BQ27520-G2 Datasheet, PDF (24/47 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated LDO

bq27520-G2
SLUSAB7A – MARCH 2011 – REVISED AUGUST 2011
Class
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Calibration
Calibration
Calibration
Calibration
Calibration
Calibration
Calibration
Calibration
Subclass
ID
82
82
82
82
82
82
82
82
82
82
82
82
82
82
104
104
104
104
104
104
104
104
Table 4-7. Data Flash Summary (continued)
Subclass
State
State
State
State
State
State
State
State
State
State
State
State
State
State
Offset
Name
1
Application Status
2
Qmax 0
4
Cycle Count 0
6
Update Status 0
7
Qmax 1
9
Cycle Count 1
11 Update Status 1
12 Cell0 Chg DOD at EoC
14 Cell1 Chg DOD at EoC
16 Avg I Last Run
18 Avg P Last Run
20 Delta Voltage
24 T Rise
26 T Time Constant
Data
Type
H1
I2
U2
H1
I2
U2
H1
I2
I2
I2
I2
I2
U2
U2
Min
Value
0x00
0
0
0x00
0
0
0x00
0
0
–32,768
–32,768
–32,768
0
0
Data
Data
Data
Data
Data
Data
Data
Data
0
CC Gain
4
CC Delta
8
CC Offset
10 ADC Offset
12 Board Offset
13 Int Temp Offset
14 Ext Temp Offset
15 Pack V Offset
F4 ⁽²⁾
F4 ⁽²⁾
I2
I2
I1
I1
I1
I1
0.1
4.7
–2.4
–500
–128
–128
–128
–128
Calibration
107
Current
1
Deadband
U1
0
Security
112
Codes
0
Unseal Key 0
Security
112
Codes
2
Unseal Key 1
Security
112
Codes
4
Unsealed to Full 0
Security
112
Codes
6
Unsealed to Full 1
Security
112
Codes
24 FactRestorkey 0
Security
112
Codes
26 FactRestorkey 1
(2) Not IEEE floating point.
(3) Display as the value EVSW displayed. Data Flash value is different.
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
H2
0x0000
5 FUNCTIONAL DESCRIPTION
Max
Value
0xff
32,767
65,535
0x03
32767
65,535
0x03
16384
16384
32,767
32,767
32,768
65535
65535
47
188
2.4
500
127
127
127
127
255
0xffff
0xffff
0xffff
0xffff
0xffff
0xffff
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Default
Value
0x00
1000
0
0x00
1000
0
0x00
0
0
–299
–1131
2
2
1000
10 ⁽³⁾
10 ⁽³⁾
–0.58 ⁽³⁾
0
0
0
0
0
5
0x3672
0x0414
0xffff
0xffff
0x0DEF
0x0FAC
Units
–
mAh
–
–
mAh
Count
–
–
–
mA
mAh
mV
num
num
mohm
mohm
mV
mV
mV
0.1°C
0.1°C
mV
mA
–
–
–
–
–
–
5.1 FUEL GAUGING
The bq27520-G2 measures the cell voltage, temperature, and current to determine battery SOC. The
bq27520-G2 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-G2 acquires and updates the battery-impedance profile during normal battery usage. It uses this
24
FUNCTIONAL DESCRIPTION
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