SLUSCU0J March 2018 – March 2022 BQ77915
A larger CHG FET gate-source resistor is required if load removal is enabled as a device of the UV recovery criteria. When the load removal circuit is enabled, the device is internally connected to Vss. Because in a UV fault, the CHG driver remains on, it creates a resistor divider path to the load detect circuit.
To ensure load removal is detected properly during a UV fault, TI recommends to use 3.3 MΩ for RGS_CHG (instead of a typical 1 MΩ when load removal is NOT required for UV recovery). RCHG can stay in 1 MΩ as recommended when using CHG FET protection components. The CHG FET rise time impact is minimized, as described in Protecting the CHG FET. On a stacked configuration, connect the LD pin as shown in Figure 10-7 if load removal is used for a UV fault recovery. If load detection is not required for a UV fault recovery, a larger value of RGS_CHG can be used (that is, 10 MΩ), and the LD pin on the upper devices can be left floating.