Fuel Gauge Accurately Predicts Battery Life in Smartphones

How much battery life do I really have left? Texas Instruments answers the question by introducing its system-side fuel gauge integrated circuit (IC) with Impedance Track technology for smart phones and other handhelds. The 2.5 mm x 4 mm gauge is reported to predict battery life with 99-percent accuracy to extend run-time, protect data and provide a better user experience for mobile handheld users.

"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 analog and logic business. "Today's announcement builds on TI's innovative battery fuel gauge technology, which is used in millions of notebook computers. Our portable device customers asked to incorporate the technology into their mobile designs -- and now they can."

Most handhelds today do not accurately gauge remaining battery capacity, but simply measure the cell voltage to guess the capacity. Traditional gauging techniques used in some handhelds require static and unreliable modeling methods that attempt to compensate for discharge rate, temperature and age of the cell, and must also model self-discharge and other non-measurable currents. Since these models have an inherent error, which is difficult to minimize, an end-user will not accurately know how much run-time remains as the battery ages.

The bq27500 directly measures the effect of a battery's discharge rate, temperature, age and other factors to accurately 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 is implemented on the host system's board, and can support an embedded or removable battery. System-side implementation allows a handheld manufacturer to save cost by designing an end-equipment that does not need extra electronics added to the battery pack. As batteries continue to shrink in size, integration of electronics on the battery becomes more of a challenge. System-side implementation of the bq27500 can control and manage other main battery management functions, such as battery pack authentication.

Posted to the site on 24th September 2007