Holtek HT7660 Cmos switched-capacitor voltage converter Datasheet

HT7660
CMOS Switched-Capacitor Voltage Converter
Features
·
·
·
·
Simple conversion of VDD to -VDD
Cascade connection (two devices are
connected, VOUT= -2 VDD)
Boost pin for higher switching frequency
Easy to use
- Requires only two external capacitors
·
·
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
·
·
Applications
·
·
·
RS-232 power supply
On board negative supply for dynamic
RAMS
Supply voltage splitter, VO= ± VDD/2
General Description
The frequency of an RC oscillator can be lowered by adding an external capacitor between
VDD and the OSC pin, or an external clock can
be connected to the OSC pin to replace the original oscillator. The LV terminal may be tied to
VSS to disable the voltage regulator. By doing
this, low voltage operation can be improved.
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 components are two low cost electrolytic capacitors.
HT7660 includes a voltage regulator, an RC oscillator and four output power MOS switches.
Block Diagram
VDD
OSC
BOOST
RC
Oscillator
CAP+
Voltage
Level Shifter
CAP
VOUT
LV
Voltage
Regulator
Logic
Network
VSS
1
November 30, 1999
HT7660
Pin Assignment
B O O
C A
V
C A
S T
P +
S S
P 1
8
2
7
3
6
4
5
V D D
O S C
L V
V O U T
H T 7 6 6 0
8 D IP /S O P
Pin Description
Pin No.
Pin Name
I/O
Internal
Connection
Description
1
BOOST
I
CMOS
Pull-low
Higher switching frequency selection input
2
CAP+
O
CMOS
This pin is connected to the positive terminal of Capacitor C1 for a charge pump
3
VSS
¾
¾
4
CAP-
O
NMOS
This pin is connected to the negative terminal of Capacitor C1 for a charge pump
5
VOUT
O
NMOS
This pin is connected to the negative terminal of Capacitor C2 for charge reservoir. Output voltage pass
through this pin
6
LV
I
¾
Floating this pin enables the voltage regulator. Connect this pin to VSS (Ground) to bypass voltage regulator and improve low voltage operation
7
OSC
I/O
8
VDD
¾
Negative power supply, ground
External clock input pin. This pin can be connected
Transmission
with an external capacitor to reduce switching freGate
quency
¾
Positive power supply
2
November 30, 1999
HT7660
Absolute Maximum Ratings
Supply Voltage ..............................-0.3V to 13V
Operating Temperature ..............-40°C to 85°C
Storage Temperature.................-50°C to 125°C
Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maximum 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 exposure to extreme conditions may affect device reliability.
Electrical Characteristics
Symbol
Parameter
VDD
Operating Voltage
ISTB
Standby Current
fOSC
System Frequency
ROUT
Output Source Resistance
VCON-EFF
Voltage Conversion Efficiency
PEFF
Power Efficiency
Ta=25°C
Test Conditions
VDD
Conditions
¾
¾
3V
5V
3V
5V
No load
¾
Min.
Typ. Max. Unit
3
¾
12
¾
26
100
¾
80
160
2.5
4
¾
5
10
¾
3V
IOUT=10mA
¾
97
150
5V
IOUT=20mA
¾
60
100
99
¾
¾
99
99.9
¾
96
¾
¾
96
98
¾
3V
5V
3V
5V
3
No load
RL=5kW
V
mA
kHz
W
%
%
November 30, 1999
HT7660
Functional Description
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 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.
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 Capacitor C2
through S2 and S4. Thereby, the voltage across
Capacitor C2 is VDD. Because the positive terminal of C2 is connected to VSS, we get a -VDD
voltage at VOUT pin.
V
D D
S 1
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.
C A P +
S 2
C 1
V
V
S S
S S
C 2
S 4
S 3
C A P -
V
O U T
= - V
D D
The operating mode of HT7660
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November 30, 1999
HT7660
Application Circuits
Simple negative voltage converter
V
V
D D
1
B O O S T
2
V D D
C A P +
L V
1 0 m F
4
C A P -
3
V O U T
D D
8
6
5
V
V S S
O U T
= -V
D D
1 0 m F
H T 7 6 6 0
Simple voltage multiplier
V
2
V D D
C A P +
D D
8
2
1 0 m F
3
4
C A P V S S
V O U T
V D D
C A P +
8
1 0 m F
5
4
3
H T 7 6 6 0
C A P -
V O U T
5
V
O U T
= - 2 V
D D
1 0 m F
V S S
H T 7 6 6 0
1 0 m F
5
November 30, 1999
HT7660
External switching frequency
V
2
V D D
C A P +
O S C
1 0 m F
4
C A P -
3
V O U T
V S S
D D
8
V
D D
1 k W
7
C M O S
G a te
5
V
O U T
1 0 m F
H T 7 6 6 0
Lower switching frequency
V
2
V D D
C A P +
O S C
1 0 m F
4
3
C A P V S S
V O U T
D D
8
C
7
O S C
5
V
O U T
1 0 m F
H T 7 6 6 0
N o te : C
O S C
is te n s o f p ic o fa r a d
6
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HT7660
Positive voltage doubler
V
2
3
8
V D D
C A P +
D 1
V S S
V O U T
D 2
5
V
1 0 m F
H T 7 6 6 0
N o te : V
D D
O U T
= 2 V
D D
- 2 V
D
1 0 m F
is fo r w a r d v o lta g e d r o p o f d io d e D 1 a n d D 2
D
Voltage splitter
V
R
4 7 m F
L 1
V
R
O U T
D D
=
V
D D -
2
V
2
E E
L 2
V D D
C A P +
L V
4 7 m F
4
3
C A P -
V O U T
8
6
5
V S S
4 7 m F
H T 7 6 6 0
V
7
E E
November 30, 1999
HT7660
Combined negative voltage converter and positive voltage doubler
V
2
8
V D D
C A P +
D D
V
D 1
1 0 m F
4
3
C A P -
D D
O U T
= 2 V
D D
1 0 m F
V S S
D 2
V
1 0 m F
D
= - V
5
V O U T
H T 7 6 6 0
N o te : V
O U T
- 2 V
D
1 0 m F
is fo r w a r d v o lta g e d r o p o f d io d e D 1 a n d D 2
8
November 30, 1999
HT7660
Holtek Semiconductor Inc. (Headquarters)
No.3 Creation Rd. II, Science-based Industrial Park, Hsinchu, Taiwan, R.O.C.
Tel: 886-3-563-1999
Fax: 886-3-563-1189
Holtek Semiconductor Inc. (Taipei Office)
5F, No.576, Sec.7 Chung Hsiao E. Rd., Taipei, Taiwan, R.O.C.
Tel: 886-2-2782-9635
Fax: 886-2-2782-9636
Fax: 886-2-2782-7128 (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: 852-2-745-8288
Fax: 852-2-742-8657
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 herein are
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 present 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.
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November 30, 1999
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