SLUSDU0 September 2019 BQ21061
When the device is out of Ship Mode and battery is above VBATUVLO with no valid input source, the battery discharge FET is turned on connecting PMID to the battery. The current flowing from BAT to PMID is not regulated, but it is monitored by the battery over-current protection (OCP) circuitry. If the battery discharge current exceed the OCP threshold, the battery discharge FET will be turned off as detailed in the Battery Short and Over Current Protection section.
If only battery is connected and the battery voltage goes below VBATUVLO, the battery discharge FET is turned off. To provide designers the most flexibility in optimizing their system, an adjustable BATUVLO is provided. Deeper discharge of the battery enables longer times between charging, but may shorten the battery life. The BATUVLO is adjustable with a fixed 150-mV hysteresis.