5

HIGH FREQUENCY 7660 DC-TO-DC

VOLTAGE CONVERTER

TC7660H

TC7660H-2 10/1/96

© 2001 Microchip Technology Inc.

DS21466A

Figure 5. Paralleling Devices Lowers Output Impedance

1

2

3

4

8

7

6

5

TC7660H

V

+

1

2

3

4

8

7

6

5

TC7660H

C1

RL

C2

C1

"n"

"1"

+

RL

1

2

3

4

8

7

6

5

TC7660H

+

V +

+

CMOS

GATE

1.0

µF

VOUT

1.0

µF

1 k

Ω

V +

Figure 6. External Clocking

Figure 7. Positive Voltage Multiplier

Positive Voltage Multiplication

The TC7660H may be employed to achieve positive

voltage multiplication using the circuit shown in Figure 7. In

this application, the pump inverter switches of the TC7660H

or twice the supply voltage minus the combined forward

of 10mA, it will be approximately 60

Ω.

Combined Negative Voltage Conversion

and Positive Supply Multiplication

Figure 8 combines the functions shown in Figures 3 and

8 to provide negative voltage conversion and positive volt-

age multiplication simultaneously. This approach would be,

for example, suitable for generating +9V and –5V from an

perform the pump and reservoir functions, respectively, for

plied positive voltage. There is a penalty in this configuration

which combines both functions, however, in that the source

impedances of the generated supplies will be somewhat

higher due to the finite impedance of the common charge

pump driver at pin 2 of the device.

1

2

3

4

8

7

6

5

+

V +

VOUT =

(2 V +) – (2 VF)

C1

D1

+

+

C3

C4

VOUT =

– (V+– VF)

C2

TC7660H

D2

+

Figure 8. Combined Negative Converter and Positive Multiplier

1

2

3

4

8

7

6

5

V+

VOUT =

(2 V+) – (2 VF)

+

C2

D1

D2

+

C1

TC7660H