SLUSDQ4 April 2019 BQ79606A-Q1
The AUX ADC has an input for a selected cell voltage. The cell voltage is measured through the CB1-6 pins. This is useful for comparing to the VC1-6 results from CELL ADC to ensure correct operation of the cell ADCs. Each cell is selectable using the DIAG_CTRL2[AUX_CELL_SEL] bit. This bit should be cleared first whenever AUX_CELL_SEL is changed. Selecting a cell using the AUX_CELL_SEL bits and enabling the function with DIAG_CTRL2[AUX_CELL_SEL_EN] routes the cell voltage from the OVUV level shifter to the AUX ADC. Additionally, selecting a cell enables the AUX_CELL measurement for the auxiliary ADC. Refer to Table 5 for more detail about AUX CELL1-6 measurements details. While the DIAG_CTRL2[AUX_CELL_SEL] bit is set to 1, the OVUV function is suspended.
The AUX ADC only supports positive voltage readings. When comparing the AUX_CELL measurement, only voltages from 0V to 5V are supported.
The data for the cell voltages is 16-bit (spread over two registers). To prevent the condition where a read of the full data results in data split between two reads (i.e. AUX_CELLH from first conversion and AUX_CELLL from second ADC conversion due to conversion update in the middle of a read), data for all registers for a single input are locked. For example, AUX_CELLL is locked for updates until AUX_CELLH is read. The BQ79606A-Q1 does not support reading only the MSB or LSB. The best practice is to group read all registers for a particular input.