MAX1044CPA+ [MAXIM]
Switched Capacitor Converter, 0.1A, 10kHz Switching Freq-Max, CMOS, PDIP8, LEAD FREE, PLASTIC, DIP-8;
| 型号： | MAX1044CPA+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Switched Capacitor Converter, 0.1A, 10kHz Switching Freq-Max, CMOS, PDIP8, LEAD FREE, PLASTIC, DIP-8 光电二极管 |
| 文件： | 总14页 (文件大小：1723K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MAX1044/ICL7660
Switched-Capacitor Voltage Converters
General Description
Features
● Miniature μMAX Package
The MAX1044 and ICL7660 are monolithic, CMOS
switched-capacitor voltage converters that invert, double,
divide, or multiply a positive input voltage. They are
pin compatible with the industry-standard ICL7660 and
LTC1044. Operation is guaranteed from 1.5V to 10V with
no external diode over the full temperature range. They
deliver 10mA with a 0.5V output drop. The MAX1044 has
a BOOST pin that raises the oscillator frequency above
the audio band and reduces external capacitor size
requirements.
● 1.5V to 10.0V Operating Supply Voltage Range
● 98% Typical Power-Conversion Efficiency
● Invert, Double, Divide, or Multiply Input Voltages
● BOOST Pin Increases Switching Frequencies
(MAX1044)
● No-Load Supply Current: 200μA Max at 5V
● No External Diode Required for Higher-Voltage
Operation
The MAX1044/ICL7660 combine low quiescent current and
high efficiency. Oscillator control circuitry and four power
MOSFET switches are included on-chip. Applications
include generating a -5V supply from a +5V logic supply
to power analog circuitry. For applications requiring more
power, the MAX660 delivers up to 100mA with a voltage
drop of less than 0.65V.
Ordering Information appears at end of data sheet.
Pin Configurations
TOP VIEW
Applications
+
● -5V Supply from +5V Logic Supply
● Personal Communications Equipment
● Portable Telephones
(N.C.) BOOST
CAP+
1
2
3
4
8
7
6
5
V+
MAX1044
ICL7660
OSC
LV
● Op-Amp Power Supplies
GND
● EIA/TIA-232E and EIA/TIA-562 Power Supplies
● Data-Acquisition Systems
● Hand-Held Instruments
CAP-
V
OUT
● Panel Meters
DIP/SO/µMAX
V+ AND CASE
Typical Operating Circuit
8
N.C.
OSC
1
7
INPUT
V+
CAP+
SUPPLY
VOLTAGE
LV
CAP+
ICL7660
2
6
MAX1044
ICL7660
V
GND
OUT
5
3
CAP-
GND
NEGATIVE
OUTPUT
VOLTAGE
4
V
OUT
CAP-
( ) ARE FOR ICL7660
TO-99
NEGATIVE VOLTAGE CONVERTER
19-4667; Rev 2; 2/17
MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Absolute Maximum Ratings
Supply Voltage (V+ to GND, or GND to V
)..................10.5V
CERDIP (derate 8.00mW/°C above +70°C)................640mW
TO-99 (derate 6.67mW/°C above +70°C) ...................533mW
Operating Temperature Ranges
MAX1044C_ _ /ICL7660C_ _.............................0°C to +70°C
MAX1044E_ _ /ICL7660E_ _ ......................... -40°C to +85°C
MAX1044M_ _ /ICL7660M_ _...................... -55°C to +125°C
Storage Temperature Range........................... -65°C to + 150°C
Lead Temperature (soldering, 10sec) .............................+300°C
OUT
Input Voltage on Pins 1, 6, and 7.......-0.3V ≤ V ≤ (V+ + 0.3V)
LV Input Current ..................................................................20μA
Output Short-Circuit Duration (V+ ≤ 5.5V) ................Continuous
IN
Continuous Power Dissipation (T = +70°C)
A
Plastic DIP (derate 9.09mW/°C above +70°C)............727mW
SO (derate 5.88mW/°C above +70°C)........................471mW
μMAX (derate 4.1mW/°C above +70°C) .....................330mW
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Electrical Characteristics
(Circuit of Figure 1, V+ = 5.0V, LV pin = 0V, BOOST pin = open, I
= 0mA, T = T
to T , unless otherwise noted.)
MAX
LOAD
A
MIN
MAX1044
ICL7660
PARAMETER
CONDITIONS
UNITS
µA
MIN TYP MAX MIN TYP MAX
T
T
T
T
= +25°C
30
200
200
200
200
80
175
225
250
250
A
A
A
A
R
= ∞,
L
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
pins 1 and 7
no connection,
LV open
Supply Current
R
R
R
= ∞, pins 1 and 7 = V+ = 3V
= 10kΩ, LV open
10
65
L
L
L
3.0
1.5
10.0
3.5
Supply Voltage
Range (Note 1)
V
= 10kΩ, LV to GND
1.5
10
T
T
T
T
T
T
T
T
= +25°C
100
130
130
150
325
325
325
400
55
100
120
140
150
250
300
300
400
A
A
A
A
A
A
A
A
I = 20mA,
L
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
= +25°C
f
= 5kHz,
OSC
LV open
Output Resistance
Ω
f
f
= 2.7kHz (ICL7660),
= 1kHz (MAX1044),
OSC
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
OSC
V+ = 2V, I = 3mA,
LV to GND
L
V+ = 5V
5
1
10
98
C
= 1pF,
OSC
LV to GND (Note 2)
Oscillator Frequency
kHz
V+ = 2V
Power Efficiency
R
R
= 5kΩ, T = +25°C, f
OSC
5kHz, LV open
95
98
95
%
%
L
A
Voltage Conversion Efficiency
= ∞, T = +25°C, LV open
97.0 99.9
99.0 99.9
L
A
Pin 1 = 0V
Pin 1 = V+
V+ = 2V
3
Oscillator Sink or
Source Current
V
= 0V or V+,
OSC
µA
LV open
T = +25°C
A
20
1.0
1.0
MΩ
kΩ
Oscillator Impedance
V+ = 5V
100
100
Note 1: The Maxim ICL7660 and MAX1044 can operate without an external output diode over the full temperature and voltage
ranges. The Maxim ICL7660 can also be used with an external output diode in series with pin 5 (cathode at V
replacing the Intersil ICL7660. Tests are performed without diode in circuit.
) when
OUT
Note 2: f
is tested with C
= 100pF to minimize the effects of test fixture capacitance loading. The 1pF frequency is
OSC
OSC
correlated to this 100pF test point, and is intended to simulate pin 7’s capacitance when the device is plugged into a
test socket with no external capacitor. For this test, the LV pin is connected to GND for comparison to the original
manufacturer’s device, which automatically connects this pin to GND for (V+ > 3V).
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Typical Operating Characteristics
(V+ = 5V; C
= 0.1μF; C1 = C2 = 10μF; LV = open; OSC = open; T = +25°C; unless otherwise noted.)
A
BYPASS
OUTPUT VOLTAGE AND OUTPUT RIPPLE
OUTPUT VOLTAGE AND OUTPUT RIPPLE
vs. LOAD CURRENT
vs. LOAD CURRENT
-2.0
-1.5
-1.0
-0.5
0
400
350
300
250
200
150
100
50
-5.0
-4.5
-4.0
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0
800
720
640
560
480
400
320
240
160
80
OUTPUT VOLTAGE
A
OUTPUT
VOLTAGE
A: MAX1044 WITH
BOOST = V+
B
A: MAX1044 WITH
BOOST = V+
B: ICL7660
C: MAX1044 WITH
BOOST = OPEN
B: ICL7660
C: MAX1044 WITH
BOOST = OPEN
C
C
B
C
A
V+ = 5V
LV = OPEN
V+ = 2V
LV = GND
B
A
OUTPUT RIPPLE
OUTPUT RIPPLE
0
0
0
1
2
3
4
5
6
7
8
9
10
0
5
10 15 20 25 30 35 40
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY AND SUPPLY CURRENT
vs. LOAD CURRENT
OUTPUT VOLTAGE AND OUTPUT RIPPLE
vs. LOAD CURRENT
100
90
80
70
60
50
40
30
20
10
0
10
9
8
7
6
5
4
3
2
1
0
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
700
630
560
490
420
350
280
210
140
70
A
OUTPUT
B
EFFICIENCY
VOLTAGE
C
A: MAX1044 WITH
BOOST = V+
B: ICL7660
C: MAX1044 WITH
BOOST = OPEN
SUPPLY CURRENT
OUTPUT
RIPPLE
C
V+ = 10V
LV = OPEN
B
A
V+ = 2V
LV = GND
0
0
1
2
3
4
5
6
7
8
9
10
0
5
10 15 20 25 30 35 40
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY AND SUPPLY CURRENT
vs. LOAD CURRENT
EFFICIENCY AND SUPPLY CURRENT
vs. LOAD CURRENT
100
90
80
70
60
50
40
30
20
10
0
50
45
40
35
30
25
20
15
10
5
100
90
80
70
60
50
40
30
20
10
0
50
45
40
35
30
25
20
15
10
5
B, C
A
A
EFFICIENCY
EFFICIENCY
B
A: MAX1044 WITH
C
A: MAX1044 WITH
BOOST = V+
B: ICL7660
C: MAX1044 WITH
BOOST = OPEN
BOOST = V+
B: ICL7660
C: MAX1044 WITH
BOOST = OPEN
SUPPLY CURRENT
SUPPLY CURRENT
V+ = 5V
LV = OPEN
V+ = 10V
LV = OPEN
0
0
0
5
10 15 20 25 30 35 40
LOAD CURRENT (mA)
0
5
10 15 20 25 30 35 40
LOAD CURRENT (mA)
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
EFFICIENCY
vs. OSCILLATOR FREQUENCY
OSCILLATOR FREQUENCY
vs. EXTERNAL CAPACITANCE
100,000
100
90
80
70
60
50
40
30
MAX1044 WITH
BOOST -V+
10,000
1000
ICL7660 AND
MAX1044 WITH
BOOST = OPEN
100
10
1
EXTERNAL
HCMOS
OSCILLATOR
0.1
1
2
3
4
5
5
10
10
10
10
10
6x10
1
10
100
1000 10,000 100,000
(pF)
OSCILLATOR FREQUENCY (Hz)
C
OSC
OSCILLATOR FREQUENCY
vs. TEMPERATURE
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
100
80
60
40
20
0
100,000
A: MAX1044 WITH
BOOST = V+
B: ICL7600
C: MAX1044 WITH
BOOST = OPEN
A
10,000
1000
0
FROM TOP TO BOTTOM AT 5V
MAX1044, BOOST = V+, LV = GND
MAX1044, BOOST = V+, LV = OPEN
ICL7660, LV = GND
ICL7660, LV = OPEN
MAX1044, BOOST = OPEN, LV = GND
B
C
MAX1044, BOOST = OPEN, LV = OPEN
-50
-25
0
25
50
75 100 125
1
2
3
4
5
6
7
8
9
10
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
QUIESCENT CURRENT
vs. OSCILLATOR FREQUENCY
10,000
1000
100
USING
EXTERNAL
CAPACITOR
USING
EXTERNAL
HCMOS
10
1
OSCILLATOR
0
1
2
3
4
5
5
10
10
10
10
10
10 5x10
OSCILLATOR FREQUENCY (Hz)
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
V+ 5V; C
= 0.1μF; C1 = C2 = 10μF; LV = open; OSC = open; T = +25°C; unless otherwise noted.)
A
BYPASS
A
QUIESCENT CURRENT
vs. TEMPERATURE
QUIESCENT CURRENT
vs. SUPPLY VOLTAGE
2000
1000
500
400
300
200
100
0
A
B
MAX1044 WITH
BOOST = V+
100
10
1
C
D
A: MAX1044, BOOST = V+, LV = GND
B: MAX1044, BOOST = V+, LV = OPEN
C: ICL7660 AND MAX1044 WITH
BOOST = OPEN, LV = GND;
ABOVE 5V, MAX1044 ONLY
D: ICL7660 AND MAX1044 WITH
ICL7660, MAX1044 WITH BOOST = OPEN
BOOST = OPEN, LV = OPEN
0.1
1
2
3
4
5
6
7
8
9
10
-50 -25
0
25
50
75 100 125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
OUTPUT RESISTANCE
vs. OSCILLATOR FREQUENCY
200
180
160
140
120
100
80
1000
900
800
700
600
500
400
300
200
100
0
EXTERNAL
HCMOS
OSCILLATOR
60
40
20
0
1
2
3
4
5
1
2
3
4
5
6
7
8
9
10
10
10
10
FREQUENCY (Hz)
10
10
SUPPLY VOLTAGE (V)
OUTPUT RESISTANCE
vs. TEMPERATURE
80
70
60
50
40
30
20
ICL7660,
MAX1044 WITH
BOOST = OPEN
MAX1044 WITH
BOOST = V+
-60 -40 -20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Pin Description
PIN
NAME
FUNCTION
BOOST
(MAX1044)
Frequency Boost. Connecting BOOST to V+ increases the oscillator frequency by a factor of six.
When the oscillator is driven externally, BOOST has no effect and should be left open.
1
N.C.
No Connection
(ICL7660)
2
3
4
CAP+
GND
CAP-
Connection to positive terminal of Charge-Pump Capacitor
Ground. For most applications, the positive terminal of the reservoir capacitor is connected to this pin.
Connection to negative terminal of Charge-Pump Capacitor
Negative Voltage Output. For most applications, the negative terminal of the reservoir capacitor is
connected to this pin.
5
6
V
OUT
LV
Low-Voltage Operation. Connect to ground for supply voltages below 3.5V.
ICL7660: Leave open for supply voltages above 5V.
Oscillator Control Input. Connecting an external capacitor reduces the oscillator frequency. Minimize stray
capacitance at this pin.
7
8
OSC
V+
Power-Supply Positive Voltage Input. (1.5V to 10V). V+ is also the substrate connection.
terminal of C1 to ground and shifts the negative terminal
to V
. This connects C1 in parallel with the reservoir
OUT
V+
capacitor C2. If the voltage across C2 is smaller than the
voltage across C1, then charge flows from C1 to C2 until the
voltages across them are equal. During successive cycles,
C1 will continue pouring charge into C2 until the voltage
across C2 reaches - (V+). In an actual voltage inverter, the
output is less than - (V+) since the switches S1–S4 have
resistance and the load drains charge from C2.
C
BYPASS
BOOST
V+
= 0.1µF
MAX1044
ICL7660
CAP+
EXTERNAL
OSCILLATOR
OSC
LV
R
L
C
C1
10µF
OSC
GND
CAP-
Additional qualities of the MAX1044/ICL7660 can be
understood by using a switched-capacitor circuit model.
Switching the bucket capacitor, C1, between the input and
output of the circuit synthesizes a resistance (Figures 3a
and 3b.)
V
V
OUT
OUT
C2
10µF
When the switch in Figure 3a is in the left position,
capacitor C1 charges to V+. When the switch moves
Figure 1. Maxim MAX1044/ICL7660 Test Circuit
to the right position, C1 is discharged to V
. The
OUT
charge transferred per cycle is: ΔQ = C1(V+ - V
If the switch is cycled at frequency f, then the resulting
).
OUT
Detailed Description
The MAX1044/ICL7660 are charge-pump voltage
converters. They work by first accumulating charge in
a bucket capacitor and then transfer it into a reservoir
capacitor. The ideal voltage inverter circuit in Figure 2
illustrates this operation.
current is: I = f x ΔQ = f x C1(V+ - V ). Rewriting
OUT
this equation in Ohm’s law form defines an equivalent
resistance synthesized by the switched-capacitor circuit
where:
V + − V
(
)
OUT
1/ ( f x C1)
and
During the first half of each cycle, switches S1 & S3
close and switches S2 & S4 open, which connects the
bucket capacitor C1 across V+ and charges C1. During the
second half of each cycle, switches S2 & S4 close and
switches S1 & S3 open, which connects the positive
I =
1
R
=
EQUIV
f x C1
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
V+
pin 8
CAP+
pin 2
S1
S2
S2
S1
V+
C1
1M
BOOST
Q
Q
pin 1
C2
2
S3
S4
OSC
pin 7
V
OUT
= -(V+)
S3
S4
V
OUT
pin 5
GND
pin 3
CAP-
pin 4
LV
pin 6
Figure 2. Ideal Voltage Inverter
Figure 4. MAX1044 and ICL7660 Functional Diagram
Design Information
The MAX1044/ICL7660 are designed to provide a simple,
compact, low-cost solution where negative or doubled
supply voltages are needed for a few low-power com-
ponents. Figure 5 shows the basic negative voltage
converter circuit. For many applications, only two external
capacitors are needed. The type of capacitor used is not
critical.
f
V+
V
OUT
C1
C2
R
LOAD
Proper Use of the Low-Voltage (LV) Pin
Figure 4 shows an internal voltage regulator inside
the MAX1044/ICL7660. Use the LV pin to bypass this
regulator, in order to improve low-voltage performance
and allow operation down to 1.5V. For low-voltage opera-
tion and compatibility with the industry-standard LTC1044
and ICL7660, the LV pin should be connected to ground
for supply voltages below 3.5V and left open for supply
voltages above 3.5V.
Figure 3a. Switched Capacitor Model
R
EQUIV
V+
V
OUT
1
R
EQUIV
=
C2
f x C1
R
LOAD
The MAX1044’s LV pin can be grounded for all operat-
ing conditions. The advantage is improved low-voltage
performance and increased oscillator frequency. The
disadvantage is increased quiescent current and reduced
efficiency at higher supply voltages. For Maxim’s ICL7660,
the LV pin must be left open for supply voltages above 5V.
Figure 3b. Equivalent Circuit
where f is one-half the oscillator frequency. This resis-
tance is a major component of the output impedance of
switched-capacitor circuits like the MAX1044/ICL7660.
When operating at low supply voltages with LV open,
connections to the LV, BOOST, and OSC pins should
be short or shielded to prevent EMI from causing
oscillator jitter.
As shown in Figure 4, the MAX1044/ICL7660 contain
MOSFET switches, the necessary transistor drive cir-
cuitry, and a timing oscillator.
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
CONNECTION
FROM V+
TO BOOST
+
+
V+
1
8
7
6
5
V
OUT
= -(V+)
V+
1
2
3
4
8
7
6
5
C
BYPASS
MAX1044
ICL7660
2
MAX1044
C1
C2
10µF
10µF
10F
C
OSC
3
*
V
OUT
= -(V+)
4
10F
*REQUIRED FOR V+ < 3.5V
Figure 5. Basic Negative Voltage Converter
Figure 6. Negative Voltage Converter with C
and BOOST
OSC
Overdriving the OSC Pin with an
External Oscillator
Oscillator Frequency Considerations
For normal operation, leave the BOOST and OSC pins
of the MAX1044/ICL7660 open and use the nominal
oscillator frequency. Increasing the frequency reduces
audio interference, output resistance, voltage ripple, and
required capacitor sizes. Decreasing frequency reduces
quiescent current and improves efficiency.
Driving OSC with an external oscillator is useful when
the frequency must be synchronized, or when higher
frequencies are required to reduce audio interference.
The MAX1044/ICL7660 can be driven up to 400kHz.
The pump and output ripple frequencies are one-half the
external clock frequency. Driving the MAX1044/ICL7660
at a higher frequency increases the ripple frequency and
allows the use of smaller capacitors. It also increases the
quiescent current.
Oscillator Frequency Specifications
The MAX1044/ICL7660 do not have a precise oscillator
frequency. Only minimum values of 1kHz and 5kHz for the
MAX1044 and a typical value of 10kHz for the ICL7660
are specified. If a specific oscillator frequency is required,
use an external oscillator to drive the OSC pin.
The OSC input threshold is V+ - 2.5V when V+ ≥ 5V, and
is V+ / 2 for V+ < 5V. If the external clock does not swing
all the way to V+, use a 10kΩ pull-up resistor (Figure 7).
Increasing Oscillator Frequency
Using the BOOST Pin
Output Voltage Considerations
The MAX1044/ICL7660 output voltage is not regulated.
The output voltages will vary under load according to the
output resistance. The output resistance is primarily a
function of oscillator frequency and the capacitor value.
Oscillator frequency, in turn, is influenced by temperature
and supply voltage. For example, with a 5V input voltage
and 10μF charge-pump capacitors, the output resistance
is typically 50Ω. Thus, the output voltage is about -5V
under light loads, and decreases to about -4.5V with a
10mA load current.
For the MAX1044, connecting the BOOST pin to the V+
pin raises the oscillator frequency by a factor of about 6.
Figure 6 shows this connection. Higher frequency opera-
tion lowers output impedance, reduces output ripple,
allows the use of smaller capacitors, and shifts switch-
ing noise out of the audio band. When the oscillator is
driven externally, BOOST has no effect and should be left
open. The BOOST pin should also be left open for normal
operation.
Reducing the Oscillator Frequency Using C
OSC
Minor supply voltage variations that are inconsequential to
digital circuits can affect some analog circuits. Therefore,
when using the MAX1044/ICL7660 for powering sensi-
tive analog circuits, the power-supply rejection ratio of
those circuits must be considered. The output ripple and
output drop increase under heavy loads. If necessary, the
MAX1044/ICL7660 output impedance can be reduced by
paralleling devices, increasing the capacitance of C1 and
C2, or connecting the MAX1044’s BOOST pin to V+ to
increase the oscillator frequency.
An external capacitor can be connected to the OSC
pin to lower the oscillator frequency (Figure 6). Lower
frequency operation improves efficiency at low load
currents by reducing the IC’s quiescent supply current.
It also increases output ripple and output impedance. This
can be offset by using larger values for C1 and C2.
Connections to the OSC pin should be short to prevent
stray capacitance from reducing the oscillator frequency.
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Efficiency, Output Ripple,
and Output Impedance
10kΩ
The power efficiency of a switched-capacitor voltage
converter is affected by the internal losses in the con-
verter IC, resistive losses of the pump capacitors, and
conversion losses during charge transfer between the
capacitors. The total power loss is:
REQUIRED
FOR TTL
V+
+
CMOS or
TTL GATE
1
8
7
6
5
V+
MAX1044
ICL7660
2
Σ PLOSS
P
+ PSWITCH + PPUMP
+ PCONVERSION
10µF
=
INTERNAL
LOSSES
3
LOSSES
CAPACITOR
LOSSES
LOSSES
V
OUT
= -(V+)
4
10µF
The internal losses are associated with the IC’s internal
functions such as driving the switches, oscillator, etc.
These losses are affected by operating conditions such as
input voltage, temperature, frequency, and connections to
the LV, BOOST, and OSC pins.
Figure 7. External Clocking
The next two losses are associated with the output resis-
tance of the voltage converter circuit. Switch losses occur
because of the on-resistances of the MOSFET switches
in the IC. Charge-pump capacitor losses occur because
of their ESR. The relationship between these losses and
the output resistance is as follows:
Inrush Current and EMI Considerations
During start-up, pump capacitors C1 and C2 must be
charged. Consequently, the MAX1044/ICL7660 develop
inrush currents during start-up. While operating, short
bursts of current are drawn from the supply to C1, and
then from C1 to C2 to replenish the charge drawn by the
load during each charge-pump cycle. If the voltage con-
verters are being powered by a high-impedance source,
the supply voltage may drop too low during the current
bursts for them to function properly. Furthermore, if the
supply or ground impedance is too high, or if the traces
between the converter IC and charge-pump capacitors
are long or have large loops, switching noise and EMI
may be generated. To reduce these effects:
PPUMP
+ PSWITCH = IOUT2 x R
OUT
CAPACITOR
LOSSES
LOSSES
where:
1
R
≅
+
OUT
f
/ 2 x C1
(
)
OSC
1) Power the MAX1044/ICL7600 from a low-impedance
source.
4(2R
+ E
) + E
SRC2
SWITCHES
SRC1
2) Add a power-supply bypass capacitor with low
effective series resistance (ESR) close to the IC
between the V+ and ground pins.
and f
is the oscillator frequency.
OSC
The first term is the effective resistance from the switched-
capacitor circuit.
3) Shorten traces between the IC and the charge-pump
capacitors.
Conversion losses occur during the transfer of charge
between capacitors C1 and C2 when there is a voltage
difference between them. The power loss is:
4) Arrange the components to keep the ground pins of
the capacitors and the IC as close as possible.
1
2
2
C1 (V +) − V
+
5) Leave extra copper on the board around the voltage
converter as power and ground planes. This is easily
done on a double-sided PC board.
)
(
OUT
2
1
P
≅
× f
/2
OSC
CONV.LOSS
2
C2 V
− 2V
V
RIPPLE
OUT RIPPLE
2
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Note that lower capacitor values can be used for lower
output currents. For example, setting the oscillator to
40Hz by connecting a 1000pF capacitor to OSC provides
the highest efficiency possible. Leaving the bucket and
Increasing Efficiency
Efficiency can be improved by lowering output voltage
ripple and output impedance. Both output voltage ripple
and output impedance can be reduced by using large
capacitors with low ESR.
reservoir capacitors at 100μF gives a maximum I
of
OUT
2mA, a no-load quiescent current of 10μA, and a power
conversion efficiency of 98%.
The output voltage ripple can be calculated by noting that
the output current is supplied solely from capacitor C2
during one-half of the charge-pump cycle.
General Precautions
1) Connecting any input terminal to voltages greater
than V+ or less than ground may cause latchup. Do
not apply any input sources operating from external
supplies before device power-up.
1
V
≅
+ 2 x ESR
I
RIPPLET
C2 OUT
2× f
x C2
OSC
Slowing the oscillator frequency reduces quiescent
current. The oscillator frequency can be reduced by
connecting a capacitor to the OSC pin.
2) Never exceed maximum supply voltage ratings.
3) Do not connect C1 and C2 with the wrong polarity.
Reducing the oscillator frequency increases the rip-
ple voltage in the MAX1044/ICL7660. Compensate by
increasing the values of the bucket and reservoir capaci-
tors. For example, in a negative voltage converter, the
pump frequency is around 4kHz or 5kHz. With the rec-
ommended 10μF bucket and reservoir capacitors, the
circuit consumes about 70μA of quiescent current while
providing 20mA of output current. Setting the oscillator to
400Hz by connecting a 100pF capacitor to OSC reduces
the quiescent current to about 15μA. Maintaining 20mA
output current capability requires increasing the bucket
and reservoir capacitors to 100μF.
4) Do not short V+ to ground for extended periods with
supply voltages above 5.5V present on other pins.
5) Ensure that V
(pin 5) does not go more positive
OUT
than GND (pin 3). Adding a diode in parallel with C2,
with the anode connected to V
will prevent this condition.
and cathode to LV,
OUT
Application Circuits
Negative Voltage Converter
Figure 8 shows a negative voltage converter, the most
popular application of the MAX1044/ICL7660. Only two
external capacitors are needed. A third power-supply
bypass capacitor is recommended (0.1μF to 10μF)
V+
+
+
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
V+
BOOST
C
MAX1044
ICL7660
BYPASS
0.1µF
MAX1044
ICL7660
V
= 2(V+) - 2V
D
OUT
C1
10µF
LV
V
C2
= -(V+)
C1
C2
OUT
10µF
Figure 9. Voltage Doubler
Figure 8. Negative Voltage Converter with BOOST and LV
Connections
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
positive voltage. This circuit has higher output imped-
ances resulting from the use of a common charge-pump
driver.
Positive Voltage Doubler
Figure 9 illustrates the recommended voltage doubler
circuit for the MAX1044/ICL7660. To reduce the volt-
age drops contributed by the diodes (V ), use Schottky
diodes. For true voltage doubling or higher output cur-
rents, use the MAX660.
D
Cascading Devices
Larger negative multiples of the supply voltage can
be obtained by cascading MAX1044/ICL7660 devices
(Figure 12). The output voltage is nominally V
=
Voltage Divider
OUT
-n(V+) where n is the number of devices cascaded. The
output voltage is reduced slightly by the output resistance
of the first device, multiplied by the quiescent current
of the second, etc. Three or more devices can be cas-
caded in this way, but output impedance rises dramati-
cally. For example, the output resistance of two cascaded
MAX1044s is approximately five times the output resis-
tance of a single voltage converter. A better solution may
be an inductive switching regulator, such as the MAX755,
MAX759, MAX764, or MAX774.
The voltage divider shown in Figure 10 splits the power
supply in half. A third capacitor can be added between V+
and V
.
OUT
Combined Positive Multiplication and
Negative Voltage Conversion
Figure 11 illustrates this dual-function circuit. Capacitors
C1 and C3 perform the bucket and reservoir functions for
generating the negative voltage. Capacitors C2 and C4
are the bucket and reservoir capacitors for the doubled
+
V+
+
V+
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
V
= -(V+)
OUT
MAX1044
ICL7660
MAX1044
ICL7660
C3
C1
10µF
LV
C1
LV
V
= 2(V+) - 2V
C4
OUT
D
1
2
V
=
V+
OUT
C2
10µF
C2
Figure 10. Voltage Divider
Figure 11. Combined Positive and Negative Converter
+
+
+
1
8
7
V+
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
MAX1044
ICL7660
MAX1044
ICL7660
MAX1044
ICL7660
2
3
4
10µF
10µF
6
5
10µF
V
= -n(V+)
OUT
1
2
3
10µF
10µF
10µF
Figure 12. Cascading MAX1044/ICL7660 for Increased Output Voltage
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Paralleling Devices
Paralleling multiple MAX1044/ICL7660s reduces output
resistance and increases current capability. As illustrated
in Figure 13, each device requires its own pump capacitor
C1, but the reservoir capacitor C2 serves all devices. The
equation for calculating output resistance is:
+
1
8
7
6
5
V+
MAX1044
ICL7660
2
3
4
C1
R
(of MAX1044 or ICL7660)
OUT
R
=
OUT
n (number of devices)
1
Shutdown Schemes
+
Figures 14a–14c illustrate three ways of adding shutdown
capability to the MAX1044/ICL7660. When using these
circuits, be aware that the additional capacitive loading
on the OSC pin will reduce the oscillator frequency. The
first circuit has the least loading on the OSC pin and has
the added advantage of controlling shutdown with a high
or low logic level, depending on the orientation of the
switching diode.
1
2
3
4
8
7
6
5
MAX1044
ICL7660
V
= -(V+)
OUT
C1
C2
n
Figure 13. Paralleling MAX1044/ICL7660 to Reduce Output
Resistance
Ordering Information
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 SO
V+
MAX1044CPA
MAX1044CSA
MAX1044C/D*
MAX1044EPA
MAX1044ESA
MAX1044MJA
ICL7660CPA
ICL7660CSA
ICL7660CUA
ICL7660C/D
10kΩ REQUIRED FOR TTL
+
V+
CMOS or
0°C to +70°C
1
2
3
4
8
7
6
5
TTL GATE
1N4148
0°C to +70°C
Dice*
MAX1044
ICL7660
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
8 Plastic DIP
8 SO
10µF
8 CERDIP**
8 Plastic DIP
8 SO
V
OUT
= -(V+)
10µF
0°C to +70°C
a)
0°C to +70°C
8 μMAX
V+
74HC03
0°C to +70°C
Dice*
OPEN-DRAIN OR
74LS03
OPEN-COLLECTOR
NAND GATES
MAX1044
ICL7660
ICL7660EPA
ICL7660ESA
ICL7660AMJA†
ICL7660AMTV†
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
-55°C to +125°C
8 Plastic DIP
8 SO
7
b)
8 CERDIP**
8 TO-99**
V+
OUTPUT
ENABLE
74HC126 OR
74LS126
TRI-STATE BUFFER
*Contact factory for dice specifications. Dice are not tested
**Contact factory for availability.
†The Maxim ICL7660 meets or exceeds all “A” and “S”
specifications.
MAX1044
ICL7660
7
c)
Figure 14a-14c. Shutdown Schemes for MAX1044/ICL7660
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Chip Topographies
MAX1044
ICL7660
GND
CAP+
BOOST
V+
0.084"
(2.1mm)
CAP+
0.076"
(1.930mm)
GND
CAP-
OSC
V+
CAP-
LV
V
OUT
V
OUT
LV
0.076"
(1.930mm)
TRANSISTOR COUNT: 72
SUBSTRATE CONNECTED TO V+
OSC
0.060"
(1.5mm)
TRANSISTOR COUNT: 71
SUBSTRATE CONNECTED TO V+
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
6 TDFN-EP
8 Plastic DIP
8 SOIC
T633-2
P8+1
S8+2
J8+2
21-0036
21-0043
21-0041
21-0045
21-0036
21-0022
90-0058
—
90-0096
—
8 CERDIP
8 µMAX
U8+1
T99-8
90-0092
—
8 TO-99
Maxim Integrated
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MAX1044/ICL7660
Switched-Capacitor Voltage Converters
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
DESCRIPTION
CHANGED
2
2/17
Updated part numbers in Ordering Information table
13
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2017 Maxim Integrated Products, Inc.
│ 14
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