ICL7660A Просмотр технического описания (PDF) - Intersil

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производитель

ICL7660A

Super Voltage Converters

Intersil 

ICL7660S, ICL7660A

V+

+

C1

-

1

8

2 ICL7660S 7

3 ICL7660A 6

4

5

-+

C2

D3

VOUT = -VIN

-

D1

C3

+

D2

VOUT = (2V+) -

(VFD1) - (VFD2)

+

- C4

FIGURE 19. COMBINED NEGATIVE VOLTAGE CONVERTER

AND POSITIVE DOUBLER

Voltage Splitting

The bidirectional characteristics can also be used to split a

high supply in half, as shown in Figure 20. The combined

load will be evenly shared between the two sides, and a high

value 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).

+

RL1

50µF

-

1

V+

8

VOUT

=

V+ -

2

V-

+

50µF

-

2 ICL7660S 7

3 ICL7660A 6

RL2

4

5

+

50µF

-

V-

FIGURE 20. SPLITTING A SUPPLY IN HALF

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”.

+8V

56k

50k

100k

50k

+8V

-

ICL7611

+

ICL8069

+

100µF -

100Ω

-

10µF

+

1

8

2 ICL7660S 7

3 ICL7660A 6

4

5

VOUT

800k

250k

VOLTAGE

ADJUST

-

100µF

+

FIGURE 21. REGULATING THE OUTPUT VOLTAGE

11

FN3179.7

January 23, 2013

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