This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ76942: REGIN and BREG

Part Number: BQ76942
Other Parts Discussed in Thread: TIDA-010247


According to TIDA-010247 ref design REGIN input received voltage from B+ (the topmost battery) through transistor-based voltage converter circuit.

Why not to take voltage from between  2nd cell + (positive) point (e.g. VC2) and pass it to 5V LDO and then to REGIN? Wouldn't it be less power dissipation - from ~7V to 5V instead of ~24V (or more) to 5V ?

What am I missing here? Will it affect cell balancing in some way?



  • Dear Leonid,

    The main reason for not connecting the 2nd cell to the LDO is for cell balancing. The LDOs can draw up to ~100mA while in operation. If you implemented what you suggested, you would be pulling an additional ~100mA from the bottom two cells that don’t pass through the remaining cells. This will create an imbalance between the cells and require balancing the top 10 or so cells down to match the lower two cells. This would generate much more heat as you balanced the remaining cells down to the bottom two cells. I hope this helps!


    Asher Nederveld

  • Thank you for detailed explanation.

    Actually, that's what I suggested by myself but wasn't sure.

    Currently looks like the best solution is to use some simple switching buck coverter to provide 5V for REGIN

  • Yeah, that is commonly what people do when they are worried about efficiency on the LDO. The tradeoff is a little bit of noise produced by the switching, but most of the time it is negligible and doesn't impact the design. That's the best solution if you are worried about the efficiency.