SLUSCU0I March 2018 – September 2020 BQ77915
An OW fault detection is when at least one of the cell voltages is measured below the OW threshold, VOW, for a duration of OW delay, tOWn_DELAY. CHG and DSG are turned off. The OW fault recovers when the cell voltage in fault is above the OW threshold + OW hysteresis, VOW_HYS, for a time of OW delay.
The tOWn_DELAY time starts when the voltage at a given cell is detected below the VOW threshold and is not from the time that the actual event of an open wire occurs. During an open-wire event, it is common that the device detects an undervoltage and/or overvoltage fault before detecting an open-wire fault. This may occur due to the differences in fault thresholds, fault delays, and the VCx pin filter capacitor values. To ensure that CHG and DSG return to normal operation mode, the OW, OV, and UV faults' recovery conditions must be met.