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TPS54140: When Vin drops less than Vout, is there any possiblity that the device is damgaed?

Oba
Genius 15770 points
Part Number: TPS54140

Hello,

My customer is investigating a case that TPS54140 was damaged in the field.
Then they have a question.

When Vin drops less than Vout, is there any possibility that the device is damaged?

Regards,
Oba

  • 0
    TI__Guru 57555 points

    Hello

    Yes, there is some possibility that the device may be damaged when the input voltage falls below the output voltage.

    There is a diode between the drain(VIN) and source(SW) of the power MOSFET inside the converter.  With a voltage on Vout, and the input held at zero volts, there will be a path from Vout to Vin through the inductor and this diode.  Even if the input is floating, a current will flow and try to charge the input caps, possibly to a high voltage due to resonance with the caps and the inductor.  This phenomenon has been seen in the past under some conditions.  Allowing current to flow through this diode can cause a parasitic to turn on or even damage the diode.  Since it is not a "true" diode but a parasitic formed when the MOSFET is constructed on the die, it is not designed to take current for more than a few 10s-100s nsec.  

    You may also want to look at these app notes: SLYT689, SLVA494

    Thanks