HT7660 datasheet(3/10 Pages) HOLTEK

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Application Circuits

Simple Negative Voltage Converter

Simple Voltage Multiplier

HT7660

Rev. 1.10

January 21, 2003

Functional Description

HT7660 needs only two external polarized electrolytic

capacitors to complete a negative voltage converter.

HT7660 has four MOS power switches: S1, S2, S3 and

S4. For the first half cycle, when S2 and S4 are open,

Capacitor C1 is charged to a voltage VDD through S1

and S3. During the second half cycle, when S1 and S3

are open, the charge on Capacitor C1 is shifted to Ca-

pacitor C2 through S2 and S4. Thereby, the voltage

across Capacitor C2 is VDD. Because the positive termi-

nal of C2 is connected to VSS, we get a

-VDD voltage at

VOUT pin.

For high voltage operation, the LV pin is left floating to

enable the voltage regulator. This can reduce the cur-

rent consumption of the RC oscillator, and thus get a

fixed switching frequency fOSC with high voltage range.

For low voltage operation, the LV pin is connected to

VSS to bypass the voltage regulator of which inherent

voltage drop can degrade the operation at low voltages.

A capacitor may be connected between VDD and pin

OSC to lower the switching fOSC, and an external clock

may be added to replace the built-in RC oscillator.

V D D

V S S

S 1

C 2

S 3

C A P +

C A P -

S 4

V S S

V O U T = - V D D

C 1

S 2

The operating mode of HT7660

B O O S T

V D D

C A P +

V S S

C A P -

H T 7 6 6 0

V D D

L V

1 0 m .

V O U T = - V D D

V O U T

C A P +

C A P -

H T 7 6 6 0

V D D

1 0 m .

C A P +

C A P -

H T 7 6 6 0

V D D

1 0 m .

V O U T

1 0 m .

V O U T = - 2 V D D

1 0 m .

V O U T

V S S

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