Datasheet HT7660 Datasheet (Holtek Semiconductor Inc)

CMOS Switched-Capacitor Voltage Converter

Features

Simple conversion of VDDto -V

·

Cascade connection (two devices are

·

connected, V
Boost pin for higher switching frequency

·

Easy to use

·

-

Requires only two external capacitors

= -2VDD)

OUT

Applications

RS-232 power supply

·

On board negative supply for dynamic

·

RAMS
Supply voltage splitter, VO= ± VDD/2

·

General Description

HT7660 is a monolithic CMOS switched-capaci­tor voltage converter. HT7660 is designed to
complete a voltage conversion from positive to
negative. The only required external compo
nents aretwo low cost electrolytic capacitors.

HT7660 includes a voltage regulator, an RC os­cillator and four output power MOS switches.

DD

HT7660

No external diode required

·

Typically with no load voltage conversion,

·

99.9% efficiency
Typical power efficiency is 98%

·

Wide operating voltage range: 3V to 12V

·

Operation amplifier supply

·

Data acquisition systems

·

Positive voltage doubler

·

The frequency of an RC oscillator can be low
ered by adding an external capacitor between
V

and the OSC pin, or an external clock can

DD

be connected to the OSC pin to replace the origi

­nal oscillator. The LV terminal may be tied to
VSS to disable the voltage regulator. By doing
this, low voltage operation can be improved.

-

-

Block Diagram

OSC

BOOST

LV

RC

Oscillator

Voltage

Regulator

VSS

Voltage

Level Shifter

Logic

Network

1 November 30, 1999

VDD

CAP+

CAP

VOUT

Pin Assignment

HT7660

BOOST

CAP+

VSS

CAP

1

2

3

-

4

VDD

8

OSC

7

LV

6

VOUT

5

H T 7 6 6 0

8 DIP/SOP

Pin Description

Pin No. Pin Name I/O

1 BOOST I

2 CAP+ O CMOS

3 VSS

4

CAP-

5 VOUT O NMOS

6LV I

7 OSC I/O

8 VDD

¾¾

O NMOS

¾¾

Internal

Connection

CMOS

Pull-low

¾

Transmission

Gate

Description

Higher switching frequency selection input

This pin is connected to the positive terminal of Ca
pacitor C1 for a charge pump

Negative power supply, ground

This pin is connected to the negative terminal of Ca
pacitor C1 for a charge pump

This pin is connected to the negative terminal of Ca
pacitor C2 for charge reservoir. Output voltage pass
through this pin

Floating this pin enables the voltage regulator. Con­nect this pin to VSS (Ground) to bypass voltage reg­ulator and improve low voltage operation

External clock input pin. This pin can be connected
with an external capacitor to reduce switching fre­quency

Positive power supply

-

-

-

2 November 30, 1999

Absolute Maximum Ratings

HT7660

Supply Voltage ..............................-0.3V to 13V

Operating Temperature ..............-40°Cto85°C

Storage Temperature.................-50°Cto125°C

Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maxi

mum Ratings² may cause substantial damage to the device. Functional operation of this device
at other conditions beyond those listed in the specification is not implied and prolonged expo
sure to extreme conditions may affect device reliability.

Electrical Characteristics

Ta=25°C

Test Conditions

Symbol Parameter

V

DD

I

STB

f

OSC

R

OUT

V

CON-EFF

P

EFF

Operating Voltage

Standby Current

System Frequency

Output Source Resistance

Voltage Conversion Efficiency

Power Efficiency

DD

Conditions

V

¾¾

3V

No load

5V

3V

¾

5V 5 10

I

OUT

I

OUT

=10mA

=20mA

3V

5V

3V

No load

5V 99 99.9

3V

5V 96 98

5kW

R

L=

Min. Typ. Max. Unit

3

¾

12 V

¾

26 100

mA

80 160

¾

2.5 4

¾

kHz

¾

97 150

¾

W

60 100

¾

99

¾¾

%

¾

96

¾¾

%

¾

-

-

3 November 30, 1999

Functional Description

HT7660 needs only two external polarized elec
trolytic capacitors to complete a negative volt
age 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 volt
age V
half cycle, when S1 and S3 are open, the charge
on Capacitor C1 is shifted to Capacitor C2
through S2 and S4. Thereby, the voltage across
Capacitor C2 is V
minal of C2 is connected to V
voltage at V

through S1 and S3. During the second

DD

. Because the positive ter

OUT

DD

pin.

, we get a -V

SS

DD

For high voltage operation, the LV pin is left

­floating to enable the voltage regulator. This

­can reduce the current consumption of the RC
oscillator, and thus get a fixed switching fre
quency Fosc with high voltage range. For low
voltage operation, the LV pin is connected to

­V

to bypass the voltage regulator of which in

SS

herent voltage drop can degrade the operation
at low voltages.

A capacitor may be connected between V
pin OSC to lower the switching Fosc, and an ex

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

HT7660

and

DD

-

-

-

V

DD

V

SS

S1

S3

CAP+

C1

CAP

S2

V

SS

C2

S4

-

V

= -V

OUT

DD

The operating mode of HT7660

4 November 30, 1999

Application Circuits

Simple negative voltage converter

HT7660

Simple voltage multiplier

2

CAP+

10mF

4

CAP

3

VSS

V

10mF

-

H T 7660

DD

VDD

VOUT

1

2

4

3

BOOST

CAP+

CAP

VSS

8

5

-

H T 7660

V

DD

10mF

VDD

LV

VOUT

V

DD

8

6

5

= -V

V

OUT

DD

10mF

8

2

4

3

CAP+

CAP

VSS

VDD

VOUT

5

10mF

= -2V

V

OUT

DD

-

H T 7660

10mF

5 November 30, 1999

External switching frequency

10mF

Lower switching frequency

10mF

2

4

3

CAP+

CAP

VSS

2

4

3

-

H T 7660

CAP+

CAP

-

VSS

VDD

OSC

VDD

OSC

HT7660

V

DD

8

1k

7

5

8

7

5

V

DD

W

CMOS
Gate

V

OUTVOUT

10mF

V

DD

C

OSC

V

OUTVOUT

10mF

H T 7660

N ote: C OSC is te n s o f p ic o fa ra d

6 November 30, 1999

Positive voltage doubler

2

3

CAP+

VSS

VDD

VOUT

HT7660

V

DD

8

D1

5

D2

V

= 2V

OUT

DD -2VD

Voltage splitter

H T 7660

10mF10mF

N ote: V D is forw ard voltage drop of diode D1 and D 2

R

L1

47mF

47mF

2

4

3

CAP+

CAP

VSS

-

H T 7660

V

V

DD

EE

R

OUT

L2

-

=

2

V

47mF

VDD

LV

VOUT

8

6

5

V

DD

V

EE

7 November 30, 1999

Combined negative voltage converter and positive voltage doubler

V

DD

8

VDD

D1

-

VOUT

5

10mF

4

2

3

CAP+

CAP

VSS

10mF

HT7660

V

= -V

OUT

DD

H T 7660

10mF

D2

10mF

N ote: V D is forw ard voltage drop of diode D1 and D 2

V

OUT

= 2VDD -2V

D

8 November 30, 1999

HT7660

Holtek Semiconductor Inc. (Headquarters)

No.3 Creation Rd. II, Science-based Industrial Park, Hsinchu, Taiwan, R.O.C.
Tel: [phone]
Fax: [phone]

Holtek Semiconductor Inc. (Taipei Office)

5F, No.576, Sec.7 Chung Hsiao E. Rd., Taipei, Taiwan, R.O.C.
Tel: [phone]
Fax: [phone]
Fax: [phone] (International sales hotline)

Holtek Semiconductor (Hong Kong) Ltd.

RM.711, Tower 2, Cheung Sha Wan Plaza, 833 Cheung Sha Wan Rd., Kowloon, Hong Kong
Tel: [phone]
Fax: [phone]

Copyright Ó 1999 by HOLTEK SEMICONDUCTOR INC.

The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek
assumes no responsibility arising from the use of the specifications described. The applications mentioned hereinare
used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications
will be suitable without further modification, nor recommends the use of its products for application that may pres
ent a risk to human life due to malfunction or otherwise. Holtek reserves the right to alter its products without prior
notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw.

9 November 30, 1999

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