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BQ76PL455A-Q1: VIO Power Input

Alex Terry
Intellectual 625 points
Part Number: BQ76PL455A-Q1

Hi, im currently designing a BMS using this IC, on the data sheet it says that for the base IC, VIO should be connected to the same power supply as the microcontroller, is it possible to use the cells being monitored for this similar to how TOP is used to power the IC?

Thanks.

  • 0
    TI__Genius 11480 points
    Hi Alex,

    Technically yes, but i strongly recommend that you do not do this. In a real system there will be noise and transients on the cells, and VIO/the MCU need clean supplies. If you do this you will likely experience a high fall out rate and many damaged ICs, as well as a potentially unreliable system. VIO is typically powered by the same supply as the MCU - usually the output of a PMIC.

    If all else fails, you may try something like a buck converter followed by an LDO to provide a clean rail if you do not want to use a PMIC.
  • 0 in reply to David Wiest Jr
    Intellectual 625 points

    Hi David,

    Thanks for your reply, thats really helped clear things up for me.

    Would the use of a voltage regulator such as UA78M33CKVURG3 enable me to supply power from the cells as this device should output a stable voltage and therefore transients and noise should be minimised?

    Thanks in advance,

    Kind Regards,

    Alex

  • 0 in reply to Alex Terry
    TI__Genius 11480 points

    Hi Alex,

    That looks like it would work well. One thing to consider - If you are taking  that linear regulator off of the second or third cell, then you will naturally create an imbalance in your battery pack as the lower cells discharge faster. This will limit the useful capacity of your battery  pack. This is why I recommend using a step  down DC-DC off of the top of the pack, followed by the LDO to clean up the signal. This will also reduce your  power dissipation as well as help keep the pack more balanced.

    If you are  ok with creating additional imbalance, the linear regulator only approach will work. If you are interested in the DC-DC approach, I suggest looking at  the SIMPLESWITCHER series and utilizing WEBBENCH. This gives you a good place  too start,

  • 0 in reply to David Wiest Jr
    Intellectual 625 points
    Hi David,

    Ah I see! That makes it a lot clearer.

    Cant thank you enough for being so helpful, have a great day.

    Kind Regards,
    Alex