The BQ76922 device integrates cell undervoltage protection (CUV), monitoring the voltage of every cell using a comparator-based circuit, and triggering a CUV alert or fault when a cell voltage falls below the CUV threshold. The CUV threshold is programmable from 1.012V to 4.048V in 50.6mV steps and is set by the Protections:CUV:Threshold configuration register. The CUV protection is enabled using the Settings:Protection:Enabled Protections A:[CUV] configuration bit.

The CUV circuitry triggers an alert signal when an undervoltage event is first detected, then will trigger a fault after a programmable detection delay, CUV_DLY, which can be set from 10ms to 6765ms in units of 3.3ms, with the actual delay being 3.3ms × (2 + setting). The setting 0x0 disables the protection. The delay is set by the Protections:CUV:Delay configuration register.

When a CUV fault is triggered, the fault will recover if the voltage rises above the CUV threshold by a value of CUV_HYS, which is programmable from 100mV to 1V in steps of 50mV, for Protections:Recovery:Time. This hysteresis level is set by the Protections:CUV:Recovery Hysteresis configuration register.

When CUV is triggered, the device will turn off the DSG FET if configured for autonomous FET control based on setting in Settings:Protection:DSG FET Protections A[CUV] (the CHG FET remains enabled if already enabled). The device will recover (if configured for autonomous recovery) based on all cell voltages being above CUV threshold + CUV_HYS. Further detail is described in the table below. Note: timing on CUV changes while cell balancing is active, as described in Table 10-4.

When a CUV fault is triggered, a snapshot of all cell voltages is captured and can be accessed through the 0x0080 CUV_SNAPSHOT() subcommand, which has format as shown below.