The BQ2407x series of devices are integrated Li-Ion linear chargers and system power pathmanagement devices targeted at space-limited portable applications. The devices operate from eithera USB port or an AC adapter and support charge currents up to 1.5 A. The input voltage range withinput overvoltage protection supports unregulated adapters. The USB input current limit accuracyand start up sequence allow the BQ2407x to meet USB-IF inrush current specifications. Additionally,the input dynamic power management (VIN-DPM) prevents the charger fromcrashing incorrectly configured USB sources.
The BQ2407x 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,supplying the system load at all times while monitoring the charge current separately. This featurereduces the number of charge and discharge cycles on the battery, allows for proper chargetermination and enables the system to run with a defective or absent battery pack.
Additionally, the regulated system input enables instant system turn-on when plugged ineven with a totally discharged battery. The power-path management architecture also lets thebattery supplement the system current requirements when the adapter cannot deliver the peak systemcurrents, thus 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 powerstage and charge current sense functions are fully integrated. The charger function has highaccuracy current and voltage regulation loops, charge status display, and charge termination. Theinput current limit and charge current are programmable using external resistors.