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19-1439; Rev 2; 4/04
SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
General Description
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 logic-
controlled 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
Small LCD Panels
GaAs PA Bias Supply
Handy-Terminals, PDAs
Battery-Operated Equipment
Typical Operating Circuit
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
MAX1719EUT
MAX1720EUT
MAX1721EUT
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
6 SOT23-6
SOT
TOP MARK
AACA
AABS
AABT
Pin Configuration
1µF
INPUT
1.5V to 5.5V
C1+
IN
C1-
OUT
MAX1721
ON SHDN
OFF
GND
NEGATIVE
OUTPUT
-1 · VIN
25mA
1µF
TOP VIEW
OUT 1
6 C1+
IN 2
C1- 3
MAX1719
MAX1720
MAX1721
5 SHDN (SHDN)
4 GND
( ) ARE FOR MAX1719
SOT23-6
________________________________________________________________ Maxim Integrated Products 1
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.

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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
(VIN = +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
Quiescent Supply Current
(Note 3)
Shutdown Supply Current
Oscillator Frequency
Voltage Conversion Efficiency
Output Resistance (Note 1)
OUT to GND
Shutdown Resistance
SHDN/ SHDN Input Logic High
SHDN/ SHDN Input Logic Low
SHDN/ SHDN Bias Current
Wake-Up Time from Shutdown
SYMBOL
CONDITIONS
MAX1720
TA = +25°C
RL = 10k
TA = 0°C to + 85°C
VIN MAX1719/MAX1721 TA = +25°C
RL = 10k
TA = 0°C to + 85°C
ICC TA = +25°C
MAX1720
MAX1719/MAX1721
ISHDN
SHDN = IN (MAX1719), TA = +25°C
SHDN = GND
(MAX1720/MAX1721) TA = +85°C
fOSC TA = +25°C
MAX1720
MAX1719/MAX1721
IOUT = 0, TA = +25°C
RO
RO, SHDN
IOUT = 10mA
TA = +25°C
TA = 0°C to +85°C
SHDN = IN (MAX1719), SHDN = GND
(MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
VIH
+2.5V VIN +5.5V
VIN (MIN) VIN +2.5V
VIL
+2.5V VIN +5.5V
VIN (MIN) VIN +2.5V
IIL, IIH
SHDN/ SHDN = GND TA = +25°C
or VIN
TA = +85°C
IOUT = 5mA
MAX1720
MAX1719/MAX1721
MIN
1.25
1.5
1.4
1.5
7
70
99
TYP
50
350
0.001
0.02
12
125
99.9
23
4
2.0
VIN - 0.2
-100
0.05
10
800
80
MAX
5.5
5.5
5.5
5.5
90
650
1
UNITS
V
µA
µA
17
kHz
180
%
50
65
12
V
0.6
V
0.2
100
nA
µs
2 _______________________________________________________________________________________

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SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
ELECTRICAL CHARACTERISTICS
(VIN = +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
CONDITIONS
MIN TYP MAX UNITS
Supply Voltage Range
VIN RL = 10k
MAX1720
MAX1719/MAX1721
1.5
1.6
5.5
V
5.5
Quiescent Current (Note 3)
MAX1720
ICC MAX1719/MAX1721
100
µA
750
Oscillator Frequency
fOSC
MAX1720
MAX1719/MAX1721
6 21
kHz
60 200
Voltage Conversion Efficiency
IOUT = 0
99 %
Output Resistance (Note 1)
RO IOUT = 10mA
65
Output Current
IOUT Continuous, long-term
25 mARMS
OUT to GND Shutdown
Resistance
SHDN = IN (MAX1719), SHDN = GND
RO, SHDN (MAX1720/MAX1721), OUT is internally
forced to GND in shutdown
12
SHDN/ SHDN Input Logic High
VIH
+2.5V VIN +5.5V
VIN (MIN) VIN +2.5V
2.1
VIN - 0.2
V
SHDN/ SHDN Input Logic Low
VIL
+2.5V VIN +5.5V
VIN (MIN) VIN +2.5V
0.6
V
0.2
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 other-
wise noted.)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
0
VIN = +1.5V
VIN = +2V
-1
-2
VIN = +3.3V
-3
-4
VIN = +5V
-5
0 5 10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
MAX1720
EFFICIENCY vs. OUTPUT CURRENT
100
90
80 VIN = +5V
70
60
50 VIN = +1.5V VIN = +2V
VIN = +3.3V
40
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
MAX1719/MAX1721
EFFICIENCY vs. OUTPUT CURRENT
100
90
80 VIN = +5V
70
60 VIN = +1.5V
50 VIN = +2V
40
VIN = +3.3V
30
20
10
0
0 5 10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
_______________________________________________________________________________________ 3

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SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25°C, unless oth-
erwise noted.)
OUTPUT RESISTANCE
vs. INPUT VOLTAGE
80
70
60
50 MAX1719/
MAX1721
40
30
MAX1720
20
10
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
OUTPUT RESISTANCE
vs. TEMPERATURE
70
VIN = +1.5V
60
50 VIN = +2V
40
VIN = +3.3V
30
VIN = +5V
20
SUPPLY CURRENT
vs. INPUT VOLTAGE
450
MAX1719/
400 MAX1721
350
300
250 -40°C +85°C
200
150
100
MAX1720
50 -40°C
+85°C
0
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
PUMP FREQUENCY
vs. TEMPERATURE
1000
VIN = +1.5V
VIN = +5V MAX1719/MAX1721
100
VIN = +5V
VIN = +1.5V
MAX1720
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
30
25
20
VIN = +5V
15
10 VIN = +3.3V
5 VIN = +1.5V
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
OUTPUT NOISE AND RIPPLE
MAX1720/21toc09
VOUT
MAX1719/
MAX1721
VOUT
MAX1720
10
-40
-15 10 35 60
TEMPERATURE (°C)
85
10
-40 -15
-10
35 60
TEMPERATURE (°C)
85
MAX1720
START-UP FROM SHUTDOWN
MAX1720/21toc10
VOUT
2V/div
RL = 1k
500µs/div
V SHDN
5V/div
MAX1720
OUTPUT CURRENT vs. CAPACITANCE
35
VIN = +4.75V, VOUT = -4.0V
30
25
VIN = +3.15V, VOUT = -2.5V
20
15
10
VIN = +1.9V, VOUT = -1.5V
5
0
0 5 10 15 20 25 30 35 40 45 50
CAPACITANCE (µF)
10µs/div
VIN = 3.3V, VOUT = -3.17V, IOUT = 5mA
20mV/div, AC-COUPLED
500
450
400
350
300
250
200
150
100
50
0
0
MAX1720
OUTPUT VOLTAGE RIPPLE
vs. CAPACITANCE
VIN = +4.75V, VOUT = -4.0V
VIN = +3.15V, VOUT = -2.5V
VIN = +1.9V, VOUT = -1.5V
5 10 15 20 25 30
CAPACITANCE (µF)
4 _______________________________________________________________________________________

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SOT23, Switched-Capacitor
Voltage Inverters with Shutdown
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.)
MAX1721
START-UP FROM SHUTDOWN
MAX1720/21toc13
VOUT
2V/div
RL = 1k
50µs/div
VSHDN
5V/div
MAX1719/MAX1721
OUTPUT CURRENT vs. CAPACITANCE
35
30 VIN = +4.75V, VOUT = -4.0V
25
20 VIN = +3.15V, VOUT = -2.5V
15
10
VIN = +1.9V, VOUT = -1.5V
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)
MAX1719/MAX1721
OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
400
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 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
CAPACITANCE (µF)
PIN
MAX1719
MAX1720
MAX1721
11
22
33
44
5–
–5
66
NAME
OUT
IN
C1-
GND
SHDN
SHDN
C1+
Pin Description
FUNCTION
Inverting Charge-Pump Output
Power-Supply Positive Voltage Input
Negative Terminal of Flying Capacitor
Ground
Noninverting Shutdown Input. Drive this pin low for normal operation; drive it high for
shutdown mode. OUT is actively pulled to ground during shutdown.
Inverting Shutdown Input. Drive this pin high for normal operation; drive it low for
shutdown mode. OUT is actively pulled to ground during shutdown.
Positive Terminal of Flying Capacitor
Detailed Description
The MAX1719/MAX1720/MAX1721 capacitive charge
pumps invert the voltage applied to their input. For high-
est 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 par-
allel 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