much battery life do I really have left? Texas Instruments Incorporated wants to
answer 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 predicts battery life with 99-percent accuracy to extend
run-time, protect data and provide a better user experience for mobile handheld
The bq27500 system-side battery fuel gauge with TI's patented Impedance Track
technology accurately measures data from a device's single-cell Li-Ion battery
to predict remaining battery capacity under all conditions, even as a battery
The tiny IC analyzes 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.
"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
As handheld systems provide more functions, the need has grown for accurate
fuel gauging to intelligently manage available power, alert the user of system
operating-time, and extend the run-time of the system as far as possible.
Accurate battery data is used by applications processors, such as TI's OMAP3410
processor with SmartReflex power and performance technologies, to optimize the
system's complete mobile power operating system. For instance, the system can
leverage low-power modes, clock gating, clock throttling and dynamic voltage and
frequency scaling capabilities based on battery capacity. The bq27500 provides
an accurate reserve energy warning, which allows a system to save data to
non-volatile memory at the end of a battery's discharge, so work is not lost
when battery life runs out.
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.
Let's see which Windows Mobile ODM might be the first to introduce TI's new
technology. At least there are good chances that devices running the TI OMAP CPU
gets this improvement, sooner or later.
Cheers ~ Arne