9

TC7660

CHARGE PUMP DC-TO-DC

VOLTAGE CONVERTER

© 2001 Microchip Technology Inc.

DS21465A

TC7660-7 9/30/96

1

2

3

4

8

7

6

5

+

VOUT = –V

–

10

µF

+

1 M

Ω

V– INPUT

C1

10

µF

TC7660

+

R

L1

R

L2

V

OUT

=

V

+

–V

–

2

50

µF

100 k

Ω

50

µF

V

+

V

–

50

µF

+

1 M

Ω

1

2

8

7

TC7660

3

4

6

5

+

–

–

Voltage Splitting

The same bidirectional characteristics used in Figure 10

can also be used to split a higher supply in half, as shown in

Figure 11. The combined load will be evenly shared be-

tween the two sides. Once again, 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 5, +15V can be converted (via +7.5V and –7.5V) to a

nominal – 15V, though with rather high series resistance

(~250

Ω).

Figure 10. Positive Voltage Conversion

Figure 11. Splitting a Supply in Half