Datasheet

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SLUS462E − SEPTEMBER 2000 − REVISED NOVEMBER 2004
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16
U1
N/C N/C
120
IN OUT
219
IN OUT
318
V
CC
VSENSE
417
ISNS AGND
516
N/C STAT2
615
APG/THM STAT1
714
VSEL CR
912
EN TMR SEL
813
GND N/C
10 11
V
CC
C2
0.1 µF
R
SNS
C1
10 µF
+
DC−
DC+
V
CC
bq24002PWP
Figure 19. Current Sensing Circuit
Charge current feedback, applied through pin ISNS,
maintains regulation around a threshold of Vilim. The
following formula calculates the value of the sense
resistor:
R
SNS
+
Vilim
I
REG
where I
REG
is the desired charging current.
Voltage Monitoring and Regulation
Voltage regulation feedback is through pin VSENSE. This
input is tied directly to the positive side of the battery pack.
The bq2400x supports cells with either coke (4.1 V) or
graphite (4.2 V) anode. Pin VSEL selects the charge
regulation voltage.
VSEL State
(see Note)
CHARGE REGULATION
VOLTAGE
Low 4.1 V
High 4.2 V
NOTE: VSEL should not be left floating.
Charge Termination
The bq2400x continues with the charge cycle until
termination by one of the two possible termination
conditions:
Maximum Charge Time: The bq2400x sets the maximum
charge time through pin TMRSEL. The TMR SEL pin
allows the user to select between three different total
charge-time timers (3, 4, 5, or 6 hours). The charge timer
is initiated after the preconditioning phase of the charge
and is reset at the beginning of a new charge cycle. Note
that in the case of a fault condition, such as an out-of-range
signal on the APG/THERM input or a thermal shutdown,
the bq2400x suspends the timer.
TMRSEL STATE CHARGE TIME
Floating
(1)
3 hours
Low 6 hours
High 4.5 hours
(1)
To improve noise immunity, it is recommended that a minimum of
10 pF capacitor be tied to Vss on a floating pin.
Minimum Current: The bq2400x monitors the charging
current during the voltage regulation phase. The bq2400x
initiates a 22-minute timer once the current falls below the
taperdet trip threshold. Fast charge is terminated once the
22-minute timer expires.
Charge Status Display
The three available options allow the user to configure the
charge status display for single LED (bq24001), two
individual LEDs (bq24002) or a bicolor LED (bq24003).
The output stage is totem pole for the bq24001 and
bq24003 and open-drain for the bq24002. The following
tables summarize the operation of the three options:
Table 1. bq24001 (Single LED)
CHARGE STATE STAT1
Precharge ON (LOW)
Fast charge ON (LOW)
FAULT Flashing (1 Hz, 50% duty cycle)
Done (>90%) OFF (HIGH)
Sleep-mode OFF (HIGH)
APG/Therm invalid OFF (HIGH)
Thermal shutdown OFF (HIGH)
Battery absent OFF (HIGH)