Vishay GS7660 Switched-capacitor voltage converter Datasheet

GS7660
Vishay
New Product
formerly General Semiconductor
Switched-Capacitor Voltage Converter
Description
The GS7660 is a monolithic CMOS switched capacitor
voltage converter, designed to be an improved direct
replacement of the popular ICL7660, MAX1044 and
LTC1044. They perform supply voltage conversions from
positive to negative for an input voltage range of +1.5V to
+6.0V to their negative complements of –1.5V to –6.0V.
The input voltage can also be doubled (VOUT = 2VIN),
halved (VOUT = VIN/2), or multiplied (VOUT = ± n.VIN).
SO-8
8 Pin Dip
Features
• Low output impedance ( typical 35Ω at VIN = 5V )
• Low quiescent current ( typical 36µA at VIN = 5V)
• High power conversion efficiency ( typical 98% )
• Simple and accurate voltage conversion from
positive to negative polarities
• Improved latch-up protection
Contained on the chip are a series Power Supply regulator, Oscillator, control Circuitry and four Power MOS
Switches. The oscillator, when unloaded, oscillates at a
nominal frequency of 10 kHz, with an Input voltage of 5.0V.
This frequency can be lowered by the addition of an external
capacitor to the “Osc” terminal or overdriven by an external
frequency source.
An Oscillator “boost” function is available to increase the
oscillator frequency which will optimize performance of
certain parameters. The Lv input can be connected to
ground to improve low voltage operation (VIN ≤ 3V), or left
open for input voltages greater than 3V to reduce power
dissipation.
• No external diodes required
Applications
• – 5V supply from + 5V logic supply
• EIA/TIA – 232E and EIA/TIA – 562 power supplies
• Portable telephones
• Data acquisition systems
• Personal communications equipment
The GS7660 provides superior performance over earlier
designs by combining low output impedance and low quiescent current with high efficiency and by eliminating diode
voltage drop losses. The only external components
required are two low cost electrolytic capacitors.
• Panel meters
• Handheld instruments
Typical Application Circuit
VIN (1.5V to 6V)
1
5
2
10µF
C1
Required for
VIN 3V
6
GS7660
+
3
7
4
8
VOUT = --VIN
+
10µF
C2
Negative Voltage Converter
Document Number 74819
24-May-02
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GS7660
Vishay
formerly General Semiconductor
Ordering Information
Order
Number
Pin Configuration
GS7660x x
GS7660IS
(Plastic SO-8)
Top View
Boost 1
8 VIN
Cap+ 2
7 OSC
GND 3
6 LV
Cap-- 4
5 VOUT
Package Outline
P: Plastic Dip
S: SO-8
Operating Junction
Temperature Range
I: –40°C to +125°C
GS7660IP
(8-Pin Plastic Dip)
Top View
Boost
1
8
VIN
Cap+
2
7
OSC
GND
3
6
LV
Cap--
4
5
VOUT
Test Circuit
10 µF
+
C1
VIN
IS
1
BOOST
2
CAP+
3
GND
LV
6
4
CAP-
VOUT
5
VIN
8
IL
OSC 7
GS7660
COSC
External
Oscillator
RL
VOUT
C2
10µF
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+
Document Number 74819
24-May-02
GS7660
Vishay
formerly General Semiconductor
Maximum Ratings Ratings at 25°C ambient temperature unless otherwise specified.
Parameter
Symbol
Value
Unit
Supply Voltage (VIN to GND)
VIN
6.0
V
Input Voltage (Pin 1, 6 and 7)
VIN
–0.3V ≤ VIN ≤ (VIN, +0.3V)
V
LV Input Current
LV1
20
µA
Output Short Circuit Duration
Continuous
Operating Junction Temperature Range
TJ
–40 to +125
°C
Storage Temperature Range
TS
–65 to +150
°C
Continuous Power Dissipation
Plastic Dip (Derate 7.9mW/°C above 70°C)
SO-8 (Derate 6mW/°C above 70°C)
PD
630
480
mW
Note: (1) Stresses beyond those listed above may cause permanent damage to the device. Operating at the levels stated above may affect device reliabllity.
Electrical Characteristics V
IN
Parameter
Supply Current
= 5.0V LVPin = open, Oscillator free running, I load = 0mA, TA = –40°C to +125°C unless otherwise noted.
Conditions
LV = Open
TA = 25°C
Pin 1,7, VIN = 3V
Supply Voltage (1)
RL = 10KΩ, LV Open
RL = 10KΩ, LV Gnd
Power Efficiency
Voltage Conversion Efficiency
Oscillator Sink or
Source Current
Oscillator Impedance
Typ
Max
–
36
70
–
–
100
–
20
–
3.0
1.5
–
–
6.0
6.0
–
35
70
–
–
110
–
–
250
–
–
370
Unit
µA
V
IL = 20mA, FOSC = 10kHz
LV = Open
TA = 25°C
IL = 3mA, FOSC = 1kHz
VIN = 2V, LV to Gnd
TA = 25°C
COSC = 0pF, LV to Gnd
Pin 1 Open
VIN = 5.0V
–
5.0
–
VIN = 2.0V
2.0
–
–
96
98
–
%
Output Resistance
Oscillator Frequency
Min
RL = 5K, FOSC =10kHz, LV = Open
Ω
kHz
LV = Open
TA = 25°C
98
99.9
–
%
VOSC = 0V or VIN
LV = Open
Pin 1 = 0V
–
–
3.0
µA
Pin 1 = VIN
–
–
20
VIN = 2.0V
–
1.0
–
mΩ
VIN = 5.0V
–
100
–
kΩ
TA = 25°C
Note: (1) The GS7660 can operate with or without an external output diode over the full temperature and voltage range. Eliminating the diode reduces voltage
drop losses.
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24-May-02
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GS7660
Vishay
formerly General Semiconductor
Ratings and
Characteristic Curves (T
A
= 25°C unless otherwise noted)
Fig. 2 – Power Efficiency
vs. Load Current (VIN = 5V)
Fig. 1 – Supply Current
vs. Supply Voltage
100
50
LV = Open
30
20
LV = GND
10
Power Efficiency (%)
Supply Current (A)
90
Boost = Open
40
Boost = Open
LV = Open
80
70
60
50
0
1
2
3
4
5
6
0
20
30
40
50
60
70
Load Current (mA)
Fig. 3 – Output Voltage
vs. Load Current (VIN = 5V)
Fig. 4 – Output Voltage
vs. Load Current (VIN = 2V)
--2.5
2
Output Voltage (V)
Boost = Open
LV = Open
--3.0
Output Voltage (V)
10
Supply Voltage (V)
--3.5
--4.0
--4.5
Boost = Open
LV = GND
1
0
--1
--2
--5.0
0
10
20
30
40
50
60
70
--40
--20
0
20
40
60
80
100
Load Current (mA)
Load Current (mA)
Fig. 5 – Oscillator Frequency
vs. Supply Voltage
Fig. 6 – Oscillator Frequency
vs. Value of COSC
120
LV = Open
LV = GND
50
40
30
LV = Open
20
LV = GND
10
5
Boost = Open
1
2
3
4
5
Supply Voltage, VIN (V)
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6
Oscillation Frequency, FOSC (KHz)
Oscillation Frequency, FOSC (KHz)
35
Boost = Vin
60
30
25
Boost = VIN
20
15
10
Boost = Open
5
0
10
100
1000
10000
External Capacitor (Pin 7 to GND), COSC (pF)
Document Number 74819
24-May-02
GS7660
Vishay
formerly General Semiconductor
Pin Description
Pin
Name
BOOST
1
N.C.
Function
Frequency Boost. Connecting BOOST to VIN increases the oscillator frequency by a factor of five.
When the oscillator is driven externally, BOOST has no effect and should be left open.
No Connection
2
CAP+
Connection to positive terminal of Charge-Pump Capacitor
3
GND
Ground. For most applications, the positive terminal of the reservoir capacitor is connected to this pin.
4
CAP–
Connection to negative terminal of Charge-Pump Capacitor
5
VOUT
Negative Voltage Output. For most applications, the negative terminal of the reservoir capacitor is
connected to this pin.
6
LV
7
OSC
8
VIN
Low-Voltage Operation. Connect to ground for supply voltages below 3.5V.
Oscillator Control Input. Connecting an external capacitor reduces the oscillator frequency.
Power Supply Positive Voltage Input. (1.5V to 6V). VIN is also the substrate connection.
Detailed Description
The GS7660 is a charge-pump voltage converter. The
basic operations is as follows: Switch pairs S1, S2 and S3,
S4 (Fig.7) are alternately closed and opened at the rate of
the oscillator frequency divided by two.
S1
S2
VIN
C1
During the first half of the cycle, when S1 and S2 are
closed and S3 and S4 are open, bucket capacitor C1 is
charged by input voltage. During the second half of the
cycle, when the switches assume the opposite state,
capacitor C1 is connected in parallel with output capacitor
C2 and any voltage differential causes a transfer of charge
from C1 to C2. This process will continue until the voltage
across C2 equals the –VIN voltage.
In normal operation, the output voltage will be less than
–VIN, since the switches have internal resistance and C2 is
being discharged by the load.
Document Number 74819
24-May-02
S3
S4
C2
VOUT = -(VIN)
Fig. 7 – Ideal Voltage Inverter
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GS7660
Vishay
formerly General Semiconductor
Design Information
f
VIN
VOUT
Low Voltage (LV) Pin
Fig. 10 (below) shows a simplified circuit diagram of the
GS7660.
C1
C2
RLOAD
Fig. 8 – Switched Capacitor Model
To better understand the theory of operation, a review of
the basic switched capacitor building block is helpful (see
Fig. 8). Referring to Fig. 8 and looking at one full cycle of
operation, the charge being drained by the load is Qavg or
IL x T (T being the time period of one full cycle).
All the charge (∆q) flowing into the output is being delivered
by the input to C1 during only half the cycle. Under steadystate condition, C1 will charge to the level of the input voltage
(VIN) and discharge to the peak level of the output voltage
(VOUT). Therefor the voltage change on C1 is VIN – VOUT.
It shows a voltage regulator between the VIN and Gnd, in
series with the Oscillator.
Grounding the LV pin removes the regulator from this
series path and improves low voltage performance down to
1.5V. For supply voltages less than 3.0V, the LV pin should
be connected to ground and left open for voltages above
3.0V.
The LV pin can be left grounded over the total range of
Input Voltages. This will improve low voltage operation and
increase oscillator frequency. The disadvantage is
increased quiescent current and reduced efficiency at
higher voltages.
VIN
pin 8
S1
CAP+
pin 2
S2
S3
S4
Qavg = ∆q = C1(Vin –Vout)
1
(Vin –Vout)
and REQUIV =
(See fig. 9)
1
f x C1
f x C1
Where f is one-half the oscillator frequency. This resistance
is a major component of the output resistance of switched
capacitor circuits.
With C1 = C2 = 10µF and Fosc = 10kHz, this resistance
represents 20Ω.
BOOST
pin 1
OSC
pin 7
Q
÷2
LV
pin 6
Q
INTERNAL
REGULATOR
IL =
1M
OSCILLATOR
IL x T = C1(Vin –Vout) or IL = f x C1(Vin –Vout) f = 1/T
GND
pin 3
VOUT
pin 5
CAPpin 4
Fig. 10 – Functional Diagram
Under the same conditions, the typical value in the
“Electrical Characteristics” section of the GS7660 is 35Ω.
REQUIV
VIN
VOUT
REQUIV =
1
f × C1
C2
RLOAD
Fig. 9 – Equivalent Impedance
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Document Number 74819
24-May-02
GS7660
Vishay
formerly General Semiconductor
Oscillator Frequency Control
For normal operation, the Boost, and Oscillator Pins
should be left open. Connecting the Boost pin to the VIN
supply will increase oscillator frequency by a factor of 5,
resulting in lower Output Impedance, less ripple, smaller
required capacitor values and moves the switching noise
out of the audio band. Lower oscillator frequency reduces
quiescent current.
VIN (1.5V to 6V)
IOUT
R1
200Ω
C1
10µF
1N914
2
7
7
3
6
6
4
5
+
2VIN
(3.0V to 12V)
8
1
8
GS7660
+ C2
10µF
500kΩ
5
The oscillator frequency can be further controlled by driving
the oscillator input from an external frequency source or
lowered , by connecting an external capacitor to the oscillator input.
Efficiency, Output Impedance and Output Ripple
The power efficiency of a switched capacitor voltage converter is dependent on the internal losses.
The total power loss is:
P outp. P switch P cap.
+
+
∑P loss =
+ P conversion
Res.
Res.
Res.
P outp. = IL2
f.C1
Res.
VIN
(1.5V to 9.0V)
1
8
8
2
7
7
3
4
f = f osc/2
+
Vd
GS7660
–
6
5
6
5
Required for
V+ < 3.0V
+
Vd
–
+
+
10µF
VOUT =
2VIN–2VD
10µF
P switch P cap.
2
+
Res.
Res. = IL 8 RSW + 4 Esr C1 + Esr C2
(
)
P conversion =
f
Figs. 11a and 11b – Voltage Doubler
[ 12 C1(Vin –Vout ) + 12 C2 (V ripple – 2 Vout. V ripple)]
2
2
2
Figure 11 shows two methods of voltage doubling. In Fig.
11a , R1 is added to ensure that doubling is not inhibited
by a non-destructive latch-up at start-up. This condition can
occur, since the ground pin (pin 3) is raised above the VIN
pin ( pin 8) during start-up.
f = f osc/2
Vripple
V ripple = IL
Voltage Doubling
1
( 2. C2
+ 2 Esr C2)
.f
f = f osc/2
R1 increases output impedance and in higher current
applications where the voltage drop across R1 exceeds a two
diode drop, the doubling circuit of Fig 11b is recommended.
The voltage doubler of Fig. 11a is more accurate at low
load currents since the voltage drop across the diode is not
reflected at the output.
Document Number 74819
24-May-02
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GS7660
Vishay
formerly General Semiconductor
Ultra Precision Voltage Divider
(VIN)
An ultra precision voltage divider is shown below in Fig. 12.
To achieve the 0.002% accuracy, the load current has to be
kept below 100nA. However with a slight loss in accuracy,
the load current can be increased.
C1
10µF +
1
8
8
2
7
7
3
6
6
3
6
4
5
5
4
5
GS7660
8
1
C1
10µF +
7
2
GS7660
VOUT =
--(VIN)
VIN (3.0V to 12V)
C1 +
10µF
1
8
8
2
7
7
3
6
6
4
5
5
1/4 CD4077
C2
20µF +
GS7660
Fig. 14 – Paralleling for Lower Output Resistance
VIN ±0.002%
2
+
C2
10µF
Paralleling For Lower Output Impedance
Required for VIN < 3V
IL ≤ 100nA
Fig. 12 – Ultra Precision Voltage Divider
Fig. 14 above shows two GS7660s connected in parallel to
achieve a lower output resistance. If the output resistance
is dominated by 1/ f C1, which is normally the case with the
GS7660, increasing C1 offers a greater advantage than
the paralleling of circuits.
Battery Splitter
Fig. 13 shows a simple solution to obtain complementary +
and – supplies from a single power supply. The output voltages are + and – half the supply voltage. Good accuracy
requires low load currents.
A disadvantage is the requirement of a floating input supply,
which in the case of a battery is not an issue.
1
VB +
(6V) –
8
7
7
3
6
6
4
5
5
2
C1
10µF
+
–
8
GS7660
+VB /2 (3.0V)
Required for VB < 6V
–VB /2 (–3.0V)
– C2
+ 10µF
Output Common
Fig. 13 – Battery Splitter
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Document Number 74819
24-May-02
GS7660
Vishay
formerly General Semiconductor
SO-8 Case Outline
5.00
4.80
8
7
6
5
4.00
3.80
6.20
5.80
1
2
3
4
Dimensions in millimeters
0.51
0.33
1.27 (typ.)
0.25
0.19
1.75
1.35
0.25
0.10
1.27
0.40
8-Pin Dip Case Outline
10.16
9.01
7.12
6.09
Dimensions in millimeters
8.26
7.62
4.96
2.92
3.81
2.92
0.56
0.35
Document Number 74819
24-May-02
0.36
0.20
0.381
(min.)
10.92
(max.)
2.54 (Typ.)
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