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LM5116: LM5116 IC design MOSFET short issue 12V

Sathya Priya
Intellectual 260 points
Part Number: LM5116

Hi Team,

We are using Power cube v3 which is capable of providing three output voltage (Output 1: 5V, Output 2: 3.3V, Output3: 12V)

Image for reference

where LM5116 buck controller and mosfet BUK6226-75C is used in the design. 

When we are giving the input supply(48V@2200mA) with battery,12V output is not coming up and we found that both HO,LO mosfet going short.

We are still getting output 1: 5V, the 5V rail looks fine but output 3:12V rail we are facing this issue.

We tried changing the mosfet again we faced the same issue: output 3:12V not coming up, short in mosfet.

For these above cases are tried without connecting any load. 

So, what causes the mosfet gone bad and affecting the 12V output rail?

Waiting for the response.

Regards,

Sathya Priya N.

  • 0
    TI__Guru 58171 points

    Hello Sathya 

    MOSFET damage can happen by (#1) Drain-Source over voltage (#2) Gate-Source over voltage (#3) Over temperature

    #1 usually happens due to a long input cable or a bad PCB design 

    #2 usually happens due to a VCC over voltage 

    #3 usually happens due to an over load, a high ambient temperature, a bad PCB design or shoot-through

    Please share the schematic for more investigation. 

    -EL

  • 0 in reply to EricLee
    Intellectual 260 points

    Hi Eric,

    Thanks for the response.

    I want to clarify one thing, initially with same bat voltage we done many testing.

    It was proper all the time.

    Once we faced the issue, after that changing the MOSFET also didn't results good.

    Can you give a clear on this. Why the MOSFET damage happen after some time.?

    Regards,

    Sathya.

  • 0 in reply to Sathya Priya
    TI__Guru 58171 points

    Hello Sathya

    The device might be damaged at the first failure. Have you replaced the IC and tested again ? 

    -EL

  • 0 in reply to EricLee
    Intellectual 260 points

    Hello Eric,

    Yes Eric.  After that also we are facing same issue.

    Mosfet got short we replaced with new one. When we powering it, Again we observed that 12V not coming up.

    and checked the rail, found that Mosfet gone bad (which we replaced with new one)

    May I know exactly Which IC you are asking for replacement?

    We need to know why exactly the mosfet going bad? whether the rail has some issue? 5V and 3.3V rail is still coming up and looks good.

    Initial for almost 1 week we used for testing, it is fine all the time. Same voltage only we are using.

    Thanks,

    Sathya Priya N.

  • 0 in reply to Sathya Priya
    TI__Guru 58171 points

    Hello Sathya.

    Can you share the schematic for more investigation ? 

    If you haven't , please check the dead-time ? Also, please double check the loop stability using Quick Start ? 

    -EL

  • 0 in reply to EricLee
    TI__Guru 58171 points

    Hello I am closing this thread since I have not heard from you for sometime.
    If you are still trying to resolve the issue, please feel free to open a new thread. Thanks
    - EL