Datasheet

MAX1758
Stand-Alone, Switch-Mode
Li+ Battery Charger with Internal 28V Switch
9
Maxim Integrated
Detailed Description
The MAX1758 includes all of the functions necessary to
charge 1, 2, 3, or 4 Li+ battery cells in series. It
includes a step-down DC-DC converter that controls
charging voltage and current. It also includes input
source current limiting, battery temperature monitoring,
battery undervoltage precharging, battery fault indica-
tion, and a state machine with timers for charge termi-
nation.
The DC-DC converter uses an internal power MOSFET
switch to convert the input voltage to the charging cur-
rent or voltage. Figure 1 shows the typical application
circuit. Figure 2 shows a typical charging sequence and
Figure 3 shows the functional diagram. The charging
current is set by the voltage at ISETOUT. The battery
voltage is measured at the BATT pin. The battery regu-
lation voltage limit 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 limit accuracy is
better than 1% while using 1% setting resistors.
27
26
1
22
10
9
20
19
21
18
D4
8
4
28
CSSP
DCIN
CSSN
VL
BST
HSD
HSD
LX
LX
PGND
CS
BATT
THM
REF
ISETIN
TO VL
SHDN
ISETOUT
MBRS340
MBRS340
VADJ
CELL
GND
CCV
CCI
CCS
TIMER1
TIMER2
R1
0.05Ω
L1
22μH
FAULT
FULLCHG
FAST CHARGE
FULL CHARGE
FAULT
FASTCHG
C2
0.1μF
C5
1nF
C6
1nF
C1
0.1μF
C3
1μF
C12
0.22μF
C10
22μF
TO
SYSTEM
LOAD
INPUT
SUPPLY
C7
0.1μF
C8
0.1μF
R4
D2
D3
D1
R5
C4
0.1μF
R6
10k
15
24
25
6
11
3
7
2
5
17
23
12
13
16
14
C15
68μF
C9
0.1μF
C13
4.7μF
C14
0.1μF
C16
0.1μF
MAX1758
+
C11
22μF
++
C17
1nF
THERM
Li+ BATTERY
1 TO 4 CELLS
C18
0.1μF
Figure 1. Typical Application Circuit