Single-cell Li-Ion fuel gauge with Impedance Track™
The Texas Instruments BQ27425YZFT-G2B is a single-cell battery monitor that uses the Impedance Track™ algorithm to report state-of-charge, voltage, current, and temperature over an I²C interface. It is designed for portable devices running on one Lithium Ion cell, where accurate remaining-capacity prediction is needed across the full discharge curve.
What the I²C interface and single-cell limit mean for the BOM
The I²C bus is the only host interface — the gauge is a slave device, so the host MCU must have an I²C port or bit-bang the protocol. No SMBus or HDQ option here; if your existing firmware stack uses one of those, budget a porting effort. Because the BQ27425YZFT-G2B supports exactly one cell, a 2-series pack requires a different gauge (e.g. the BQ27426 or a multi-cell device). The single-cell limit is hard — the internal voltage divider and coulomb counter are scaled for a 1S configuration.
Package and assembly note: 15-DSBGA
The 15-bump DSBGA (0.5 mm pitch, 0.3 mm ball diameter) requires a solder-mask-defined pad and a stencil aperture matched to the ball size. The small package means the PCB fan-out is tight — a 4-layer board with microvias is typical for production, though a 2-layer board with dog-bone fan-out works for prototyping if the trace width and spacing are within the fabricator's capability.