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LM46002: A nunber of units have failed with the high-side switch short-circuited

Robert Pearce
Prodigy 155 points
Part Number: LM46002

We are in pilot production ~80 units and we have 3 of these synchronus regulators on the board.  One is for 5V out and the other two are for 3V3 out.

Around four devices have failed in various positions..  The symptom is input to output short, say pin 1 to pin 13 (VIN to SW)

The input voltage is <12V.  We have 4u7 of capacitance at the input and 30uF at the output.

We do have a capacitor in the the BIAS pin .

If the boards aren't dead on arrival then they work fine.

What should I be looking at ?  The design seems to be in line with your rcommendations.  Is this a process issue?

  • 0
    TI__Mastermind 25590 points

    Robert,

    "If the boards aren't dead on arrival then they work fine." Are you receiving damaged boards from the fab? If so, it may be an assembly issue or possibly ESD.

    I've seen boards where disconnected or unsoldered pins can cause the device to become damaged. I would recommend probing the damaged boards to see if all the pins are making proper connection to the board. Also check to ensure they're not shorting to nearby pins or elsewhere.

    -Sam

  • 0 in reply to Samuel Jaffe
    Prodigy 155 points

    Dear Sam,

    Thanks for your reply.  I agree that some sort of process problem, possibly ESD, has to be on the list for investigation.

    However for a bit more context, there a lot of parts on this board (>1000) and there are other TSSOPs or similar pitch devices.

    So whilst a process issue is possible, I might reasonable expect to see other problems.

    I could show you the circuit privately, if that would help.

    Rob

  • 0 in reply to Robert Pearce
    TI__Mastermind 25590 points

    Rob,

    It could be that the footprint/model of LM46002 has an issue or the information wasn't received by the fab house correctly. That would explain why it's only with this one device.

    I've requested friendship on E2E so you can send me your circuit files in a private direct message.

    -Sam