BQ24740_07 Datasheet, PDF (2/32 Pages) Texas Instruments – Host-controlled Multi-chemistry Battery Charger with Low Input Power Detect

bq24740
SLUS736 – DECEMBER 2006
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 bq24740 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. If the adapter
current is above the programmed low-power threshold, a signal is sent to host so that the system optimizes its
power performance according to what is available from the adapter.
ADAPTER+
ADAPTER-
EXTPWR
TYPICAL APPLICATION
C16 C17
10 mF 10 mF
C18
10 mF
C1
10 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
R2
66.5 kW
1%
VREF
R3
10 kW
DAC
HOST
R4
10 kW
R5
10 kW
C4
1 mF
DAC
ADC
C5 100 pF
C6 C7
10 mF 10 mF
SYSTEM
ACN
ACP
PVCC
ACDET
AGND
HIDRV
bq24740 PH
EXTPWR
BTST
SRSET
ACSET
VREF
REGN
LODRV
PGND
C8
1 mF
Q4
FDS6680A
C9
L1
D1 BAT54 ^{0.1 mF}
8.2 mH
C11
C10
10 mF
1 mF
C13
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-
IADSLP
DPMDET
LPMD
CELLS
SRP
SRN
BAT
CHGEN
VDAC
VADJ
LPREF
ISYNSET
IADAPT PowerPad
R6
33 kW
VREF
R7
200 kW
R8
24.9 kW
C15
0.1 mF
R9 1.8 MW
(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 1. Typical System Schematic, Voltage and Current Programmed by DAC
2
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