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DRV8262: Part shorts power supply immediately

Richard Wilson
Prodigy 10 points
Part Number: DRV8262

Tool/software:

In my application, the part drives two brushed DC motors, one at a time. The voltage is 54V and the current is less than 2A.

For development, I used a 60V lab power supply, and everything seemed to work as intended.

I then installed the PC board in the target location, and the part shorted VM to ground immediately and blew the 2A fuse. (the LCD backlight did not flash) An ohmmeter now reads 1.4 ohms from VM to ground. The big difference is that the supply was driven by a stiff 54V supply, four car batteries in series. The power was supplied suddenly by closing a switch. 5V is derived from the 54V, so all logic signals would initially be low.

Is this a known problem? What can I do to reliably use this part (or some other part) in my application?

DRV8262_schem.pdf

  • 0
    TI__Genius 11861 points

    Hi Richard,

    Thanks for the question.

    Is there a supply waveform that we can refer to to understand the case better?

    Thanks,

    Ibinu

  • 0 in reply to Ibinu Alaudeen Nadeera
    Prodigy 10 points

    I don't understand how this would be useful. The supply is four car batteries, and the waveform would be a straight line. There might be very small variations as other loads turn on and off, but that would not be significant in the few milliseconds when the problem occurred. (Could the battery charger be outputting high voltage spikes? Maybe. I'll try an AC measurement. I don't have a scope available, I'm in the middle of wilderness. My Fluke multimeter on Max/Min setting never registers anything higher than 54V or lower than 53V over a couple days.)

    As long as I'm rambling, the previous version used a home-made H-bridge with two NFETS and two PFETS, and operated reliably for more than a decade. Except when someone assembled the needle valve incorrectly, which made it difficult to turn, which caused the protective fuse to blow, which caused a helpful person to put in a larger fuse, which caused the magic smoke to escape. Application: hydroelectric plant at https://www.holdenvillage.org/

  • 0 in reply to Richard Wilson
    TI__Genius 11861 points

    Hi Richard,

    Just to be clear i was referring to probing the supply voltage close to the device pin using an oscilloscope. I wanted to see when the switch is closed does it cause a ringing in the supply pins.

    Hope that clarifies.

    Thanks,

    Ibinu

  • 0 in reply to Ibinu Alaudeen Nadeera
    Prodigy 10 points

    My one board now has a shorted DRV8262, so I don't have another one to destroy, and I don't have a storage scope anyway. There is perhaps 40 feet of (12 gauge?) wire to the batteries, and 10uF+ of ceramic caps on the board, so I suppose there could be some kind of ringing when the power switch is closed. I'm thinking I might try an inrush current limiter thermistor to calm things down on the next version of the board.

  • 0 in reply to Richard Wilson
    TI__Mastermind 19740 points

    Hi Richard,

    Car batteries typically have a high current capacity with no current limit like on the power supply. The device will see a very high inrush current that will exceed the ITRIP threshold and damage the device. Adding an inrush current limiter would help and it would also help to limit the inrush current by using a soft start (slowly increase PWM duty cycle on startup). The long wires also add inductance that affect the current on startup or PWM. 

    Best,

    David