BQ27505 Datasheet, PDF (23/42 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge

Not Recommended for New Designs
bq27505
www.ti.com
Class
Gas Gauging
Gas Gauging
Gas Gauging
Gas Gauging
Subclass
ID
81
81
81
81
Table 4-7. Data Flash Summary (continued)
Subclass
Current
Thresholds
Current
Thresholds
Current
Thresholds
Current
Thresholds
Offset
Name
4
Quit Current
6
Dsg Relax Time
8
Chg Relax Time
9
Quit Relax Time
Data
Type
I2
U2
U1
U1
Min
Value
0
0
0
0
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
Gas Gauging
82
State
State
State
State
State
State
State
State
State
State
State
State
0
IT Enable
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
14 Cell1 Chg dod at EoC
16 Avg I Last Run
18 Avg P Last Run
H1
0x00
H1
0x00
I2
0
U2
0
H1
0x00
I2
0
U2
0
H1
0x00
I2
0
I2
0
I2
–32,768
I2
–32,768
Calibration
104
Calibration
104
Calibration
104
Calibration
104
Calibration
104
Calibration
104
Calibration
104
Calibration
104
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
Security
112
Codes
Security
112
Codes
Security
112
Codes
0
Unseal Key 0
2
Unseal Key 1
4
Full-Access Key 0
6
Full-Access Key 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
5 FUNCTIONAL DESCRIPTION
SLUS884 – FEBRUARY 2009
Max
Value
1000
8191
255
63
0x03
0xff
32,767
65,535
0x03
32767
65,535
0x03
16384
16384
32,767
32,767
47
188
2.4
500
127
127
127
127
255
0xffff
0xffff
0xffff
0xffff
Default
Value
40
60
60
1
0x00
0x00
1000
0
0x00
1000
0
0x00
0
0
–299
–1131
10 ⁽³⁾
10 ⁽³⁾
–0.088 ⁽³⁾
0
0
0
0
0
5
0x3672
0x0414
0xffff
0xffff
Units
mA
s
s
s
–
–
mAh
–
–
mAh
Count
–
–
–
mA
mAh
mohm
mohm
mV
mV
mV
0.1°C
0.1°C
mV
mA
–
–
–
–
5.1 FUEL GAUGING
The bq27505 measures the cell voltage, temperature, and current to determine battery SOC. The
bq27505 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 bq27505
acquires and updates the battery-impedance profile during normal battery usage. It uses this profile, along
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FUNCTIONAL DESCRIPTION
23