High Accuracy Battery Fuel Gauge IC
STMicroelectronics has unveiled its latest battery fuel-gauging device featuring patented innovations that improve long-term accuracy. This tiny chip, the STC3115, can be used in high-volume handheld electronics, and has already been selected by Samsung for some of its recent smartphones. Battery charge indicators – or fuel gauges – have become essential for managing devices such as smartphones, laptops or digital cameras. Accurate “time-remaining” predictions enhance the user’s experience, and can be critical in certain types of portable electronics such as medical devices. Even so, many of today’s fuel-gauging electronics are susceptible to errors caused by battery aging, reduced charging efficiency, leakage, variations in system power demand, and temperature effects.
To enhance fuel-gauging accuracy, ST has combined several important advances in its latest adaptive fuel-gauge IC, the STC3115. Until now, leading devices have used Coulomb counting to monitor energy entering and leaving the battery, and periodic voltage-mode state-of-charge measurements to adjust the Coulomb counter for accuracy. The STC3115 uses both sets of measurements continuously, with OptimGauge™, an adaptive algorithm that tracks the state of charge and corrects the battery model.
The STC3115 further enhances accuracy by measuring true initial battery open-circuit voltage and preventing measurement disruptions when connecting the charger or launching an app. The charging inhibitor is a patented feature that significantly improves accuracy. Aging and temperature compensation are built in, and the voltage measurement accuracy is 0.25%.
Additional value-added features of the new IC include a low-power mode that reduces operating current to only 0.45µA while continuing to monitor the battery, and a 2µA standby mode. An Under-Voltage Lockout (UVLO) filter prevents short-term fluctuations in battery voltage from causing unwanted system resets. In addition, the STC3115 saves bill-of-materials costs by operating directly from the battery voltage without requiring its own voltage regulator.
Key features of STC3115:
- The OptimGauge algorithm, which adjusts the battery charge/discharge model over the battery’s life
- Industry-standard I2C connection to application processor
- Programmable with different battery profiles at manufacture, for flexibility
- Monitors batteries up to 4.5V
- Monitors multi-cell packs when used with TS941ILT low-power buffer
- Dedicated “battery-present” input simplifies battery replacement
- Dedicated alarm output, activated if battery voltage falls below threshold level
- The STC3115 is in full production in a 1.4 × 2.0mm chip-scale package, priced from $.95 in quantities of 1,000 pieces. If your company has high-volume requirements please contact your local ST sales office.