ETC ICL828IH-T

ICL828
TM
Data Sheet
June 2000
Switched-Capacitor Voltage Inverter
Features
The ICL828 IC performs supply voltage conversions from
positive to negative for an input range of +1.5V to +5.5V
resulting in complementary output voltages of -1.5V to -5.5V.
The ICL828 has a 12kHz internal oscillator and requires two
capacitors to invert the supply voltage. Cascading may be
made to increase the output voltage. The high efficiency
(greater than 90% over most of the load-current range) and
low operating current (60µA typical) make these devices
ideal for both battery-powered and board-level voltage
conversion applications.
• 5-Lead SOT23-5 Package
File Number
4835.1
• 99% Open Circuit Voltage Conversion Efficiency
• Inverts Input Supply Voltage
• High Power Supply Efficiency
• Input Voltage Range . . . . . . . . . . . . . . . . . . +1.5V to +5.5V
• May be Cascaded to Increase Output Voltage
• Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25mA
• Quiescent Current . . . . . . . . . . . . . . . . . . . . . . . . . . 60µA
Ordering Information
PART
NUMBER
ICL828IH-T
TEMP.
RANGE (oC)
-40 to 85
• Pin for Pin Compatible to MAX828
PACKAGE
PKG. NO BRAND
5 Lead SOT23 P5.064
828
• Small Package Size
Applications
• Simple Conversion . . . . . . . . . . . . . . . . . . . . . +5V to -5V
Block Diagram
• Voltage Multiplication . . . . . . . . . . . . . . . . . . VOUT = -nVIN
• Supply Splitter
- Operational Amplifiers
- Bias Supplies
NEGATIVE VOLTAGE CONVERTER
OUTPUT
VOLTAGE
OUT
C1+
1
5
+
INPUT
VOLTAGE
2
IN
+
4
3
C1-
• Hand Held Products
- Cell Phones
- PDAs
- GPS
- Pagers
• LCD Panels
GND
Pinout
ICL828 (SOT23)
TOP VIEW
1
OUT
1
IN
2
C1-
3
5
C1+
4
GND
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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ICL828
Absolute Maximum Ratings
Thermal Information
IN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6.0V, -0.3V
OUT to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -6.0V, +0.3V
OUT Output CURRENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA
OUT Short-circuit to GND . . . . . . . . . . . . . . . . . . . . . . . . . Indefinite
Thermal Resistance (Typical, Note 1)
θJA (oC/W)
SOT23 Package
240
Maximum Junction Temperature (Plastic Package) . . . . . . . .150oC
Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . -40oC to 85oC
Supply Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . 1.5V to 5.5V
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
1. θJA is measured with the component mounted on a low effective thermal conductivity test board in free air. (See Tech Brief TB379 for details.).
VIN = +5V, C1 = C2 = 10µF, TA = -40oC to 85oC, Unless Otherwise Specified
Electrical Specifications
PARAMETER
SYMBOL
Supply Current
TEST CONDITIONS
ICC
Minimum Supply Voltage
VCC
MIN
TYP
MAX
UNITS
25oC
-
60
90
µA
-40oC to 85oC
-
-
115
µA
RL = 10K, 25oC
1.25
1.0
-
V
RL = 10K, -40oC to 85oC
1.5
-
-
V
Maximum Supply Voltage
VCC
RL = 10K
-
-
5.5
V
Oscillator Frequency
fOSC
-40oC to 85oC
6
-
20
kHz
Power Efficiency
PEFF
RL = 10K, 25oC
-
98
-
%
Voltage Conversion Efficiency
VOUT / VIN
Output Resistance
RL = Open
ROUT
95
99.9
-
%
IOUT = 5mA, 25oC
-
20
50
Ω
IOUT = 5mA, -40 to 85oC
-
-
65
Ω
Typical Performance Curves
45
500
OUTPUT VOLTAGE RIPPLE (mV)
OUTPUT RESISTANCE (Ω)
40
35
30
25
20
15
10
5
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
FIGURE 1. OUTPUT RESISTANCE vs SUPPLY VOLTAGE
2
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5
400
VIN = 3.15V, VOUT = -2.5V
300
VIN = 1.9V, VOUT = -1.5V
200
VIN = 4.75V, VOUT = -4.0V
100
0
1.5
20
40
60
CAPACITANCE (µF)
FIGURE 2. OUTPUT VOLTAGE RIPPLE vs CAPACITANCE
80
ICL828
Typical Performance Curves
(Continued)
70
60
60
SUPPLY CURRENT (µA)
50
VIN = 1.5V
ROUT (Ω)
40
30
VIN = 3.3V
20
VIN = 5V
50
40
30
20
10
0
-40
10
-30 -20 -10
0
10
20
30
40
50
60
70
0
1.5
80
2.0
2.5
TEMPERATURE (oC)
FIGURE 3. ROUT vs TEMPERATURE
3.5
4.0
4.5
5.0
FIGURE 4. SUPPLY CURRENT vs VOLTAGE
100
16
95
14
VIN = 5V
VIN = 3.3V
90
12
EFFICIENCY (%)
FREQUENCY (kHz)
3.0
SUPPLY VOLTAGE (V)
10
VIN = 1.5V
8
6
80
75
4
70
2
65
0
-40 -30 -20 -10
VIN = 5V
85
VIN = 3.3V
VIN = 2V
60
0
10
20
30
40
50
60
70
0
80
10
TEMPERATURE (oC)
20
30
40
50
OUTPUT CURRENT (mA)
FIGURE 5. OSCILLATOR FREQUENCY vs TEMPERATURE
FIGURE 6. EFFICIENCY vs OUTPUT CURRENT
60
80
VIN = 4.75V, VOUT = -4V
70
40
SUPPLY CURRENT (µA)
OUTPUT CURRENT (mA)
50
VIN = 3.15V, VOUT = -2.5V
30
20
VIN = 1.9V, VOUT = -1.5V
10
60
VIN = 5V
50
VIN = 3.3V
40
30
20
VIN = 1.5V
10
0
1.5
20
40
60
CAPACITANCE (µF)
FIGURE 7. OUTPUT CURRENT vs CAPACITANCE
3
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80
0
-40 -30 -20 -10
0
10
20
30
40
50
60
70
TEMPERATURE (oC)
FIGURE 8. SUPPLY CURRENT vs TEMPERATURE
80
ICL828
Test Circuit
VIN
RL
VOUT
1
2
3
+ C3
OUT
C 1+
5
C 1-
+ C1
+ 10µF
GND
4
NOTE: VIN = +5V, C1 = C2 = C3 , TA = 25oC, unless otherwise noted.
FIGURE 9. TEST CIRCUIT
S1
5
Energy is lost only in the transfer of charge between
capacitors if a change in voltage occurs.
2
2
1
E = --- C 1 ( V 1 – V 2 )
2
10µF
10µF
2
4. The losses due to the 1/fC terms is small.
The energy lost is defined by:
C2
IN
3. The impedances of the pump and reservoir capacitors are
negligible at the pump frequency.
S2
IN
Where V1 and V2 are the voltages on C1 during the pump
and transfer cycles. If the impedances of C1 and C2 are
relatively high at the pump frequency (refer to Figure 10)
compared to the value of RL , there will be a substantial
difference in the voltages V1 and V2 . Therefore it is not only
desirable to make C2 as large as possible to eliminate output
voltage ripple, but also to employ a correspondingly large
value for C1 in order to achieve maximum efficiency of
operation.
Negative Voltage Converter
C1
4
C2
S4
S3
3
1
OUT
V OUT = -V IN
FIGURE 10. IDEALIZED NEGATIVE VOLTAGE CONVERTER
Description
The ICL828 contains all the necessary circuitry to complete
a negative converter, utilizing two external inexpensive 10µF
polarized electrolytic capacitor. The mode of operation of the
device may be understood by considering Figure 10 which
shows an idealized negative voltage converter.
Capacitor C1 is charged to a voltage, VIN , for the half cycle
when switches S1 and S3 are closed (Note: switches S2 and
S4 are open during this half cycle). During the second half
cycle of operation, switches S2 and S4 are closed, with S1
and S2 open, thereby shifting capacitor C1 negatively by VIN
Volts. Charge is then transferred from C1 to C2 such that the
voltage on C2 is exactly VIN , assuming ideal switches and
no load on C2 .
Theoretical Power Efficiency
Considerations
In theory a voltage converter can approach 100% efficiency
if certain conditions are met:
1. The driver circuitry consumes minimal power.
2. The output switches have extremely low ON resistance
and virtually no offset.
4
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The output characteristics of the circuit on the first page can
be approximated by an ideal voltage source in series with a
resistance (Figure 11). The voltage source has a value of
-(VIN). The output impedance (RO) is a function of the ON
resistance of the internal MOS switches (shown in Figure
10), the switching frequency, the value of C1 and C2 , and the
ESR (equivalent series resistance) of C1 and C2 . A good
first order approximation for RO is:
R O = 2 ( R sw1 + R sw3 + ESRC 1 )
+ 2 ( R sw2 + R sw4 + ESRC 1 ) + 1 ⁄ ( fpump ) ( C1 ) + ESRC 2
Rsw, the switch resistance, is a function of supply voltage
and temperature (see Figure 3). Careful selection of
capacitors will minimize the output resistance, and low
capacitor ESR will lower the ESR term.
VOUT
-
RO
V IN
+
FIGURE 11. EQUIVALENT CIRCUIT
Output Ripple
ESR also affects the ripple voltage seen at the output. The
total ripple is determined by 2 voltages, A and B, as shown in
Figure 12. Segment A is the voltage drop across the ESR of
C2 at the instant it goes from being charged by C1 (current
flowing into C2) to being discharged through the load
(current flowing out of C2). The magnitude of this current
change is 2 x I OUT, hence the total drop is 2 x IOUT x
ESRC2V. Segment B is the voltage change across C2 during
time t1, the half of the cycle when C2 supplies current the
ICL828
load. The drop at B is IOUT x t1 /C 2V. The peak-to-peak
ripple voltage is the sum of these voltage drops:
V
t1
1
RIPPLE ≅  ------------------------------------------- + 2 ESRC 2 × I OUT
 2 × C Xf

2 PUMP
B
0
Again, a low ESR capacitor will result in a higher
performance output.
Positive Voltage Doubling
The ICL828 may be employed to achieve positive voltage
doubling using the circuit shown in Figure 13. In this
application, the pump inverter switches of the ICL828 are
used to charge C1 to a voltage level of VIN -VF where VIN is
the supply voltage and VF is the forward voltage on C1 plus
the supply voltage (VIN) is applied through diode D2 to
capacitor C2 . The voltage thus created on C2 becomes
(2VIN) - (2VF) or twice the supply voltage minus the
combined forward voltage drops of diodes D1 and D2 .
The source impedance of the output (VOUT) will depend on
the output current.
V
A
-(VIN)
FIGURE 12. OUTPUT RIPPLE
V+
D1
5
1
-
C1
2
D2
+
VOUT =
(2V IN) - (2VF)
4
3
+
C2
NOTE: D1 and D2 can be any suitable diode.
FIGURE 13. POSITIVE VOLTAGE DOUBLER
Combined Negative Conversion and
Positive Supply Doubling
Figure 14 combines the functions shown on front page and
Figure 13 to provide negative voltage conversion and
positive voltage doubling simultaneously. This approach
would be, for example, suitable for generating +9V and -5V
from an existing +5V supply. In this instance capacitors C1
and C3 perform the pump and reservoir functions
respectively for the generation of the negative voltage, while
capacitors C2 and C4 are pump and reservoir respectively
for the doubled positive voltage. There is a penalty in this
configuration which combines both functions, however, in
that the source impedances of the generated supplies will be
somewhat higher due to the finite impedance of the common
charge pump driver at pin 2 of the device.
VIN
VOUT = -VIN
- C3
5
1
+
+
D1
2
4
3
C1
D2
-
VOUT = (2V IN) (VFD1) - (VFD2)
+
C2
+
- C4
FIGURE 14. COMBINED NEGATIVE VOLTAGE AND POSITIVE
DOUBLER
Cascading Devices
The ICL828 may be cascaded to produce a larger
multiplication supply voltage (see Figure 15). The output
voltage is:
+
1
OUT
C1+
C2
5
1
VOUT = -n(VIN),
where n is an integer representing the number of devices
cascaded.
The resulting output resistance would be approximately the
sum of the individual ICL828 ROUT values.
+V IN 2
2
IN
C1-
5
IN
1
3
C1+
OUT
n
GND
4
3
C1 -
GND
4
+
C3
C1
+
VOUT
C4
+
VOUT = - nVIN
FIGURE 15. CASCADING TO INCREASE OUTPUT VOLTAGE
5
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ICL828
Voltage Splitting
100
The bidirectional characteristics of the switches of the
ICL828 can be used to split a higher supply in half as shown
below.
EFFICIENCY (%)
+VIN
+
-
C2
C1 = C2 = C3 = 47µF
80
70
+
-
90
VOUT
C3
OUT
GND
C+
(VOUT = 1/2VIN)
60
0
INPUT
C1-
-
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (mA)
GND
+
FIGURE 18. EFFICIENCY vs OUTPUT CURRENT FOR SPLIT
SUPPLY APPLICATION
C1
FIGURE 16. SPLIT SUPPLY APPLICATION
2.5
Equivalent Circuit
ROUT
VIN = 5V
OUTPUT VOLTAGE (V)
The combined load will be evenly shared between the two
external capacitors because the switches share the load in
parallel, the output resistance is approximately half of the
standard voltage inverter.
2.3
2.1
1.9
1.7
1/2
VIN
1.5
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (mA)
FIGURE 17.
Typical value for ROUT in the above equivalent circuit would
be 6Ω to 7Ω for an input voltage of 5V. The power efficiency
for the circuit would be:
PEFF = (IOUT*VOUT)/(1/2(VIN*IOUT))+(VIN*IQ)
Typical values for ICL828 in this application,
IQ = 22µA, ROUT = 6Ω to 7Ω
and VOUT = 1/2VIN*RLOAD/(ROUT + RLOAD).
The ICL828 used as a voltage splitting circuit is an efficient
means to providing a split supply application as shown in
Figures 16 through 19.
6
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FIGURE 19. OUTPUT CURRENT vs OUTPUT VOLTAGE FOR
SPLIT SUPPLY APPLICATIONS
ICL828
Small Outline Transistor Plastic Packages (SOT23-5)
P5.064
D
5 LEAD SMALL OUTLINE TRANSISTOR PLASTIC PACKAGE
e1
INCHES
L
E
CL
CL
e
E1
b
CL
0.20 (0.008) M
α
C
C
CL
A A2
A1
SEATING
PLANE
MIN
MAX
MIN
MAX
NOTES
A
0.036
0.057
0.90
1.45
-
A1
0.000
0.0059
0.00
0.15
-
A2
0.036
0.051
0.90
1.30
-
b
0.0138
0.0196
0.35
0.50
-
C
0.0036
0.0078
0.09
0.20
-
D
0.111
0.118
2.80
3.00
3
E
0.103
0.118
2.60
3.00
-
E1
0.060
0.068
1.50
1.75
3
e
0.0374 Ref
0.95 Ref
-
e1
0.0748 Ref
1.90 Ref
-
L
0.004
N
-C-
MILLIMETERS
SYMBOL
α
0.023
0.10
5
0o
0.60
4, 5
5
10o
0o
6
10o
Rev. 0 10/98
0.10 (0.004) C
NOTES:
1. Dimensioning and tolerances per ANSI 14.5M-1982.
2. Package conforms to EIAJ SC-74A (1992).
3. Dimensions D and E1 are exclusive of mold flash, protrusions, or
gate burrs.
4. Footlength L measured at reference to seating plane.
5. “L” is the length of flat foot surface for soldering to substrate.
6. “N” is the number of terminal positions.
7. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact.
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Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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