The Texas Instruments BQ25125 is a highly integrated battery charge management IC that combines the most common functions for wearable devices: Linear charger, load switch, manual reset with timer, regulated output, and battery voltage monitor. The integrated buck converter is a high efficiency, low IQ switcher employing DCS-Control that increases light load efficiency down to 10µA load currents.
The low quiescent current through operation and shutdown allows maximum battery life. The device maintains charge currents from 5mA to 300mA. The input current limit, buck converter output voltage, charge current, LDO output voltage, and other parameters are programmable through the I2C interface.
The battery is charged utilising a standard Li-Ion charge profile with three phases: constant current, constant voltage, and precharge. A voltage-based JEITA compatible battery pack thermistor monitoring input (TS) is incorporated monitoring battery temperature and automatically changing charge parameters to stop the battery from charging outside of its safe temperature range. The charger is optimised for 5V USB input, with 20V tolerance to withstand line transients. The buck converter is operated from the input or battery. When in battery-only mode, the device can run from a battery up to 4.65V.
A configurable load switch enables system optimisation by disconnecting rarely used devices. The manual reset with timer enables multiple different configuration options for wake are reset optimisation. A simple voltage based monitor gives battery level information to the host in 2% increments from 60% to 100% of the programmed V(BATREG).