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TPS57060-Q1: TPS57060 Brownout Failure

Part Number: TPS57060-Q1


I have experienced a failure with the TPS57060, where the device blew catastrophically when the input supply was momentarily interrupted (seconds). 

The circuit has been reproduced a few times prior to this occurrence without any  such failure.

The circuit is a +50V to +28V step-down configuration, designed using TI online design wizard, and the component values and tolerances were selected/checked as per TPS57060 datasheet. I suspect that this may be a known problem one may experience with Switch-mode PSUs?? 

My suspicion is that the input interruption reverted the circuit to start-up conditions while there was still significant charge on output capacitors, and the  for some reason compromised the device. If this were true, I am yet to figure out how.

Is there someone here who may able to corroborate my theory or alternatively propose another explanation?

  • I can think of two causes.

    The first is as you mentioned.  If the input supply should drop below the output voltage and the output capacitors

    are allowed to discharge, with current flowing from the SW pin to the VIN pin, then this large surge current can

    easily damage the device.  The current path is through the top side MOSFET body diode.

    The other possibility is an over-voltage surge on you input that exceeded the Abs max rating of the device.

    In the first case, a Schottky diode from Vout to VIN will help to divert the current away from the internal MOSFET body diode.

    In the second case, some kind of surge suppressor may be needed.

  • Thank you Frank for the sanity check. As I stated, it seemed like the only logical explanation, but till now, I just could not figure what was happening inside the device under this failure condition. The diode from output to input did occur to me, but  I've only ever seen this used in linear regulator circuits and wondered if it would be applicable to SMPS designs.

    The over-voltage case can also not be discounted, given the precise failure condition involved the physical, hot disconnection and reconnection of the input 50V input supply (high inductance of banana lead into a lab DC supply).

    Thanks again for your insights.

  • OK; I will close this post.