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LMZ12002: Broken LMZ12002

Michael SI
Prodigy 50 points
Part Number: LMZ12002
Other Parts Discussed in Thread: LMZ14201, LMZ12001,

Hello,

we use in our power supply four DC/DC converters (2x LMZ12002, 1x LMZ12001 and 1x LMZ14201). In the last batch we ordered (25 pcbs), 11 of the pcbs were not working because one or two of the LMZ12002 were broken: output voltage equals input voltage or output voltage = 0. Soldering out the broken LMZ12002 and replacing it by a new one fixed the problem.

We have no order the next batch now and I was wondering what we can do to avoid these problems. Therefore, I have the following questions:

  • Is the LMZ12002 less robust than the LMZ12001 and LMZ14201? Because this one was the only type which did not work.
  • How likely is it that the parts were damaged on arrival before being soldered in? (I know - this is impossible to answer). Or is the handling very critical (ESD)?
  • Do you have any suggestions what we can do nail down where the problem is coming from?

I have attached the circuit - maybe there is also something which can be improved there.

Have a nice day
Michael

  • 0
    TI__Guru 50120 points
    Hi Michael,

    Do you have the solder profile used during assembly of these devices onto the board? The devices goes through final testing (ATE) to ensure the part is functional and to datasheet specifications before being packaged and delivered to customers. I don't believe this part is any more susceptible to issues compared to the other devices you've mentioned.

    Also do you have any date/lot code for these devices? I can ask the customer quality engineer to see if there might be an track record in the past for parts from that specific lot.

    I don't see anything wrong with your schematic. It looks okay and follows the recommendations detailed in the datasheet.

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

    Can you give me an update on this? I'd like to make sure that this isn't a solder/mounting issue and is an application issue.

    Regards,
    Jimmy
  • 0 in reply to Jimmy Hua
    Prodigy 50 points

    Hi Jimmy,

    thanks that you are pushing to get more insights into the issue.

    I wrote an email to our pcb manufacturer and assembler so we should get the information which you have asked for soon.

    We currently are running a new batch, so it is very important so settle this.

    Have a nice day
    Michael

  • 0 in reply to Michael SI
    TI__Guru 50120 points

    Hi Michael,

    Thank you for the reply. Please keep me updated on this. In the mean time, if you have failure boards that have not been modified, I'd recommend sending it in for FA through the customer return link. 

  • 0 in reply to Jimmy Hua
    Prodigy 50 points

    Dear Jimmy,

    the switchers have been ordered from Mouser 28th of February, 2018 (926-LM12002TZXADJNPB).

    The date code is 1706+57082855em7.

    'Unfortunately', we have repaired all pcbs already. The next time I'll send one in in case this should happen again - which hopefully is not the case. Thanks for all the information, I did not that customer returns are possible.

    Have a nice day
    Michael

  • 0 in reply to Michael SI
    TI__Guru 50120 points
    Hi Michael,

    Thank you for the information. If you have any further questions please let me know. Also if this issue does happen again feel free to reply to this message so we can reopen this thread and continue troubleshooting. Customer returns help us understand customer issues and improve quality screening of the part so anything sent in will be most valuable.

    Regards,
    Jimmy