The bq2409x series of devices are highly integrated Li-ion and Li-Pol linear chargers
devices targeted at space-limited portable applications. The devices operate from either a USB port
or AC adapter. The high input voltage range with input overvoltage protection supports low-cost
The bq2409x 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 programmed via an
external resistor. The fast charge current value is also programmable via an external
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