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TPS40170 Chip Blows Up; Package Hole Near Pins 18, 19, 20

David Merriman
Prodigy 235 points
Other Parts Discussed in Thread: TPS40170

We have had 3 instances, different boards, over the last year, from a total of 20 boards built. We power the board with either 24VDC or 48VDC power supply and the power supply is connected/removed, no switches to turn board on and off. The power supply cable is 6 or 10 feet long. My initial question i do you know why this area of the chip (pins 18, 19 and 20) would be physically damaged? I can add the schematic later and discuss, but I was hoping this situation may have happened to others. I'm thinking we should not connect/disconnect DC input power, but use AC switch on DC power supply?

  • 0
    TI__Mastermind 24075 points
    Hi Dave,

    If you do input power supply hot plug and unplug, it is possible that voltage applied to TPS40170 VIN pin (pin 19) is above its abs SPEC.
    You can probe the voltage to confirm it.

    How is the ENABLE pin voltage during hot plug an unplug, it is low or high?

    I suggest to use AC switch on DC power supply to turn on and off VIN.

    Thanks
    Qian
  • 0 in reply to Qian Chen
    Prodigy 235 points
    Qian,

    Thank you for the timely response. The ENABLE pin is controlled through a voltage divider between the input voltage and ground such that the part is enabled at an input voltage above ~20.6V. If insertion/removal of the input power cable at the connector is causing spikes (which we are assuming), the voltage at the ENABLE pin would also be spiking.

    We are mostly curious about the specific location on the IC package that keeps blowing. Can you explain approximately what is on the die at the location of the hole? Is there a reason that this location is damaged?

    We agree that a switch on the power supply should have been added, and going forward, it will be.
  • 0 in reply to David Merriman
    TI__Mastermind 24075 points

    Hi, Dave

    The VIN pin (pin 19) will be exposed to the voltage spike, probably that's why the damage happens around pin 18, 19, 20 area.

    I don't know the exact circuit in that area. Most like is internal LDO circuit.

    Thanks

    Qian