bq27421-G1 System-Side Impedance Track Fuel Gauges Texas Instruments bq27421-G1 System-Side Impedance Track™ Fuel Gauges are an easy-to-configure microcontroller peripheral that provides system-side fuel gauging for single-cell Li-Ion batteries. These devices require minimal user configuration and system microcontroller firmware development. The bq27421-G1 uses the patented Impedance Track algorithm for fuel gauging and provides information such as remaining battery capacity (mAh), state-of-charge (%), and battery voltage (mV). Battery fuel gauging with the TI bq27421-G1 requires connections only to PACK+ (P+) and PACK- (P-) for a removable battery pack or embedded battery circuit. The tiny 9-pin 1.62mm x 1.58mm x 0.5mm pitch CSP package is ideal for space-constrained applications.