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BQ40Z60 EVM R31 Fail

Jim Sheahan
Prodigy 175 points
Other Parts Discussed in Thread: BQ40Z60

What might cause the 10 ohm series resistor connected to VCC to blow?  I have been using the EVM for months, then last Tuesday R31 fails, and ultimately the BQ40Z60 blows a small hole through the top of the chip, but it still operates from battery (no charging of course).

  • 0
    TI__Expert 5090 points
    Hi Jim,

    I'm sorry for the delay - many of our team are out over the holidays, so it may take awhile before someone can chime in on your case. I'm not really familiar with this device myself, unfortunately. Do you think there was an excessive current flowing through that resistor into VCC, and that caused both the hole in the chip as well as the resistor to fail? I'm surprised the chip could still operate at all after undergoing such a violent episode!

    Terry
  • 0 in reply to -Terry
    Prodigy 175 points

    Hi Terry,

    My apologies for the delayed response as well.  Really not sure what caused it to blow.  Like I had mentioned, I had been using the board for months charging from  old laptop power supply of 19.5V.  A colleague and I tried to figure out what may have caused it, the only thing we could think of is that I may have inadvertently reversed connection which took VCC below -.3V.  I don't remember doing that, but that seems to be the only reasonable explanation.  I have already purchased a new EVM board, and a current limiting power supply, so hopefully this won't happen again.

    BTW, I know you mentioned that this is not your area of expertise, but I have been having real difficulty finding good explanation of the setting in the Battery Management application.  Info seems to be spread out in a number of PDFs.  I am still not fully up to speed on how to properly configure the device.  I have it working, but not so sure I have it working correctly, as there may be many parameters still set for 3 series cells, the project I am working on uses 2 series cells.

    Thanks in advance for your time.

    - Jim

  • 0 in reply to Jim Sheahan
    TI__Guru 73830 points
    Jim
    I work with this device. The best place to go to find information on changing the number of series cells is the EVM User's Guide. The quick start section provides the jumpers and parameters to do this. Fortunately, most of the parameters in the gauge are set at the cell level and there are not a lot of changes required to update the number of series cells.
    Tom