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LM51551-Q1: What is the difference between the Q1 and non Q1 versions of LM51551

Felipe Schneider
Prodigy 80 points
Part Number: LM51551-Q1
Other Parts Discussed in Thread: LM51551, LM5155, LM5155-Q1, CSD18543Q3A, CSD

Hi guys, it is not very clear to me what the differences between those two versions of the LM51551 non-synchronous controller are. Can someone clarify it? (LM51551 vs LM51551-Q1)

I already know that there is an additional hicup protection between the versions of LM5155 and LM51551.

Regards, Felipe!

  • 0
    TI__Mastermind 21720 points

    Hi Felipe,

    Thanks for reaching out with your questions and for considering the LM5155 or LM51551 in your design.

    Functionally there is no difference between the Q versions and the none Q versions for the device. 

    The major difference between the none Q version and the Q versions is related to reliability qualification. The Q version follows the typical requirements for an automotive application which is AECQ-100. The none Q version follows a slightly different more generic flow.

    The other major difference is the package, The none Q device (LM5155,LM51551) don't have a wettable flank where the Q versions have a wettable flank on the pins (LM5155-Q1 , LM5155-Q1).

    I hope that answers your questions. Please let me if you have any other questions.

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    Prodigy 80 points

    Thank you for your answer, Garrett.

    Indeed I had already used the LM5155 (not the 1 or 1-Q1 ending) in my design, which is a 25V 4A boost, making a pair with the TI CSD18543Q3A mosfet. However, a large number of premature failures have been happening and I am struggling to find the root cause of those premature failures. Eventually, those failures blow the LM and CSD apart...

    I have noticed (not through a scientific method yet) that a problematic dehumidification phase and small electrostatic discharges during PCB manipulation might strongly interfere in the final boost failure rate. Have you seen some similar cases?

  • 0 in reply to Felipe Schneider
    TI__Mastermind 21720 points

    Hi Felipe,

    What was failing in the circuit? Was it the MOSET? 100W is a little large for a non-synchronous boost as the diode can dissipate quite a bit of power. What is the input voltage during the failures?

    I have not seen any cases like you mention above. 

    Thanks,

    Garrett