Semiconductor Components Industries, LLC, 2001
April, 2001 – Rev. 1 1Publication Order Number:
MAX1720/D
MAX1720
Switched Capacitor
Voltage Inverter
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 6 7 A, and a power saving s hutdown i nput
is provided to further reduce the current to a mere 0.4 A. The device
contains a 12 kHz oscillator that drives four low resistance MOSFET
switches, yielding a low output resistance of 26 and a voltage
conversion efficiency of 99%. This device requires only two external
10F capacitors for a complete inverter making it an ideal solution for
numerous b attery p owered a nd b oard l evel a pplications. The M AX1720
is available in the space saving TSOP–6 (SOT–23–6) package.
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 A
Power Saving Shutdown Input for a Reduced Current of 0.4 A
Operation at 12 kHz
Low Output Resistance of 26
Space Saving TSOP–6 (SOT–23–6) Package
Typical Applications
LCD Panel Bias
Cellular Telephones
Pagers
Personal Digital Assistants
Electronic Games
Digital Cameras
Camcorders
Hand Held Instruments
6
4
2
3
1
Figure 1. Typical Application
–Vout
Vin 5
This device contains 77 active transistors.
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PIN CONNECTIONS
1
3GND
Vout
2
C– 4
C+
6
(Top View)
TSOP–6
SN SUFFIX
CASE 318G
MARKING
DIAGRAM
Device Package Shipping
ORDERING INFORMATION
MAX1720EUT TSOP–6 3000 Tape & Reel
5SHDN
EACYW
1
6
1
6
EAC= Device Code
Y = Year
W = Work Week
Vin
MAX1720
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2
MAXIMUM RATINGS*
Rating Symbol Value Unit
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Input Voltage Range (Vin to GND)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
Vin
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
–0.3 to 6.0
ÁÁÁÁ
ÁÁÁÁ
V
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Output Voltage Range (Vout to GND)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
Vout
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
–6.0 to 0.3
ÁÁÁÁ
ÁÁÁÁ
V
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Output Current (Note 1.)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
Iout
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
100
ÁÁÁÁ
ÁÁÁÁ
mA
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Output Short Circuit Duration (Vout to GND, Note 1.)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
tSC
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
Indefinite
ÁÁÁÁ
ÁÁÁÁ
sec
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Operating Junction Temperature
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
TJ
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
150
ÁÁÁÁ
ÁÁÁÁ
°C
Power Dissipation and Thermal Characteristics
Thermal Resistance, Junction to Air
Maximum Power Dissipation @ TA = 70°CRθJA
PD256
313 °C/W
mW
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Storage Temperature
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
Tstg
ÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁ
–55 to 150
ÁÁÁÁ
ÁÁÁÁ
°C
*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 µF, C2 = 10 µF, 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 Unit
Operating Supply Voltage Range (SHDN = Vin, RL = 10 k) Vin 1.5 to 5.5 1.15 to 6.0 V
Supply Current Device Operating (SHDN = 5.0 V, RL = )
TA = 25°C
TA = 85°C
Iin
67
72 90
100
µA
Supply Current Device Shutdown (SHDN = 0 V)
TA = 25°C
TA = 85°C
ISHDN
0.4
1.6
µA
Oscillator Frequency
TA = 25°C
TA = –40°C to 85°C
fOSC 8.4
6.0 12
15.6
21
kHz
Output Resistance (Iout = 25 mA, Note 2.) Rout 26 50
Voltage Conversion Efficiency (RL = ) VEFF 99 99.9 %
Power Conversion Efficiency (RL = 1.0 k) PEFF 96 %
Shutdown Input Threshold Voltage (Vin = 1.5 V to 5.5 V)
High State, Device Operating
Low State, Device Shutdown
Vth(SHDN)
0.6 Vin
0.5 Vin
V
Shutdown Input Bias Current
High State, Device Operating, SHDN = 5.0 V
TA = 25°C
TA = 85°C
Low State, Device Shutdown, SHDN = 0 V
TA = 25°C
TA = 85°C
IIH
IIL
5.0
100
5.0
100
pA
Wake–Up T ime from Shutdown (RL = 1.0 k) tWKUP 1.2 ms
1. Maximum Package power dissipation limits must be observed to ensure that the maximum junction temperature is not exceeded.
TJTA(PDRJA)
2. Capacitors C1 and C2 contribution is approximately 20% of the total output resistance.
MAX1720
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3
Vin, SUPPLY VOLTAGE (V)
fOSC, OSCILLATOR FREQUENCY (kHz)
1.5 3.02.52.0 3.5 4.0 4.5 5.0
0
35
30
25
20
502010
15
10
5
040
C1, C2, C3, CAPACITANCE (µF)
Iout, OUTPUT CURRENT (mA)
30
Rout, OUTPUT RESISTANCE ()
Vin, SUPPLY VOLTAGE (V)
80
70
60
50
40
30
10.5
10.0
11.0
11.5
12.0
12.5
13.0
70
50
80
40
60
20
90
Figure 2. Output Resistance vs. Supply Voltage Figure 3. Output Resistance vs. Ambient
Temperature
Figure 4. Output Current vs. Capacitance Figure 5. Output Voltage Ripple vs.
Capacitance
Figure 6. Supply Current vs. Supply Voltage Figure 7. Oscillator Frequency vs. Ambient
Temperature
30
TA, AMBIENT TEMPERATURE (°C)
–50 25 10
0
–25 0 50 75
Rout, OUTPUT RESISTANCE ()
05
0
2010 4030
200
100
250
50
150
0
300
350
400
Vout, OUTPUT VOLTAGE RIPPLE (mVp–p)
Iin, SUPPLY CURRENT (µA)
–50 25 10
0
–25 0 50 75
TA, AMBIENT TEMPERATURE (°C)
C1, C2, C3, CAPACITANCE (µF)
Vin = 1.5 V
TA = 85°C
Figure 14 Test Setup
Vin = 2.0 V
Vin = 3.3 V
Vin = 5.0 V
Vin = 4.75 V
Vout = –4.00 V
Vin = 3.15 V
Vout = –2.50 V
Vin = 1.90 V
Vout = –1.50 V
Figure 14 Test Setup
TA = 25°C
Figure 14 Test Setup
RL =
TA = 25°CTA = –40°CVin = 1.5 V
Vin = 3.3 V
Vin = 5.0 V
Figure 14 Test Setup
Figure 14 Test Setup
TA = 25°C
20
60
40
80
70
50
30
90
100
1.0 5.03.52.5 5.54.54.03.02.01.5
Figure 14 Test Setup
TA = 25°C
Vin = 4.75 V
Vout = –4.00 V
Vin = 3.15 V
Vout = –2.50 V
Vin = 1.90 V
Vout = –1.50 V
MAX1720
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4
5.0
4.5
3.5
4.0
3.0
2.5
1.5
80
60
90
50
70
40
100
1.00
0
–2.0
30
–5.0
2010
Vout, OUTPUT VOLTAGE (V)
–6.0
Iout, OUTPUT CURRENT (mA)
Figure 8. Output Voltage vs. Output Current Figure 9. Power Conversion Efficiency vs.
Output Current
, POWER CONVERSION EFFICIENCY (%)
Figure 10. Output Voltage Ripple and Noise
TIME = 25 µs / Div.
Figure 11. Shutdown Supply Current vs.
Ambient Temperature
TA, AMBIENT TEMPERATURE (°C)
ISHDN, SHUTDOWN SUPPLY CURRENT (µA)
OUTPUT VOLTAGE RIPPLE AND
NOISE = 10 mV / Div. AC COUPLED
Figure 12. Supply Voltage vs. Shutdown Input
Voltage Threshold
Vth(SHND), SHUTDOWN INPUT VOLTAGE THRESHOLD (V)
Figure 13. Wakeup Time From Shutdown
TIME = 500 µs / Div.
Vin, SUPPLY VOLTAGE (V)
WAKEUP TIME FROM SHUTDOWN
0.0
0.5 2.52.01.51.0 3.0
–50 50 75250 100–25
0.50
1.25
0.75
0.25
1.50
1.75
Iout, OUTPUT CURRENT (mA)
–4.0
–3.0
–1.0
40 50 0 302010 40 50
2.0
Low State,
Device Shutdown
Vin = 2.0 V
Vin = 3.3 V
Vin = 5.0 V
RL = 10 k
SHDN = GND
Figure 14 Test Setup
TA = 25°C
Vin = 1.5 V
Vin = 3.3 V
Vin = 5.0 V
Vin = 1.5 V
Vin = 2.0 V
Vin = 3.3 V
Figure 14 Test Setup
Vin = 3.3 V
Iout = 5.0 mA
TA = 25°C
TA = 25°C
High State,
Device Operating
Figure 14 Test Setup
TA = 25°C
Vin = 5.0 V
Vin = 5.0 V
RL = 1.0 k
TA = 25°C
Vout = 1.0 V/Div.
SHDN = 5.0V/Div.
MAX1720
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5
6
4
2
3
1OSC
–Vout
C1
C2RL
+
+C3
Vin
+
Figure 14. Test Setup/Voltage Inverter
5
C1 = C2 = C3 = 10 F
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.
Figure 15. Ideal Switched Capacitor Charge Pump
S3 S4
C2
C1
S1 S2
Vin
–Vout
From Osc
APPLICATIONS INFORMATION
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 nominal
at 25°C with V in = 5.0 V. Vout is approximately –5.0 V at light
loads, and drops according to the equation below:
VDROP Iout Rout
Vout (Vin VDROP)
Charge Pump Efficiency
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.
PLOSS(2,3,4) Iout2Rout Iout2
1
(fOSC)C18RSWITCH 4ESRC1ESRC2
(eq. 1)
The 1/(fOSC)(C1) term in Equation 1 i s the ef fective 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 . T he o utput v oltage r ipple i s g iven b y Equation 3 .
0.5C2(VRIPPLE22VoutVRIPPLE)] fOSC
PLOSS [0.5C
1(Vin2Vout2)
(eq. 2)
VRIPPLE Iout
(fOSC)(C2)2(Iout)(ESRC2)
(eq. 3)
RL
C2
C1
Vin Vout
f
Figure 16. Ideal Switched Capacitor Model
RL
C2
Vin Vout
REQUIV
REQUIV 1
fC1
Figure 17. Equivalent Output Resistance
MAX1720
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6
Capacitor Selection
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.
Table 1. Output Resistance vs. Capacitance
(C1 = C2 = C3), Vin = 4.75 V and Vout = –4.0 V
C1 = C2 = C3
(F) Rout
()
0.7 129.1
1.4 69.5
3.3 37.0
7.3 26.5
10 25.9
24 24.1
50 24
Table 2. Output Voltage Ripple vs. Capacitance
(C1 = C2 = C3), Vin = 4.75 V and Vout = –4.0 V
C1 = C2 = C3
(F) Output Voltage Ripple
(mV)
0.7 382
1.4 342
3.3 255
7.3 164
10 132
24 59
50 38
Input Supply Bypassing
The input voltage, Vin should be capacitively bypassed to
reduce AC impedance and minimize noise ef fects due to the
switching internals in the device. If the device is loaded from
Vout to GND, it is recommended that a lar ge value capacitor
(at least equal to C1) be connected from Vin to GND. If the
device is loaded from V in to Vout, a small (0.7 µF) capacitor
between the pins is suf ficient.
Voltage Inverter
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 t o –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.
Layout Considerations
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.
Capacitor Resources
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.
Table 3. Capacitor Types
Manufacturer/Contact Part Types/Series
AVX TPS
AVX
843–448–9411
TPS
www.avxcorp.com
Cornell Dubilier ESRD
Cornell
D
u
bilier
508–996–8561
ll d bili
ESRD
www.cornell–dubilier.com
San
y
o/Os–con SN
Sanyo/Os–con
619–661–6835
id / ht
SN
SVP
www.sanyovideo.com/oscon.htm
Visha
y
593D
Vishay
603–224–1961
ih
593D
594
www.vishay.com
MAX1720
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7
6
4
2
3
1OSC
Capacitors = 10 µF
+
+
Vin 5
+
–Vout
Figure 18. Voltage Inverter
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.
Figure 19. Inverter Load Regulation,
Output Voltage vs. Output Current
0
–2.0
30
–5.0
2010
Vout, OUTPUT VOLTAGE (V)
–6.0
0
Iout, OUTPUT CURRENT (mA)
–4.0
–3.0
–1.0
40 50
TA = 25°C
Vin = 3.3 V
Vin = 5.0 V
MAX1720
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8
Figure 20. Cascaded Devices for Increased Negative Output Voltage
+
6
4
2
3
1OSC
Capacitors = 10 µF
+
Vin
5
+
6
4
2
3
1OSC +
5
–Vout
+
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.
Figure 21. Cascade Load Regulation, Output
Voltage vs. Output Current
–2.0
–4.0
–10.0
0
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
02040
–6.0
–8.0
10 30
A
B
TA = 25°C
A 5.0 140
B 3.0 174
Curve Vin (V) Rout ()
MAX1720
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9
+
6
4
2
3
1OSC
Capacitors = 10 µF
+
+
Vin 5
+ +
–Vout
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.
0
0
–2.0
2010
–4.0
–6.0
–10.0 30 40
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
–8.0
Figure 23. Doubler Load Regulation,
Output Voltage vs. Output Current
A
B
TA = 25°C
C
D
A 3.0 1N4148
B 3.0 MBRA120E
Curve Vin (V) All Diodes
124
115
Rout ()
C 5.0 1N4148
D 5.0 MBRA120E
96
94
MAX1720
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10
+
6
4
2
3
1OSC
Capacitors = 10 µF
+
+
Vin 5
+ +
–Vout
++
Figure 24. Negative Output Voltage Tripler
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.
–6.0
Iout, OUTPUT CURRENT
Vout, OUTPUT VOLTAGE
040302010 50
–10.0
–4.0
–12.0
–8.0
–16.0
–2.0
0
–14.0
Figure 25. Tripler Load Regulation, Output
Voltage vs. Output Current
A
B
TA = 25°C
C
D
A 3.0 1N4148
B 3.0 MBRA120E
Curve Vin (V) All Diodes
267
250
Rout ()
C 5.0 1N4148
D 5.0 MBRA120E
205
195
MAX1720
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11
+
+
6
4
2
3
1OSC
Capacitors = 10 µF
+
Vin 5Vout
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
8.0
6.0
4.0
2.0
0
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
02010 30 40
Figure 27. Doubler Load Regulation, Output
Voltage vs. Output Current
A
B
TA = 25°C
C
D
A 3.0 1N4148
B 3.0 MBRA120E
Curve Vin (V) All Diodes
32
26
Rout ()
C 5.0 1N4148
D 5.0 MBRA120E
26
21
MAX1720
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12
+
+
6
4
2
3
1OSC
Capacitors = 10 µF
+
Vin 5Vout
+
+
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.
6.0
2.0
4.0
0
8.0
10.0
12.0
14.0
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
0302010 40
Figure 29. Tripler Load Regulation, Output
Voltage vs. Output Current
A
B
TA = 25°C
C
D
A 3.0 1N4148
B 3.0 MBRA120E
Curve Vin (V) All Diodes
111
97
Rout ()
C 5.0 1N4148
D 5.0 MBRA120E
85
75
MAX1720
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13
+
6
4
2
3
1OSC
+
Vin 5
–Vout
+
Figure 30. Load Regulated Negative Output Voltage
Capacitors = 10 µF
100 k
A zener diode can be used with the shutdown input to provide closed loop regulation performance. This significantly reduces
the converters 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 converters 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 A. The performance characteristics for the above converter are shown
below. Note that the dashed curve sections represent the converters open loop performance.
0
–2.0
302010
Vout, OUTPUT VOLTAGE (V)
–5.0
–1.0
Iout, OUTPUT CURRENT (mA)
–4.0
–3.0
40 6050
Figure 31. Load Regulation, Output Voltage vs.
Output Current
A
B
TA = 25°C
A 3.3 V 4.5
B 5.0 V 6.5
Curve Vin (V) Vz (V)
–2.8
–3.8
Vout (V)
MAX1720
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14
Capacitors = 10 µF
+
6
4
2
3
1OSC
+
Vin 5
–Vout
+
R1
R2
10 k
Figure 32. Line and Load Regulated Negative Output Voltage
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 converters open loop performance.
–2.0
–3.0
–1.0
–4.0
–5.0
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
030 7010 20 40 50 60
Figure 33. Load Regulation, Output Voltage vs.
Output Current
A
B
TA = 25°C
A 3.0 5.0 k
B 5.0 20 k
Curve Vin (V) R2 ()
–1.8
–3.6
Vout (V)
10 k
10 k
R1 ()
–2.0
–3.0
–1.0
–4.0
1.0 3.02.0 4.0 5.0 6.
0
0
Vin, INPUT VOLTAGE (V)
Vout, OUTPUT VOLTAGE (V)
Figure 34. Line Regulation, Output Voltage vs.
Input Current
Iout = 25 mA
R1 = 10 k
R2 = 20 k
TA = 25°C
MAX1720
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15
+
6
4
2
3
1OSC
Capacitors = 10 µF
Vin 5
6
4
2
3
1OSC
+
5
–Vout
+
+
Figure 35. Paralleling Devices for Increased Negative Output Current
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.
0
0
–1.0
–2.0
403020
–3.0
–4.0
–5.0 10 50 80 100
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
60 70 90
Figure 36. Parallel Load Regulation, Output
Voltage vs. Output Current
A
B
TA = 25°C
A 5.0
B 3.0
Curve Vin (V)
14.5
17
Rout ()
MAX1720
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16
+
6
4
2
3
1OSC
+
Vin 5
–Vout
Q1
C3
–Vout = Vin –VBE(Q1) VBE(Q2) –2 VF
+C2
Q2C1
C1 = C2 = 470 µF
C3 = 220 µF
Q1 = PZT751
Q2 = PZT651
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 ohms.
–2.8
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
0 0.4 0.50.30.20.1 0.6
–3.2
–2.6
–3.0
–2.4
–2.2
Figure 38. Current Boosted Load Regulation,
Output Voltage vs. Output Current
Vin = 5.0 V
Rout = 0.9
TA = 25°C
MAX1720
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17
Figure 39. Line and Load Regulated Negative Output Voltage
with High Current Capability
+
6
4
2
3
1OSC
+
Vin 5
–Vout
Q1
C3
+C2
Q2
C1
C1 = C2 = 470 µF
C3 = 220 µF
Q1 = PZT751
Q2 = PZT651
R1
R2
10 k
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.
–2.6
Iout, OUTPUT CURRENT (A)
Vout, OUTPUT VOLTAGE (V)
0 0.4 0.50.30.20.1 0.6
–3.2
–2.4
–2.8
–2.2
Figure 40. Current Boosted Load Regulation,
Output Voltage vs. Output Current
Vin = 5.0 V
Rout = 0.9
R1 = 10 k
R2 = 9.0 k
TA = 25°C
–3.0
–1.4
Vout, OUTPUT VOLTAGE (V)
3.0 5.0 5.54.54.03.5 6.0
–2.4
–1.2
–1.6
–1.0
–1.8
Vin, INPUT VOLTAGE (V)
–2.0
–2.2
Figure 41. Current Boosted Line Regulation,
Output Voltage vs. Input Voltage
Iout = 100 mA
R1 = 10 k
R2 = 9 k
TA = 25°C
MAX1720
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18
Figure 42. Positive Output Voltage Doubler with High Current Capability
+
6
4
2
3
1OSC
+
Vin 5
Vout
Q1
C3
+C2
Q2C1
Capacitors = 220 µF
Q1 = PZT751
Q2 = PZT651
50
50
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 ohms.
8.0
Iout, OUTPUT CURRENT (A)
Vout, OUTPUT VOLTAGE (V)
0 0.4 0.50.30.20.1 0.6
6.8
8.4
7.6
8.8
Figure 43. Positive Doubler with Current Boosted
Load Regulation, Output Voltage vs. Output Current
Vin = 5.0 V
Rout = 1.9
TA = 25°C
7.2
MAX1720
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19
Figure 44. Line and Load Regulated Positive Output Voltage Doubler with High Current Capability
+
6
4
2
3
1OSC
+
Vin 5
Vout
Q1
C3
+C2
Q2
C1
Capacitors = 220 µF
Q1 = PZT751
Q2 = PZT651
R2
R1
10 k 50
50
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
Iout, OUTPUT CURRENT (A)
Vout, OUTPUT VOLTAGE (V)
0 0.4 0.50.30.20.1 0.6
6.8
8.4
7.6
8.8
Figure 45. Current Boosted Close Loop Load
Regulation, Output Voltage vs. Output Current
Vin = 5.0 V
Rout = 1.9 Open Loop
Rout = 0.5 Closed Loop
R1 = 10 k
R2 = 51.3 k
TA = 25°C
7.2
6.0
Vin, INPUT VOLTGE (V)
Vout, OUTPUT VOLTAGE (V)
1.0 4.0 5.03.02.0 6.0
1.0
7.0
5.0
8.0
Figure 46. Current Boosted Close Loop Line
Regulation, Output Voltage vs. Input Voltage
Iout = 100 mA
R1 = 10 k
R2 = 51.3 k
TA = 25°C
4.0
3.0
2.0
MAX1720
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20
6
4
2
3
1OSC
Capacitors = 10 µF
+
Vin = –5.0 V
5
+
+
Figure 47. Negative Input Voltage Splitter
C
C
+C
Vout = –2.5 V
C
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 ohms.
0
–1.5
–1.7
–1.9
403020
–2.1
–2.3
–2.5 10 50 80
Iout, OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
60 70
Figure 48. Negative Voltage Splitter Load
Regulation, Output Voltage vs. Output Current
TA = 25°C
Rout = 10
MAX1720
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21
+
6
4
2
3
1OSC
+
Vin 5
–Vout
+
Figure 49. Combination of a Closed Loop Negative Inverter with a Positive Output Voltage Doubler
Capacitors = 10 µF
10 k
+
+
R1
R2
+Vout
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 –V ref (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.
–4.0
–5.0
–3.0
8.0
9.0
Iout, NEGATIVE INVERTER OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
02010 30
Figure 50. Load Regulation, Output Voltage vs.
Output Current
8.0
7.0
9.0
10.0
Iout, POSITIVE DOUBLER OUTPUT CURRENT (mA)
Vout, OUTPUT VOLTAGE (V)
0302010 50
Figure 51. Load Regulation, Output Voltage vs.
Output Current
R1 = 10 k
R2 = 20 k
TA = 25°C
40
Negative Inverter Iout = 15 mA
Negative Inverter
Positive Doubler
Iout = 15 mA
Rout = 45 – Open Loop
Rout = 2 – Closed Loop
R1 = 10 k, R2 = 20 k
TA = 25°C
MAX1720
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22
Figure 52. Inverter Circuit Board Layout, Top View Copper Side
Vin
GND
IC1 C1
Inverter Size = 0.5 in x 0.2 in
Area = 0.10 in2, 64.5 mm2
–Vout
GND
C3+
C2
+
SHDN
+
0.5
TAPING FORM
PIN 1
USER DIRECTION OF FEED
Component Taping Orientation for TSOP–6 Devices
Standard Reel Component Orientation
(Mark Right Side Up)
DEVICE
MARKING
TSOP–6
Package Tape Width (W) Pitch (P) Part Per Full Reel Diameter
8 mm 4 mm 3000 7 inches
Tape & Reel Specifications Table