MAX8731A Maxim Integrated Products, MAX8731A Datasheet - Page 14

• Manufacturer Part Number: MAX8731A
• Description: SMBus Level 2 Battery Charger
• Manufacturer: Maxim Integrated Products

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SMBus Level 2 Battery Charger
with Remote Sense
The typical application circuit is shown in Figure 1. The
MAX8731A includes all the functions necessary to
charge Li+, NiMH, and NiCd smart batteries. A high-
efficiency, synchronous-rectified, step-down DC-DC
converter is used to implement a precision constant-
current, constant-voltage charger. The DC-DC convert-
er drives a high-side n-channel MOSFET and provides
synchronous rectification with a low-side n-channel
MOSFET. The charge current and input current-sense
Figure 1. Typical Dual-Battery Application Circuit
14
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ADAPTER
INPUT
Detailed Description
KBC
1μF
INPUT
D1
C1
VDD
SDA
SCL
0.01μF
49.9kΩ
150kΩ
10kΩ
10kΩ
LDO
C4
R3
R1
R5
R8
10kΩ
10kΩ
100kΩ
R4
R7
10kΩ
R6
R13
N
0.01μF
0.1μF
0.1μF
C6
0.01μF
C3
C5
C2
100kΩ
C7
1μF
R2
DCIN
ACIN
ACOK
V
SCL
SDA
IINP
CCV
CCI
CCS
REF
DD
DAC
MAX8731A
C8
0.1μF
BP
BATSEL
PGND
CSSN
CSSP
FBSB
FBSA
GND
CSIP
CSIN
LDO
DLO
V
BST
DHI
amplifiers have low input-offset error (±64µV typ),
allowing the use of small-valued sense resistors.
The MAX8731A features a voltage-regulation loop
(CCV) and two current-regulation loops (CCI and CCS).
The loops operate independently of each other. The
CCV voltage-regulation loop monitors either FBSA or
FBSB to ensure that its voltage never exceeds the volt-
age set by the ChargeVoltage() command. The CCI
battery current-regulation loop monitors the current
delivered to the selected battery to ensure that it never
exceeds the current limit set by the ChargeCurrent()
CC
LX
100Ω
100Ω
R10
D2
R9
C10
0.1μF
C12
1μF
C9
220pF
R11
1Ω
R12
33Ω
N1
C11
1μF
LDO
BATTERY
SELECTOR
A
N3
RS1
10mΩ
N1, N2,: SI4800BDY
N3: SI4810BDY
C
10μF
DHI
IN1
RS2
10mΩ
L1
4.3μH
BATTERY
L1: SUMIDA
CEP125-4R3MC-U
B
V
C
10μF
OUT
OUT1
SYSTEM
C
10μF
N2
LOAD
IN2
C
10μF
OUT2