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TPS63020: Failure of the bottom Mosfet (L1 half bridge)

Eric LEROY
Prodigy 20 points
Part Number: TPS63020

Hello,

TPS63020 is used to supply a modem 2/3G

The input voltage is 5Vdc,  Vout =3.6Vdc

the output capacitor : Cout= 1 000µF 6.3V

This is a new electronic board, but the previous version was made in more than 200,000pcs without failure (Upgraded by the quality department)
On the new product, on average 4 products out of 250 are short circuit L1 / GND after the first electronical test.


The layout and layout have not changed between the two versions

The test bench is in the process of investigating its behavior.

I would like to discuss causes of the mosfet BOTTOM failure of L1:
- If the ENABLE input is floating  during the test phase and a voltage is applied to VIN
- If a voltage is applied only to VOut
- Fast  ON / OFF
- Passage betwwen buck and boost in fast time slots
-  MOSFET RSOA (note in the datasheet)

-etc...

  • 0
    TI__Expert 5425 points
    If L1 breaks I think it is most likely due to an overvoltage condition. It could be caused for example by fast turn on and off if the supply cable has significant inductance.
    The device is designed for having only voltage on VOUT. It can change from buck to boost operation from cycle to cycle. If EN is floating it is either on or off, but it should not get damaged just by that.