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| BQ2406X Datasheet, PDF (15/31 Pages) Texas Instruments – 1A SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION | |||
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Table 3. Charge Status
Charge State
Precharge in progress
Fast charge in progress
Done (termination enabled only)
Charge Suspend (temperature)
Timer Fault
Charger off
Selected Input power over-voltage detected
Battery absent
Batteryshort
STAT1
ON
ON
OFF
OFF
bq2406x
SLUS689 â JUNE 2006
STAT2
ON
OFF
ON
OFF
BATTERY CHARGING: CONSTANT CURRENT PHASE
The bq2406x family offers on-chip current regulation. The current regulation is defined by the value of the
resistor connected to ISET pin.
During a charge cycle the fast charge current IO(OUT) is applied to the battery if the battery voltage is above the
V(LOWV) threshold (2.95 V typ):
I(OUT)
+
IO(OUT)
+
V(SET) KSET)
RISET
(3)
Where K(SET) is the output current set factor and V(SET) is the output current set voltage.
During a charge cycle if the battery voltage is below the V(LOWV) threshold a pre-charge current I(PRECHG) is
applied to the battery. This feature revives deeply discharged cells.
I(OUT)
+
I (PRECHG)
+
V(PRECHG)
RISET
KSET) IO(OUT)
X 10
(4)
Where K(SET) is the output current set factor and V(PRECHG) is the precharge set voltage.
CHARGE CURRENT TRANSLATOR
When the charge function is enabled internal circuits generate a current proportional to the charge current at pin
ISET, this current, when applied to the external charge current programming resistor RISET generates an analog
voltage that can be used by an external host to measure the charge current:
V(ISET) + I(OUT)
RISET
K(SET)
(5)
BATTERY VOLTAGE REGULATION
The battery pack voltage is sensed through the BAT pin, which is tied directly to the positive side of the battery
pack. The bq2406x monitors the battery pack voltage between the BAT and VSS pins. When the battery voltage
rises to VO(REG) threshold the voltage regulation phase begins and the charging current begins to taper down.
The voltage regulation threshold VO(REG) is fixed by an internal IC voltage reference. Two charge regulation
voltages are available: 4.2 V (typ., bq24060/61/62/63/64) and 4.36 V (typ., bq24065/66).
PRE-CHARGE TIMER
The bq2406x family activates an internal safety timer during the battery pre-conditioning phase. If the TMR pin is
left open (floating) the pre-charge timer is disabled. The charge safety timer time-out value is set by the external
resistor connected to TMR pin, RTMR and the timeout constants K(PCHG) and T(CHG) :
T(PCHG) = K(PCHG)Ã T(CHG)
The pre-charge timer operation is detailed in Table 4.
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