BQ2084-V140_14 Datasheet, PDF (18/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
SLUS664B – JULY 2005 – REVISED AUGUST 2006
www.ti.com
The bq2084-V140 detects a current taper termination when the pack voltage is greater than Charging
Voltage (DF 0x3a-0x3b) minus Current Taper Qualification Voltage (DF 0x4d-0x4e) and the
AverageCurrent() is below the Current Taper Threshold (DF 0x4b-0x4c), but greater than the Charge
Detection Current in DF 0x113-0x114, for a period of Current Taper Window (DF 0x4f).
Once the bq2084-V140 detects a Primary Charge Termination, the bq2084-V140 sets the
TERMINATE_CHARGE_ ALARM and FULLY_CHARGED bits in BatteryStatus(), and turns off the charge
FET via the bq29312. The charge FET is turned on when discharge current is detected and is greater than
Discharge Detection Current (DF 0x115-0x116), to minimize IR losses. The TERMINATE_CHARGE_
ALARM is cleared if charge current is no longer detected or the pack is removed, but returns if charging is
attempted while the FULLY_CHARGED bit is set.
The bq2084-V140 clears the FULLY_CHARGED and TERMINATE_CHARGE_ALARM bit when
RelativeStateOfCharge() is less than the programmed Fully Charged Clear %. See Table 13 for a summary
of BatteryStatus() alarm and status bit operation.
Cell Balancing
The bq2084-V140 balances the cells during charge by discharging those cells above the threshold set in Cell
Balance Threshold DF 0xe8-0xe9, if the maximum difference in cell voltages exceeds the value programmed in
Cell Balance Min DF 0xec. For cell balancing, the bq2084-V140 measures the cell voltages at an interval set in
Cell Balance Interval DF 0xed. On the basis of the cell voltages, the bq2084-V140 either selects the appropriate
cell to discharge or adjusts the cell balance threshold up by the value programmed in Cell Balance Window
0xea-0xeb when all cells exceed the cell balance threshold or the highest cell exceeds the cell balance threshold
by the cell balance window.
Cell balancing only occurs when charging current is detected and the cell balance threshold is reset to the value
in Cell Balance Threshold at the start of every charge cycle. The threshold is only adjusted once during any
balance interval.
If the cells are severely imbalanced during charging, where VCELL_(MAX) - VCELL_(MIN) > Cell Imbalance Threshold
AND SBS. Current()> Balance IMAX for a period of Cell Imbalance time then the CIM bit in PF Status is set.
NAME
Cell Balance Threshold
Cell Balance Min
Cell Balance Window
Cell Balance Interval
Cell Imbalance Threshold
Balance IMAX
Cell Imbalance Time
Table 6. Cell Balancing and Cell Imbalance Programming
DF ADDRESS
DESCRIPTION
0xe8-0xe9
Sets the maximum voltage in mV that each cell must achieve to initiate cell balancing.
Programming Cell Balance Threshold to 65,535 disables cell balancing.
0xec
Sets in mV the cell differential that must exist to initiate cell balancing
0xea-0xeb
Sets in mV the amount that the cell balance threshold increases during cell balancing
0xed
Sets the cell balancing time interval in seconds.
0xee-0xef
Sets the severe imbalance fault limit for cell imbalance detection
0xf2-0xf3
Sets the charge current required to allow a cell imbalance to be detected
0x134
Sets the time period during which a cell imbalance must be selected for the bq2084 to enter
PF mode.
DISPLAY PORT
General
The display port drives a 3-, 4-, or 5-LED bar-graph display. The display is activated by a logic signal on the
DISP input. The bq2084-V140 can display RM in either a relative or absolute mode with each LED representing
a percentage of the full-battery reference. In relative mode, the bq2084-V140 uses FCC as the full-battery
reference; in absolute mode, it uses Design Capacity (DC). The DMODE bit in Pack Configuration DF 0x28
programs the bq2084-V140 for the absolute or relative display mode. The LED bits program the 3-, 4-, or 5-LED
option.
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