The BQ76922 device includes optional capability for the customer to calibrate each cell voltage gain and the gain for the stack voltage, the PACK pin voltage, and the LD pin voltage individually, and multifunction pin general ADC measurements. Separate offset calibration values are included for use with the cell voltage measurements, TOS (stack), PACK, and LD voltage measurements. Similarly, gains determined during calibration are written into configuration parameters for each individual cell voltage gain, the stack voltage gain, the PACK pin voltage gain, the LD pin voltage gain, and the multifunction pin general purpose ADCIN measurement gain.

If values for the calibration gain configuration are not written, the BQ76922 device will use factory trim or default values for the respective gain values. When a calibration gain configuration value is written, the device will use that in place of any factory trim or default gain. The raw ADC measurement data (in units of counts) is corrected by first subtracting a stored ADC offset trim value, then the gain is applied, then an individual stored offset is subtracted, before the final voltage value is reported.

The factory trim values for the Cell Gain parameters can be read from the Cell Gain data memory registers while in FULLACCESS mode but not in CONFIG_UPDATE mode, if the data memory values have not been overwritten. While in CONFIG_UPDATE mode, the Cell Gain values will read back either with all zeros, if they have not been overwritten, or whatever values have been written to these registers. Upon exiting CONFIG_UPDATE mode, readback of the Cell Gain parameters will provide the values presently used in operation.

Further detail on calibration procedures can be found in the BQ76922 Technical Reference Manual.

The effective fullscale digital range of the cell measurement is 5 × VREF1, and the effective fullscale digital range of the ADCIN measurement is 1.667 × VREF1, although the voltages applied for these measurement should be limited based on the specifications in Section 6.