BQ24704 Datasheet, PDF (2/31 Pages) Texas Instruments – Low Cost, Host-Controlled Li-Ion and Li-Polymer Battery Charger With Low Iq

bq24704
SLUS838 – MAY 2009........................................................................................................................................................................................................ www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
DESCRIPTION (CONTINUED)
The bq24704 features Dynamic Power Management (DPM) and input power limiting. These features reduce
battery charge current when the input power limit is reached to avoid overloading the AC adapter when supplying
the load and the battery charger simultaneously. A highly-accurate current-sense amplifier enables precise
measurement of input current from the AC adapter to monitor the overall system power.
ADAPTER +
ADAPTER–
R10
2Ω
C1
2.2 µF
P
P
Q1 (ACFET) Q2 (ACFET)
SI4435
SI4435
Controlled by
HOST
C2
R1
0.1 µF
432 kΩ
1%
R_AC
0.01 Ω
C3
0.1 µF
ACGOOD
R2
66.5 kΩ
1%
VREF
R3
10 kΩ
GPIO
HOST
DAC
ADC
R4
C4
10 kΩ
1 µF
10 kΩ
R15
C5
100 pF
D2
BAT54
C6 ^C7
10 µF ^{10 µF}
SYSTEM
ACN
ACP
ACDET
AGND
ACGOOD
SRSET
ACSET
VREF
bq24704
PVCC
HIDRV
PH
BTST
REGN
LODRV
PGND
C8
0.1 µF
C9
Q3(BATFET)
SI4435
Controlled by
HOST
Q4
FDS6680A
L1
8.2 µH
P
R_SR
0.01 Ω
D1 BAT54 ^{0.1 µF}
C11
10 µF
C10
1 µF
C13
0.1 µF
Q5
FDS6680A
C14
0.1 µF
DPMDET
CELLS
CHGEN
VADJ
SRP
SRN
BAT
ISYNSET
IADAPT PowerPad
R6
20 kΩ
C15
0.1 µF
C12
10 µF
PACK+
PACK–
(1) Pull-up rail could be either VREF or other system rail.
(2) SRSET/ACSET could come from either DAC or resistor dividers.
(3) V_IN = 20 V, V_BAT = 3-cell Li-Ion, I_CHARGE = 3 A, I_{ADAPTER_LIMIT} = 4 A
Figure 1. Typical System Schematic, Voltage and Current Programmed by DAC
2
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