New ST Battery Fuel Gauge IC Provides Reliable Mobile Runtime

18th February 2013

ES Admin

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Datasheet

STMicroelectronics announces 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.

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 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 x 2.0mm chip-scale package, priced from $.95 in quantities of 1,000 pieces.