ST unveils "Fuel Gauge" battery IC for mobile devices
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 ageing, 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.
ST says 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 percent.
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.
The STC3115 is in full production in a 1.4 x 2.0mm chip-scale package, priced from $.95 in quantities of 1,000 pieces. LArger volumes may be available.
