ZHCSI54A September 2016 – May 2018 BQ25890H
PRODUCTION DATA.
The device has built-in safety timer to prevent extended charging cycle due to abnormal battery conditions. The safety timer is 4 hours when the battery is below VBATLOWV threshold. The user can program fast charge safety timer through I2C (CHG_TIMER bits). When safety timer expires, the fault register CHRG_FAULT bits are set to 11 and an INT is asserted to the host. The safety timer feature can be disabled via I2C by setting EN_TIMER bit.
During input voltage, current or thermal regulation, the safety timer counts at half clock rate as the actual charge current is likely to be below the register setting. For example, if the charger is in input current regulation (IDPM_STAT = 1) throughout the whole charging cycle, and the safety time is set to 5 hours, the safety timer will expire in 10 hours. This half clock rate feature can be disabled by writing 0 to TMR2X_EN bit.