ICL7660IJA Maxim Integrated Products, ICL7660IJA Datasheet - Page 10

• Manufacturer Part Number: ICL7660IJA
• Description: Charge Pumps
• Manufacturer: Maxim Integrated Products

Specifications of ICL7660IJA

• Function: Inverting, Step Up
• Output Voltage: - 1.5 V to - 10 V, 3 V to 20 V
• Output Current: 20 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: CDIP-8 Narrow
• Minimum Operating Temperature: - 20 C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Figure 9 illustrates the recommended voltage doubler
circuit for the MAX1044/ICL7660. To reduce the voltage
drops contributed by the diodes (V
diodes. For true voltage doubling or higher output cur-
rents, use the MAX660.
The voltage divider shown in Figure 10 splits the power
supply in half. A third capacitor can be added between
V+ and V
Figure 11 illustrates this dual-function circuit.
Capacitors C1 and C3 perform the bucket and reser-
voir functions for generating the negative voltage.
Capacitors C2 and C4 are the bucket and reservoir
Switched-Capacitor Voltage Converters
Figure 12. Cascading MAX1044/ICL7660 for Increased Output Voltage
10
Figure 10. Voltage Divider
10µF
______________________________________________________________________________________
V
OUT
10µF
Combined Positive Multiplication and
C1
=
OUT
1
2
V+
1
2
3
4
.
Negative Voltage Conversion
MAX1044
ICL7660
C2
10µF
1
1
2
3
4
Positive Voltage Doubler
MAX1044
ICL7660
8
7
6
5
10µF
Voltage Divider
10µF
V+
D
LV
), use Schottky
8
7
6
5
1
2
3
4
V+
MAX1044
ICL7660
2
Figure 11. Combined Positive and Negative Converter
capacitors for the doubled positive voltage. This circuit
has higher output impedances resulting from the use of
a common charge-pump driver.
Larger negative multiples of the supply voltage can be
obtained by cascading MAX1044/ICL7660 devices
(Figure 12). The output voltage is nominally V
where n is the number of devices cascaded. The out-
put voltage is reduced slightly by the output resistance
of the first device, multiplied by the quiescent current of
the second, etc. Three or more devices can be cascaded
in this way, but output impedance rises dramatically.
For example, the output resistance of two cascaded
MAX1044s is approximately five times the output resis-
tance of a single voltage converter. A better solution
may be an inductive switching regulator, such as the
MAX755, MAX759, MAX764, or MAX774.
C1
8
7
6
5
10µF
1
2
3
4
10µF
MAX1044
ICL7660
1
2
3
4
C2
MAX1044
ICL7660
LV
Cascading Devices
3
8
7
6
5
V+
V
OUT
8
7
6
5
= 2(V+) - 2V
OUT
V
V
OUT
OUT
C3
C4
10µF
= -(V+)
= -n(V+)
= -n(V+)
D