MAX1757 Maxim, MAX1757 Datasheet - Page 9

• Manufacturer Part Number: MAX1757
• Description: Stand-Alone / Switch-Mode Li Battery Charger with Internal 14V Switch
• Manufacturer: Maxim

Figure 1. Typical Application Circuit
The MAX1757 includes all of the functions necessary to
charge 1, 2, or 3 Li+ battery cells in series. It includes a
step-down DC-DC converter that controls charging
voltage and current. It also includes input source cur-
rent limiting, battery temperature monitoring, battery
undervoltage precharging, battery fault indication, and
a state machine with timers for charge termination.
The DC-DC converter uses an internal power MOSFET
switch to convert the input voltage to the charging cur-
SUPPLY
INPUT
Li+ Battery Charger with Internal 14V Switch
D1
FAST CHARGE
FULL CHARGE
_______________________________________________________________________________________
D2
0.1µF
FAULT
C4
MBR5340
C3
1µF
General Description
C17
1nF
R4
R5
TO VL
10k
R6
0.1µF
0.1µF
1nF
1nF
C1
C2
C5
C6
C7
0.1µF
17
11
25
24
23
12
13
15
16
14
28
5
2
3
7
6
DCIN
FASTCHG
FULLCHG
FAULT
SHDN
REF
ISETIN
ISETOUT
VADJ
CELL
GND
CCV
CCI
CCS
TIMER1
TIMER2
MAX1757
Stand-Alone, Switch-Mode
CSSP
CSSN
PGND
BATT
THM
HSD
HSD
BST
CS
VL
LX
LX
22
10
9
20
19
21
27
26
1
18
8
4
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 charg-
ing current is set by the voltage at ISETOUT. The bat-
tery regulation voltage is measured at the BATT pin.
The battery 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 accu-
racy is better than 1% while using 1% setting resistors.
C8
0.1µF
C9
0.1µF
D3
C14
0.1µF
C16
0.1µF
C18
0.1µF
C13
4.7µF
THERM
D4
MBR5340
C15
68µF
R1
0.05Ω
22µH
L1
+
C12
0.22µF
+
Li+ BATTERY
1 TO 3 CELLS
C10
22µF
+
C11
22µF
TO
SYSTEM
LOAD
9