ICL7660S, ICL7660A

FN3179 Rev 7.01

Page 11 of 14

Feb 10, 2020

resistor to the LV pin ensures start-up. Because the switches

share the load in parallel, the output impedance is much lower

than in the standard circuits, and higher currents can be drawn

from the device. By using this circuit, and then the circuit of

Figure 15, +15V can be converted, via +7.5 and -7.5, to a

nominal -15V, although with rather high series output

resistance (

250Ω).

Regulated Negative Voltage Supply

In some cases, the output impedance of the ICL7660S and

ICL7660A can be a problem, particularly if the load current

varies substantially. The circuit of Figure 21 can be used to

overcome this by controlling the input voltage, via an ICL7611

low-power CMOS op amp, in such a way as to maintain a

nearly constant output voltage. Direct feedback is inadvisable,

since the ICL7660S’s and ICL7660A’s output does not respond

instantaneously to change in input, but only after the switching

delay. The circuit shown supplies enough delay to

accommodate the ICL7660S and ICL7660A, while maintaining

adequate feedback. An increase in pump and storage

capacitors is desirable, and the values shown provide an

output impedance of less than 5Ω to a load of 10mA.

Other Applications

Further information on the operation and use of the ICL7660S

and ICL7660A may be found in application note AN051,

“Principles and Applications of the ICL7660 CMOS Voltage

Converter”.

Revision History

1

2

3

4

8

7

6

5

+

-

+

-

50µF

50µF

+

-

50µF

RL1

VOUT = V+ - V-

2

ICL7660S

V+

V-

RL2

FIGURE 20. SPLITTING A SUPPLY IN HALF

ICL7660A

1

2

3

4

8

7

6

5

+

-

100µF

ICL7660S

100µF

VOUT

+

-

10µF

ICL7611

+

-

100



50k

+8V

100k

50k

ICL8069

56k

+8V

800k

250k

VOLTAGE

ADJUST

+

-

FIGURE 21. REGULATING THE OUTPUT VOLTAGE

ICL7660A

Rev.

Date

Description

7.01

Feb 10, 2020

Updated Ordering Information table.

Added Revision History

Updated Disclaimer.