The bq2423x series of devices are highly integrated Li-ion linear chargers and system
power-path management devices targeted at space-limited portable applications. The devices operate
from either a USB port or ac adapter and support charge currents between 25 mA and 500 mA. The
high-input-voltage range with input overvoltage protection supports low-cost, unregulated adapters.
The USB input current limit accuracy and start-up sequence allow the bq2423x to meet USB-IF inrush
current specification. Additionally, the input dynamic power management
(VIN-DPM) prevents the charger from crashing poorly designed or incorrectly
configured USB sources.
The bq2423x features dynamic power-path management (DPPM) that powers the system while
simultaneously and independently charging the battery. The DPPM circuit reduces the charge current
when the input current limit causes the system output to fall to the DPPM threshold, thus supplying
the system load at all times while monitoring the charge current separately. This feature reduces
the number of charge and discharge cycles on the battery, allows for proper charge termination, and
enables the system to run with a defective or absent battery pack. Additionally, this enables
instant system turn-on even with a totally discharged battery. The power-path management
architecture also permits the battery to supplement the system current requirements when the
adapter cannot deliver the peak system currents, enabling the use of a smaller adapter.
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 the 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 input current limit and charge current are programmable using external