Datasheet

U1
N/C N/C
1 20
IN OUT
2 19
IN OUT
3 18
VCC VSENSE
4 17
ISNS AGND
5 16
N/C STAT2
6 15
APG/THM STAT1
7 14
VSEL CR
9 12
EN TMR SEL
8 13
GND N/C
10 11
bq24005PWP
TEMP
PACK+
PACK-
RT1
C3
0.22 µF
+
-
Battery Pack
RT2
NTC Thermistor
bq24004
bq24005
bq24006
www.ti.com SLUS476F –DECEMBER 2000–REVISED MAY 2012
Charge Qualification and Preconditioning
The APG/THERM input can also be configured to
monitor either the adapter power or the battery
The bq2400x starts a charge cycle when power is
temperature using a thermistor. The bq2400x
applied while a battery is present. Charge
suspends charge if this input is outside the limits set
qualification is based on battery voltage and the
by the user. Refer to the APG/THERM input section
APG/THERM input.
for additional details.
As shown in the block diagram, the internal LowV
comparator output prevents fast-charging a deeply APG/THERM Input
depleted battery. When set, charging current is
The bq2400x continuously monitors temperature or
provided by a dedicated precharge current source.
system input voltage by measuring the voltage
The precharge timer limits the precharge duration.
between the APG/THERM (adapter power
The precharge current also minimizes heat
good/thermistor) and GND. For temperature, a
dissipation in the pass element during the initial stage
negative- or a positive-temperature coefficient
of charge.
thermistor (NTC, PTC) and an external voltage
divider typically develop this voltage (see Figure 16).
The bq2400x compares this voltage against its
internal V
(TP1)
and V
(TP2)
thresholds to determine if
charging is allowed. (See Figure 17.)
Figure 16. Temperature Sensing Circuit
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