BQ27546-G1 Datasheet, PDF (10/38 Pages) Texas Instruments – nullSingle-Cell Li-Ion Battery Fuel Gauge

bq27546-G1
SLUSC53A – MAY 2015 – REVISED DECEMBER 2015
9.2 Functional Block Diagram
REGIN
CE
REG25
VCC
HDQ
SCL
SDA
2.5-V LDO
+
Power Mgt
Communications
HDQ/I²C
Oscillator
System Clock
Impedance
Track
Engine
www.ti.com
ADC
Divider
Temp
Sensor
Co_- ulomb
Counter
BAT
TS
SRP
SRN
Peripherals
SE
Program Memory
Data Memory
VSS
9.3 Feature Description
9.3.1 Fuel Gauging
The bq27546-G1 fuel gauge measures the cell voltage, temperature, and current to determine battery SOC
based on the Impedance Track algorithm. (For more information, refer to the Theory and Implementation of
Impedance Track Battery Fuel-Gauging Algorithm Application Report [SLUA450].) The device monitors charge
and discharge activity by sensing the voltage across a small-value resistor (5-mΩ to 20-mΩ typical) between the
SRP and SRN pins and in series with the cell. By integrating the charge passing through the battery, the battery
SOC is adjusted during battery charge or discharge.
The total battery capacity is found by comparing states of charge before and after applying the load with the
amount of charge passed. When an application load is applied, the impedance of the cell is measured by
comparing the OCV obtained from a predefined function for present SOC with the measured voltage under load.
Measurements of OCV and charge integration determine chemical state of charge and chemical capacity
(Qmax). The initial Qmax values are taken from a cell manufacturer's data sheet multiplied by the number of
parallel cells. It is also used for the value in Design Capacity. The fuel gauge acquires and updates the battery-
impedance profile during normal battery usage. It uses this profile, along with SOC and the Qmax value, to
determine FullChargeCapacity() and StateOfCharge(), specifically for the present load and temperature.
FullChargeCapacity() is reported as capacity available from a fully charged battery under the present load and
temperature until Voltage() reaches the Terminate Voltage. NominalAvailableCapacity() and
FullAvailableCapacity() are the uncompensated (no or light load) versions of RemainingCapacity() and
FullChargeCapacity(), respectively.
9.3.2 Impedance Track Variables
The bq27546-G1 fuel gauge has several data flash variables that permit the user to customize the Impedance
Track algorithm for optimized performance. These variables depend on the power characteristics of the
application, as well as the cell itself.
10
Submit Documentation Feedback
Product Folder Links: bq27546-G1
Copyright © 2015, Texas Instruments Incorporated