Single-cell Li-Ion linear charger in a 3x2 WSON
The BQ25040DQCR is a single-cell lithium-ion linear charger IC from Texas Instruments, designed for space-constrained portable equipment where a small footprint and low BOM count matter more than fast charge times. It delivers a programmable constant charge current up to 1.1 A, regulating the battery voltage to 4.2 V from a supply rail as high as 6.7 V. The 10-WFDFN exposed-pad package (3x2 mm body, 10-WSON supplier device package) keeps the thermal path short — the pad under the IC carries the heat from the pass transistor into the PCB copper, so the layout engineer should stitch vias under the pad to a ground plane for the full 1.1 A output without hitting the thermal shutdown threshold.
Charge current and protection thresholds
Charging current is constant and programmable via an external resistor — the 1.1 A max figure is the ceiling, but the actual set-point is chosen by the resistor value, so the BOM cost engineer can dial in a lower current (e.g. 500 mA) to use a smaller inductor-free path and reduce the thermal budget. On-chip fault protection covers over-temperature (with a junction-temperature monitor that throttles or shuts down the charger) and over-voltage on the input supply — no external supervisor needed for these two failure modes.