250 mA linear charger in a 0.9 mm² footprint
The Texas Instruments BQ25100BYFPR is a single-cell linear charger IC for Lithium Ion/Polymer battery packs, delivering a programmable charge current up to 250 mA. It integrates pass transistor, current sensing, and thermal regulation in a 6-bump DSBGA package that measures roughly 0.9 mm × 0.9 mm — small enough for a wearable earbud or a medical patch.
Charge termination and protection
The charger terminates at a battery pack voltage of 4.284 V, matching the standard Li-ion 4.2 V cell with a small overcharge margin. Fault protection covers over-temperature, over-voltage, and short-circuit conditions — the chip shuts down before the cell or the board trace sees damage. The USB interface simplifies connection to a standard 5 V USB port or a regulated wall adapter; the input supply maximum is 6.45 V, so a 5 V rail leaves enough headroom for the linear regulator dropout without risking overvoltage.
For a BOM that expects to run for another 18–24 months, this part does not force a respin.