MAX1044C [MAXIM]
Switched-Capacitor Voltage Converters;
| 型号： | MAX1044C |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Switched-Capacitor Voltage Converters |
| 文件： | 总12页 (文件大小：118K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4667; Rev 1; 7/94
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ Miniature µMAX Package
The MAX1044 a nd ICL7660 a re monolithic , CMOS
switched-capacitor voltage converters that invert, dou-
ble, 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
The MAX1044/ICL7660 combine low quiescent current
and high efficiency. Oscillator control circuitry and four
p owe r MOSFET s witc he s a re inc lud e d on-c hip .
Applications include generating a -5V supply from a
+5V logic supply to power analog circuitry. For applica-
tions requiring more power, the MAX660 delivers up to
100mA with a voltage drop of less than 0.65V.
Operation
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
8 Plastic DIP
8 SO
MAX1044CPA
MAX1044CSA
MAX1044C/D
MAX1044EPA
Dice*
________________________Ap p lic a t io n s
-5V Supply from +5V Logic Supply
Personal Communications Equipment
Portable Telephones
8 Plastic DIP
Ordering Information continued at end of data sheet.
* Contact factory for dice specifications.
_________________P in Co n fig u ra t io n s
Op-Amp Power Supplies
EIA/TIA-232E and EIA/TIA-562 Power Supplies
Data-Acquisition Systems
TOP VIEW
Hand-Held Instruments
(N.C.) BOOST
CAP+
1
2
3
4
8
7
6
5
V+
Panel Meters
OSC
LV
MAX1044
ICL7660
GND
__________Typ ic a l Op e ra t in g Circ u it
CAP-
V
OUT
DIP/SO/µMAX
INPUT
SUPPLY
V+ AND CASE
V+
CAP+
VOLTAGE
8
N.C.
2
OSC
1
7
MAX1044
ICL7660
LV
CAP+
6
ICL7660
CAP-
GND
NEGATIVE
OUTPUT
VOLTAGE
V
OUT
V
GND
OUT
5
3
4
CAP-
NEGATIVE VOLTAGE CONVERTER
( ) ARE FOR ICL7660
TO-99
________________________________________________________________ Maxim Integrated Products
1
Ca ll t o ll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 fo r fre e s a m p le s o r lit e ra t u re .
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V+ to GND, or GND to VOUT)....................10.5V
Input Voltage on Pins 1, 6, and 7 .........-0.3V ≤ VIN ≤ (V+ + 0.3V)
LV Input Current ..................................................................20µA
Output Short-Circuit Duration (V+ ≤ 5.5V)..................Continuous
Continuous Power Dissipation (TA = +70°C)
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
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, ILOAD = 0mA, TA = TMIN to TMAX, unless otherwise noted.)
MAX1044
MIN TYP MAX
ICL7660
MIN TYP MAX
PARAMETER
CONDITIONS
UNITS
µA
MAX14/ICL760
T
A
= +25°C
30 200
200
80 175
225
R
= ∞,
L
T
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
A
pins 1 and 7
no connection,
LV open
Supply Current
T
A
200
250
T
A
200
250
R
R
R
= ∞, pins 1 and 7 = V+ = 3V
10
L
L
L
= 10kΩ, LV open
3.0
1.5
10.0
3.5
Supply Voltage
Range (Note 1)
V
= 10kΩ, LV to GND
1.5
10
65 100
130
T
= +25°C
55 100
120
A
I
= 20mA,
= 5kHz,
L
T
A
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
= +25°C
f
OSC
T
A
130
140
LV open
T
A
150
150
Output Resistance
Ω
T
A
325
250
f
= 2.7kHz (ICL7660),
= 1kHz (MAX1044),
OSC
T
A
= 0°C to +70°C
= -40°C to +85°C
= -55°C to +125°C
325
300
f
OSC
V+ = 2V, IL = 3mA,
LV to GND
T
A
325
300
T
A
400
400
V+ = 5V
V+ = 2V
5
1
10
C
= 1pF,
OSC
Oscillator Frequency
kHz
LV to GND (Note 2)
Power Efficiency
R
R
= 5kΩ, T = +25°C, f
5kHz, LV open
95 98
95 98
%
%
L
L
A
OSC
Voltage Conversion Efficiency
= ∞, T = +25°C, LV open
97.0 99.9
99.0 99.9
A
Pin 1 = 0V
Pin 1 = V+
V+ = 2V
3
Oscillator Sink or
Source Current
V
= 0V or V+, LV open
µA
OSC
20
1.0
1.0
MΩ
kΩ
Oscillator Impedance
T = +25°C
A
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 ) when
OUT
replacing the Intersil ICL7660. Tests are performed without diode in circuit.
Note 2: f is tested with C = 100pF to minimize the effects of test fixture capacitance loading. The 1pF frequency is correlat-
OSC
OSC
ed 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).
2
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(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
vs. LOAD CURRENT
OUTPUT VOLTAGE and OUTPUT RIPPLE
vs. LOAD CURRENT
OUTPUT VOLTAGE and OUTPUT RIPPLE
vs. LOAD CURRENT
-2.0
-1.5
400
800
720
-10
-9
700
630
560
490
-5.0
-4.5
-4.0
A
OUTPUT VOLTAGE
A
OUTPUT
VOLTAGE
OUTPUT
B
350
300
250
VOLTAGE
C
-8
640
560
480
400
320
240
160
80
A: MAX1044 with
B
A: MAX1044 with
BOOST = V+
B: ICL7660
C: MAX1044 with
BOOST = OPEN
A: MAX1044 with
BOOST = V+
B: ICL7660
-7
-6
-5
-4
-3
-2
-1
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
BOOST = V+
B: ICL7660
420
350
280
C: MAX1044 with
BOOST = OPEN
-1.0 C: MAX1044 with
BOOST = OPEN
200
150
C
C
B
OUTPUT
RIPPLE
C
C
V+ = 10V
LV = OPEN
V+ = 5V
LV = OPEN
210
140
V+ = 2V
LV = GND
-0.5
100
B
B
A
50
0
70
0
A
A
OUTPUT RIPPLE
OUTPUT RIPPLE
0
0
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)
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
EFFICIENCY and SUPPLY CURRENT
vs. LOAD CURRENT
10
9
100
90
50
45
40
35
50
45
40
35
100
90
100
90
B, C
A
A
EFFICIENCY
EFFICIENCY
EFFICIENCY
B
8
80
80
80
A: MAX1044 with
C
A: MAX1044 with
BOOST = V+
B: ICL7660
C: MAX1044 with
BOOST = OPEN
7
70
60
50
40
30
20
10
70
60
50
40
30
20
10
70
60
50
40
30
20
10
BOOST = V+
B: ICL7660
C: MAX1044 with
BOOST = OPEN
6
5
30
25
30
25
SUPPLY CURRENT
4
3
2
1
SUPPLY CURRENT 20
SUPPLY CURRENT
20
15
10
5
15
10
5
V+ = 5V
LV = OPEN
V+ = 2V
LV = GND
V+ = 10V
LV = OPEN
0
0
0
0
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)
0
5
10 15 20 25 30 35 40
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY
vs. OSCILLATOR FREQUENCY
OSCILLATOR FREQUENCY
vs. EXTERNAL CAPACITANCE
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
100
100,000
100,000
10,000
1000
MAX1044 with
BOOST -V+
90
80
70
60
50
40
30
10,000
1000
ICL7660 and
MAX1044 with
BOOST = OPEN
100
10
1
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
MAX1044, BOOST = OPEN, LV = OPEN
EXTERNAL
HCMOS
OSCILLATOR
0.1
100
1
2
3
4
5
5
6x10
10
10
10
10
10
1
10
100
C
1000 10,000 100,000
(pF)
1
2
3
4
5
6
7
8
9
10
OSCILLATOR FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
OSC
_______________________________________________________________________________________
3
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V+ = 5V; C
= 0.1µF; C1 = C2 = 10µF; LV = open; OSC = open; T = +25°C; unless otherwise noted.)
A
BYPASS
OSCILLATOR FREQUENCY
vs. TEMPERATURE
QUIESCENT CURRENT
vs. OSCILLATOR FREQUENCY
100
80
10,000
A: MAX1044 with
BOOST = V+
B: ICL7600
C: MAX1044 with
BOOST = OPEN
1000
100
10
A
60
40
USING
EXTERNAL
CAPACITOR
USING
20
EXTERNAL
HCMOS
OSCILLATOR
B
C
MAX14/ICL760
0
-50
1
10
0
1
2
3
4
5
10 5x10
5
-25
0
25
50 75 100 125
10
10
10
10
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (Hz)
QUIESCENT CURRENT
vs. TEMPERATURE
QUIESCENT CURRENT
vs. SUPPLY VOLTAGE
500
400
2000
1000
A
B
MAX1044 with
BOOST = V+
300
200
100
10
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
BOOST = OPEN, LV = OPEN
100
0
1
ICL7660, MAX1044 with BOOST = OPEN
0.1
-50 -25
0
25
50
75 100 125
1
2
3
4
5
6
7
8
9
10
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
OUTPUT RESISTANCE
vs. OSCILLATOR FREQUENCY
OUTPUT RESISTANCE
vs. TEMPERATURE
200
1000
80
70
EXTERNAL
HCMOS
OSCILLATOR
180
160
140
900
800
700
ICL7660,
MAX1044 with
BOOST = OPEN
60
50
40
120
100
80
600
500
400
300
200
100
60
40
MAX1044 with
BOOST = V+
30
20
20
0
0
10
1
2
3
4
5
10
1
2
3
4
5
6
7
8
9
10
10
10
FREQUENCY (Hz)
10
-60 -40 -20
0
20 40 60 80 100 120 140
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
_____________________________________________________________ P in De s c rip t io n
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.
(ICL7660)
No Connection
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
Low-Voltage Operation. Connect to ground for supply voltages below 3.5V.
ICL7660: Leave open for supply voltages above 5V.
LV
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.
During the first half of each cycle, switches S1 & S3
close and switches S2 & S4 open, which connects the
V+
b uc ke t c a p a c itor C1 a c ros s V+ a nd c ha rg e s C1.
C
BYPASS
During the second half of each cycle, switches S2 & S4
close and switches S1 & S3 open, which connects the
positive terminal of C1 to ground and shifts the nega-
BOOST
V+
= 0.1µF
EXTERNAL
OSCILLATOR
MAX1044
CAP+ ICL7660 OSC
tive terminal to V
. This connects C1 in parallel with
OUT
the reservoir 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.
R
L
C
C1
10µF
OSC
GND
CAP-
LV
V
V
OUT
OUT
C2
10µF
Additional qualities of the MAX1044/ICL7660 can be
und e rs tood b y us ing a s witc he d -c a p a c itor c irc uit
model. Switching the bucket capacitor, C1, between
the input and output of the circuit synthesizes a resis-
tance (Figures 3a and 3b.)
Figure 1. Maxim MAX1044/ICL7660 Test Circuit
_______________De t a ile d De s c rip t io n
When the switch in Figure 3a is in the left position,
capacitor C1 charges to V+. When the switch moves to
The MAX1044/ICL7660 are charge-pump voltage con-
verters. 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.
the rig ht p os ition, C1 is d is c ha rg e d to V
. The
OUT
charge transferred per cycle is: ∆Q = C1(V+ - V
). If
OUT
the switch is cycled at frequency f, then the resulting
_______________________________________________________________________________________
5
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
current is: I = f x ∆Q = f x C1(V+ - V
). Rewriting this
OUT
equation in Ohm’s law form defines an equivalent resis-
tance synthesized by the switched-capacitor circuit
where:
S1
S3
S2
V+
(V+ - V
)
OUT
I =
C1
1 / (f x C1)
and
1
C2
R
=
S4
EQUIV
f x C1
V
OUT
= -(V+)
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.
As shown in Figure 4, the MAX1044/ICL7660 contain
MOSFET switches, the necessary transistor drive cir-
cuitry, and a timing oscillator.
MAX14/ICL760
Figure 2. Ideal Voltage Inverter
________________De s ig n In fo rm a t io n
The MAX1044/ICL7660 a re d e s ig ne d to p rovid e a
simple, compact, low-cost solution where negative or
doubled supply voltages are needed for a few low-
power components. Figure 5 shows the basic negative
voltage converter circuit. For many applications, only
two e xte rna l c a p a c itors a re ne e d e d . The typ e of
capacitor used is not critical.
f
V+
V
OUT
P ro p e r Us e o f t h e Lo w -Vo lt a g e (LV) P in
Figure 4 shows an internal voltage regulator inside the
MAX1044/ICL7660. Us e the LV p in to b yp a s s this
regulator, in order to improve low-voltage performance
C1
C2
R
LOAD
Figure 3a. Switched Capacitor Model
V+
pin 8
CAP+
pin 2
S2
S1
1M
BOOST
R
EQUIV
V+
V
OUT
Q
Q
pin 1
1
÷ 2
R
=
EQUIV
f × C1
OSC
pin 7
C2
R
LOAD
S3
S4
V
OUT
pin 5
GND
pin 3
CAP-
pin 4
LV
pin 6
Figure 4. MAX1044 and ICL7660 Functional Diagram
Figure 3b. Equivalent Circuit
6
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
CONNECTION
FROM V+
TO BOOST
V+
1
2
3
4
8
7
6
5
V
OUT
= -(V+)
V+
1
2
3
4
8
7
6
5
C
BYPASS
MAX1044
ICL7660
C1
10µF
C2
10µF
MAX1044
10µF
C
OSC
*
V
OUT
= -(V+)
10µF
*REQUIRED FOR V+ < 3.5V
Figure 5. Basic Negative Voltage Converter
Figure 6. Negative Voltage Converter with COSC and BOOST
a nd a llow op e ra tion d own to 1.5V. For low-volta g e
operation and compatibility with the industry-standard
LTC1044 and ICL7660, the LV pin should be connect-
ed to ground for supply voltages below 3.5V and left
open for supply voltages above 3.5V.
Figure 6 shows this connection. Higher frequency oper-
ation 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.
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
d is a d va nta g e is inc re a s e d q uie s c e nt c urre nt a nd
re d uc e d e ffic ie nc y a t hig he r s up p ly volta g e s . For
Maxim’s ICL7660, the LV pin must be left open for
supply voltages above 5V.
Reducing the Oscillator Frequency Using C
OSC
An external capacitor can be connected to the OSC pin
to lowe r the os c illa tor fre q ue nc y (Fig ure 6). Lowe r
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.
When operating at low supply voltages with LV open,
connections to the LV, BOOST, and OSC pins should
b e s hort or s hie ld e d to p re ve nt EMI from c a us ing
oscillator jitter.
Connections to the OSC pin should be short to prevent
stray capacitance from reducing the oscillator frequency.
Os c illa t o r Fre q u e n c y Co n s id e ra t io n s
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.
Overdriving the OSC Pin with an External Oscillator
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 e xte rna l c loc k fre q ue nc y. Driving the
MAX1044/ICL7660 at a higher frequency increases the
rip p le fre q ue nc y a nd a llows the us e of s ma lle r
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 a nd a typ ic a l va lue 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
For the MAX1044, connecting the BOOST pin to the V+
Ou t p u t Vo lt a g e Co n s id e ra t io n s
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
pin raises the oscillator frequency by a factor of about 6.
_______________________________________________________________________________________
7
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
switching noise and EMI may be generated. To reduce
these effects:
10kΩ
REQUIRED
FOR TTL
V+
1) Power the MAX1044/ICL7600 from a low-impedance
source.
2) Ad d a p owe r-s up p ly b yp a s s c a p a c itor with low
effective series resistance (ESR) close to the IC
between the V+ and ground pins.
CMOS or
TTL GATE
1
2
3
4
8
7
6
5
V+
MAX1044
ICL7660
3) Shorten traces between the IC and the charge-pump
capacitors.
10µF
4) Arrange the components to keep the ground pins of
the capacitors and the IC as close as possible.
V
= -(V+)
OUT
10µF
5) Leave extra copper on the board around the voltage
c onve rte r a s p owe r a nd g round p la ne s . This is
easily done on a double-sided PC board.
Figure 7. External Clocking
Effic ie n c y, Ou t p u t Rip p le ,
a n d Ou t p u t Im p e d a n c e
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:
MAX14/ICL760
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.
∑ P
= PINTERNAL +P
+P
PUMP
+P
CONVERSION
LOSSES
LOSS
SWITCH
LOSSES
Minor supply voltage variations that are inconsequential
to d ig ita l c irc uits c a n a ffe c t s ome a na log c irc uits .
The re fore , whe n us ing the MAX1044/ICL7660 for
powering sensitive analog circuits, the power-supply
rejection ratio of those circuits must be considered.
The outp ut rip p le a nd outp ut d rop inc re a s e und e r
heavy loads. If necessary, the MAX1044/ICL7660 out-
put impedance can be reduced by paralleling devices,
increasing the capacitance of C1 and C2, or connect-
ing the MAX1044’s BOOST pin to V+ to increase the
oscillator frequency.
LOSSES
CAPACITOR
LOSSES
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 connec-
tions to the LV, BOOST, and OSC pins.
The next two losses are associated with the output
resistance of the voltage converter circuit. Switch losses
occur because of the on-resistances of the MOSFET
s witc he s in the IC. Cha rg e -p ump c a p a c itor los s e s
occur because of their ESR. The relationship between
these losses and the output resistance is as follows:
In ru s h Cu rre n t a n d EMI Co n s id e ra t io n s
During start-up, pump capacitors C1 and C2 must be
charged. Consequently, the MAX1044/ICL7660 devel-
op 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
volta g e c onve rte rs a re b e ing p owe re d b y a hig h-
impedance source, the supply voltage may drop too
low during the current bursts for them to function prop-
erly. 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,
2
PPUMP
CAPACITOR
LOSSES
+ PSWITCH = I
LOSSES
x R
OUT
OUT
where:
1
R
+
OUT
(f
/ 2) x C1
OSC
4 2R
(
+ ESR
+ ESR
)
C1 C2
SWITCHES
and f
is the oscillator frequency.
OSC
8
_______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
The firs t te rm is the e ffe c tive re s is ta nc e from the
switched-capacitor circuit.
oscillator to 400Hz by connecting a 100pF capacitor to
OSC reduces the quiescent current to about 15µA.
Maintaining 20mA output current capability requires
inc re a s ing the b uc ke t a nd re s e rvoir c a p a c itors to
100µF.
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:
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 pro-
vides the highest efficiency possible. Leaving the bucket
and reservoir capacitors at 100µF gives a maximum
1
2
2
2
P
=
C1 (V+) − V
+
CONV.LOSS
OUT
1
2
2
C2
V
− 2V
V
x f
/ 2
RIPPLE
OUT RIPPLE
OSC
I
of 2mA, a no-load quiescent current of 10µA, and
OUT
a power conversion efficiency of 98%.
Increasing Efficiency
Efficiency can be improved by lowering output voltage
ripple and output impedance. Both output voltage rip-
ple and output impedance can be reduced by using
large capacitors with low ESR.
Ge n e ra l P re c a u t io n s
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.
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.
2) Never exceed maximum supply voltage ratings.
3) Do not connect C1 and C2 with the wrong polarity.
1
4) Do not short V+ to ground for extended periods with
supply voltages above 5.5V present on other pins.
V
+ 2 x ESR
I
OUT
RIPPLE
C2
2 x f
x C2
OSC
5) Ensure that V
(pin 5) does not go more positive
OUT
Slowing the oscillator frequency reduces quiescent cur-
rent. The oscillator frequency can be reduced by con-
necting a capacitor to the OSC pin.
than GND (pin 3). Adding a diode in parallel with
C2, with the anode connected to V and cathode
to LV, will prevent this condition.
OUT
Reducing the oscillator frequency increases the ripple
volta g e in the MAX1044/ICL7660. Comp e nsa te b y
inc re a s ing the va lue s of the b uc ke t a nd re s e rvoir
capacitors. For example, in a negative voltage converter,
the pump frequency is around 4kHz or 5kHz. With the
recommended 10µF bucket and reservoir capacitors,
the circuit consumes about 70µA of quiescent current
while providing 20mA of output current. Setting the
________________Ap p lic a t io n Circ u it s
Ne g a t ive Vo lt a g e Co n ve rt e r
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
MAX1044
ICL7660
C
BYPASS
0.1µF
V
= 2(V+) - 2V
D
OUT
MAX1044
ICL7660
C1
10µF
C1
C2
LV
V
OUT
= -(V+)
C2
10µF
Figure 9. Voltage Doubler
Figure 8. Negative Voltage Converter with BOOST and LV
Connections
_______________________________________________________________________________________
9
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
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
OUT
= 2(V+) - 2V
D
1
2
V
OUT
=
V+
C2
10µF
C2
C4
Figure 10. Voltage Divider
Figure 11. Combined Positive and Negative Converter
MAX14/ICL760
capacitors for the doubled positive voltage. This circuit
has higher output impedances resulting from the use of
a common charge-pump driver.
P o s it ive Vo lt a g e Do u b le r
Figure 9 illustrates the recommended voltage doubler
circuit for the MAX1044/ICL7660. To reduce the voltage
drops contributed by the diodes (V ), use Schottky
diodes. For true voltage doubling or higher output cur-
rents, use the MAX660.
D
Ca s c a d in g De vic e s
Larger negative multiples of the supply voltage can be
ob ta ine d b y c a s c a d ing MAX1044/ICL7660 d e vic e s
(Figure 12). The output voltage is nominally V
= -n(V+)
Vo lt a g e Divid e r
The voltage divider shown in Figure 10 splits the power
supply in half. A third capacitor can be added between
OUT
where n is the number of devices cascaded. The out-
put 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 cascaded
in this way, but output impedance rises dramatically.
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.
V+ and V
.
OUT
Co m b in e d P o s it ive Mu lt ip lic a t io n a n d
Ne g a t ive Vo lt a g e Co n ve rs io n
Fig ure 11 illus tra te s this d ua l-func tion c irc uit.
Capacitors C1 and C3 perform the bucket and reser-
voir func tions for g e ne ra ting the ne g a tive volta g e .
Capacitors C2 and C4 are the bucket and reservoir
1
2
3
4
8
7
6
5
V+
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
MAX1044
ICL7660
MAX1044
ICL7660
MAX1044
ICL7660
10µF
10µF
10µF
V
= -n(V+)
OUT
1
2
3
10µF
10µF
10µF
Figure 12. Cascading MAX1044/ICL7660 for Increased Output Voltage
10 ______________________________________________________________________________________
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
MAX14/ICL760
P a ra lle lin g De vic e s
Paralleling multiple MAX1044/ICL7660s reduces output
resistance and increases current capability. As illus-
trated 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
2
3
4
8
7
6
5
V+
MAX1044
ICL7660
C1
R
(of MAX1044 or ICL7660)
OUT
n (number of devices)
R
=
OUT
1
S h u t d o w n S c h e m e s
Figures 14a–14c illustrate three ways of adding shut-
down capability to the MAX1044/ICL7660. When using
these circuits, be aware that the additional capacitive
loading on the OSC pin will reduce the oscillator fre-
quency. 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
_Ord e rin g In fo rm a t io n (c o n t in u e d )
V+
10kΩ REQUIRED FOR TTL
PART
TEMP. RANGE
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
PIN-PACKAGE
8 SO
V+
CMOS or
TTL GATE
1
2
3
4
8
7
6
5
MAX1044ESA
MAX1044MJA
ICL7660CPA
ICL7660CSA
ICL7660CUA
ICL7660C/D
ICL7660EPA
ICL7660ESA
1N4148
8 CERDIP**
8 Plastic DIP
8 SO
MAX1044
ICL7660
10µF
0°C to +70°C
0°C to +70°C
8 µMAX
0°C to +70°C
Dice*
V
OUT
= -(V+)
-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
10µF
†
a)
ICL7660AMJA
8 CERDIP**
8 TO-99**
†
V+
ICL7660AMTV
74HC03
OPEN-DRAIN OR
74LS03
OPEN-COLLECTOR
NAND GATES
* Contact factory for dice specifications.
MAX1044
ICL7660
7
** Contact factory for availability.
†
The Maxim ICL7660 meets or exceeds all “A” and “S”
specifications.
b)
c)
V+
OUTPUT
ENABLE
74HC126 OR
74LS126
TRI-STATE BUFFER
MAX1044
ICL7660
7
Figure 14a-14c. Shutdown Schemes for MAX1044/ICL7660
______________________________________________________________________________________ 11
S w it c h e d -Ca p a c it o r Vo lt a g e Co n ve rt e rs
__________________________________________________________Ch ip To p o g ra p h ie s
MAX1044
CAP+
ICL7660
GND
BOOST
V+
0. 084"
CAP+
GND
(2. 1mm)
0. 076"
(1. 930mm)
OSC
CAP-
CAP-
V+
LV
V
OUT
V
OUT
MAX14/ICL760
LV
OSC
0. 060"
0. 076"
(1. 930mm)
(1. 5mm)
TRANSISTOR COUNT: 72
SUBSTRATE CONNECTED TO V+
TRANSISTOR COUNT: 71
SUBSTRATE CONNECTED TO V+
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.036
MAX
0.044
0.008
0.014
0.007
0.120
0.120
MIN
0.91
0.10
0.25
0.13
2.95
2.95
MAX
1.11
0.20
0.36
0.18
3.05
3.05
A
A1 0.004
B
C
D
E
e
0.010
0.005
0.116
0.116
E
H
0.0256
0.65
H
L
0.188
0.016
0°
0.198
0.026
6°
4.78
0.41
0°
5.03
0.66
6°
α
21-0036
D
C
α
A
8-PIN µMAX
0.127mm
0.004 in
PACKAGE
e
B
A1
L
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1994 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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