800 mA charge current, 4.2 V termination — single-cell Li-ion charger in a 2x2 mm WSON
The Texas Instruments BQ24050DSQT is a linear charger IC for single-cell Lithium Ion or Polymer batteries. It delivers a programmable constant charge current up to 800 mA and terminates at 4.2 V — the standard full-charge voltage for most single-cell Li-ion packs. The wide input range, accepting up to 28 V, lets it connect directly to a USB port or an unregulated wall adapter without a front-end regulator.
Thermal and protection features for a small-footprint charger
Packaged in a 10-WFDFN exposed pad (2x2 mm), the BQ24050DSQT relies on the PCB copper area under the pad to sink heat during constant-current charging. At 800 mA the power dissipation in a linear regulator is significant — the thermal pad layout directly sets the practical charge current limit without triggering the over-temperature protection. Built-in fault protection covers over-temperature, over-voltage, and short-circuit conditions. The programmable current feature lets the designer set the charge rate to match the battery capacity.