6

TC7660H

HIGH FREQUENCY 7660 DC-TO-DC

VOLTAGE CONVERTER

TC7660H-2 10/1/96

© 2001 Microchip Technology Inc.

DS21466A

Efficient Positive Voltage Multiplication/

Conversion

Since the switches that allow the charge pumping op-

eration are bidirectional, the charge transfer can be per-

formed backwards as easily as forwards. Figure 9 shows a

TC7660H transforming –5V to +5V (or +5V to +10V, etc.).

The only problem here is that the internal clock and switch-

drive section will not operate until some positive voltage has

been generated. An initial inefficient pump, as shown in

Figure 9, could be used to start this circuit up, after which it

will bypass the diode and resistor shown dotted in

Figure 9.

1

2

3

4

8

7

6

5

+

VOUT = –V

–

1.0

µF

+

1 M

Ω

V– INPUT

C1

1.0

µF

TC7660H

Figure 9. Positive Voltage Conversion

500

450

400

200

150

100

50

0

–55

–25

0

+25

+50

+75 +100 +125

Output Source Resistance vs. Temperature

V + = +2V

V + = +5V

78

10k

1k

100

Ω

TA = +25°C

Output Source Resistance vs. Supply Voltage

6

5

4

3

2

1

0

SUPPLY VOLTAGE (V)

TEMPERATURE (

°C)

IOUT = 1 mA

10

Ω

OUTPUT CURRENT (mA)

0

0

Output Voltage vs. Output Current

–1

–2

–3

–4

–5

–6

–7

–8

–9

–10

10

20 30 40 50

60 70 80

90 100

TA = +25°C

LV OPEN

LOAD CURRENT (mA)

Output Voltage vs. Load Current

1

0

5

4

3

2

0

–1

–2

–3

–4

–5

10

20

30

40

50

60

70

80

TA = +25°C

V+ = +5V

SLOPE 55

Ω