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TPS63802: Part fails after few months of normal operation

Vladimir Rappoport
Prodigy 10 points
Part Number: TPS63802

Tool/software:

A regulator is built using TPS63802DLAR. It takes the power (VD on schematic) from a single Li-Ion cell and converts it to 4V. A typical load current is 300-500mA with very short bursts up to 1A. The enable signal is 0V/2.5V. About 1000 boards were built, and so far two parts failed after several months. Once failed, they take sink about 100mA from the power source even with the enable pin at 0V. The enable function still works, i.e. there is 4V on the output with enable pin high and 0V with enable low. I am attaching the schematic and the layout. The PCB has four layers with a massive ground pour on the top and bottom plus the ground plane with frequent vias, so the part doesn't get hot.

What can go wrong?

  • 0
    TI__Mastermind 18610 points

    Hi Vladimir,

    The two failed parts has normal function to regulate the Vout, but they will additionally sink 100mA, right?

    Please check the following items:

    1. Is there a AB swap experiment performed? I'd like to check does the sink current follow the chip or the board?
    2. For the failed units, please measure the resistance between the VIN/VOUT/L1/L2 pin and GND pin.
    3. If available, please check the voltage at the L1 and L2 with enough bandwidth. 

    Regarding the schematic and layout.

    • No concern on the schematic. But for the layout, the major one that should to be improved is that connect the GND pin and the Cout GND at the same layer. And also, the input cap and output cap can be adjusted to put more close to the chip.
    • You may refer to the following layout example.

    Regards 

    Lei