USB linear charger for single-cell Li-Ion packs
The BQ24079RGTT from Texas Instruments is a linear battery charger IC designed for single-cell Lithium Ion packs, accepting power from a USB port or a regulated adapter. The charge current is constant and programmable up to 1.5 A, with a programmable timer to terminate the charge cycle. The IC integrates over-temperature, over-voltage, reverse-current, and short-circuit fault protection, reducing the external component count for a safe charging solution.
1.5 A charge current and thermal envelope
The 1.5 A maximum charge current is set by an external resistor; the charge current can be programmed lower to match the thermal budget of the 16-VFQFN exposed-pad package.
Fault protection and charge termination
Over-voltage protection clamps the input to safe levels for the battery; reverse-current blocking prevents the pack from discharging back into the input when the supply is removed. Short-circuit and over-temperature protection shut down the charger under fault conditions without latch-up. The programmable timer provides a backup termination method if the battery never reaches the 4.1 V full-charge threshold — useful for deeply depleted cells or high-impedance connections.