Board-level fit for a single-cell Li-Ion pack gauge
The BQ27350PW is a single-cell Li-Ion/Polymer fuel gauge from Texas Instruments' Impedance Track™ series — the algorithm learns the battery's impedance profile over charge/discharge cycles, so reported state-of-charge accuracy improves with use rather than drifting. It communicates over an I²C bus, which means the host MCU reads remaining capacity, voltage, and current through a standard two-wire interface — no external ADC or coulomb-counter needed. The 20-TSSOP package (0.65 mm pitch, 4.40 mm body width) fits on a 2-layer board with careful fan-out, but the fine pitch makes hand-solder rework tricky — a stencil and reflow profile tuned for TSSOP are recommended for production.
NRND — what that means for your BOM
Texas Instruments lists the BQ27350PW as NRND (Not Recommended for New Designs) — the part is still orderable for existing production runs, but TI will not qualify it for new projects. If you are migrating a design, you will need to evaluate a different fuel-gauge family (e.g., BQ274xx series) with a board spin.
Battery Authentication stops counterfeit packs
The BQ27350PW includes a Battery Authentication function — the host can challenge the gauge to verify the pack is genuine, which blocks aftermarket or counterfeit battery swaps in field-deployed equipment. The I²C interface carries both the fuel-gauge data and the authentication handshake on the same bus — no extra pins needed. Pull-up resistors (typically 4.7 kΩ to 10 kΩ) must be on the board; the gauge does not include them internally.