The bq21040 device is a highly integrated Li-Ion and Li-Pol linear battery charger device
targeted at space-limited portable applications. The device operates from either a USB port or AC
adapter. The high input voltage range with input overvoltage protection supports low-cost
The bq21040 has a single power output that charges the battery. A system load can be
placed in parallel with the battery as long as the average system load does not keep the battery
from charging fully during the 10 hour safety timer.
The battery is charged in three phases: conditioning, constant current and constant
voltage. In all charge phases, an internal control loop monitors the IC junction temperature and
reduces the charge current if an internal temperature threshold is exceeded.
The charger power stage and charge current sense functions are fully integrated. The
charger function has high accuracy current and voltage regulation loops, charge status display, and
charge termination. The pre-charge current and termination current threshold are fixed to 20% and
10%, respectively. The fast charge current value is programmable through an external
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