BQ2085 Datasheet, PDF (18/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
Table 8. Display Mode for Four LEDs
CONDITION
RELATIVE OR ABSOLUTE
StateOfCharge( )
EDV0 = 1
<25%
≥25%, < 50%
≥50%, < 75%
≥75%
FOUR-LED DISPLAY OPTION
LED1
OFF
ON
ON
ON
ON
LED2
OFF
OFF
ON
ON
ON
LED3
OFF
OFF
OFF
ON
ON
LED4
OFF
OFF
OFF
OFF
ON
Table 9. Display Mode for Three LEDs
CONDITION
RELATIVE OR ABSOLUTE
StateOfCharge( )
EDV0 = 1
<34%
≥34%, < 67%
≥67%
THREE-LED DISPLAY OPTION
LED1
OFF
ON
ON
ON
LED2
OFF
OFF
ON
ON
LED3
OFF
OFF
OFF
ON
Li-Ion Protector Control
The bq2085 provides protection for Li-Ion batteries, as shown in Table 10. The bq2085 uses the bq29311 to
measure and report individual series cell voltages. The bq2085 determines if a voltage protection condition has
been breached and turns off the respective control FET via I²C communication to the bq29311. It is
recommended that the bq2085 protection control be validated by two successive measurements by setting
VOD=1 in Misc Configuration.
The bq29311 can detect and protect the load from an overcurrent (OC) or short circuit (SC). The bq29311 alerts
the bq2085 with the XALERT output when ever an overcurrent or short circuit threshold is breached in either
the charge or discharge directions.
The bq2085 asserts CVOV and instructs the bq29311 to turn off the charge FET if an Overvoltage or
Overtemperature condition exists, or if AverageCurrent( ) ≥ Fast-Charging Current + Over Current Margin
(Prolonged Overcurrent condition in Table 6). The bq2085 does not turn off the charge FET if there is a discharge
current > 50 mA. The bq2085 instructs the bq29311 to turn on the charge FET when Overvoltage and
Overtemperature conditions no longer exist, and AverageCurrent( ) < 256 mA (if Prolonged Overcurrent
generated the fault condition).
The bq2085 asserts CVUV and instructs the bq29311 to turn off the discharge FET if an Overdischarged
condition exists, or if AverageCurrent( ) ≤ – overload current (Overload). The bq2085 does not turn off the
discharge FET if there is a charge current ≥ 50 mA. The bq2085 instructs the bq29311 to turn on the discharge
FET when the Overdischarged condition no longer exists and AverageCurrent( ) > –256 mA (if Overload
generated the fault condition).
Table 10. bq2085 to bq29311 Interface (FET Protection Control)
Battery State (Table 6)
CVOV = 1: Prolonged Overcurrent, Overvoltage, Overtemperature
CVOV = CVUV = 0
CVUV = 1: Overload, Overdischarged
NOTES: 13. State determined by bq29311
14. On if there is a discharge current ≥ 50 mA
15. On if there is a charge current ≥50 mA.
DISCHARGING FET
Normal (see Note 13)
Normal (see Note 13)
Off (see Note 15)
CHARGING FET
Off (see Note 14)
Normal (see Note 13)
Normal (see Note 13)
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