ETC MAX1720

MAX1720
Switched Capacitor Voltage
Inverter with Shutdown
The MAX1720 is a CMOS charge pump voltage inverter that is
designed for operation over an input voltage range of 1.15 V to 5.5 V
with an output current capability in excess of 50 mA. The operating
current consumption is only 67 mA, and a power saving shutdown
input is provided to further reduce the current to a mere 0.4 mA. The
device contains a 12 kHz oscillator that drives four low resistance
MOSFET switches, yielding a low output resistance of 26 W and a
voltage conversion efficiency of 99%. This device requires only two
external 10 mF capacitors for a complete inverter making it an ideal
solution for numerous battery powered and board level applications.
The MAX1720 is available in the space saving TSOP−6 package.
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TSOP−6
SN SUFFIX
CASE 318G
6
1
Features
•
•
•
•
•
•
•
•
Operating Voltage Range of 1.15 V to 5.5 V
Output Current Capability in Excess of 50 mA
Low Current Consumption of 67 mA
Power Saving Shutdown Input for a Reduced Current of 0.4 mA
Operation at 12 kHz
Low Output Resistance of 26 W
Space Saving TSOP−6 Package
Pb−Free Package is Available
EACAYW G
G
1
EAC = Device Code
A
= Assembly Location
Y
= Year
W
= Work Week
G
= Pb−Free Package
(Note: Microdot may be in either location)
Typical Applications
•
•
•
•
•
•
•
•
MARKING DIAGRAM
LCD Panel Bias
Cellular Telephones
Pagers
Personal Digital Assistants
Electronic Games
Digital Cameras
Camcorders
Hand Held Instruments
PIN CONNECTIONS
Vout
1
6
C+
Vin
2
5
SHDN
C−
3
4
GND
−Vout
Vin
1
6
2
5
3
4
(Top View)
ORDERING INFORMATION
Figure 1. Typical Application
December, 2005 − Rev. 3
Package
Shipping †
MAX1720EUT
TSOP−6
3000 Tape & Reel
TSOP−6
(Pb−Free)
3000 Tape & Reel
MAX1720EUTG
This device contains 77 active transistors.
© Semiconductor Components Industries, LLC, 2005
Device
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
1
Publication Order Number:
MAX1720/D
MAX1720
MAXIMUM RATINGS*
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Rating
Symbol
Value
Unit
Input Voltage Range (Vin to GND)
Vin
−0.3 to 6.0
V
Output Voltage Range (Vout to GND)
Vout
−6.0 to 0.3
V
Output Current (Note 1)
Iout
100
mA
Output Short Circuit Duration (Vout to GND, Note 1)
tSC
Indefinite
sec
Operating Junction Temperature
TJ
150
°C
Power Dissipation and Thermal Characteristics
Thermal Resistance, Junction−to−Air
Maximum Power Dissipation @ TA = 70°C
RqJA
PD
256
313
°C/W
mW
Storage Temperature
Tstg
−55 to 150
°C
Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.
*ESD Ratings
ESD Machine Model Protection up to 200 V, Class B
ESD Human Body Model Protection up to 2000 V, Class 2
ELECTRICAL CHARACTERISTICS (Vin = 5.0 V, C1 = 10 mF, C2 = 10 mF, TA = −40°C to 85°C, typical values shown are for TA = 25°C
unless otherwise noted. See Figure 14 for Test Setup.)
Characteristic
Symbol
Min
Typ
Max
Operating Supply Voltage Range (SHDN = Vin, RL = 10 k)
Vin
1.5 to 5.5
1.15 to 6.0
−
Supply Current Device Operating (SHDN = 5.0 V, RL = R)
TA = 25°C
TA = 85°C
Iin
Unit
V
mA
−
−
67
72
90
100
−
−
0.4
1.6
−
−
8.4
6.0
12
−
15.6
21
mA
Supply Current Device Shutdown (SHDN = 0 V)
TA = 25°C
TA = 85°C
ISHDN
Oscillator Frequency
TA = 25°C
TA = −40°C to 85°C
fOSC
Output Resistance (Iout = 25 mA, Note 2)
Rout
−
26
50
W
Voltage Conversion Efficiency (RL = R)
VEFF
99
99.9
−
%
PEFF
−
96
−
%
−
−
0.6 Vin
0.5 Vin
−
−
Power Conversion Efficiency (RL = 1.0 k)
Shutdown Input Threshold Voltage (Vin = 1.5 V to 5.5 V)
High State, Device Operating
Low State, Device Shutdown
kHz
Vth(SHDN)
Shutdown Input Bias Current
High State, Device Operating, SHDN = 5.0 V
TA = 2
TA = 85°C5°C
Low State, Device Shutdown, SHDN = 0 V
TA = 25°C
TA = 85°C
V
pA
IIH
−
−
5.0
100
−
−
−
−
5.0
100
−
−
−
1.2
−
IIL
Wake−Up Time from Shutdown (RL = 1.0 k)
tWKUP
ms
1. Maximum Package power dissipation limits must be observed to ensure that the maximum junction temperature is not exceeded.
TJ + TA ) (PD RqJA)
2. Capacitors C1 and C2 contribution is approximately 20% of the total output resistance.
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2
MAX1720
90
Figure 14 Test Setup
TA = 25°C
90
Rout, OUTPUT RESISTANCE (W)
Rout, OUTPUT RESISTANCE (W)
100
80
70
60
50
40
30
20
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Figure 14 Test Setup
80
70
Vin = 1.5 V
Vin = 2.0 V
60
50
Vin = 3.3 V
40
30
Vin = 5.0 V
20
−50
5.5
Vin, SUPPLY VOLTAGE (V)
Vout, OUTPUT VOLTAGE RIPPLE (mVp−p)
Iout, OUTPUT CURRENT (mA)
30
Vin = 4.75 V
Vout = −4.00 V
20
Vin = 3.15 V
Vout = −2.50 V
10
Vin = 1.90 V
Vout = −1.50 V
5
Figure 14 Test Setup
TA = 25°C
0
0
10
20
30
40
Vin = 4.75 V
Vout = −4.00 V
300
250
200
Vin = 3.15 V
Vout = −2.50 V
150
Vin = 1.90 V
Vout = −1.50 V
100
50
0
10
20
30
40
C1, C2, C3, CAPACITANCE (mF)
C1, C2, C3, CAPACITANCE (mF)
Figure 4. Output Current vs. Capacitance
Figure 5. Output Voltage Ripple vs.
Capacitance
Figure 14 Test Setup
RL = ∞
70
TA = 85°C
60
TA = 25°C
50
TA = −40°C
40
2.0
2.5
3.0
3.5
4.0
100
Figure 14 Test Setup
TA = 25°C
350
0
fOSC, OSCILLATOR FREQUENCY (kHz)
Iin, SUPPLY CURRENT (mA)
75
400
50
80
30
1.5
50
Figure 3. Output Resistance vs. Ambient
Temperature
35
15
25
0
TA, AMBIENT TEMPERATURE (°C)
Figure 2. Output Resistance vs. Supply Voltage
25
−25
4.5
5.0
13.0
Figure 14 Test Setup
12.5
Vin = 5.0 V
12.0
11.5
11.0
Vin = 1.5 V
10.5
10.0
−50
Vin = 3.3 V
−25
0
25
50
75
Vin, SUPPLY VOLTAGE (V)
TA, AMBIENT TEMPERATURE (°C)
Figure 6. Supply Current vs. Supply Voltage
Figure 7. Oscillator Frequency vs. Ambient
Temperature
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3
50
100
h, POWER CONVERSION EFFICIENCY (%)
MAX1720
Vout, OUTPUT VOLTAGE (V)
0.0
100
Figure 14 Test Setup
TA = 25°C
Vin = 2.0 V
−1.0
Vin = 3.3 V
−2.0
−3.0
Vin = 5.0 V
−4.0
−5.0
−6.0
10
20
30
40
50
90
80
70
Vin = 1.5 V
60
Vin = 2.0 V
50
40
0
10
20
30
40
Figure 8. Output Voltage vs. Output Current
Figure 9. Power Conversion Efficiency vs.
Output Current
ISHDN, SHUTDOWN SUPPLY CURRENT (mA)
Iout, OUTPUT CURRENT (mA)
Figure 14 Test Setup
Vin = 3.3 V
Iout = 5.0 mA
TA = 25°C
1.50
Vin = 5.0 V
RL = 10 kW
SHDN = GND
Vin = 3.3 V
1.25
1.00
0.75
Vin = 1.5 V
0.50
0.25
−50
−25
0
25
50
75
TIME = 25 ms / Div.
TA, AMBIENT TEMPERATURE (°C)
Figure 10. Output Voltage Ripple and Noise
Figure 11. Shutdown Supply Current vs.
Ambient Temperature
WAKEUP TIME FROM SHUTDOWN
SHDN = 5.0V/Div.
TA = 25°C
4.5
4.0
Low State,
Device Shutdown
3.5
3.0
High State,
Device Operating
2.5
2.0
1.5
0.5
1.0
1.5
2.0
2.5
Vin = 5.0 V
RL = 1.0 kW
TA = 25°C
Vout = 1.0 V/Div.
3.0
TIME = 500 ms / Div.
Vth(SHND), SHUTDOWN INPUT VOLTAGE THRESHOLD (V)
Figure 12. Supply Voltage vs. Shutdown Input
Voltage Threshold
Figure 13. Wakeup Time From Shutdown
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4
50
1.75
5.0
Vin, SUPPLY VOLTAGE (V)
Vin = 5.0 V
Vin = 3.3 V
Iout, OUTPUT CURRENT (mA)
OUTPUT VOLTAGE RIPPLE AND
NOISE = 10 mV / Div. AC COUPLED
0
Figure 14 Test Setup
TA = 25°C
100
MAX1720
Charge Pump Efficiency
−Vout
C
+ 2
6
1
The overall power conversion efficiency of the charge
pump is affected by four factors:
1. Losses from power consumed by the internal
oscillator, switch drive, etc. (which vary with input
voltage, temperature and oscillator frequency).
2. I2R losses due to the on−resistance of the MOSFET
switches on−board the charge pump.
3. Charge pump capacitor losses due to Equivalent
Series Resistance (ESR).
4. Losses that occur during charge transfer from the
commutation capacitor to the output capacitor when
a voltage difference between the two capacitors
exists.
Most of the conversion losses are due to factors 2, 3 and 4.
These losses are given by Equation 1.
RL
OSC
Vin
+
2
5
3
4
+
C1
C3
C1 = C2 = C3 = 10 mF
Figure 14. Test Setup/Voltage Inverter
DETAILED OPERATING DESCRIPTION
The MAX1720 charge pump converter inverts the voltage
applied to the Vin pin. Conversion consists of a two−phase
operation (Figure 15). During the first phase, switches S2 and
S4 are open and S1 and S3 are closed. During this time, C1
charges to the voltage on Vin and load current is supplied from
C2. During the second phase, S2 and S4 are closed, and S1 and
S3 are open. This action connects C1 across C2, restoring
charge to C2.
S1
ƪ
P
+ I out 2
LOSS(2,3,4)
1
(f
OSC
)C1
) 8R
SWITCH
R out ^ I out 2
) 4ESR
C1
) ESR
C2
(eq. 1)
The 1/(fOSC)(C1) term in Equation 1 is the effective output
resistance of an ideal switched capacitor circuit (Figures 16
and 17).
The losses due to charge transfer above are also shown in
Equation 2. The output voltage ripple is given by Equation 3.
S2
Vin
C1
PLOSS + [ 0.5C 1 (Vin 2 * Vout 2)
) 0.5C2 (VRIPPLE 2 * 2VoutVRIPPLE)]
fOSC
(eq. 2)
C2
S3
ƫ
S4
V
−Vout
RIPPLE
+
Iout
(f
)(C )
OSC 2
) 2(I out)(ESR )
C2
(eq. 3)
From Osc
f
Vin
Vout
Figure 15. Ideal Switched Capacitor Charge Pump
C1
APPLICATIONS INFORMATION
C2
RL
Output Voltage Considerations
The MAX1720 performs voltage conversion but does not
provide regulation. The output voltage will drop in a linear
manner with respect to load current. The value of this
equivalent output resistance is approximately 26 W nominal
at 25°C with Vin = 5.0 V. Vout is approximately −5.0 V at light
loads, and drops according to the equation below:
Figure 16. Ideal Switched Capacitor Model
REQUIV
Vin
VDROP + Iout Rout
Vout + * (Vin * VDROP)
Vout
R
EQUIV
+
f
1
C1
C2
RL
Figure 17. Equivalent Output Resistance
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MAX1720
Capacitor Selection
Voltage Inverter
In order to maintain the lowest output resistance and
output ripple voltage, it is recommended that low ESR
capacitors be used. Additionally, larger values of C1 will
lower the output resistance and larger values of C2 will
reduce output voltage ripple. (See Equation 3).
Table 1 shows various values of C1, C2 and C3 with the
corresponding output resistance values at 25°C. Table 2
shows the output voltage ripple for various values of C1, C2
and C3. The data in Tables 1 and 2 was measured not
calculated.
The most common application for a charge pump is the
voltage inverter (Figure 14). This application uses two or
three external capacitors. The C1 (pump capacitor) and C2
(output capacitor) are required. The input bypass capacitor,
C3, may be necessary depending on the application. The
output is equal to −Vin plus any voltage drops due to loading.
Refer to Tables 1 and 2 for capacitor selection. The test setup
used for the majority of the characterization is shown in
Figure 14.
Table 1. Output Resistance vs. Capacitance
(C1 = C2 = C3), Vin = 4.75 V and Vout = −4.0 V
Layout Considerations
C1 = C2 = C3
(mF)
Rout
(W)
0.7
129.1
As with any switching power supply circuit, good layout
practice is recommended. Mount components as close
together as possible to minimize stray inductance and
capacitance. Also, use a large ground plane to minimize noise
leakage into other circuitry.
1.4
69.5
Capacitor Resources
3.3
37.0
7.3
26.5
10
25.9
24
24.1
Selecting the proper type of capacitor can reduce switching
loss. Low ESR capacitors are recommended. The MAX1720
was characterized using the capacitors listed in Table 3. This
list identifies low ESR capacitors for the voltage inverter
application.
50
24
Table 3. Capacitor Types
Manufacturer/Contact
Table 2. Output Voltage Ripple vs. Capacitance
(C1 = C2 = C3), Vin = 4.75 V and Vout = −4.0 V
C1 = C2 = C3
(mF)
Output Voltage Ripple
(mV)
0.7
382
1.4
342
3.3
255
7.3
164
10
132
24
59
50
38
Part Types/Series
AVX
843−448−9411
www.avxcorp.com
TPS
Cornell Dubilier
508−996−8561
www.cornell−dubilier.com
ESRD
Sanyo/Os−con
619−661−6835
www.sanyovideo.com/oscon.htm
SN
SVP
Vishay
603−224−1961
www.vishay.com
593D
594
Input Supply Bypassing
−Vout
The input voltage, Vin should be capacitively bypassed to
reduce AC impedance and minimize noise effects due to the
switching internals in the device. If the device is loaded from
Vout to GND, it is recommended that a large value capacitor
(at least equal to C1) be connected from Vin to GND. If the
device is loaded from Vin to Vout, a small (0.7 mF) capacitor
between the pins is sufficient.
OSC
+
Vin
6
1
+
2
5
+
3
4
Capacitors = 10 mF
Figure 18. Voltage Inverter
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6
MAX1720
The MAX1720 primary function is a voltage inverter. The device will convert 5.0 V into −5.0 V with light loads. Two capacitors
are required for the inverter to function. A third capacitor, the input bypass capacitor, may be required depending on the power
source for the inverter. The performance for this device is illustrated below.
Vout, OUTPUT VOLTAGE (V)
0
TA = 25°C
−1.0
Vin = 3.3 V
−2.0
−3.0
Vin = 5.0 V
−4.0
−5.0
−6.0
0
10
20
30
40
Iout, OUTPUT CURRENT (mA)
50
Figure 19. Inverter Load Regulation, Output Voltage vs. Output Current
Vin
−Vout
6
1
+
+
2
6
1
OSC
OSC
+
5
+
2
5
3
4
+
3
4
Capacitors = 10 mF
Figure 20. Cascaded Devices for Increased Negative Output Voltage
Two or more devices can be cascaded for increased output voltage. Under light load conditions, the output voltage is
approximately equal to −Vin times the number of stages. The converter output resistance increases dramatically with each
additional stage. This is due to a reduction of input voltage to each successive stage as the converter output is loaded. Note that
the ground connection for each successive stage must connect to the negative output of the previous stage. The performance
characteristics for a converter consisting of two cascaded devices are shown below.
0
Vout, OUTPUT VOLTAGE (V)
TA = 25°C
−2.0
B
−4.0
A
−6.0
−8.0
−10.0
0
10
20
30
Iout, OUTPUT CURRENT (mA)
40
Figure 21. Cascade Load Regulation, Output Voltage vs. Output Current
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Curve
Vin (V)
Rout (W)
A
5.0
140
B
3.0
174
MAX1720
6
1
OSC
Vin
2
+
−Vout
5
+
+
3
+
+
4
Capacitors = 10 mF
Figure 22. Negative Output Voltage Doubler
A single device can be used to construct a negative voltage doubler. The output voltage is approximately equal to −2Vin minus
the forward voltage drop of each external diode. The performance characteristics for the above converter are shown below.
Note that curves A and C show the circuit performance with economical 1N4148 diodes, while curves B and D are with lower
loss MBRA120E Schottky diodes.
Vout, OUTPUT VOLTAGE (V)
0
TA = 25°C
−2.0
Curve
Vin (V)
All Diodes
Rout (W)
A
3.0
1N4148
124
B
3.0
MBRA120E
115
C
5.0
1N4148
96
D
5.0
MBRA120E
94
A
−4.0
B
−6.0
C
−8.0
D
−10.0
30
10
20
Iout, OUTPUT CURRENT (mA)
0
40
Figure 23. Doubler Load Regulation, Output Voltage vs. Output Current
6
1
OSC
Vin
+
2
−Vout
5
+
+
3
+
+
4
Capacitors = 10 mF
Figure 24. Negative Output Voltage Tripler
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8
+
+
MAX1720
A single device can be used to construct a negative voltage tripler. The output voltage is approximately equal to −3Vin minus
the forward voltage drop of each external diode. The performance characteristics for the above converter are shown below.
Note that curves A and C show the circuit performance with economical 1N4148 diodes, while curves B and D are with lower
loss MBRA120E Schottky diodes.
0
Vout, OUTPUT VOLTAGE
−2.0
A
−4.0
B
−6.0
C
−8.0
D
−10.0
Curve
Vin (V)
All Diodes
Rout (W)
A
3.0
1N4148
267
B
3.0
MBRA120E
250
C
5.0
1N4148
205
D
5.0
MBRA120E
195
−12.0
−14.0
TA = 25°C
−16.0
0
10
20
30
Iout, OUTPUT CURRENT
40
50
Figure 25. Tripler Load Regulation, Output Voltage vs. Output Current
6
1
OSC
+
Vin
+
2
5
3
4
+
Vout
Capacitors = 10 mF
Figure 26. Positive Output Voltage Doubler
A single device can be used to construct a positive voltage doubler. The output voltage is approximately equal to 2Vin minus
the forward voltage drop of each external diode. The performance characteristics for the above converter are shown below.
Note that curves A and C show the circuit performance with economical 1N4148 diodes, while curves B and D are with lower
loss MBRA120E Schottky diodes.
10.0
Vout, OUTPUT VOLTAGE (V)
D
8.0
C
6.0
Curve
Vin (V)
All Diodes
Rout (W)
A
3.0
1N4148
32
B
3.0
MBRA120E
26
C
5.0
1N4148
26
D
5.0
MBRA120E
21
B
4.0
A
2.0
TA = 25°C
0
0
10
20
30
Iout, OUTPUT CURRENT (mA)
40
Figure 27. Doubler Load Regulation, Output Voltage vs. Output Current
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MAX1720
6
1
OSC
+
Vin
+
2
+
Vout
5
+
3
+
4
Capacitors = 10 mF
Figure 28. Positive Output Voltage Tripler
A single device can be used to construct a positive voltage tripler. The output voltage is approximately equal to 3Vin minus
the forward voltage drop of each external diode. The performance characteristics for the above converter are shown below.
Note that curves A and C show the circuit performance with economical 1N4148 diodes, while curves B and D are with lower
loss MBRA120E Schottky diodes.
Vout, OUTPUT VOLTAGE (V)
14.0
D
Curve
Vin (V)
All Diodes
Rout (W)
A
3.0
1N4148
111
B
3.0
MBRA120E
97
C
5.0
1N4148
85
D
5.0
MBRA120E
75
12.0
10.0
C
8.0
6.0
B
4.0
2.0
A
TA = 25°C
0
0
10
20
30
Iout, OUTPUT CURRENT (mA)
40
Figure 29. Tripler Load Regulation, Output Voltage vs. Output Current
−Vout
+
6
1
OSC
Vin
+
2
5
+
100 k
3
4
Capacitors = 10 mF
Figure 30. Load Regulated Negative Output Voltage
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MAX1720
A zener diode can be used with the shutdown input to provide closed loop regulation performance. This significantly reduces
the converter’s output resistance and dramatically enhances the load regulation. For closed loop operation, the desired
regulated output voltage must be lower in magnitude than −Vin. The output will regulate at a level of −VZ + Vth(SHDN). Note that
the shutdown input voltage threshold is typically 0.5 Vin and therefore, the regulated output voltage will change proportional
to the converter’s input. This characteristic will not present a problem when used in applications with constant input voltage.
In this case the zener breakdown was measured at 25 mA. The performance characteristics for the above converter are shown
below. Note that the dashed curve sections represent the converter’s open loop performance.
Vout, OUTPUT VOLTAGE (V)
−1.0
TA = 25°C
−2.0
A
−3.0
B
Curve
Vin (V)
Vz (V)
Vout (V)
A
3.3 V
4.5
−2.8
B
5.0 V
6.5
−3.8
−4.0
−5.0
0
10
20
30
40
50
60
Iout, OUTPUT CURRENT (mA)
Figure 31. Load Regulation, Output Voltage vs.
Output Current
−Vout
R1
6
1
+
OSC
Vin
+
2
5
3
4
+
R2
10 k
Capacitors = 10 mF
Figure 32. Line and Load Regulated Negative Output Voltage
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11
MAX1720
An adjustable shunt regulator can be used with the shutdown input to give excellent closed loop regulation performance. The
shunt regulator acts as a comparator with a precise input offset voltage which significantly reduces the converter’s output
resistance and dramatically enhances the line and load regulation. For closed loop operation, the desired regulated output
voltage must be lower in magnitude than −Vin. The output will regulate at a level of −Vref (R2/R1 + 1). The adjustable shunt
regulator can be from either the TLV431 or TL431 families. The comparator offset or reference voltage is 1.25 V or 2.5 V
respectively. The performance characteristics for the converter are shown below. Note that the dashed curve sections represent
the converter’s open loop performance.
0
Iout = 25 mA
R1 = 10 k
R2 = 20 k
TA = 25°C
Vout, OUTPUT VOLTAGE (V)
Vout, OUTPUT VOLTAGE (V)
−1.0
A
−2.0
−3.0
B
−4.0
−1.0
−2.0
−3.0
TA = 25°C
−5.0
0
10
20
30
40
50
60
70
−4.0
1.0
2.0
3.0
4.0
5.0
6.0
Iout, OUTPUT CURRENT (mA)
Vin, INPUT VOLTAGE (V)
Figure 33. Load Regulation, Output Voltage vs.
Output Current
Figure 34. Line Regulation, Output Voltage vs.
Input Current
Curve
Vin (V)
R1 (W)
R2 (W)
Vout (V)
A
3.0
10 k
5.0 k
−1.8
B
5.0
10 k
20 k
−3.6
−Vout
+
6
1
1
OSC
Vin
+
6
OSC
2
5
2
5
3
4
3
4
+
+
Capacitors = 10 mF
Figure 35. Paralleling Devices for Increased Negative Output Current
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12
MAX1720
An increase in converter output current capability with a reduction in output resistance can be obtained by paralleling two or more
devices. The output current capability is approximately equal to the number of devices paralleled. A single shared output capacitor
is sufficient for proper operation but each device does require it’s own pump capacitor. Note that the output ripple frequency will
be complex since the oscillators are not synchronized. The performance characteristics for a converter consisting of two paralleled
devices is shown below.
Curve
Vin (V)
Rout (W)
A
5.0
14.5
B
3.0
17
Vout, OUTPUT VOLTAGE (V)
0
TA = 25°C
−1.0
B
−2.0
−3.0
A
−4.0
−5.0
0
10
20
30
40
50
60
70
80
90
100
Iout, OUTPUT CURRENT (mA)
Figure 36. Parallel Load Regulation, Output
Voltage vs. Output Current
Q2
6
1
+
Q1
2
5
3
4
−Vout
+
OSC
Vin
C1
C3
+
C2
C1 = C2 = 470 mF
C3 = 220 mF
Q1 = PZT751
Q2 = PZT651
−Vout = Vin −VBE(Q1) − VBE(Q2) −2 VF
Figure 37. External Switch for Increased Negative Output Current
The output current capability of the MAX1720 can be extended beyond 600 mA with the addition of two external switch
transistors and two Schottky diodes. The output voltage is approximately equal to −Vin minus the sum of the base emitter drops of
both transistors and the forward voltage of both diodes. The performance characteristics for the converter are shown below. Note
that the output resistance is reduced to 0.9 W.
Vout, OUTPUT VOLTAGE (V)
−2.2
−2.4
−2.6
−2.8
Vin = 5.0 V
Rout = 0.9 W
TA = 25°C
−3.0
−3.2
0
0.1
0.2
0.3
0.4
Iout, OUTPUT CURRENT (mA)
0.5
0.6
Figure 38. Current Boosted Load Regulation, Output Voltage vs. Output Current
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13
MAX1720
10 k
R2
Q2
R1
C1
−Vout
6
1
+
OSC
Vin
+
2
5
3
4
C2
+
Q1
C3
C1 = C2 = 470 mF
C3 = 220 mF
Q1 = PZT751
Q2 = PZT651
Figure 39. Line and Load Regulated Negative Output Voltage
with High Current Capability
This converter is a combination of Figures 37 and 32. It provides a line and load regulated output of −2.36 V at up to 450 mA
with an input voltage of 5.0 V. The output will regulate at a level of −Vref (R2/R1 + 1). The performance characteristics are shown
below. Note, the dashed line is the open loop and the solid line is the closed loop performance.
−1.0
Vout, OUTPUT VOLTAGE (V)
Vout, OUTPUT VOLTAGE (V)
−2.2
−2.4
−2.6
−2.8
Vin = 5.0 V
Rout = 0.9 W
R1 = 10 kW
R2 = 9.0 kW
TA = 25°C
−3.0
−3.2
0
0.1
0.2
0.3
0.4
Iout, OUTPUT CURRENT (A)
0.5
0.6
Iout = 100 mA
R1 = 10 k
R2 = 9 kW
TA = 25°C
−1.2
−1.4
−1.6
−1.8
−2.0
−2.2
−2.4
3.0
Figure 40. Current Boosted Load Regulation,
Output Voltage vs. Output Current
3.5
4.0
4.5
5.0
Vin, INPUT VOLTAGE (V)
Figure 41. Current Boosted Line Regulation,
Output Voltage vs. Input Voltage
50
Q2
C1
Vout
6
1
+
50
OSC
Q1
Vin
+
2
5
3
4
5.5
+
C2
C3
Capacitors = 220 mF
Q1 = PZT751
Q2 = PZT651
Figure 42. Positive Output Voltage Doubler with High Current Capability
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14
6.0
MAX1720
The MAX1720 can be configured to produce a positive output voltage doubler with current capability in excess of 500 mA.
This is accomplished with the addition of two external switch transistors and two Schottky diodes. The output voltage is
approximately equal to 2Vin minus the sum of the base emitter drops of both transistors and the forward voltage of both diodes.
The performance characteristics for the converter is shown below. Note that the output resistance is reduced to 1.9 W.
Vout, OUTPUT VOLTAGE (V)
8.8
Vin = 5.0 V
Rout = 1.9 W
TA = 25°C
8.4
8.0
7.6
7.2
6.8
0
0.1
0.2
0.3
0.4
Iout, OUTPUT CURRENT (A)
0.5
0.6
Figure 43. Positive Doubler with Current Boosted Load Regulation, Output Voltage vs. Output Current
R1
50
10 k
Q2
50
OSC
Q1
Vin
+
2
5
3
4
R2
+
6
1
C3
Vout
+
C1
C2
Capacitors = 220 mF
Q1 = PZT751
Q2 = PZT651
Figure 44. Line and Load Regulated Positive Output Voltage Doubler with High Current Capability
This converter is a combination of Figures 42 and the shunt regulator to close the loop. In this case the anode of the regulator
is connected to ground. This convert provides a line and load regulated output of 7.6 V at up to 300 mA with an input voltage
of 5.0 V. The output will regulate at a level of Vref (R2/R1 + 1). The open loop configuration is the dashed line and the closed
loop is the solid line. The performance characteristics are shown below.
8.0
Vin = 5.0 V
Rout = 1.9 W Open Loop
Rout = 0.5 W Closed Loop
R1 = 10 k
R2 = 51.3 kW
TA = 25°C
8.4
8.0
Vout, OUTPUT VOLTAGE (V)
Vout, OUTPUT VOLTAGE (V)
8.8
7.6
7.2
6.8
0
0.1
0.2
0.3
0.4
Iout, OUTPUT CURRENT (A)
0.5
0.6
7.0
6.0
5.0
4.0
Iout = 100 mA
R1 = 10 k
R2 = 51.3 kW
TA = 25°C
3.0
2.0
1.0
1.0
Figure 45. Current Boosted Close Loop Load
Regulation, Output Voltage vs. Output Current
2.0
3.0
4.0
Vin, INPUT VOLTGE (V)
5.0
Figure 46. Current Boosted Close Loop Line
Regulation, Output Voltage vs. Input Voltage
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15
6.0
MAX1720
Vin = −5.0 V
+
+
OSC
C
C
+
6
1
C
2
5
3
4
Vout = −2.5 V
C
+
Capacitors = 10 mF
Figure 47. Negative Input Voltage Splitter
A single device can be used to split a negative input voltage. The output voltage is approximately equal to −Vin/2. The
performance characteristics are shown below. Note that the converter has an output resistance of 10 W.
Vout, OUTPUT VOLTAGE (V)
−1.5
TA = 25°C
Rout = 10 W
−1.7
−1.9
−2.1
−2.3
−2.5
0
10
20
30
40
50
60
Iout, OUTPUT CURRENT (mA)
70
80
Figure 48. Negative Voltage Splitter Load Regulation, Output Voltage vs. Output Current
−Vout
R1
R2
6
1
+
OSC
Vin
+
2
5
10 k
3
4
+
+
+
+Vout
Capacitors = 10 mF
Figure 49. Combination of a Closed Loop Negative Inverter with a Positive Output Voltage Doubler
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16
MAX1720
All of the previously shown converter circuits have only single outputs. Applications requiring multiple outputs can be
constructed by incorporating combinations of the former circuits. The converter shown above combines Figures 26 and 32 to
form a regulated negative output inverter with a non−regulated positive output doubler. The magnitude of −Vout is controlled
by the resistor values and follows the relationship −Vref (R2/R1 + 1). Since the positive output is not within the feedback loop,
its output voltage will increase as the negative output load increases. This cross regulation characteristic is shown in the upper
portion of Figure 50. The dashed line is the open loop and the solid line is the closed loop configuration for the load regulation.
The load regulation for the positive doubler with a constant load on the −Vout is shown in Figure 51.
10.0
Vout, OUTPUT VOLTAGE (V)
Vout, OUTPUT VOLTAGE (V)
9.0
Positive Doubler
Iout = 15 mA
8.0
−3.0
Negative Inverter
−4.0
Rout = 45 W − Open Loop
Rout = 2 W − Closed Loop
R1 = 10 k, R2 = 20 k
TA = 25°C
−5.0
0
9.0
8.0
Negative Inverter Iout = 15 mA
R1 = 10 kW
R2 = 20 kW
TA = 25°C
7.0
10
20
30
Iout, NEGATIVE INVERTER OUTPUT CURRENT (mA)
0
10
20
30
40
50
Iout, POSITIVE DOUBLER OUTPUT CURRENT (mA)
Figure 51. Load Regulation, Output
Voltage vs. Output Current
Figure 50. Load Regulation, Output
Voltage vs. Output Current
+
IC1
C1
C2
Vin
−Vout
SHDN
GND
C3
+
GND
+
0.5″
Inverter Size = 0.5 in x 0.2 in
Area = 0.10 in2, 64.5 mm2
Figure 52. Inverter Circuit Board Layout, Top View Copper Side
TAPING FORM
Component Taping Orientation for TSOP−6 Devices
USER DIRECTION OF FEED
DEVICE
MARKING
PIN 1
Standard Reel Component Orientation
(Mark Right Side Up)
Tape & Reel Specifications Table
Package
TSOP−6
Tape Width (W)
8 mm
Pitch (P)
Part Per Full Reel
Diameter
4 mm
3000
7 inches
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17
MAX1720
PACKAGE DIMENSIONS
TSOP−6
CASE 318G−02
ISSUE P
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. MAXIMUM LEAD THICKNESS INCLUDES LEAD
FINISH THICKNESS. MINIMUM LEAD
THICKNESS IS THE MINIMUM THICKNESS OF
BASE MATERIAL.
4. DIMENSIONS A AND B DO NOT INCLUDE
MOLD FLASH, PROTRUSIONS, OR GATE
BURRS.
D
6
HE
1
5
4
2
3
E
b
e
q
c
A
0.05 (0.002)
L
A1
DIM
A
A1
b
c
D
E
e
L
HE
q
MIN
0.90
0.01
0.25
0.10
2.90
1.30
0.85
0.20
2.50
0°
MILLIMETERS
NOM
MAX
1.00
1.10
0.06
0.10
0.38
0.50
0.18
0.26
3.00
3.10
1.50
1.70
0.95
1.05
0.40
0.60
2.75
3.00
10°
−
MIN
0.035
0.001
0.010
0.004
0.114
0.051
0.034
0.008
0.099
0°
INCHES
NOM
0.039
0.002
0.014
0.007
0.118
0.059
0.037
0.016
0.108
−
MAX
0.043
0.004
0.020
0.010
0.122
0.067
0.041
0.024
0.118
10°
SOLDERING FOOTPRINT*
2.4
0.094
1.9
0.075
0.95
0.037
0.95
0.037
0.7
0.028
1.0
0.039
SCALE 10:1
mm Ǔ
ǒinches
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
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Phone: 480−829−7710 or 800−344−3860 Toll Free USA/Canada Japan: ON Semiconductor, Japan Customer Focus Center
2−9−1 Kamimeguro, Meguro−ku, Tokyo, Japan 153−0051
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ON Semiconductor Website: http://onsemi.com
Order Literature: http://www.onsemi.com/litorder
For additional information, please contact your
local Sales Representative.
MAX1720/D
19-1439; Rev 2; 4/04
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
The ultra-small MAX1719/MAX1720/MAX1721 monolithic,
CMOS charge-pump inverters accept input voltages
ranging from +1.5V to +5.5V. The MAX1720 operates at
12kHz, and the MAX1719/MAX1721 operate at 125kHz.
High efficiency, small external components, and logiccontrolled shutdown make these devices ideal for both
battery-powered and board-level voltage conversion
applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. A typical MAX1719/
MAX1720/MAX1721 application is generating a -5V
supply from a +5V logic supply to power analog circuitry.
All three parts come in a 6-pin SOT23 package and can
deliver a continuous 25mA output current.
For pin-compatible SOT23 switched-capacitor voltage
inverters without shutdown (5-pin SOT23), see the
MAX828/MAX829 and MAX870/MAX871 data sheets. For
applications requiring more power, the MAX860/MAX861
deliver up to 50mA. For regulated outputs (up to -2 x VIN),
refer to the MAX868. The MAX860/MAX861 and MAX868
are available in space-saving µMAX packages.
Applications
Local Negative Supply from a Positive Supply
Features
♦ 1nA Logic-Controlled Shutdown
♦ 6-Pin SOT23 Package
♦ 99.9% Voltage Conversion Efficiency
♦ 50µA Quiescent Current (MAX1720)
♦ +1.5V to +5.5V Input Voltage Range
♦ 25mA Output Current
♦ Requires Only Two 1µF Capacitors
(MAX1719/MAX1721)
Ordering Information
PART
TEMP RANGE
PINPACKAGE
SOT
TOP MARK
MAX1719EUT
-40°C to +85°C
6 SOT23-6
AACA
MAX1720EUT
-40°C to +85°C
6 SOT23-6
AABS
MAX1721EUT
-40°C to +85°C
6 SOT23-6
AABT
Small LCD Panels
GaAs PA Bias Supply
Handy-Terminals, PDAs
Battery-Operated Equipment
Pin Configuration
Typical Operating Circuit
1µF
INPUT
1.5V to 5.5V
C1+
TOP VIEW
C1OUT
IN
MAX1721
NEGATIVE
OUTPUT
-1 · VIN
25mA
OFF
1
IN
2
C1-
3
MAX1719
MAX1720
MAX1721
6
C1+
5
SHDN (SHDN)
4
GND
1µF
SHDN
ON
OUT
GND
SOT23-6
( ) ARE FOR MAX1719
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1719/MAX1720/MAX1721
General Description
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V
OUT to GND .............................................................-6V to +0.3V
C1+, SHDN, SHDN to GND .........................-0.3V to (VIN + 0.3V)
C1- to GND...............................................(VOUT - 0.3V) to +0.3V
OUT Output Current..........................................................100mA
OUT Short Circuit to GND..............................................Indefinite
Continuous Power Dissipation (TA = +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C).................696mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
(V IN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = 10µF (MAX1720), C1 = C2 = 1µF
(MAX1719/MAX1721), circuit of Figure 1, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Supply Voltage Range
SYMBOL
VIN
Quiescent Supply Current
(Note 3)
ICC
Shutdown Supply Current
ISHDN
Oscillator Frequency
fOSC
Voltage Conversion Efficiency
Output Resistance (Note 1)
OUT to GND
Shutdown Resistance
RO
RO, SHDN
VIH
SHDN/ SHDN Input Logic Low
VIL
Wake-Up Time from Shutdown
2
IIL, IIH
MIN
TYP
MAX1720
RL = 10kΩ
TA = 0°C to + 85°C
1.5
5.5
MAX1719/MAX1721
RL = 10kΩ
TA = +25°C
1.4
5.5
TA = 0°C to + 85°C
1.5
5.5
TA = +25°C
1.25
MAX
TA = +25°C
50
90
MAX1719/MAX1721
350
650
0.001
1
SHDN = IN (MAX1719), TA = +25°C
SHDN = GND
(MAX1720/MAX1721) TA = +85°C
TA = +25°C
IOUT = 10mA
12
17
MAX1719/MAX1721
70
125
180
99
99.9
TA = +25°C
23
TA = 0°C to +85°C
4
12
2.0
+2.5V ≤ VIN ≤ +5.5V
0.6
VIN (MIN) ≤ VIN ≤ +2.5V
0.2
IOUT = 5mA
Ω
Ω
V
VIN - 0.2
-100
kHz
%
50
65
SHDN = IN (MAX1719), SHDN = GND
(MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
SHDN/ SHDN = GND TA = +25°C
or VIN
TA = +85°C
µA
µA
7
VIN (MIN) ≤ VIN ≤ +2.5V
V
0.02
MAX1720
+2.5V ≤ VIN ≤ +5.5V
UNITS
5.5
MAX1720
IOUT = 0, TA = +25°C
SHDN/ SHDN Input Logic High
SHDN/ SHDN Bias Current
CONDITIONS
0.05
10
MAX1720
800
MAX1719/MAX1721
80
_______________________________________________________________________________________
100
V
nA
µs
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
(V IN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = 10µF (MAX1720), C1 = C2 = 1µF
(MAX1719/MAX1721), circuit of Figure 1, TA = -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
Supply Voltage Range
VIN
Quiescent Current (Note 3)
ICC
Oscillator Frequency
fOSC
Voltage Conversion Efficiency
Output Resistance (Note 1)
Output Current
RO
IOUT
OUT to GND Shutdown
Resistance
RO, SHDN
SHDN/ SHDN Input Logic High
VIH
SHDN/ SHDN Input Logic Low
VIL
CONDITIONS
RL = 10kΩ
MIN
TYP
MAX
MAX1720
1.5
5.5
MAX1719/MAX1721
1.6
5.5
MAX1720
100
MAX1719/MAX1721
750
MAX1720
6
21
MAX1719/MAX1721
60
200
IOUT = 0
99
UNITS
V
µA
kHz
%
IOUT = 10mA
65
Ω
Continuous, long-term
25
mARMS
SHDN = IN (MAX1719), SHDN = GND
(MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
12
Ω
+2.5V ≤ VIN ≤ +5.5V
2.1
VIN (MIN) ≤ VIN ≤ +2.5V
V
VIN - 0.2
+2.5V ≤ VIN ≤ +5.5V
0.6
VIN (MIN) ≤ VIN ≤ +2.5V
0.2
V
Note 1: Capacitor contribution (ESR component plus (1/fOSC) · C) is approximately 20% of output impedance.
Note 2: All specifications from -40°C to +85°C are guaranteed by design, not production tested.
Note 3: The MAX1719/MAX1720/MAX1721 may draw high supply current during startup, up to the minimum operating supply voltage.
To guarantee proper startup, the input supply must be capable of delivering 90mA more than the maximum load current.
Typical Operating Characteristics
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25°C, unless otherwise noted.)
90
-2
VIN = +3.3V
-3
-4
VIN = +5V
-5
VIN = +5V
80
EFFICIENCY (%)
OUTPUT VOLTAGE (V)
-1
100
70
60
VIN = +1.5V
50
VIN = +2V
VIN = +3.3V
40
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
90
VIN = +5V
80
70
60
VIN = +1.5V
50
VIN = +3.3V
VIN = +2V
40
30
30
20
20
10
10
0
0
0
100
EFFICIENCY (%)
VIN = +2V
MAX1720/21toc02
VIN = +1.5V
MAX1720/21toc01
0
MAX1719/MAX1721
EFFICIENCY vs. OUTPUT CURRENT
MAX1720
EFFICIENCY vs. OUTPUT CURRENT
MAX1720/21toc03
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
_______________________________________________________________________________________
3
MAX1719/MAX1720/MAX1721
ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1719/
MAX1721
30
MAX1720
250
-40°C
150
MAX1720
-40°C
50
10
2.0
2.5
3.0
3.5
4.0
4.5
5.0
+85°C
0
1.5
5.5
2.0
2.5
INPUT VOLTAGE (V)
FREQUENCY (kHz)
VIN = +2V
40
VIN = +3.3V
30
35
5.0
60
MAX1720/21toc06
VIN = +1.5V
-40
-15
85
VOUT
MAX1719/
MAX1721
VOUT
MAX1720
-15
-10
MAX1720
35
60
35
VIN = +4.75V, VOUT = -4.0V
30
OUTPUT CURRENT (mA)
60
MAX1719/MAX1721
MAX1720
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
25
VIN = +3.15V, VOUT = -2.5V
20
15
10
10µs/div
VIN = 3.3V, VOUT = -3.17V, IOUT = 5mA
20mV/div, AC-COUPLED
85
MAX1720
OUTPUT CURRENT vs. CAPACITANCE
V SHDN
5V/div
35
OUTPUT NOISE AND RIPPLE
MAX1720
START-UP FROM SHUTDOWN
VOUT
2V/div
10
TEMPERATURE (°C)
100
10
-40
85
MAX1720/21toc10
VIN = +1.9V, VOUT = -1.5V
5
500
450
400
VIN = +4.75V, VOUT = -4.0V
350
300
VIN = +3.15V, VOUT = -2.5V
250
200
VIN = +1.9V, VOUT = -1.5V
150
100
50
0
4
5
5.5
TEMPERATURE (°C)
RL = 1kΩ
VIN = +3.3V
0
4.5
TEMPERATURE (°C)
500µs/div
10
MAX1720/21toc08
VIN = +1.5V
VIN = +5V
VIN = +5V
VIN = +1.5V
10
10
VIN = +5V
15
MAX1720/21toc09
VIN = +5V
-15
4.0
1000
MAX1720/21toc07
VIN = +1.5V
60
-40
3.5
20
PUMP FREQUENCY
vs. TEMPERATURE
70
20
3.0
25
INPUT VOLTAGE (V)
OUTPUT RESISTANCE
vs. TEMPERATURE
50
MAX1720/21toc05
200
100
20
1.5
+85°C
OUTPUT VOLTAGE RIPPLE (mVp-p)
40
300
MAX1720/21toc11
50
350
30
MAX1720/21toc12
60
MAX1719/
MAX1721
400
SUPPLY CURRENT (µA)
70
OUTPUT RESISTANCE (Ω)
450
MAX1720/21toc04
80
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT (nA)
OUTPUT RESISTANCE
vs. INPUT VOLTAGE
OUTPUT RESISTANCE (Ω)
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
0
0
5
10 15 20 25 30 35 40 45 50
CAPACITANCE (µF)
0
5
10
15
20
CAPACITANCE (µF)
_______________________________________________________________________________________
25
30
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
MAX1719/MAX1721
OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
MAX1719/MAX1721
OUTPUT CURRENT vs. CAPACITANCE
VIN = +4.75V, VOUT = -4.0V
VSHDN
5V/div
OUTPUT CURRENT (mA)
30
VOUT
2V/div
MAX1720/21toc14
35
25
VIN = +3.15V, VOUT = -2.5V
20
15
10
VIN = +1.9V, VOUT = -1.5V
5
350
300
VIN = +4.75V, VOUT = -4.0V
250
200
VIN = +3.15V, VOUT = -2.5V
150
VIN = +1.9V, VOUT = -1.5V
100
50
0
0
0
50µs/div
400
MAX1720/21toc15
MAX1720/21toc13
OUTPUT VOLTAGE RIPPLE (mVp-p)
MAX1721
START-UP FROM SHUTDOWN
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
CAPACITANCE (µF)
CAPACITANCE (µF)
RL = 1kΩ
Pin Description
PIN
MAX1719
MAX1720
MAX1721
NAME
FUNCTION
1
1
OUT
2
2
IN
3
3
C1-
4
4
GND
Ground
5
–
SHDN
Noninverting Shutdown Input. Drive this pin low for normal operation; drive it high for
shutdown mode. OUT is actively pulled to ground during shutdown.
–
5
SHDN
Inverting Shutdown Input. Drive this pin high for normal operation; drive it low for
shutdown mode. OUT is actively pulled to ground during shutdown.
6
6
C1+
Inverting Charge-Pump Output
Power-Supply Positive Voltage Input
Negative Terminal of Flying Capacitor
Positive Terminal of Flying Capacitor
Detailed Description
The MAX1719/MAX1720/MAX1721 capacitive charge
pumps invert the voltage applied to their input. For highest performance, use low equivalent series resistance
(ESR) capacitors (e.g., ceramic).
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is level
shifted downward by VIN volts. This connects C1 in parallel with the reservoir capacitor C2. If the voltage across
C2 is smaller than the voltage across C1, charge flows
from C1 to C2 until the voltage across C2 reaches
-VIN. The actual voltage at the output is more positive
than -VIN, since switches S1–S4 have resistance and the
load drains charge from C2.
_______________________________________________________________________________________
5
MAX1719/MAX1720/MAX1721
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25°C, unless
otherwise noted.)
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
f
C1
1µF (10µF)
INPUT
1.5V to 5.5V
2
6
C1+
5
3
C1-
IN
OUT
C3
1µF (10µF)
ON
OFF
V+
1
RL
MAX1719*
MAX1721
SHDN
NEGATIVE
OUTPUT
-1 · VIN
25mA
C2
C1
RL
C2
1µF (10µF)
Figure 3a. Switched-Capacitor Model
GND
4
REQUIV
V+
NOTE: ( ) CAPACITORS ARE FOR MAX1720.
*ON/OFF POLARITY OF SHDN IS REVERSED FOR MAX1719.
VOUT
1
REQUIV =
f × C1
Figure 1. Typical Application Circuit
S1
VOUT
C2
RL
S2
IN
Figure 3b. Equivalent Circuit
C1
S3
S4
where the output impedance is roughly approximated
by:
C2
VOUT = -(VIN)
Figure 2. Ideal Voltage Inverter
Charge-Pump Output
The MAX1719/MAX1720/MAX1721 are not voltage regulators: the charge pumps’ output resistance is
approximately 23Ω at room temperature (with VIN =
+5V), and VOUT approaches -5V when lightly loaded.
VOUT will droop toward GND as load current increases.
The droop of the negative supply (VDROOP-) equals the
current draw from OUT (IOUT) times the negative converter’s output resistance (RO):
VDROOP- = IOUT x RO
The negative output voltage will be:
VOUT = -(VIN - VDROOP-)
Efficiency Considerations
The efficiency of the MAX1719/MAX1720/MAX1721 is
dominated by its quiescent supply current (IQ) at low
output current and by its output impedance (ROUT) at
higher output current; it is given by:
η≅
6
IOUT
IOUT + IQ
 IOUT × ROUT 
1 −

VIN


ROUT ≅
1
(fOSC )
× C1
+ 2RSW + 4ESRC1 + ESRC2
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
RSW is the sum of the charge pump’s internal switch
resistances (typically 8Ω to 9Ω at VIN = +5V). The typical output impedance is more accurately determined
from the Typical Operating Characteristics.
Shutdown Mode
The MAX1719/MAX1720/MAX1721 have a logic-controlled shutdown input. Driving SHDN low places the
MAX1720/MAX1721 in a low-power shutdown mode.
The MAX1719’s shutdown input is inverted from that of
the MAX1720/MAX1721. Driving SHDN high places the
MAX1719 in a low-power shutdown mode. The chargepump switching halts, supply current is reduced to
1nA, and OUT is actively pulled to ground through a 4Ω
resistance.
Applications Information
Capacitor Selection
To maintain the lowest output resistance, use capacitors with low ESR (Table 1). The charge-pump output
resistance is a function of C1’s and C2’s ESR.
Therefore, minimizing the charge-pump capacitor’s
ESR minimizes the total output resistance. Table 2
gives suggested capacitor values for minimizing output
resistance or minimizing capacitor size.
_______________________________________________________________________________________
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
…
2
3
4
C1
6
Output Capacitor (C2)
Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
VRIPPLE =
MAX1719
MAX1720
MAX1721
“1”
+VIN
2
3
4
C1
1
6
MAX1719
MAX1720
MAX1721
“n”
1
…
5
C2
SHDN (MAX1719)
SHDN (MAX1720/
MAX1721)
VOUT
C2
5
VOUT = -nVIN
Figure 4. Cascading MAX1719s or MAX1720s or MAX1721s
to Increase Output Voltage
IOUT
+ 2 × IOUT × ESRC2
2 × fOSC × C2
Cascading Devices
Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 x VIN, but this is reduced slightly
by the output resistance of the first device multiplied by
the quiescent current of the second. When cascading
more than two devices, the output resistance rises dramatically. For applications requiring larger negative
voltages, see the MAX865 and MAX868 data sheets.
The maximum load current and startup current of the
nth cascaded circuit must not exceed the maximum
output current capability of the (n - 1)th circuit to ensure
proper startup.
Input Bypass Capacitor (C3)
Bypass the incoming supply to reduce its AC impedance
and the impact of the MAX1719/MAX1720/MAX1721’s
switching noise. A bypass capacitor with a value equal
to that of C1 is recommended.
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This application requires only two external components—capacitors
C1 and C2—plus a bypass capacitor, if necessary.
Refer to the Capacitor Selection section for suggested
capacitor types.
Table 1. Low-ESR Capacitor Manufacturers
PRODUCTION
METHOD
Surface-Mount
Tantalum
Surface-Mount
Ceramic
MANUFACTURER
SERIES
PHONE
FAX
AVX
TPS series
803-946-0690
803-626-3123
Matsuo
267 series
714-969-2491
714-960-6492
Sprague
593D, 595D series
603-224-1961
603-224-1430
AVX
X7R
803-946-0690
803-626-3123
Matsuo
X7R
714-969-2491
714-960-6492
Table 2. Capacitor Selection for Minimum Output Resistance or Capacitor Size
fOSC
CAPACITORS TO MINIMIZE
OUTPUT RESISTANCE
(RO = 23Ω, TYP)
C1 = C2
MAX1720
12kHz
10µF
3.3µF
MAX1719/MAX1721
125kHz
1µF
0.33µF
PART
CAPACITORS TO MINIMIZE SIZE
(RO = 40Ω, TYP)
C1 = C2
_______________________________________________________________________________________
7
MAX1719/MAX1720/MAX1721
Flying Capacitor (C1)
Increasing the flying capacitor’s value reduces the output resistance. Above a certain point, increasing C1’s
capacitance has a negligible effect because the output
resistance becomes dominated by the internal switch
resistance and capacitor ESR.
MAX1719/MAX1720/MAX1721
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
2
3
C1
4
6
SHDN (MAX1719)
SHDN (MAX1720/
MAX1721)
MAX1719
MAX1720
MAX1721
“1”
SHDN (MAX1719)
SHDN (MAX1720)
(MAX1721)
…
+VIN
2
3
4
C1
1
6
…
5
+VIN
5
3
MAX1719
MAX1720
MAX1721
“n”
C1
1
4
VOUT
6
D1, D2 = 1N4148
2
MAX1719
MAX1720
MAX1721
D1
1
VOUT = -VIN
5
VOUT = -VIN
C2
D2
C2
RO OF SINGLE DEVICE
RO = NUMBER OF DEVICES
C4
C3
Figure 5. Paralleling MAX1719s or MAX1720s or MAX1721s to
Reduce Output Resistance
Figure 6. Combined Doubler and Inverter
Paralleling Devices
Paralleling multiple MAX1719s, MAX1720s, or
MAX1721s reduces the output resistance. Each device
requires its own pump capacitor (C1), but the reservoir
capacitor (C2) serves all devices (Figure 5). Increase
C2’s value by a factor of n, where n is the number of
parallel devices. Figure 5 shows the equation for calculating output resistance.
Combined Doubler/Inverter
In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 25mA.
VOUT = (2VIN) (VFD1) - (VFD2)
GND
MAX1719
MAX1720
MAX1721
4
V+
RL
OUT
1
Figure 7. Heavy Load Connected to a Positive Supply
OUT require a Schottky diode (1N5817) between GND
and OUT, with the anode connected to OUT (Figure 7).
Layout and Grounding
Good layout is important, primarily for good noise performance. To ensure good layout, mount all components as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
Heavy Load Connected to a
Positive Supply
Under heavy loads, where a higher supply is sourcing
current into OUT, the OUT supply must not be pulled
above ground. Applications that sink heavy current into
Chip Information
TRANSISTOR COUNT: 85
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