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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 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 MAX packages. 1nA Logic-Controlled Shutdown 6-Pin SOT23 Package 99.9% Voltage Conversion Efficiency 50A Quiescent Current (MAX1720) +1.5V to +5.5V Input Voltage Range 25mA Output Current Requires Only Two 1F Capacitors (MAX1719/MAX1721)
Features
MAX1719/MAX1720/MAX1721
Ordering Information
PART MAX1719EUT TEMP RANGE -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 6 SOT23-6 6 SOT23-6 6 SOT23-6 SOT TOP MARK AACA AABS AABT
Applications
Local Negative Supply from a Positive Supply Small LCD Panels GaAs PA Bias Supply Handy-Terminals, PDAs Battery-Operated Equipment
MAX1720EUT MAX1721EUT
Typical Operating Circuit
1F
Pin Configuration
TOP VIEW
INPUT 1.5V to 5.5V
C1+ IN
C1OUT
NEGATIVE OUTPUT -1 * VIN 25mA 1F
OUT
1
6
C1+
IN
2
MAX1721
ON OFF SHDN GND
MAX1719 MAX1720 MAX1721
5
SHDN (SHDN)
C1-
3
4
GND
SOT23-6
( ) ARE FOR MAX1719
________________________________________________________________ Maxim Integrated Products
1
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
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 = +70C) 6-Pin SOT23 (derate 8.7mW/C above +70C).................696mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = 10F (MAX1720), C1 = C2 = 1F (MAX1719/MAX1721), circuit of Figure 1, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL MAX1720 RL = 10k MAX1719/MAX1721 RL = 10k TA = +25C CONDITIONS TA = +25C TA = 0C to + 85C TA = +25C TA = 0C to + 85C MAX1720 MAX1719/MAX1721 MIN 1.25 1.5 1.4 1.5 50 350 0.001 0.02 7 70 99 TA = +25C TA = 0C to +85C 4 2.0 VIN - 0.2 0.6 0.2 -100 0.05 10 800 80 100 12 125 99.9 23 50 65 12 17 180 kHz TYP MAX 5.5 5.5 5.5 5.5 90 650 1 A A V UNITS
Supply Voltage Range
VIN
Quiescent Supply Current (Note 3) Shutdown Supply Current
ICC
ISHDN
SHDN = IN (MAX1719), TA = +25C SHDN = GND (MAX1720/MAX1721) TA = +85C TA = +25C IOUT = 0, TA = +25C MAX1720 MAX1719/MAX1721
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
fOSC
%

RO
IOUT = 10mA
RO, SHDN
SHDN = IN (MAX1719), SHDN = GND (MAX1720/MAX1721), OUT is internally forced to GND in shutdown +2.5V VIN +5.5V VIN (MIN) VIN +2.5V +2.5V VIN +5.5V VIN (MIN) VIN +2.5V SHDN/ SHDN = GND TA = +25C or VIN TA = +85C IOUT = 5mA MAX1720 MAX1719/MAX1721
VIH VIL IIL, IIH
V V nA s
2
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
ELECTRICAL CHARACTERISTICS
(V IN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = 10F (MAX1720), C1 = C2 = 1F (MAX1719/MAX1721), circuit of Figure 1, TA = -40C to +85C, unless otherwise noted.) (Note 2) PARAMETER Supply Voltage Range Quiescent Current (Note 3) Oscillator Frequency Voltage Conversion Efficiency Output Resistance (Note 1) Output Current OUT to GND Shutdown Resistance SHDN/ SHDN Input Logic High SHDN/ SHDN Input Logic Low RO IOUT RO, SHDN SYMBOL VIN ICC fOSC RL = 10k MAX1720 MAX1719/MAX1721 MAX1720 MAX1719/MAX1721 IOUT = 0 IOUT = 10mA Continuous, long-term SHDN = IN (MAX1719), SHDN = GND (MAX1720/MAX1721), OUT is internally forced to GND in shutdown +2.5V VIN +5.5V VIN (MIN) VIN +2.5V +2.5V VIN +5.5V VIN (MIN) VIN +2.5V 2.1 VIN - 0.2 0.6 0.2 6 60 99 65 25 12 CONDITIONS MAX1720 MAX1719/MAX1721 MIN 1.5 1.6 TYP MAX 5.5 5.5 100 750 21 200 UNITS V A kHz
%
mARMS
VIH VIL
V V
Note 1: Capacitor contribution (ESR component plus (1/fOSC) * C) is approximately 20% of output impedance. Note 2: All specifications from -40C to +85C 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 = +25C, unless otherwise noted.)
OUTPUT VOLTAGE vs. OUTPUT CURRENT
MAX1720/21toc01
MAX1720 EFFICIENCY vs. OUTPUT CURRENT
MAX1720/21toc02
MAX1719/MAX1721 EFFICIENCY vs. OUTPUT CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VIN = +1.5V VIN = +2V VIN = +3.3V VIN = +5V
MAX1720/21toc03
0 VIN = +1.5V -1 OUTPUT VOLTAGE (V) VIN = +2V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 VIN = +1.5V VIN = +2V VIN = +3.3V VIN = +5V
100
-2 VIN = +3.3V -3
-4 VIN = +5V -5 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA)
20 10 0 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)
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25C, unless otherwise noted.)
OUTPUT RESISTANCE vs. INPUT VOLTAGE
MAX1720/21toc04
SUPPLY CURRENT vs. INPUT VOLTAGE
400 SUPPLY CURRENT (A) 350 300 250 200 150 100 50 -40C +85C 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 MAX1720 -40C +85C MAX1719/ MAX1721
MAX1720/21toc05
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT (nA)
MAX1720/21toc06
80 70 OUTPUT RESISTANCE () 60 50 40 30 MAX1720 20 10 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 MAX1719/ MAX1721
450
30 25 20 15 10 5 0 -40 -15 10 35 60 VIN = +5V VIN = +3.3V VIN = +1.5V
5.5
0 1.5
85
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
TEMPERATURE (C)
OUTPUT RESISTANCE vs. TEMPERATURE
VIN = +1.5V 60 OUTPUT RESISTANCE () 50 40 VIN = +3.3V 30 20 10 -40 -15 10 35 60 85 TEMPERATURE (C) VIN = +5V VIN = +2V
MAX1720/21toc07
PUMP FREQUENCY vs. TEMPERATURE
MAX1720/21toc08
OUTPUT NOISE AND RIPPLE
MAX1720/21toc09
70
1000
FREQUENCY (kHz)
VIN = +1.5V VIN = +5V 100
VOUT MAX1719/ MAX1721
MAX1719/MAX1721
VOUT MAX1720 VIN = +5V VIN = +1.5V 10 -40 MAX1720
-15
-10
35
60
85
TEMPERATURE (C)
10s/div VIN = 3.3V, VOUT = -3.17V, IOUT = 5mA 20mV/div, AC-COUPLED
MAX1720 START-UP FROM SHUTDOWN
MAX1720/21toc10
MAX1720 OUTPUT CURRENT vs. CAPACITANCE
MAX1720/21toc11
MAX1720 OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
450 OUTPUT VOLTAGE RIPPLE (mVp-p) 400 350 300 250 200 150 100 50 0 VIN = +1.9V, VOUT = -1.5V VIN = +4.75V, VOUT = -4.0V VIN = +3.15V, VOUT = -2.5V
MAX1720/21toc12
35 VIN = +4.75V, VOUT = -4.0V 30 OUTPUT CURRENT (mA) VOUT 2V/div 25 VIN = +3.15V, VOUT = -2.5V 20 15 10 5 0 VIN = +1.9V, VOUT = -1.5V
500
V SHDN 5V/div 500s/div RL = 1k
0
5
10 15 20 25 30 35 40 45 50 CAPACITANCE (F)
0
5
10
15
20
25
30
CAPACITANCE (F)
4
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +5V, SHDN = GND (MAX1719), SHDN = IN (MAX1720/MAX1721), C1 = C2 = C3, TA = +25C, unless otherwise noted.)
MAX1721 START-UP FROM SHUTDOWN
MAX1720/21toc13
MAX1719/MAX1721 OUTPUT CURRENT vs. CAPACITANCE
MAX1720/21toc14
MAX1719/MAX1721 OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
350 300 VIN = +4.75V, VOUT = -4.0V 250 200 150 100 50 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 CAPACITANCE (F) VIN = +3.15V, VOUT = -2.5V VIN = +1.9V, VOUT = -1.5V
MAX1720/21toc15
35 30 VOUT 2V/div OUTPUT CURRENT (mA) 25 20 15 10 VIN = +1.9V, VOUT = -1.5V 5 0 VIN = +3.15V, VOUT = -2.5V VIN = +4.75V, VOUT = -4.0V
400 OUTPUT VOLTAGE RIPPLE (mVp-p)
VSHDN 5V/div 50s/div RL = 1k
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 CAPACITANCE (F)
Pin Description
PIN MAX1719 MAX1720 MAX1721 NAME FUNCTION
1
2 3 4 5 - 6
1
2 3 4 - 5 6
OUT IN C1GND SHDN SHDN C1+
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 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.
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5
SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
C1 1F (10F) INPUT 1.5V to 5.5V C3 1F (10F) ON OFF 5 SHDN 6 C1+ IN 3 C1OUT
f
V+ NEGATIVE OUTPUT -1 * VIN 25mA C2 1F (10F) VOUT
2
1 RL
C1
C2
RL
MAX1719* MAX1721
GND 4
Figure 3a. Switched-Capacitor Model
REQUIV V+ 1 REQUIV = f x C1 C2 VOUT RL
NOTE: ( ) CAPACITORS ARE FOR MAX1720. *ON/OFF POLARITY OF SHDN IS REVERSED FOR MAX1719.
Figure 1. Typical Application Circuit
S1 IN C1 S2
Figure 3b. Equivalent Circuit
S3
S4
C2 VOUT = -(VIN)
where the output impedance is roughly approximated by: ROUT
(fOSC )
1 x C1
+ 2RSW + 4ESRC1 + ESRC2
Figure 2. Ideal Voltage Inverter
Charge-Pump Output
The MAX1719/MAX1720/MAX1721 are not voltage regulators: the charge pumps' output resistance is approximately 23 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-)
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 8 to 9 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 4 resistance.
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: IOUT IOUT + IQ IOUT x ROUT 1 - VIN
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.
6
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown 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. 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 = IOUT + 2 x IOUT x ESRC2 2 x fOSC x C2
...
2 3 C1 4 6 MAX1719 MAX1720 MAX1721 "1" 5 SHDN (MAX1719) SHDN (MAX1720/ MAX1721) +VIN 3 C1 1 4 6 2 MAX1719 MAX1720 MAX1721 "n" 5
1
VOUT C2
...
C2
VOUT = -nVIN
Figure 4. Cascading MAX1719s or MAX1720s or MAX1721s to Increase Output Voltage
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 AVX Matsuo Sprague AVX Matsuo SERIES TPS series 267 series 593D, 595D series X7R X7R PHONE 803-946-0690 714-969-2491 603-224-1961 803-946-0690 714-969-2491 FAX 803-626-3123 714-960-6492 603-224-1430 803-626-3123 714-960-6492
Table 2. Capacitor Selection for Minimum Output Resistance or Capacitor Size
PART MAX1720 MAX1719/MAX1721 fOSC 12kHz 125kHz CAPACITORS TO MINIMIZE OUTPUT RESISTANCE (RO = 23, TYP) C1 = C2 10F 1F CAPACITORS TO MINIMIZE SIZE (RO = 40, TYP) C1 = C2 3.3F 0.33F 7
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SOT23, Switched-Capacitor Voltage Inverters with Shutdown MAX1719/MAX1720/MAX1721
+VIN 2 3 C1 4 6 SHDN (MAX1719) SHDN (MAX1720/ MAX1721) MAX1719 MAX1720 MAX1721 "1" 5 3 C1 1 4 6 MAX1719 MAX1720 MAX1721 "n" 5 VOUT = -VIN C2
...
2
SHDN (MAX1719) SHDN (MAX1720) (MAX1721) 3 C1 4 6
5 2 MAX1719 MAX1720 MAX1721
+VIN D1, D2 = 1N4148
1
VOUT
D1 1 C2 D2 VOUT = (2VIN) (VFD1) - (VFD2) VOUT = -VIN
...
RO OF SINGLE DEVICE RO = NUMBER OF DEVICES
C3
C4
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.
MAX1719 MAX1720 MAX1721
GND
4
V+ RL
OUT
1
Figure 7. Heavy Load Connected to a Positive Supply
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.
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
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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