Datasheet

Note that this circuit (with or without the MAX8212) can be
used to provide 5V from four alkaline cells. The initial volt-
age is approximately 6V, and the output is maintained at
5V even when the battery voltage falls to less than 2V.
Dual-Tracking Regulator
A MAX634 inverting regulator is combined with a
MAX630 in Figure 8 to provide a dual-tracking ±15V
output from a 9V battery. The reference for the -15V
output is derived from the positive output through R3
and R4. Both regulators are set to maximize output
power at low-battery voltage by reducing the oscillator
frequency, through LBR, when V
BATT
falls to 7.2V.
MAX630/MAX4193
CMOS Micropower Step-Up
Switching Regulator
______________________________________________________________________________________ 11
MAX630
3V
R3
249kΩ
R4
499kΩ
R
1
540kΩ
R
2
200kΩ
C1
100pF
C
X
47pF
LBD
8
C
X
GND
2
L
X
4
1
LBR
L
X
470μH
1N4148
+5V OUT
470μF
15V
3
5
+V
S
7
V
FB
6
I
C
Figure 5. 3V to 5V Converter with Low-Battery Frequency Shift
MAX8212
MAX630
10MΩ
HYST
OUT
2
THRESHOLD
3
GND
5
82.4MΩ
390kΩ
9V
BATTERY
1.3MΩ
1MΩ
1
LBR
2MΩ
560kΩ
7
6
I
C
V
FB
47pF
100pF
LBD
8
C
X
L
X
2
3
GND
4
1MΩ
+V
S
5
1.0mH
470μF
25V
Figure 7. Battery Life Extension Down to 3V In
MAX630
LINE-POWERED
+5V INPUT
1N4001
200kΩ
100kΩ
680Ω
1N5817
3.6V
NICAD
BATTERY
470μH
1
LBR
8
LBD
GND
4
C
X
L
X
2
3
280kΩ
100kΩ
1N5817
UNINTERRUPTABLE
+5V OUTPUT
470μF
15V
5
+V
S
7
V
FB
6
I
C
POWER FAIL
47pF
Figure 6. Uninterruptable +5V Supply