled   Delivering Power  24.46          92.00                  Low        8
port11      Enabled   Delivering Power  24.46          92.10                  Low        8
port12      Enabled   Delivering Power  24.46          92.60                  Low        8
port13      Enabled   Delivering Power  24.46          92.90                  Low        8
port14      Enabled   Delivering Power  24.46          92.20                  Low        8
port15      Enabled   Delivering Power  24.46          92.50                  Low        8
port16      Enabled   Delivering Power  24.46          92.60                  Low        8
port17      Enabled   Delivering Power  60.00          40.70                  Low        5
port18      Enabled   Delivering Power  60.00          56.60                  Low        6

 

 

Bryant

  • 0 in reply to Cheng Shian Yan
    TI__Mastermind 36220 points

    It seems that it is an application problem right? Can you help check what is the dedicate problem related to MCU? For example, can you debug one of MCUs in test 2?

    Otherwise, it will be really hard for me to give you suggestions.

  • 0 in reply to Eason Zhou
    Prodigy 121 points

    Hi Eason,

    What further information we shoudl provide for you? 

    Yes, we are working on test 2. However, test 1 and 2 are almost the same, but the POE port limit.

    In our structure, CPLD will inform MCU if two PSUs are present and good. If any PSU is unplugged, CPLD will assert the signal low to inform MCU. Then, MCU will to turn off partal POE port witin 780W(This feature is provided by TI). Therefore, we are unshare what different behavior MCU will be when POE port is loaded with 60W/90W.

    Additionally, could it be an issue if we set all port to low/high?

    Thank.

    bryant

  • 0 in reply to Cheng Shian Yan
    Prodigy 121 points

    Add more findings

    1. Adjust the POE load from 90W to 85W on the POE loder side.

    We found when the port load is more than 90W that could result in the issue. On my side, I adjusted all POE loader to 85W with 1.5m cable, and the POE load of the switch will be less than 90W. I tried a few times and did not observe the issue.

    2. Adjust the port limit from 90W to 95W on the switch side

    I’ve adjusted the port limit from 90W to 95W. The issue still occurred when the POE loader required 90W PoE load( the switch supplied around 90-92W at each port).

    Note:

    MCU is equal to MSP430

    MSP430 and TPS23881 are within the switch

    CPLD keep updating the status of two PSUs to MSP430 through one GPIO.

    Turn on/off POE port is controlled by MSP430

    bryant

  • 0 in reply to Cheng Shian Yan
    TI__Mastermind 36220 points

    Hi Bryant,

    I think I can't give your any suggestion that what happens to MCU. You must know that there is software part between your application performance and the MCU. I don't know about your software and have no knowledege and experience on your application, so I can't tell you want happens and why it have this action. I think what you need to do is to tell me what the software action on MCU level (Like GPIO control/ communicaiton abnormal) is not as your wanted. Than I can give you suggetion from MCU level.

    That is why I ask you whether you can debug the code. Then We can jump the application and talk about MCU through the MCU performance controlled by software.  

    Eason Zhou said:
    can you debug one of MCUs in test 2?

    Eason

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