Linear battery chargers from TI maximize AC adapter and USB input power

TI’s new bq24072, bq24073, bq24074 and bq24075 chargers integrate a high number of features in a 3 mm x 3 mm QFN. The chargers incorporate a 28-V, 1.5-A input FET, a 5-A battery FET, current sensor, reverse blocking protection, thermal regulation and other battery management features. The devices support up to 1.5 A in charging mode and up to 5 A in discharge mode, which allows them to support higher currents from RF power amplifiers, such as those found in a GSM application.

The four bq2407x chargers also provide a unique power path management feature to simultaneously charge the battery and power the system. This reduces the number of charge and discharge cycles on the battery, enables proper charge termination and allows the system to turn on instantly, even if a battery is depleted. The battery charging rate is dynamically adjusted based on system voltage to ensure proper operation. Additionally, the battery can supplement the system’s current requirements when an adapter cannot deliver the peak system currents, giving a designer the option of using a smaller adapter.

The bq2407x family offers an input voltage-based dynamic power management function in USB mode that monitors the input voltage and limits the input current if the input voltage drops below a preset value. This prevents the system from crashing USB sources that are incorrectly configured or poorly designed.

The bq2407x chargers support a high-input voltage rating of 28 V with a 6.6-V or 10.5-V over-voltage protection threshold, which allows a designer to select an inexpensive adapter to help lower system cost. The adapter input current limit is programmable with a resistor up to 1.5 A. In addition, the devices also comply with USB charging standards, such as USB-IF, by limiting the USB input current to 100 mA or 500 mA.

The devices charge the battery in three phases, including conditioning, constant current and constant voltage. System output voltage of the bq24072 automatically matches the battery’s voltage. The bq24073 and bq24074 have a fixed output voltage of 4.4 V, while the bq24075 is set at 5.5 V. The bq24075 incorporates a battery SYSOFF function that disconnects the battery from the system, enabling a system with TI’s bq27510 Impedance Track™ battery fuel gauge (www.ti.com/bq27510) to measure open circuit voltage and predict remaining battery capacity.