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TPS26624-25EVM: TPS26624-25EVM output terminal burned out capacitor

user6342742
Prodigy 180 points
Part Number: TPS26624-25EVM

Dear,

         Hello ! We use TPS26624-25EVM to design a circuit as shown in the figure below. The voltage input is 36V. It is found that the capacitor C20 occasionally burns out. I don’t know what caused it. May I ask if there is a problem with the circuit design.

  • 0
    TI__Guru** 105361 points

    Hi,

    Can you share part number of C20. Is C21 fine ?

    Are there any other loads other than DC-regulator on VDD rail ?

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 180 points

    Hi，

         I'm so sorry.The above is the latest design. Yesterday, when many samples were tested, it was found that C21 was occasionally broken down. And explain that R18 and D8 are not welded. The part number of C20 and C21 is CC0805KKX5R9BB106. But if we replace C20 and C21 with capacitors whose part number is GRM21BR61H106KE43L, C20 or C21 will still be broken down. Other capacitors C4 use part number CL31B106KBHNNNE, C13 uses part number GRM188R71H104KA93D, and C24 uses part number C1608X7R1H103KT000N. And there are not any other loads other than DC-regulator on VDD rail.

  • 0 in reply to user6342742
    Prodigy 180 points

    Hi，

         Please help to see if it is the peripheral circuit parameter design of TPS26624-25EVM that affects C20 and C21, or the value of C20 and C21 is used unreasonably, or whether the subsequent DCDC power supply design affects C20 and C21. Thank you.

  • 0 in reply to user6342742
    TI__Guru** 105361 points

    Hi,

    Schematic and capacitor parts looks good to me.

    As we know, usually capacitor fails due to over voltage stress. Is there any specific test condition where the capacitors are failing ? for example... startup, powering down or while loading the output of DC-DC ?. 

    Best Regards, 

    Rakesh

  • 0 in reply to Rakesh
    Prodigy 180 points

    Hi,

       Some of the test conditions are when the power supply is just powered on, and some are in the process of multiple power-on. Now about 100pcs has been tested, and about 10pcs capacitor C20 or C21 is broken down. Can C20 or C21 be replaced with a small capacitance value for testing? Can a capacitance value be recommended? Or if you have any other suggestions, please give me some advice. The following is our PCB layout, please take a look at whether the PCB layout is unreasonable. Thank you.

  • 0 in reply to user6342742
    Prodigy 180 points

    Hi,

        To add that the total load of our product is only more than 30 mA, and the load is very low.

  • 0 in reply to user6342742
    TI__Guru** 105361 points

    Hi,

    The output capacitance value is determined by the load. As such, eFuse does not need any output capacitance but for noise filtering and absorbing fast slew-rate voltages, we recommend to use at least 0.1uF at the output of the eFuse.

    You can replace C20/C21 with any capacitance between 0.1uF to 1uF and proceed.

    Best Regards, 

    Rakesh