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LMZ14203: Unknown failure mode in new design

Gene Mirro
Prodigy 160 points
Part Number: LMZ14203

We have a new design with the LMZ14203TZ-ADJ/NOPB converter.  We have roughly 50% failure rate at power-up.  I can't find anything obviously wrong with the board or design.  Can you give me a list of things that will destroy these units?  These units have built-in protection against a wide range of failures.  We already have protection against reverse input voltage, and input overvoltage.  Output loading is very light.  What am I missing?  Thanks.

  • 0
    TI__Guru 50120 points

    Hi Gene,

    Can you provide me the following:

    • schematic
    • PCB
    • solder profile 
    • date code/ top mark of the device

    Just to clarify, on power-up the device does not switch and regulate the output? What condition and symptoms are you seeing in your application? 

    Regards,
    Jimmy

  • 0 in reply to Jimmy Hua
    Prodigy 160 points

    This is what I can share so far.  3.3V_APBI has no load.  Load on 5V_CPLD is roughly 250mA.  +24V power is coming from a current-limited lab supply.  D318 and D22 provide reverse polarity protection.  TVS1 provides overvoltage protection.  F9 is a resettable fuse. 

  • 0 in reply to Gene Mirro
    TI__Guru 50120 points

    Hi Gene,

    Can you provide your schematic with a better resolution. Perhaps one image of the circuit before the 24V and one of the two LMZ14203 regulator circuit. Currently the image you provided is slightly blurry and hard to read.

    Also, do you have the solder profile during SMT assembly? I want to make sure that the temperatures used during mounting didn't affect the module.

    For the failed board, I'd recommend you submit a customer return for FA using the attached link so that we can further investigate the failure mechanism. 

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points
    Hi Gene,

    Do you have any updates on the solder profile used during assembly? Also if you can have the image split, that should allow me to see the schematic more clearly.

    Regards,
    Jimmy
  • 0 in reply to Jimmy Hua
    Prodigy 160 points

    The problem has not repeated.  I suspect there is nothing wrong with the design or the chips.  Is there some way to delete this thread?

  • 0 in reply to Gene Mirro
    TI__Guru 50120 points
    Hi Gene,

    Thank you for the update. I can just close this thread .

    Regards,
    Jimmy