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LM5149: LM5149 damage issue check

Part Number: LM5149

Hi Sir,

 My customer use dual LM5149 at their system and please check schematic as attached. In their field test, both of the LM5149 will be failed when 56V power adaptor is plugged. VCC and VDDA pin short to GND. Would you please helping to check what they can do to prevent the damage condition? Thanks for your kindly help.

Best regards,

Gary Teng


  • Hi Gary,

    The schematic looks OK, I wouldnt expect any damage to VCC or VDDA.

    Are you using VCCX? I see a test point there. VCCX should be GND if not used.

    If using external VCCX and VIN is down, that can damage the internal LDO.

    Also, that MOSFET is not logic-level, it will not turn on fully at VGS of 5V.

    You need to use a MOSFET that is logic level, the datasheet usually has specs for VGS=4.5V.

    Hope this helps,