BQ27520-G3 Datasheet, PDF (25/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

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Class
Calibration
Calibration
Calibration
Calibration
Calibration
Temp Model
Temp Model
Temp Model
Temp Model
Temp Model
Temp Model
Temp Model
Temp Model
Temp Model
Calibration
Security
Security
Security
Security
Security
Security
Subclass
ID
104
104
104
104
104
106
106
106
106
106
106
106
106
106
107
112
112
112
112
112
112
Table 4-7. Data Flash Summary (continued)
Subclass
Data
Data
Data
Data
Data
Offset
Name
10 ADC Offset
12 Board Offset
13 Int Temp Offset
14 Ext Temp Offset
15 Pack V Offset
Data
Type
I2
I1
I1
I1
I1
Min
Value
–500
–128
–128
–128
–128
Data
Data
Data
Data
Data
Data
Data
Data
Data
0
Ext a Coef 1
2
Ext a Coef 2
4
Ext a Coef 3
6
Ext a Coef 4
8
Ext a Coef 5
10 Ext b Coef 1
12 Ext b Coef 2
14 Ext b Coef 3
16 Ext b Coef 4
I2
-32768
I2
-32768
I2
-32768
I2
-32768
I2
-32768
I2
-32768
I2
-32768
I2
-32768
I2
-32768
Current
1
Deadband
U1
0
Codes
Codes
Codes
Codes
Codes
Codes
0
Unseal Key 0
2
Unseal Key 1
4
Unsealed to Full 0
6
Unsealed to Full 1
8
FactRestorkey 0
FactRestorkey 1
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
bq27520-G3
SLUSAP0 – DECEMBER 2011
Max
Value
500
127
127
127
127
32767
32767
32767
32767
32767
32767
32767
32767
32767
255
0xffff
0xffff
0xffff
0xffff
0xffff
0xffff
Default
Value
0
0
0
0
0
-11130
19142
-19262
28203
892
328
-605
-2443
4696
5
0x3672
0x0414
0xffff
0xffff
0x0DEF
0x0FAC
Units
mV
mV
0.1°C
0.1°C
mV
num
num
num
num
num
num
num
num
num
mA
–
–
–
–
–
–
5 FUNCTIONAL DESCRIPTION
5.1 FUEL GAUGING
The bq27520-G3 measures the cell voltage, temperature, and current to determine battery SOC. The
bq27520-G3 monitors charge and discharge activity by sensing the voltage across a small-value resistor
(5 mΩ to 20 mΩ typ.) between the SRP and SRN pins and in series with the cell. By integrating charge
passing through the battery, the battery’s 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 manufacturers' data sheet
multiplied by the number of parallel cells. It is also used for the value in Design Capacity. The
bq27520-G3 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.
The bq27520-G3 has two flags accessed by the Flags( ) function that warns when the battery’s SOC has
fallen to critical levels. When RemainingCapacity( ) falls below the first capacity threshold, specified in
SOC1 Set Threshold, the [SOC1] (State of Charge Initial) flag is set. The flag is cleared once
RemainingCapacity( ) rises above SOC1 Set Threshold. The bq27520-G3’s BAT_LOW pin automatically
reflects the status of the [SOC1] flag. This flag is enabled when BL_INT bit in Operation Configuration B
is set. All units are in mAh.
Copyright © 2011, Texas Instruments Incorporated
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FUNCTIONAL DESCRIPTION
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