BQ2084-V140_14 Datasheet, PDF (21/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
www.ti.com
SLUS664B – JULY 2005 – REVISED AUGUST 2006
AFE Configuration
The AFE protection limits are programmed as specified in the bq29312 data sheet.
AFE Over Load DF 0xc5 sets the AFE overload protection threshold.
AFE Over Load Delay DF 0xc6 sets the delay timing for overload protection.
AFE Short Circuit in Charge DF 0xc7 sets the AFE short circuit in charge protection threshold and delay
time.
AFE Short Circuit in Discharge DF 0xc8 sets the AFE short circuit in discharge protection threshold and
delay time.
SMBus command 0x46 can be used to string-read the AFE RAM with the AFE address 0x00 first, if the
bq2084-V140 is not sealed as indicated by bit 5 of PackStatus.
Table 11. Overcurrent Protection
NR=1
AFE OLV
AFE SCC
FAILURE
FET STATUS
CHG on, ZVCHG off, DSG off
CHG off, ZVCHG off, DSG on
AFE SCD
CHG on, ZVCHG off, DSG off
GG Charge OC (set by DF 0x12a to 0x12c) CHG off, ZVCHG off, DSG on
GG Discharge OC (set by DF 0x12d to 0x12f) CHG on, ZVCHG off, DSG off
NR=0
FAILURE
FET STATUS
AFE OLV
All FETs off
AFE SCC
All FETs off
AFE SCD
All FETs off
GG Charge OC (set by DF 0x12a to 0x12c) All FETs off
GG Discharge OC (set by DF 0x12d to 0x12f) All FETs off
CLEAR CONDITIONS
Same AFE SCD
Average Current ()< Clear Fail Current (DF 0x61/2) for
Fault Reset Time (DF 0x130), or discharge current >
discharge detection current (DF 0x115/6)
Average Current () ≤ -Clear Fail Current (DF 0x61/2) for
Fault Reset Time (DF 0x130), or charge current > charge
detection current (DF 0x113/4)
Same AFE SCC
Same AFE SCD
RRES=high
PRES=high
PRES=high
PRES=high
PRES=high
EXIT CONDITIONS
The AFE protection features can also recover automatically after AFE Recovery Time (DF 0x160) if the AFE
Recovery Time is set to a nonzero value. When the protection feature is recovered in this manner, it does not
re-trigger for AFE Hold Off Time (DF 0x161).
AFE Integrity Check
The bq2084-V140 checks the programming of the AFE registers at a period determined by AFE Check Time DF
0xfb. The units of the check period are seconds unless the bq2084-V140 is in sleep mode, in which case the
period is AFE Check Time x Sleep Current Multiplier (DF 0xfd). If the data is not correct, the bq2084-V140
increments an internal counter until it reaches the AFE Fail Limit (DF 0xe4). Setting AFE Check Time to 0
disables this function.
When the internal AFE Fail counter reaches AFE Fail Limit, then the AFE bit in PF Status is set.
AFE Watchdog Fault and Clear
The bq29312 has a feature where the 32-kHz output (CLKOUT, pin 35) of the bq2084-V140 is used to drive its
internal clock. If this clock fails, a fault is declared in the AFE. See the bq29312 data sheet for further details.
The fault is cleared automatically on return of the 32-kHz input via the bq2084-V140 CLKOUT pin.
Permanent Failure Mode (SAFE Output)
The SAFE output of the bq2084-V140 provides an additional level of safety control. The active low safety output
can blow a fuse or control another switch on the basis of temperature, pack-voltage cell-voltage, CHG FET
Failure, severe cell imbalance, or an integrity check of the AFE and Data Flash configuration registers.
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