Datasheet

Stand-Alone Switch-Mode
Lithium-Ion Battery-Charger Controller
Detailed Description
The MAX1737 includes all of the functions necessary to
charge between one and four series Li+ battery cells. It
includes a high-efficiency synchronous-rectified step-
down DC-DC converter that controls charging voltage
and current. It also includes input source-current limit-
ing, battery temperature monitoring, battery undervolt-
age precharging, battery fault indication, and a state
machine with timers for charge termination.
The DC-DC converter uses an external dual N-channel
MOSFET as a switch and a synchronous rectifier to
convert the input voltage to the charging current or volt-
age. The typical application circuit is shown in Figure 1.
Figure 2 shows a typical charging sequence and
Figure 3 shows the block diagram. Charging current is
set by the voltage at ISETOUT and the voltage across
R18. The battery voltage is measured at the BATT pin.
The battery regulation voltage is set to 4.2V per cell
and can be adjusted ±5% by changing the voltage at
the VADJ pin. By limiting the adjust range, the voltage
27
26
22
23
25
24
21
20
19
7
4
28
CSSP
DCIN
CSSN
VLO
BST
DHI
LX
DLO
PGND
CS
BATT
THM
REF
ISETIN
VL
SHDN
ISETOUT
VADJ
CELL
GND
CCV
CCI
CCS
TIMER1
TIMER2
R12
Li+
BATTERY
(1 TO 4 CELLS)
L1
R18
22μH
FAULT
FULLCHG
FULL CHARGE
FAST CHARGE
FAULT
FASTCHG
C6
47nF
C13
1nF
C14
1nF
1nF
C5
47nF
C4
C3
1μF
C1
4.7μF
C18
22μF
C19
22μF
SYSTEM
LOAD
INPUT
SUPPLY
C2
0.1μF
C7
0.1μF
C8
0.1μF
R1
10k
R8
D1
D3
D2
R9
0.1μF
16
11
9
6
12
3
8
2
5
18
1
10
13
14
17
15
0.1μF
0.1μF
C15
68μF
C9
0.1μF
C11
0.1μF
C10
0.1μF
MAX1737
++
THERMISTOR
Figure 1. Typical Application Circuit
Maxim Integrated
9
MAX1737