The device detects a UV fault when the battery voltage measured is below the UV threshold (V_UVP). If this condition exists for longer than the UV delay (t_UVP), the DSG output is driven to V_FETOFF to turn off the DSG FET.

The device includes a UV_SHUT option which may be enabled during factory configuration. If this option is enabled, during the UV fault state the device goes into SHUTDOWN mode to preserve the battery. In SHUTDOWN mode, the BQ2980 will drive the CHG output to the PACK voltage, putting the device into ZVCHG mode (the BQ2982 does not enable this ZVCHG mode). That means, the CHG FET can be turned on if a charger is connected and both VDD and PACK meet the ZVCHG turn-on conditions (see Section 7.3.9 for more details). The PACK pin is internally pulled to VSS through R_PACK-VSS. This is to determine if the charger is disconnected on the PACK+ terminal before shutting down the device. It is also to ensure the device does not falsely wake up from SHUTDOWN mode due to noise.

The UV status is released and the DSG output rises to HIGH, that is, V_DSG = VDD × (1 + A_FETON), if one of the following conditions occurs:

• When V_BAT is > (V_UVP + V_{UVP_HYS}) and the discharge load is removed or
• When V_BAT is > V_UVP and a charger is connected.

The device detects that the charger is attached if (V_PACK – V_BAT) > 700-mV typical. To detect for load removal, the device checks if (V_BAT – V_PACK) < 400-mV typical.

If the UV_SHUT option is disabled, during a UV fault DSG is turned off and the device does not go into SHUTDOWN. The power consumption is reduced to I_FETOFF. The PACK pin is still internally pulled to VSS through R_PACK-VSS. To recover UV with this option, one of the following conditions must occur:

• When V_BAT is > (V_UVP + V_{UVP_HYS}) or
• When V_BAT is > V_UVP and a charger is connected.