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LMR64010: IC Burns out on power up

Mike Thomas
Prodigy 20 points
Part Number: LMR64010

I've designed the LMR64010XMFX/NOPB into a circuit to convert 12V to 24V. I've checked the schematic multiple times for accuracy according to the datasheet. I've checked that the fab populated the correct components. The only load on this supply on power-up is the LED shown. The original chip on board wasn't working, so I replaced it with a new one. Immediately upon power-up, the LMR64010 burns out. The burn is by Pin 5, the 12V input.

The diode still measures good. Resistor values measure correct. LED is still operational. Capacitor values measure correct.

Here is my schematic:


Here is the layout:

Any ideas on what I'm doing wrong?

Thanks,

Mike

  • 0
    Prodigy 20 points

    So I downloaded the Spice simulation model, and simulated the same circuit from the datasheet. It worked perfectly and created 24V. The schematic in my design is the same.

  • +1 in reply to Mike Thomas
    TI__Genius 12300 points

    Hi Mike,

    I don't find problems in your schematic and layout.

    Based on your description, I think the reason may be over voltage on the VIN pin. Do you use a very long wire between the Vin power source and the device? If possible, could you help replace a new device, power on and capture the voltage waveform on the device VIN pin? Although there will be high risk to damage one more device.

    Please also help measure the resistances between the following three pairs?

    • SW pin and FB pin of the damaged chip
    • FB node and GND of the board
    • VOUT node(D1 cathode) and GND of the board 

    Regards

    Lei

  • 0 in reply to Lei Zhong
    Prodigy 20 points

    Thank you for your help.

    I did technically have a long wire on the VIN pin, a 2.2uH inductor to attempt to reduce inrush current.

    In simulation, this inductor created a large ringing in the 12V supply, up to 13V.

    I removed and shorted the 2.2uH, put a new IC on, and it successfully created 24V.

    Thanks for taking the time to help.