SLUUBT5C November 2018 – June 2021 BQ40Z80
Typically under CUV (Cell Undervoltage) conditions, the LED operation is not allowed to preserve remaining battery charge. However, under certain situations even under CUV conditions, the LED operation will be allowed; that is, either with PF active with the [LEDPFON] bit set or with the charger connected with charging active. Additionally, an option is provided to turn on the LED even under CUV without the charger present by setting the [LEDIFCUV] bit in the LED configuration register. This option must be used with care so as to not run the battery too low.