BQ24004_12 Datasheet, PDF (13/27 Pages) Texas Instruments – TWO-CELL Li-ION CHARGE MANAGEMENT IC

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