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LM5121: LM5121-5V to 10V boost converter output capacitor failure during initial power on

SHIJU R
Prodigy 200 points
Part Number: LM5121

Hi,

I am using LM5121 for my DC-DC design for 5V input to 10V output at 5A load requirement,i used 2 Nos of 100uF tant capacitor at output along with 4 ceramic capacitors.During initial power on one of the TANT capacitor failed and become short circuit. Iam not able to identify the issue,Kindly help me to analysis my design.

thanks regards

  • 0
    TI__Mastermind 21720 points

    Hi SHIJU R,

    Thanks for reaching out with your questions and for using the LM5121.

    Can you please post the schematic of your design? What voltage rating are the tantalum capacitors? Are you seeing this every time the device starts up?

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    Prodigy 200 points

    Thank you Garrett for your reply

    Capacitor voltage rating is 25V, Every start up problem is not there, the first power on the  issue came after that capaciotr replaced, then it is working.

    Capaciotr C3 only failing,whcih is the tantalum capacitor comes first in the output loop.(before tantalum 4 cermic are avalibale in the loop).

  • 0 in reply to SHIJU R
    TI__Mastermind 21720 points

    Hi SHIJU

    Just to confirm it the tantalum capacitor is connected closer to the switching node when it is damaged? If that is the case the RMS current running through the tantalum capacitor might be higher than the rated RMS current. When the capacitor is place closer to the switch node the higher frequency ripple currents could run through the tantalum capacitor damaging it.

    Please let me know if you have any questions.

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    Prodigy 200 points

    Hi Garrett

    tantalum capacitor is not connected closer to the switching node,There is four ceramic capacitors are available before tantalum capacitor in the output loop.The mentioned issue we faced during the first power ON of the module.whether any inrush current during the power on is caused to damage the capacitor????.

    Thanks,

    SHIJU.R

  • 0 in reply to SHIJU R
    Prodigy 200 points

    Hi Garrett,

    In my design i was used two different MOSFETs in high side and low side switch (PSMN1R3-30YL-115 at HO and RJK0301DPB-02#J0 at LO) , Whether this can create a problem during power on???

    Thanks,

    SHIJU.R

  • 0 in reply to SHIJU R
    TI__Mastermind 21720 points

    Shiju,

    Please provide your schematic and layout files. This will help to debug the issue.

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    TI__Guru* 78100 points

    Hi Shiju,

    We haven't seen any updates for more than a week.  Can we assume the issue has been resolved and close the thread now?  You are welcome to re-open this thread by adding a new post.

    Thank you and good luck in your project.

    Thanks,

    Youhao