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19-1305; Rev 1; 8/98
Switched-Capacitor Voltage Doublers
General Description
The ultra-small MAX1682/MAX1683 monolithic, CMOS charge-pump voltage doublers accept input voltages ranging from +2.0V to +5.5V. Their high voltage-conversion efficiency (over 98%) and low operating current (110A for MAX1682) make these devices ideal for both battery-powered and board-level voltage-doubler applications. Oscillator control circuitry and four power MOSFET switches are included on-chip. The MAX1682 operates at 12kHz and the MAX1683 operates at 35kHz. A typical application includes generating a 6V supply to power an LCD display in a hand-held PDA. Both parts are available in a 5-pin SOT23 package and can deliver 30mA with a typical voltage drop of 600mV.
____________________________Features
o 5-Pin SOT23 Package o +2.0V to +5.5V Input Voltage Range o 98% Voltage-Conversion Efficiency o 110A Quiescent Current (MAX1682) o Requires Only Two Capacitors o Up to 45mA Output Current
MAX1682/MAX1683
________________________Applications
Small LCD Panels Cell Phones Handy-Terminals PDAs
PART MAX1682C/D
Ordering Information
TEMP. RANGE 0C to +70C PINPACKAGE Dice* 5 SOT23-5 Dice* 5 SOT23-5 SOT TOP MARK -- ACLL -- ACCM
MAX1682EUK-T -40C to +85C MAX1683C/D 0C to +70C MAX1683EUK-T -40C to +85C
Typical Operating Circuit
Note: These parts are available in tape-and-reel only. Minimum order quantity is 2500 pieces. *Dice are tested at TA = +25C.
5
C1+
IN
4
VIN
INPUT SUPPLY VOLTAGE
Pin Configuration
C1
MAX1682 MAX1683
3 C1-
TOP VIEW
GND 1 OUT 2 OUTPUT VOLTAGE 2 x VIN C2 C1- 3 4 IN 5 C1+
OUT 2
MAX1682 MAX1683
1
GND
VOLTAGE DOUBLER
SOT23-5
________________________________________________________________ Maxim Integrated Products
1
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Switched-Capacitor Voltage Doublers MAX1682/MAX1683
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................+6V to -0.3V OUT to GND .......................................................+12V, VIN - 0.3V OUT Output Current............................................................50mA Output Short-Circuit Duration .................................1sec (Note 1) Continuous Power Dissipation (TA = +70C) SOT23-5 (derate 7.1mW/C above +70C)...................571mW Operating Temperature Range MAX1682EUK/MAX1683EUK ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
Note 1: Avoid shorting OUT to GND, as it may damage the device. For temperatures above +85C, shorting OUT to GND even instantaneously will damage the device.
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 = +5.0V, capacitor values from Table 2, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER No-Load Supply Current Supply Voltage Range Minimum Operating Voltage Oscillator Frequency Output Resistance Voltage Conversion Efficiency TA = +25C RLOAD = 10k (Note 2) TA = +25C IOUT = 5mA IOUT = 0mA, TA = +25C MAX1682 MAX1683 TA = +25C TA = 0C to +85C 98 99.9 8.4 24.5 CONDITIONS MAX1682 MAX1683 TA = +25C TA = 0C to +85C 2.0 2.1 MIN TYP 110 230 1.7 1.8 1 12 35 20 15.6 45.5 50 65 MAX 145 310 5.5 5.5 UNITS A V V kHz %
Note 2: Once started, the MAX1682/MAX1683 typically operate down to 1V.
ELECTRICAL CHARACTERISTICS
(VIN = +5.0V, capacitor values from Table 2, TA = -40C to +85C, unless otherwise noted.) (Note 3) PARAMETER No-Load Supply Current Supply-Voltage Range Oscillator Frequency Output Resistance Voltage Conversion Efficiency MAX1682 MAX1683 RLOAD = 10k MAX1682 MAX1683 IOUT = 5mA IOUT = 0mA 97 2.3 6.6 17.5 CONDITIONS MIN TYP MAX 160 350 5.5 18.6 57.8 65 UNITS A V kHz %
Note 3: Specifications at -40C to +85C are guaranteed by design.
2
_______________________________________________________________________________________
Switched-Capacitor Voltage Doublers
Typical Operating Characteristics
(Typical Operating Circuit, VIN = +5V, C1 = C2 = 10F for the MAX1682 and 3.3F for the MAX1683, TA = +25C, unless otherwise noted.)
OUTPUT RESISTANCE vs. SUPPLY VOLTAGE
80 OUTPUT RESISTANCE () 70 60 50 MAX1682, C1 = C2 = 10F 40 30 20 MAX1683, C1 = C2 = 10F 10 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN (V) 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) MAX1683, C1 = C2 = 3.3F
MAX1682/83 TOC1
MAX1682/MAX1683
MAX1682 OUTPUT RESISTANCE vs. TEMPERATURE
MAX1682/83 TOC02
MAX1683 OUTPUT RESISTANCE vs. TEMPERATURE
35 OUTPUT RESISTANCE () 30 25 20 15 VIN = 5V 10 5 ILOAD = 5mA 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) VIN = 3.3V
MAX1682/83 TOC03
90
40 35 OUTPUT RESISTANCE () 30 25 20 15 10 5 ILOAD = 5mA VIN = 5V VIN = 3.3V VIN = 2V
40 VIN = 2V
MAX1682 OUTPUT RESISTANCE vs. CAPACITANCE
MAX1682/83 TOC4
MAX1683 OUTPUT RESISTANCE vs. CAPITANCE
MAX1682/83 TOC05
MAX1682 OUTPUT VOLTAGE RIPPLE vs. OUTPUT CURRENT
700 600 VRIPPLE (mV) 500 400 300 200 100 0 C1 = C2 = 10F C1 = C2 = 33F C1 = C2 = 3.3F
MAX1682/83 TOC06
120 100 OUTPUT RESISTANCE () 80 60 VIN = 2V 40 20 0 0 5 10 VIN = 5V 15 20 VIN = 3.3V 25 30
50 45 OUTPUT RESISTANCE () 40 35 30 25 20 15 10 5 0 VIN = 5V VIN = 3.3V VIN = 2V
800
35
0
5
10
15
20
25
30
35
0
5
10
15
20 IOUT (mA)
25
30
35
40
CAPACITANCE (F)
CAPACITANCE (F)
MAX1683 OUTPUT VOLTAGE RIPPLE vs. OUTPUT CURRENT
900 800 700 VRIPPLE (mV) 600 500 400 300 200 100 0 0 5 10 15 20 IOUT (mA) 25 30 35 40 0 C1 = C2 = 10F C1 = C2 = 3.3F C1 = C2 =1F
MAX1682/83 TOC07
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1682/83 TOC09
1000
300 250 SUPPLY CURRENT (A) 200 150 100 50 MAX1683
MAX1682
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
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Switched-Capacitor Voltage Doublers MAX1682/MAX1683
Typical Operating Characteristics (continued)
(Typical Operating Circuit, VIN = +5V, C1 = C2 = 10F for the MAX1682 and 3.3F for the MAX1683, TA = +25C, unless otherwise noted.)
MAX1682 OSCILLATOR FREQUENCY vs. TEMPERATURE
MAX1682/83 TOC10
MAX1683 OSCILLATOR FREQUENCY vs. TEMPERATURE
MAX1682/83 TOC11
MAX1682 OUTPUT VOLTAGE vs. OUTPUT CURRENT
9 8 OUTPUT VOLTAGE (V) 7 6 5 4 3 2 1 VIN = 2V VIN = 3.3V VIN = 5V
MAX1682/83 TOC12
12.5 OSCILLATOR FREQUENCY (kHz)
40 OSCILLATOR FREQUENCY (kHz) 38 VIN = 5V 36 34 32 30 28 VIN = 3.3V VIN = 2V
10
VIN = 5V 12.0 VIN = 3.3V
11.5 VIN = 2V
11.0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA) TEMPERATURE (C)
MAX1683 OUTPUT VOLTAGE vs. OUTPUT CURRENT
MAX1682/83 TOC13
MAX1682 EFFICIENCY vs. LOAD CURRENT
MAX1682/83 TOC14
MAX1683 EFFICIENCY vs. LOAD CURRENT
98 96 EFFICIENCY (%) 94 92 90 88 86 84 82 80 VIN = 2V VIN = 3.3V VIN = 5V
MAX1682/83 TOC15
10 9 8 OUTPUT VOLTAGE (V) 7 6 5 4 3 2 1 0 0 5 VIN = 2V VIN = 3.3V VIN = 5V
100 98 96 EFFICIENCY (%) 94 92 90 88 86 84 82 80 VIN = 2V VIN = 3.3V VIN = 5V
100
10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA)
0
5
10
15
20
25
30
0
5
10
15
20
25
30
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAX1682 OUTPUT RIPPLE
MAX1682toc16
MAX1683 OUTPUT RIPPLE
MAX1682toc17
START-UP VOLTAGE vs. RESISTIVE LOAD
MAX1683 2.0
MAX1682toc18
2.5
VOUT 20mV/div
VOUT 20mV/div
VSTART (V)
1.5 MAX1682
1.0
0.5
0 20s/div ILOAD = 5mA, VIN = 5V, C1 = C2 = 10F 20s/div ILOAD = 5mA, VIN = 5V, C1 = 3.3F, C2 = 10F 700 300 100 70 30 10 7 3 1 0.7 0.3 RLOAD (k)
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_______________________________________________________________________________________
Switched-Capacitor Voltage Doublers
_____________________Pin Description
PIN 1 2 3 4 5 NAME GND OUT C1IN C1+ Ground Doubled Output Voltage. Connect C2 between OUT and GND. Negative Terminal of the Flying Capacitor Input Supply Positive Terminal of the Flying Capacitor FUNCTION
Efficiency Considerations
The power efficiency of a switched-capacitor voltage converter is affected by three factors: the internal losses in the converter IC, the resistive losses of the capacitors, and the conversion losses during charge transfer between the capacitors. The total power loss is: PLOSS = PINTERNAL LOSSES + PPUMP CAPACITOR LOSSES + PCONVERSION LOSSES The internal losses are associated with the IC's internal functions, such as driving the switches, oscillator, etc. These losses are affected by operating conditions such as input voltage, temperature, and frequency. The next two losses are associated with the voltage converter circuit's output resistance. Switch losses occur because of the on-resistance of the MOSFET switches in the IC. Charge-pump capacitor losses occur because of their ESR. The relationship between these losses and the output resistance is as follows: PPUMP CAPACITOR LOSSES + PSWITCH LOSSES = IOUT ROUT x ROUT 1 + 2RSWITCHES + 4ESRC1 fOSC x C1
2
MAX1682/MAX1683
_______________Detailed Description
The MAX1682/MAX1683 capacitive charge pumps double the voltage applied to their input. Figure 1 shows a simplified functional diagram of an ideal voltage doubler. During the first half-cycle, switches S1 and S2 close, and capacitor C1 charges to VIN. During the second half cycle, S1 and S2 open, S3 and S4 close, and C1 is level shifted upward by VIN volts. This connects C1 to the reservoir capacitor C2, allowing energy to be delivered to the output as necessary. The actual voltage is slightly lower than 2 x VIN , since switches S1-S4 have resistance and the load drains charge from C2.
(
)
Charge-Pump Output
The MAX1682/MAX1683 have a finite output resistance of about 20 (Table 2). As the load current increases, the devices' output voltage (VOUT) droops. The droop equals the current drawn from VOUT times the circuit's output impedance (RS), as follows: VDROOP = IOUT x RS VOUT = 2 x VIN - VDROOP
+ ESRC2 where fOSC is the oscillator frequency. The first term is the effective resistance from an ideal switchedcapacitor circuit (Figures 2a and 2b).
f
V+ VOUT C2 C1 RL
S1 VIN C1
S3
Figure 2a. Switched-Capacitor Model
VOUT C2 REQUIV V+ 1 REQUIV = f x C1 VIN C2 RL VOUT
S2
S4
Figure 1. Simplified Functional Diagram of Ideal Voltage Doubler
Figure 2b. Equivalent Circuit
5
_______________________________________________________________________________________
Switched-Capacitor Voltage Doublers MAX1682/MAX1683
Conversion losses occur during the charge transfer between C1 and C2 when there is a voltage difference between them. The power loss is: 2 2 PCONVERSION LOSS = 1/ 2C1 4VIN - VOUT + 2 1/ 2C2 2VOUT VRIPPLE - V RIPPLE x fOSC where VRIPPLE is the peak-to-peak output voltage ripple determined by the output capacitor and load current (see Output Capacitor section). Choose capacitor values that decrease the output resistance (see Flying Capacitor section). Using a larger flying capacitor reduces the output impedance and improves efficiency (see the Efficiency Considerations section). 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 (see the Output Resistance vs. Capacitance graph in the Typical Operating Characteristics). Table 2 lists the most desirable capacitor values--those that produce a low output resistance. But when space is a constraint, it may be necessary to sacrifice low output resistance for the sake of small capacitor size. Table 3 demonstrates how the capacitor affects output resistance.
Output Capacitor (C2)
Increasing the output capacitance reduces the output ripple voltage. Decreasing its ESR reduces both output resistance and ripple. Smaller capacitance values can be used with light loads. Use the following equation to calculate the peak-to-peak ripple: VRIPPLE = IOUT / (fOSC x C2) + 2 x IOUT x ESRC2
Applications Information
Flying Capacitor (C1)
To maintain the lowest output resistance, use capacitors with low ESR. Suitable capacitor manufacturers are listed in Table 1. The charge-pump output resistance is a function of C1 and C2's ESR and the internal switch resistance, as shown in the equation for R OUT in the Efficiency Considerations section. Minimizing the charge-pump capacitor's ESR minimizes the total resistance. Suggested values are listed in Tables 2 and 3.
Input Bypass Capacitor
Bypass the incoming supply to reduce its AC impedance and the impact of the MAX1682/MAX1683's switching noise. When loaded, the circuit draws a continuous current of 2 x IOUT. A 0.1F bypass capacitor is sufficient.
Table 1. Recommended Capacitor Manufacturers
PRODUCTION METHOD MANUFACTURER AVX Surface-Mount Tantalum Matsuo Sprague Surface-Mount Ceramic AVX Matsuo SERIES TPS 267 593D, 595D X7R X7R PHONE 803-946-0690 714-969-2491 603-224-1961 803-946-0590 714-969-2491 FAX 803-448-2170 714-960-6492 603-224-1430 803-626-3123 714-960-6492
Table 2. Suggested Capacitor Values for Low Output Resistance
PART MAX1682 MAX1683 FREQUENCY (kHz) 12 35 CAPACITOR VALUE (F) 10 3.3 TYPICAL ROUT () 20 20
Table 3. Suggested Capacitor Values for Minimum Size
PART MAX1682 MAX1683 FREQUENCY (kHz) 12 35 CAPACITOR VALUE (F) 3.3 1 TYPICAL ROUT () 35 35
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Switched-Capacitor Voltage Doublers
Cascading Devices
Devices can be cascaded to produce an even larger voltage (Figure 3). The unloaded output voltage is nominally (n + 1) x VIN, where n is the number of voltage doublers used. This voltage is reduced by the output resistance of the first device multiplied by the quiescent current of the second. The output resistance increases when devices are cascaded. Using a two-stage doubler as an example, output resistance can be approximated as ROUT = 2 x ROUT1 + ROUT2 , where ROUT1 is the output resistance of the first stage and ROUT2 is the output resistance of the second stage. A typical value for a two-stage voltage doubler is 60 (with C1 at 10F for MAX1682 and 3.3F for MAX1683). For n stages with the same C1 value, ROUT = (2n - 1) x ROUT1.
Paralleling Devices
Paralleling multiple MAX1682 or MAX1683s reduces the output resistance. Each device requires its own pump capacitor (C1), but the reservoir capacitor (C2) serves all devices (Figure 4). Increase C2's value by a factor of n, where n is the number of parallel devices. Figure 4 shows the equation for calculating output resistance.
MAX1682/MAX1683
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.
INPUT SUPPLY VOLTAGE
INPUT SUPPLY VOLTAGE
C1+
IN
C1+
IN
C1+
IN
MAX1682 MAX1683
C1 GND C1
C1+
IN
MAX1682
GND MAX1683 OUTPUT VOLTAGE OUT C1 GND
MAX1682 MAX1683
C1 GND
MAX1682 MAX1683
OUTPUT VOLTAGE OUT
C1C1OUT C2
C1C2 C1OUT
ROUT = ROUT OF SINGLE DEVICE NUMBER OF DEVICES
C2
Figure 3. Cascading Devices
Figure 4. Paralleling Devices
_______________________________________________________________________________________
7
Switched-Capacitor Voltage Doublers MAX1682/MAX1683
___________________Chip Information
TRANSISTOR COUNT: 97 SUBSTRATE CONNECTED TO OUT
________________________________________________________Package Information
SOT5L.EPS
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) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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