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Chapter 1
SLUUAC9A – December 2013 – Revised May 2015
General Description
The bq27441-G1 battery fuel gauge accurately predicts the battery capacity and other operational
characteristics of a single, Li-based, rechargeable cell. It can be interrogated by a system processor to
provide cell information, such as state-of-charge (SOC). The device is orderable in two predefined
standard configurations:
•
The bq27441-G1A fuel gauge is predefined for LiCoO
2
-based batteries for 4.2-V maximum charge
voltage.
•
The bq27441-G1B fuel gauge is predefined for LiCoO
2
-based batteries for 4.3-V or 4.35-V maximum
charge voltage.
Unlike some other Impedance Track™ fuel gauges, the bq27441-G1 cannot be programmed with specific
battery chemistry profiles. For many battery types and applications, the predefined standard chemistry
profiles available in the bq27441-G1A or bq27441-G1B fuel gauge are sufficient matches from a gauging
perspective.
Information is accessed through a series of commands, called
Standard Commands
. Further capabilities
are provided by the additional
Extended Commands
set. Both sets of commands, indicated by the general
format
Command()
, are used to read and write information contained within the control and status
registers, as well as its data locations. Commands are sent from the system to the gauge using the I
2
C
serial communications engine, and can be executed during application development, system manufacture,
or end-equipment operation.
The key to the high-accuracy, fuel gauging prediction is Texas Instruments proprietary Impedance Track™
algorithm. This algorithm uses cell measurements, characteristics, and properties to create SOC
predictions that can achieve high accuracy across a wide variety of operating conditions and over the
lifetime of the battery.
The fuel gauge measures the charging and discharging of the battery by monitoring the voltage across a
small-value, external sense resistor. Cell impedance is computed based on current, open-circuit voltage
(OCV), and cell voltage under loading conditions.
The fuel gauge uses an integrated temperature sensor for estimating cell temperature. Alternatively, the
system processor can provide temperature data for the fuel gauge.
To minimize power consumption, the fuel gauge has several power modes: INITIALIZATION, NORMAL,
SLEEP, HIBERNATE, and SHUTDOWN. The fuel gauge passes automatically between these modes,
depending upon the occurrence of specific events, though a system processor can initiate some of these
modes directly.
6
General Description
SLUUAC9A – December 2013 – Revised May 2015
Copyright © 2013–2015, Texas Instruments Incorporated