TC7660_02 datasheet(9/18 Pages) MICROCHIP

9 / 18 page

 2002 Microchip Technology Inc.

DS21465B-page 9

TC7660

FIGURE 5-7:

Combined Negative

Converter And Positive Multiplier.

5.7

Efficient Positive Voltage

Multiplication/Conversion

Since the switches that allow the charge pumping

operation are bidirectional, the charge transfer can be

performed

backwards

easily

forwards.

Figure 5-8 shows a TC7660 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 ini-

tial inefficient pump, as shown in Figure 5-7, could be

used to start this circuit up, after which it will bypass the

other (D1 and D2 in Figure 5-7 would never turn on), or

else the diode and resistor shown dotted in Figure 5-8

can be used to "force" the internal regulator on.

FIGURE 5-8:

Positive Voltage

Conversion.

VOUT =

TC7660

V+

(2 V+) - (2 VF)

VOUT

= -V+

VOUT = -V

Ω

V - input

TC7660

10 µF

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