Single-cell Li-ion fuel gauge with I²C
The BQ27505YZGT-J4 is a battery monitor IC from Texas Instruments' Impedance Track™ series, designed for single-cell Lithium Ion packs. It communicates over an I²C bus, making it straightforward to integrate with most microcontrollers without dedicated ADC pins. The Impedance Track™ algorithm continuously learns battery impedance and state-of-charge, giving a more accurate fuel gauge than simple voltage-based methods — especially under varying load and temperature.
Industrial temperature range and compact package
Housed in a 12-DSBGA (0.5 mm pitch, 0.4 mm ball diameter), the package footprint is roughly 2.5 mm × 2.5 mm. The small size saves board space but demands a controlled solder-paste stencil and reflow profile — a standard lab rework station can handle it with practice.