BQ24705 Datasheet, PDF (2/30 Pages) Texas Instruments – Host-Controlled Multi-Chemistry Battery Charger With Low Input Power Detect

bq24705
SLUS779 – DECEMBER 2007
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 bq24705 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-
R5
4W
C1
1 mF
P
P
Q1 (ACFET) Q2 (ACFET)
SI4435
SI4435
Controlled by
HOST
C2
R1
0.1 mF
432 kW
1%
R_AC
0.010 W
C3
0.1 mF
ACGOOD
R2
66.5 kW
1%
DAC
HOST
VREF
R3
10 kW
R4
10 kW
C4
1 mF
DAC
ADC
C5 100 pF
C6 C7
10 mF 10 mF
SYSTEM
ACN
ACP
PVCC
ACDET
AGND
HIDRV
bq24705 PH
ACGOOD
BTST
SRSET
ACSET
VREF
REGN
LODRV
PGND
C8
0.1 mF
Q4
FDS6680A
C9
L1
D1 BAT54 ^{0.1 mF}
4.7 mH
C11
C10
10 mF
1 mF
C^C1¹3³
Q5 ^{0.1 mF}
FDS6680A
P
R SR
0.010 W
C14
0.1 mF
Q3(BATFET)
SI4435
Controlled by
HOST
C12
10 mF
PACK+
PACK-
DPMDET
CELLS
CHGEN
SRP
SRN
BAT
VADJ
ISYNSET
IADAPT
PowerPad
R6
68 kW
C15
0.1 mF
(1) Pull-up rail could be either VREF or other system rail .
(2) SRSET/ACSET could come from either DAC or resistor dividers .
V_IN = 20 V, V_BAT = 3-cell Li-Ion, I_CHARGE = 3 A, I_{ADAPTER_LIMIT} = 4 A
Figure 2. Typical System Schematic, Voltage and Current Programmed by DAC
2
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