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Original question:

TPS22950: Inquiry about the cause of failure of TPS22950

TPS22950: Part failure

Timber Lock
Prodigy 20 points
Part Number: TPS22950

I have a question with regards to the TPS22950. I am testing a design in which two loadswitches are used in parallel (basic block diagram attached). The reasoning behind the circuit was that a usb port could be used as both a source and a sink. When the device was used as a sink a 500mA current limit should be applied and as a source 100mA. With the two complementary load switches, 1 for sourcing and 1 for sinking of which only 1 is on at the time would implement this functionality. However in reality we see this the LS, which is not enabled, break (short between Vin and Vout). So this is when a usb cable is connected when the device is not powered yet, so the 5V0 is still low. There is protection in place to prevent voltage spikes when plugging in the cable (which has been verified). Is there something fundamentally wrong with the setup shown below?

  • 0
    TI__Mastermind 18510 points

    Hi Timber,

    Welcome to e2e!

    When each device has reverse voltage across it, do you disable each TPS22950 using the ON pin?

    Thanks?

  • 0 in reply to Patrick Shalton
    Prodigy 20 points

    Yes when the device is used as a sink 5V0 is still low, which is used to power the whole circuit (apart from some logic that will enable the ls in forward mode after approx 100ms). So initially both enables are on, but also Vin is still at 0v. Does it need some voltage at the input for the reverse current protection to work?

  • 0 in reply to Timber Lock
    TI__Mastermind 18510 points

    Hi Timber,

    The TPS22950 reverse current blocking is enabled in two ways: when the device is disabled and when VOUT is 44mV higher than VIN. But, if a lot of instantaneous current flows across the body diode of the power FET or a lower current that doesn't trigger reverse current blocking continuously flows across the body diode, the device can be damaged.

    I recommend disabling each respective TPS22950 when it should be blocking reverse current, I suspect that you will not see any more TPS22950 failures then.

    Thanks,

    Patrick