BQ24745_14 Datasheet, PDF (2/39 Pages) Texas Instruments – SMBus-Controlled Multi-Chemistry Battery

bq24745
SLUS761D – DECEMBER 2007 – REVISED OCTOBER 2011
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 bq24745 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 adaptor 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, 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
performance to the power available from the adapter. An integrated comparator monitors the input current
through the current-sense amplifier, and indicates when the input current exceeds a programmable threshold
limit.
TYPICAL APPLICATIONS
V_IN = 20 V, V_BAT = 4-cell Li-Ion, I_CHARGE = 4.5 A
ADAPTER +
ADAPTER -
RC1
2.2Ω
C1
2.2u
R1
309k
1%
Q1 (ACFET) Q2 (RBFET)
SI4835BDY SI4835BDY
RC6
10Ω
P
P
Controlled by
HOST
C2
0.1u
C6
1u
RAC
0.010
C3
0.1u
R2
49.9k
1%
+3.3V_ALWAYS
OR
+5V_ALWAYS
R3
10k
27 _CSSN
28 _CSSP
22 _DCIN
2 _ACIN
12 _GND
UGATE ²⁴
bq24745 ^{PHASE 23}
11 _VDDSMB
BOOT ²⁵
D1
VDDP ²¹
13 _ACOK
DISCRETE
LOGIC
R10 R11
10k 10k
3 _VREF
C4 1uF
LGATE ²⁰
PGND ¹⁹
R12
10k
HOST
(EC)
Dig I/O
SMBus
DISCRETE
LOGIC
C5 100pF
26 _ICOUT
7 _CE
9 _SDA
10 _SCL
8 _VICM
14 _NC
16 _NC
CSOP ¹⁸
CSON ¹⁷
VFB ¹⁵
ICREF ¹
EAO ⁴
EAI 5
FBO ⁶
C14
10uF
C15
10uF
CHRG_IN
Q3
FDS6680A
C7
0.1uF
BAT 54
L1
5.6uH
C8
C10
1u
0.1uF
Q4
FDS6680A
RSR
0.010
C9
0.1uF
C13
2x10u
PACK +
PACK -
R22
100 Ω
C17
0.1uF
C23
R19
51pF
7.5k
C21
R21 R20
2000pF 200k 20k
C22
130pF
(1) Pullup rail could be either VREF or other system rail.
Figure 1. Typical System Schematic Using External Input-Current Comparator (Discrete Logic) Instead of
Internal Comparator
2
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