BQ24742 Datasheet, PDF (2/35 Pages) Texas Instruments – Li-Ion or Li-Polymer Battery Charger with Low Iq and Accurate Trickle Charge

bq24741, bq24742
SLUS875B – MARCH 2009 – REVISED OCTOBER 2009
www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
DESCRIPTION (CONTINUED)
The bq24741/2 features resistor-programmable PWM switching frequency and accurate 150mA trickle charge
(with 20 mΩ sensing resistor), which can be enabled via the TRICKLE pin. The bq24741/2 also 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 high-accuracy current sense amplifier enables accurate measurement of input current from the
AC adapter, allowing monitoring 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.
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ADAPTER +
ADAPTER -
R11
2Ω
C1
2.2 µF
P
P
Q1 (ACFET) Q2 (ACFET)
SI4435
SI4435
Controlled by
HOST
C2
R1
432 kΩ
0.1 µF
1%
R_AC
0.010 Ω
C3
0.1 µF
EXTPWR
R2
66.5 kΩ
1%
R3 ^VREF
10 kΩ
R4
R5
C4
10 kΩ
10 kΩ
1 µF
GPIO
HOST
ISET_PWM
(D = 0.72, V_peak = VDAC)
ADC
R15
10 kΩ
120 kΩ
R14
C13
100 nF
C5
100 pF
VREF
R12
102 kΩ
1%
R13
64.9 kΩ
1%
R16
10 Ω
D2
BAT54
C6
C7
10 µF 10 µF
ACN
ACP
PVCC
ACDET
AGND
HIDRV
EXTPWR
VREF
SW
BTST
bq24741/2 ^REGN
TRICKLE
DPMDET
LPMOD
CELLS
CE
VDAC
ISET
LODRV
PGND
CSP
CSN
BAT
IADAPT
LPREF
VADJ
ACSET
PowerPad ^FSET
C8
0.1 µF
C9
D1 BAT54 _{0.1 µF}
C10
1 µF
Q3(BATFET)
SI4435
Controlled by
HOST
Q4_A
FDS8978
L1
P
RSR
0.020 Ω
10 µH
C11
10 µF
C13
0.1 µF
Q4_B
FDS8978
C14
0.1 µF
C12
10 µF
VREF
R9
60.4 kΩ
1%
R6
97.6 kΩ
R10
40.2 kΩ
1%
VREF
R7
73.2 kΩ
1%
R8
26.7 kΩ
1%
C15
0.1 µF
SYSTEM
PACK+
PACK-
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F_S = 400 kHz, 90 W Adapter, V_ADAPTER = 19 V, V_BAT = 3-cell Li-Ion (4.2V/cell), I_charge = 3.6 A, I_{adapter_limit} = 4.0 A
Figure 1. Typical System Schematic, Voltage, and Current Programmed by Resistor
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