The BS pin is for accurately monitoring the cell voltage. As the charging and discharging currents increase, a difference in voltage between P- and Vss. The BS pin is connected to the VSS pin inside the IC via resistor RBSS during charging and normal operation, so it is not affected by the charging and discharging currents. Therefore, it is possible to monitor the cell voltage using the voltage between the P+ and BS pins, even during fast charging. For detailed conditions, please refer to the data sheet of each product ”■ Operation - 7. Battery voltage monitor pin (BS pin) ".