BQ27510-G2 Datasheet, PDF (25/38 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Direct Battery Connection

bq27510-G2
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SLUS948 – AUGUST 2010
The recommended thermistor circuit uses an external 103AT-type thermistor. Additional circuit information for
connecting this thermistor to the bq27510-G2 is shown in REFERENCE SCHEMATIC.
OVER-TEMPERATURE INDICATION
Over-Temperature: Charge
If during charging, Temperature( ) reaches the threshold of OT Chg for a period of OT Chg Time and
AverageCurrent( ) > Chg Current Threshold, then the [OTC] bit of Flags( ) is set.
If OT Chg Time = 0 then feature is completely disabled. When Temperature( ) falls to OT Chg Recovery, the
[OTC] bit of Flags( ) is reset.
Over-Temperature: Discharge
If during discharging, Temperature( ) reaches the threshold of OT Dsg for a period of OT Dsg Time, and
AverageCurrent( ) ≤ Dsg Current Threshold, then the [OTD] bit of Flags( ) is set.
If OT Dsg Time = 0 then feature is completely disabled.
CHARGING AND CHARGE-TERMINATION INDICATORS
Detecting Charge Termination
For proper bq27510-G2 operation, the cell charging voltage must be specified by the user. The default value for
this variable is Charging Voltage = 4200mV.
The bq27510-G2 detects charge termination when (1) during 2 consecutive periods of Current Taper Window,
the AverageCurrent( ) is < Taper Current, (2) during the same periods, the accumulated change in capacity >
0.25mAh/ / Current Taper Window, and (3) Voltage( ) > Charging Voltage – Taper Voltage. When this occurs,
the [CHG] bit of Flags( ) is cleared. Also, if the [RMFCC] bit of Operation Configuration is set, and
RemainingCapacity( ) is set equal to FullChargeCapacity( ).
Charge Inhibit
When PFC = 1, the bq27510-G2 can indicate when battery temperature has fallen below or risen above
predefined thresholds (Charge Inhibit Temp Low and Charge Inhibit Temp High, respectively). In this mode,
the BAT_LOW/BAT_GD line is made high to indicate this condition, and is returned to its low state, once battery
temperature returns to the range [Charge Inhibit Temp Low + Temp Hys, Charge Inhibit Temp High – Temp
Hys].
When PFC = 0 or 2, the bq27510-G2 must be queried by the system in order to determine the battery
temperature. At that time, the bq27510-G2 will sample the temperature. This saves battery energy when
operating from battery, as periodic temperature updates are avoided during charging mode.
POWER MODES
The bq27510-G2 has four power modes: NORMAL, SLEEP, HIBERNATE and BAT INSERT CHECK. In
NORMAL mode, the bq27510-G2 is fully powered and can execute any allowable task. In SLEEP mode the fuel
gauge exists in a reduced-power state, periodically taking measurements and performing calculations. In
HIBERNATE mode, the fuel gauge is in a very low power state, but can be woken up by communication. Finally,
the BAT INSERT CHECK mode is a powered-up, but low-power halted, state, where the bq27510-G2 resides
when no battery is inserted into the system.
The relationship between these modes is shown in Figure 3.
NORMAL Mode
The fuel gauge is in NORMAL Mode when not in any other power mode. During this mode, AverageCurrent( ),
Voltage( ) and Temperature( ) measurements are taken, and the interface data set is updated. Decisions to
change states are also made. This mode is exited by activating a different power mode.
Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithm minimizes
the time the fuel gauge remains in this mode.
Copyright © 2010, Texas Instruments Incorporated
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