Datasheet
Not Recommended for New Designs
bq27505
www.ti.com
SLUS884–FEBRUARY 2009
Table 4-7. Data Flash Summary (continued)
Subclass Data Min Max Default
Class Subclass Offset Name Units
ID Type Value Value Value
Current
Gas Gauging 81 4 Quit Current I2 0 1000 40 mA
Thresholds
Current
Gas Gauging 81 6 Dsg Relax Time U2 0 8191 60 s
Thresholds
Current
Gas Gauging 81 8 Chg Relax Time U1 0 255 60 s
Thresholds
Current
Gas Gauging 81 9 Quit Relax Time U1 0 63 1 s
Thresholds
Gas Gauging 82 State 0 IT Enable H1 0x00 0x03 0x00 –
Gas Gauging 82 State 1 Application Status H1 0x00 0xff 0x00 –
Gas Gauging 82 State 2 Qmax 0 I2 0 32,767 1000 mAh
Gas Gauging 82 State 4 Cycle Count 0 U2 0 65,535 0 –
Gas Gauging 82 State 6 Update Status 0 H1 0x00 0x03 0x00 –
Gas Gauging 82 State 7 Qmax 1 I2 0 32767 1000 mAh
Gas Gauging 82 State 9 Cycle Count 1 U2 0 65,535 0 Count
Gas Gauging 82 State 11 Update Status 1 H1 0x00 0x03 0x00 –
Gas Gauging 82 State 12 Cell0 Chg dod I2 0 16384 0 –
Gas Gauging 82 State 14 Cell1 Chg dod at EoC I2 0 16384 0 –
Gas Gauging 82 State 16 Avg I Last Run I2 –32,768 32,767 –299 mA
Gas Gauging 82 State 18 Avg P Last Run I2 –32,768 32,767 –1131 mAh
Calibration 104 Data 0 CC Gain F4
(2)
0.1 47 10
(3)
mohm
Calibration 104 Data 4 CC Delta F4
(2)
4.7 188 10
(3)
mohm
Calibration 104 Data 8 CC Offset I2 –2.4 2.4 –0.088
(3)
mV
Calibration 104 Data 10 ADC Offset I2 –500 500 0 mV
Calibration 104 Data 12 Board Offset I1 –128 127 0 mV
Calibration 104 Data 13 Int Temp Offset I1 –128 127 0 0.1°C
Calibration 104 Data 14 Ext Temp Offset I1 –128 127 0 0.1°C
Calibration 104 Data 15 Pack V Offset I1 –128 127 0 mV
Calibration 107 Current 1 Deadband U1 0 255 5 mA
Security 112 Codes 0 Unseal Key 0 H2 0x0000 0xffff 0x3672 –
Security 112 Codes 2 Unseal Key 1 H2 0x0000 0xffff 0x0414 –
Security 112 Codes 4 Full-Access Key 0 H2 0x0000 0xffff 0xffff –
Security 112 Codes 6 Full-Access Key 1 H2 0x0000 0xffff 0xffff –
(2) Not IEEE floating point.
(3) Display as the value EVSW displayed. Data Flash value is different.
5 FUNCTIONAL DESCRIPTION
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
Copyright © 2009, Texas Instruments Incorporated FUNCTIONAL DESCRIPTION 23
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