The bq2423x series of devices are highly integrated Li-ion linear chargers and systempower-path management devices targeted at space-limited portable applications. The devices operatefrom either a USB port or ac adapter and support charge currents between 25 mA and 500 mA. Thehigh-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 inrushcurrent specification. Additionally, the input dynamic power management(VIN-DPM) prevents the charger from crashing poorly designed or incorrectlyconfigured USB sources.
The bq2423x features dynamic power-path management (DPPM) that powers the system whilesimultaneously and independently charging the battery. The DPPM circuit reduces the charge currentwhen the input current limit causes the system output to fall to the DPPM threshold, thus supplyingthe system load at all times while monitoring the charge current separately. This feature reducesthe number of charge and discharge cycles on the battery, allows for proper charge termination, andenables the system to run with a defective or absent battery pack. Additionally, this enablesinstant system turn-on even with a totally discharged battery. The power-path managementarchitecture also permits the battery to supplement the system current requirements when theadapter cannot deliver the peak system currents, enabling the use of a smaller adapter.
The battery is charged in three phases: conditioning, constant current, and constantvoltage. In all charge phases, an internal control loop monitors the IC junction temperature andreduces the charge current if the internal temperature threshold is exceeded.
The charger power stage and charge current sense functions are fully integrated. Thecharger function has high-accuracy current and voltage regulation loops, charge status display, andcharge termination. The input current limit and charge current are programmable using externalresistors.