Smartphones Get More Accurate Battery Gauge

Texas Instruments has adapted its fuel gauge laptop battery technology to work in smart phone or PDAs. The technology will allow users to accurately gauge how much runtime is left in their mobile devices.

TI says that its battery fuel gauge technology is currently used in millions of notebook computers, but had faced requests from its portable device customers to incorporate the technology into their mobile designs. So TI integrated its system-side fuel gauge integrated circuit (IC), with its impedance track technology, to extend this functionality into smart phones and other handhelds.

The result, TI claims, is that a single cell, Li-ion powered application can run longer on a smart phone or PDA, thanks to the battery fuel gauge.

"As mobile devices add more functionality, such as high-definition video and data transmission, consumers want to operate their devices just like notebook computers and expect to know remaining battery capacity," said Dave Heacock, senior vice president of TI's high-volume analogue and logic business.

TI says that bq27500 system-side battery fuel gauge with the impedance track technology measures (with 99 percent accuracy) data from a device's single-cell Li-Ion battery to predict remaining battery capacity under all conditions, even as a battery ages.

The IC analyses precise state-of-charge by correlating between a battery's voltage and cell impedance (or resistance), and its current integration to adjust remaining state-of-charge up or down the predicted discharge curve.

The bq27500 directly measures the effect of a battery's discharge rate, temperature, age and other factors to predict remaining life within one percent error. By measuring and storing real-time battery impedance values, the IC automatically adjusts to changes in full capacity as a battery ages. State-of-charge and full capacity are calculated from the voltage and impedance measurements, eliminating the need to re-learn from a charge and discharge cycle.

The bq27500 resides on the system's main board, and can support an embedded or removable battery. It is available today in a 12-pin, 2.5 mm x 4 mm SON package, and the device's suggested retail pricing is US$1.35 in 1,000-piece quantities.

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