BQ27621-G1_16 Datasheet, PDF (9/26 Pages) Texas Instruments – System-Side Fuel Gauge With Dynamic Voltage Correlation

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bq27621-G1
SLUSBB3E – DECEMBER 2013 – REVISED JANUARY 2016
8.3 Feature Description
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 system to gauge using the I²C serial communications engine, and
can be executed during application development, system manufacture, or end-equipment operation.
The key to the fuel gauging prediction of the bq27621-G1 fuel gauge is Texas Instruments proprietary Dynamic
Voltage Correlation algorithm. This algorithm eliminates the need for a sense resistor when calculating remaining
battery capacity (mAh) and state-of-charge (%). This algorithm uses cell voltage measurements and cell
characteristics to create state-of-charge predictions that can achieve high accuracy across a wide variety of
operating conditions.
The fuel gauge estimates charge and discharge activity by monitoring the cell voltage. Cell impedance is
computed based on estimated current, open-circuit voltage (OCV), and cell voltage under loaded 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.
8.4 Device Functional Modes
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.
The gauge can be configured and used in a matter of minutes by following the Quickstart Guide for bq27621-G1
(SLUUAP5). The information in that document is sufficient for most applications. For further customization and
options, more exhaustive details can be found in the bq27621-G1 Technical Reference Manual (SLUUAD4).
8.5 Programming
8.5.1 Data Commands
8.5.1.1 Standard Data Commands
The bq27621-G1 uses a series of 2-byte standard commands to enable system reading and writing of battery
information. Each standard command has an associated command-code pair, as indicated in Table 1. Because
each command consists of two bytes of data, two consecutive I²C transmissions must be executed both to
initiate the command function, and to read or write the corresponding two bytes of data. Additional details are
found in the bq27621-G1 Technical Reference Manual (SLUUAD4).
NOTE
Data values read by the host may be invalid during initialization for a period of up to 3
seconds.
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