The BQ25611DRTWR is a single-cell Li-Ion or Li-Polymer battery charger from Texas Instruments, rated for a max charge current of 3.2 A. The I²C interface lets a host controller set the charge current and timer limits. It lives in a 24-WFQFN exposed-pad package (4x4 mm body), which means the thermal pad under the IC is the primary heat path. On a 2-layer board the pad needs a via array to the ground plane; on a 4-layer board the inner planes pull heat away fast enough to sustain the 3.2 A charge rate at 85°C ambient.
Key ratings that drive the BOM decision
The battery pack voltage range is 4.6 V to 5.15 V. The regulation loop clamps at the programmed target. Supply voltage max is 13.5 V, so a 5 V USB input or a 9 V wall wart is fine; a 12 V rail is within spec but leaves only 1.5 V headroom above the 5.15 V pack ceiling — the linear regulator stage will dissipate the difference as heat, so the thermal budget needs checking at high charge current. Fault protection covers over-current, over-temperature, and over-voltage — the chip shuts itself down before the cell sees a runaway charge. The timer is programmable via I²C.
The base product number BQ25611 covers the family; the DRTWR suffix identifies the 24-WQFN package and reel orientation. Sourced per RFQ — no stock-holding claim, but the active status means lead times are typically short through distribution.