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DLPC350: Fault status asserted when PCB is cooled below 16 degrees C

Anders Guldahl
Intellectual 385 points
Part Number: DLPC350

We're having an issue on one of our pcb's which design is based on the lightcrafter 4500 eval kit design. When the board is cooled below 15-16 degrees C and power is applied, the DLPC350 asserts the Fault Status signal and doesn't boot up to normal operation.  

When the board gets back to room temperature, the board again is fully functional and works fine.  Some times the heart-beat LED is lit as well as fault status, some times not. All supply voltages and power good-signal etc. are OK. The next step which we haven't tried yet is selectively cooling parts of the board.

Questions: 

1. Anyone seen this issue before? Any tips on how we should proceed to debug the issue?
2. What kind of fault conditions does the DLPC350 firmware check before asserting the fault-status flag?

  • 0
    TI__Mastermind 20045 points
    Hello Anders,

    Just to confirm this is one of your own custom boards, correct? I haven't heard of this issue before. 15-16 degrees C should be well within the range of appropriate operating conditions. Perhaps there were some PCB guidelines that weren't properly followed on your board that manifest during a temperature change. Have you seen this with our 4500 EVM? Are you able to query the DLPC350 with an I2C command to get the status (Hardware, System, or Main status)? This would better help identify the problem.
  • 0 in reply to Kyle Rakos
    Intellectual 385 points
    This is our own board, I do suspect manufacturing issues, but difficult to debug without any insight into why the dlpc350 might indicate a fault condition. Thanks for the tip with I2C, If that is operational during fault condition I will try that. USB-connection which we mainly use is not up and running at least.

    1. The fault condition flags listed in the programmers manual are the only flags accessible to debug a fault condition?
    Is it possible to get some more information on how the different fault conditions might be corrected?
    The programmers manual just says: "Any error condition indicates a fault condition and it must be corrected."
    2. For instance if the issue is "Internal Initialization"- error or "forced swap"-error, how can that be corrected?
  • 0 in reply to Anders Guldahl
    TI__Mastermind 20045 points
    Hello Anders,

    Let me know if you are able to get status information using I2C. This information would definitely help get us closer to the root cause. After we understand the condition, I will have to investigate possible corrections (I don't have a generic list of faults and corrections unfortunately). If you are able to query all of the listed flags and they are all good we will see if there are any other ways to indicate faults.

    Another question I have for you is are you seeing this issue on multiple boards? It sounds like it could be a soldering issue. Perhaps there is a bad connection or two that manifests over different temperature ranges.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Intellectual 385 points
    Hi again,

    I've tried the I2C connection, but when the fault-condition occurs, the I2C-slave clock (SCL) on the dlpc350 is stuck low, it is impossible to get any communication going. SDA is not stuck low though, so this might be a software-issue with the I2C-driver in the dlpc350?

    Soldering issue is one of the things we suspect. I will do some more debugging with freeze-spray next week, and maybe send the board for x-ray.

    Thanks so far for the feedback!
  • 0 in reply to Anders Guldahl
    TI__Mastermind 20045 points
    Thanks for the update. Let me know what you find and we will than see how to best assist you.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    TI__Mastermind 20045 points
    Hello Anders,

    Any progress update on this?

    Thanks,
    Kyle