Standalone 1-cell 1.5-A linear battery charger, Power Path, 4.2-V VBAT and 5.5-V VOUT

The BQ2407x series of devices are 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 an AC adapter and support charge currents up to 1.5 A. The input voltage range with input overvoltage protection supports unregulated adapters. The USB input current limit accuracy and start up sequence allow the BQ2407x to meet USB-IF inrush current specifications. Additionally, the input dynamic power management (VIN-DPM) prevents the charger from crashing incorrectly configured USB sources.

The BQ2407x 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, the regulated system

input enables instant system turn-on when plugged in even with a totally discharged

battery. The power path management architecture also lets the battery supplement the

system current requirements when the adapter cannot deliver the peak system

currents, thus 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 resistors.