BQ27621-G1_16 Datasheet, PDF (14/26 Pages) Texas Instruments – System-Side Fuel Gauge With Dynamic Voltage Correlation

bq27621-G1
SLUSBB3E – DECEMBER 2013 – REVISED JANUARY 2016
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The Texas Instruments bq27621-G1 fuel gauge accurately predicts the battery capacity and other operational
characteristics of a single Li-base rechargeable cell.
9.2 Typical Application
Figure 9. Reference (EVM) Schematic
9.2.1 Design Requirements
The bq27621-G1 fuel gauge is predefined for LiCoO2-based batteries, which have 4.2-V, 4.3-V, and 4.35-V
maximum charging voltages. One orderable part number contains three different battery profiles, which can be
selected using I²C commands. Please refer to the bq27621-G1 Technical Reference Manual (SLUUAD4) for the
procedure to select alternate chemistry profiles.
9.2.2 Detailed Design Procedure
9.2.2.1 BAT Voltage Sense Input
A ceramic capacitor at the input to the BAT pin is used to bypass AC voltage ripple to ground, greatly reducing
its influence on battery voltage measurements. It proves most effective in applications with load profiles that
exhibit high-frequency current pulses (that is, cell phones) but is recommended for use in all applications to
reduce noise on this sensitive high-impedance measurement node.
9.2.2.2 Integrated LDO Capacitor
The fuel gauge has an integrated LDO with an output on the VDD pin of approximately 1.8 V. A capacitor of
value at least 0.47 μF should be connected between the VDD pin and VSS. The capacitor should be placed
close to the gauge IC and have short traces to both the VDD pin and VSS.
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