SLUUC54C February 2020 – March 2024 BQ27Z558 , BQ27Z561 , BQ27Z561-R2
The design of some battery charging systems may have a not insignificant impedance between the charger and battery terminals. In this case, a voltage compensation feature handles system level IR drops to ensure the correct charging voltage is supplied at the battery terminals. Program the System Resistance register with the measured resistance in milliohms (mΩ) between the battery terminals and charger terminals. To enable this feature, set the configuration bit [COMP_IR] in (default 0) the Charging Configuration register.
This feature works as follows:
ChargingVoltage() = charging_voltage + ChargingCurrent() × System Resistance
where charging_voltage was computed as a result of a selected configuration; from the JEITA table and any applied degradations.