Single-cell Li-Ion fuel gauge with Impedance Track™
The Texas Instruments BQ27501DRZR is a battery monitor IC from the Impedance Track™ series, designed to report the state-of-charge of a single-cell Lithium Ion battery pack over an I²C interface. It integrates the fuel-gauging algorithm that learns the battery's impedance over time, so the reported capacity stays accurate as the cell ages.
What the single-cell limit means for your BOM
The BQ27501DRZR is specified for a single-cell Li-Ion pack only. If your design uses a 2-cell or higher series stack, this part will not work — the internal voltage divider and algorithm assume a single-cell voltage range. For multi-cell applications, look at the BQ40Zxx series or a stacked gauge with cell-balancing support. The I²C interface keeps the host-side wiring to two lines (SDA, SCL) plus an interrupt line for the alert output. Pull-up resistors should be sized for the bus capacitance and the target data rate; the datasheet recommends 1.8 kΩ to 10 kΩ for standard-mode operation.
Package and footprint for layout
The BQ27501DRZR comes in a 12-VFDFN Exposed Pad package, also referred to as 12-SON (2.5x4 mm). The 0.50 mm pitch requires a solder-mask-defined pad with a stencil aperture sized for the paste volume — a 0.25 mm aperture is a typical starting point.