ZHCSKH8C December 2009 – December 2019 BQ24072T , BQ24075T , BQ24079T
PRODUCTION DATA.
Some adapters implement a half rectifier topology, which causes the adapter output voltage to fall below the battery voltage during part of the cycle. To enable operation with adapters under those conditions, the BQ2407xT family keeps the charger on for at least 20 msec (typical) after the input power puts the part in sleep mode. This feature enables use of external adapters using 50 Hz networks. The input must not drop below the UVLO voltage for the charger to work properly. Thus, the battery voltage should be above the UVLO to help prevent the input from dropping out. Additional input capacitance may be needed.
When the input is between VUVLO and VIN(DT), the device enters sleep mode. After entering sleep mode for 20 ms the internal FET connection between the IN and OUT pin is disabled and pulling the input to ground will not discharge the battery, other than the leakage on the BAT pin. If one has a full 1000mAHr battery and the leakage is 10 μA, then it would take 1000 mAHr/10μA = 100000 hours (11.4 years) to discharge the battery. The battery ‘s self discharge is typically 5 times higher than this.