Datasheet

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LI-ION PROTECTION
Protection Configuration
bq2084-V143
SLUS732 – SEPTEMBER 2006
Table 9. Display Mode for Three LEDs (continued)
CONDITION
THREE-LED DISPLAY OPTION
RELATIVE OR ABSOLUTE
StateOfCharge() LED1 LED2 LED3
≤ 34%, < 67% ON ON OFF
≤ 67% ON ON ON
The bq2084-V143 along with the bq29312 provides protection for Li-ion batteries, as shown in Table 10 . The
bq2084-V143 measures temperature and current and uses the bq29312 to measure individual cell voltage. The
bq2084-V143 uses this information to determine protection requirements and control the safety FETs or SAFE
output as necessary. It is recommended that the bq2084-V143 protection control be validated by two successive
measurements by setting VOD=1 in Misc Configuration.
The bq29312 can independently detect and protect the load from an overload (OL) or short circuit in charge
(SCC) or discharge (SCD). The bq29312 sets the appropriate FET state and then alerts the bq2084-V143 with
the XALERT output whenever a protection threshold is breached and its associated delay time has expired. The
bq2084-V143 then determines if and when the FETs should be turned back on.
Table 10. CVOV and CVUV Flags in PackStatus()
FLAG SET CONDITION DSG FET CHG FET CLEAR CONDITION
(1)
Voltage() = ChargingVoltage() + Over
ON OFF
(2)
Voltage() < ChargingVoltage()
Voltage Margin
CVOV
VCELL
(ANY)
= Cell Over Voltage ON OFF
(2)
VCELL
(ALL)
< Cell Over Voltage Reset
CVUV VCELL
(ANY)
= Cell Under Voltage
(3)
ON VCELL
(ALL)
> Cell Under Voltage Reset
AverageCurrent() < - Over Load Current OFF
(3)
ON AverageCurrent() < - Current Fault Clear Threshold
(1) Clear is detected and controlled by the bq2084-V143.
(2) On if there is a discharge current ≤ 150 mA
(3) On if there is a charge current ≤ 50 mA
1
st
Level Cell Voltage Thresholds
The cell undervoltage (VUV) and overvoltage (VOV) limits are programmed in Cell Under Voltage and Cell Over
Voltage DF 0x65-0x66, DF 0x63-0x64, respectively. Both value s are stored in mV. Cell Over Voltage Reset DF
0xe0-0xe1 and Cell Under Voltage Reset 0xe2-0xe3 set the reset points in mV for these safety parameters.
Safety Overvoltage Threshold
The safety voltage threshold is programmed in Safety Over Voltage DF 0x6b-0x6c. It is stored in mV. Exceeding
the Safety Voltage for a period determined by the MISC Config VOD bit causes permanent failure if enabled by
PFConfig.
Overcurrent Thresholds
Discharge current threshold is programmed in Discharge OC Threshold DF 0x12d-0x12e. The discharge
overcurrent must exist for time programmed in Discharge OC Time DF 0x12f. When a discharge overcurrent
condition is detected the discharge FET is turned off. Similarly, a charge overcurrent is programmed in Charge
OC ThresholdDF 0x12a-0x12b. The charge overcurrent must exist for the time programmed in Charge OC Time
DF 0x12c or Charge OC Time DF 0x12c. When a charge overcurrent condition is detected, the charge FET is
turned off.
Temperature Thresholds
The Safety Over Temperature in Charge (SOTC) threshold is programmed in Safety Over Temperature in
Charge DF 0x75-0x76 and Safety Over Temperature in Discharge (SOTD) threshold is programmed in Safety
Over Temperature in Discharge DF 0x77-0x78.
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