Single-cell Li-ion fuel gauge with Impedance Track™
The BQ27421YZFT-G1B is a single-cell Lithium Ion battery monitor from Texas Instruments' Impedance Track™ series. It reports remaining capacity, state-of-charge, and voltage over an I²C interface, with the Impedance Track™ algorithm learning the battery's impedance in real time for improved accuracy over simple voltage-based gauges.
I²C host interface and single-cell constraint
The I²C bus is the only communication channel — the host reads gauge data on demand, no interrupt pin. The single-cell requirement is non-negotiable: this part monitors exactly one series cell. For 2-to-4-cell packs, the BQ2084DBT-V143 uses an SMBus interface and supports multiple cells, but its temperature range stops at 85°C.
Active production, 9-DSBGA package
The 9-UFBGA, DSBGA package with 0.50 mm pitch demands careful PCB layout — the 9-DSBGA footprint is small, so ensure the solder mask and stencil aperture match the TI recommended land pattern.