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TPS63070: Shorts to ground after a USB connection

user4725373
Expert 1645 points
Part Number: TPS63070
Other Parts Discussed in Thread: BQ25606

Hi,

I just created a discussion in the Battery Charger forum, but I think it's more suited here.

We are testing a prototype which runs on batteries and can be charged with USB. The charger is a BQ25606, and the buck-boost is a TPS63070.

Everything worked well, the battery charger worked and the circuit was stable. But at one time, we plugged the USB for 20 minutes (not the first time that we do so), and then the circuit stopped working.

I cut the trace between V_CHARGER_OUT and the VIN of the TPS63070, plugged 4V (from a power supply) directly to the input of the TPS, and there was clearly a short (500 mA consumed, which was the limit of the power supply).

I then applied 3.3V to the output of the TPS63070, and the circuit operated normally. So I really think that the TPS63070 is burned. Moreover, I did an Ohm test between VIN of the TPS63070 and GND and I measured 7 Ohms.

Does anyone have an idea about what happened? We did plug the USB before without problems for long periods.

  • 0
    TI__Guru 65170 points

    Hello user4725373,

    Without a detailed failure analysis, it will be highly speculative to try to find a root cause.

    As first speculation, I think it is possible that voltage spikes during plug-in cause such a damage (either above or below the abs max ratings). Do you have some spike reduction circuitry applied to the USB input?

    Please follow the information below for the failure analysis process if you want to get a detailed analysis:

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Expert 1645 points

    Hi Brigitte,

    Yes, there is a TVS diode on VBUS.

  • 0 in reply to Brigitte
    Expert 1645 points
    We have 5 LEDs on the PCB to indicate the level of the battery (0-20%, 21-40%, 41-60%, 61-80%, 81-100%).

    The USB was charging and the 5 LEDs were on. Then, we unplugged the USB, and the LEDs now indicated 40% charge (it was higher than 40% before we started charging). But the microcontroller and the circuit still worked.

    We then unplugged the batteries, and tried using a power supply instead of batteries, but the TPS63070 was now shorted to ground.

    Would it be better to create a support case? I don't really want to return the buck-boost, but I think a schematic analysis would help.
  • 0 in reply to user4725373
    TI__Guru 65170 points
    Hello user4725373,

    Yes, I think starting a support case would be the right way to go.

    Best regards,
    Brigitte
  • 0 in reply to Brigitte
    TI__Guru 65170 points
    Hello user4725373,

    I haven’t heard back so I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)

    Thanks,
    Brigitte
  • 0 in reply to Brigitte
    Expert 1645 points

    Hi Brigitte,

    I'm currently getting help from the engineers of the battery management forums. I think we can close this thread.

    Thank you,

    Fred