MAX630EJA MAXIM [Maxim Integrated Products], MAX630EJA Datasheet - Page 11

• Manufacturer Part Number: MAX630EJA
• Description: CMOS Micropower Step-Up Switching Regulator
• Manufacturer: MAXIM [Maxim Integrated Products]

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.
A MAX634 inverting regulator is combined with a
MAX630 in Figure 8 to provide a dual-tracking ±15V
Figure 5. 3V to 5V Converter with Low-Battery Frequency Shift
Figure 7. Battery Life Extension Down to 3V In
3V
R3
249kΩ
R4
499kΩ
100pF
2.4MΩ
390kΩ
C1
1
______________________________________________________________________________________
LBR
10MΩ
LBD
8
47pF
L
C
X
MAX630
X
470μH
Dual-Tracking Regulator
C
X
2
2
3
HYST
THRESHOLD
GND
L
+V
V
X
FB
4
3
I
MAX8212
S
C
1N4148
5
6
7
GND
8
5
BATTERY
OUT
R
540kΩ
R
200kΩ
1
2
9V
470μF
15V
+5V OUT
CMOS Micropower Step-Up
1.3MΩ
1MΩ
1
1.0mH
LBR
LBD
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
Figure 6. Uninterruptable +5V Supply
8
BATTERY
NICAD
100pF
1N5817
3.6V
MAX630
Switching Regulator
LINE-POWERED
C
L
X
X
3
2
+5V INPUT
47pF
200kΩ
100kΩ
GND
+V
680Ω
V
5
S
4
FB
I
C
6
7
1MΩ
1N4001
1
8
LBR
LBD
GND
MAX630
4
470μH
2MΩ
560kΩ
BATT
C
L
X
X
3
2
+V
V
FB
470μF
25V
I
47pF
C
S
1N5817
5
6
7
falls to 7.2V.
UNINTERRUPTABLE
280kΩ
100kΩ
+5V OUTPUT
POWER FAIL
470μF
15V
11