BQ24751B Datasheet, PDF (2/38 Pages) Texas Instruments – Host-Controlled Multi-Chemistry Battery Charger with Low Iq and System Power Selector

Not Recommended For New Designs
bq24751B
SLUS835A – JULY 2008 – REVISED MARCH 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 bq24751B controls external switches to prevent battery discharge back to the input, connect the adapter to
the system, and to connect the battery to the system using 6-V gate drives for better system efficiency. For
maximum system safety, inrush-power limiting provides instantaneous response to high input voltage multiplied
by current. This AC Overpower protection (ACOP) feature limits the input-switch power to the programmed level
on the ACOP pin, and latches off if the high-power condition persists to prevent overheating.
The bq24751B 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
Q1 (ACFET)
SI4435
P
Q2 (ACFET)
SI4435
C2
0.1 µF
RAC
0.010 Ω
C3
0.1 µF
/ACGOOD
R1
432 kΩ
1%
R3
422 kΩ
1%
DAC
R2
66.5 kΩ
1%
VREF
R5
10 kΩ
R4
71 kΩ
1%
HOST
GPIO
C4
0.1 µF
DAC
ADC
C5
100 pF
ACN
PVCC
ACP
/ACDRV
ACDET
/BATDRV
AGND
HIDRV
bq24751B ^PH
/ACGOOD
BTST
OVPSET
REGN
SRSET
ACSET
VREF
LEARN
CELLS
/CHGEN
VDAC
VADJ
IADAPT
LODRV
PGND
SRP
SRN
BAT
ACOP
PowerPad
C6 C7
10 µF 10 µF
SYSTEM
C8
0.1 µF
Q4
FDS6680A
L1
8.2 µH
P
RSR
0.010 Ω
D1
C9
BAT54 0.1 µF
C10
1 µF
C11
10 µF
C13
Q5 ^{0.1 µF}
FDS6680A
C14
0.1 µF
Q3(BATFET)
SI4435
C12
10 µF
PACK+
PACK-
C16
0.47 µF
C15
0.1 µF
(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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