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BQ76940: BQ76940

Big Bill
Expert 1980 points
Part Number: BQ76940

Dear All:

    I find the equation in the 7.3.1.1.6 chapter. but i don't understand  it.

    V(BAT) = 4 x GAIN x ADC(cell) + (#Cells x OFFSET)   How did this equation come about?  thanks~

  • 0
    TI__Guru 54715 points
    Hi Big Bill,
    The bq769x0 sums the ADC values and divides by 4 to store the value in the battery voltage register. The divide by 4 was needed because of the size of the register.
    To get the battery voltage back from the value in the register, you need to multiply by 4.
    Since the part has the average gain and offset for the cells, the value is multiplied by that gain. Since each used cell will have an offset best known as the average offset, the number of used cells is multiplied by the stored average offset to get a value for the battery. Offset should not be applied to unused cells.