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19-0239; Rev 1; 11/96
50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
_______________General Description
The MAX860/MAX861 charge-pump voltage converters invert input voltages ranging from +1.5V to +5.5V, or double input voltages ranging from +2.5V to +5.5V. Because of their high switching frequencies, these devices use only two small, low-cost capacitors. Their 50mA output makes switching regulators unnecessary, eliminating inductors and their associated cost, size, and EMI. Greater than 90% efficiency over most of the load-current range, combined with a typical operating current of only 200A (MAX860), provides ideal performance for both battery-powered and board-level voltage-conversion applications. A frequency-control (FC) pin provides three switchingfrequencies to optimize capacitor size and quiescent current and to prevent interference with sensitive circuitry. Each device has a unique set of three available ---- --- frequencies. A shutdown (SHDN) pin reduces current consumption to less than 1A. The MAX860/MAX861 are suitable for use in applications where the ICL7660 and MAX660's switching frequencies are too low. The MAX860/MAX861 are available in 8-pin MAX and SO packages.
____________________________Features
o 8-Pin, 1.11mm High MAX Package o Invert or Double the Input Supply Voltage o Three Selectable Switching Frequencies o High Frequency Reduces Capacitor Size o 87% Efficiency at 50mA o 200A Quiescent Current (MAX860) o 1A Shutdown Supply Current o 600mV Voltage Drop at 50mA Load o 12 Output Resistance
MAX860/MAX861
______________Ordering Information
PART MAX860ISA MAX860IUA MAX860C/D MAX860ESA MAX860MJA MAX861ISA MAX861IUA MAX861C/D MAX861ESA MAX861MJA TEMP. RANGE -25C to +85C -25C to +85C 0C to +70C -40C to +85C -55C to +125C -25C to +85C -25C to +85C 0C to +70C -40C to +85C -55C to +125C PIN-PACKAGE 8 SO 8 MAX Dice* 8 SO 8 CERDIP 8 SO 8 MAX Dice* 8 SO 8 CERDIP
________________________Applications
Portable Computers Medical Instruments Interface Power Supplies Hand-Held Instruments Operational-Amplifier Power Supplies
__________Typical Operating Circuit
1 2 3 C1 10F 4 FC MAX860 VDD 8 7 6 5 INPUT VOLTAGE +1.5V TO +5.5V
* Dice are tested at TA = +25C, DC parameters only. Contact factory for availability.
MAX861
C1+ GND C1-
SHDN LV OUT
__________________Pin Configuration
INVERTED NEGATIVE OUTPUT 10F C2
TOP VIEW
VOLTAGE INVERTER
FC 1
INPUT VOLTAGE +2.5V TO +5.5V 1 2 3 C1 10F 4 FC MAX860 VDD 8 7 6 5 DOUBLED POSITIVE OUTPUT 10F C2
8 7
VDD SHDN LV OUT
C1+ 2 GND 3 C1- 4
MAX861
MAX860 MAX861
6 5
C1+ GND C1-
SHDN LV OUT
SO/MAX
POSITIVE VOLTAGE DOUBLER
________________________________________________________________ Maxim Integrated Products
1
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VDD to GND or GND to OUT) ...................+6.0V -- - ----- Input Voltage Range (LV, FC, S H D N ) ...................(OUT - 0.3V) to (VDD + 0.3V) Continuous Output Current (OUT, VDD) .............................60mA Output Short-Circuit to GND (Note 1)...................................1sec Continuous Power Dissipation (TA = +70C) SO (derate 5.88mW/C above +70C) .........................471mW MAX (derate 4.10mW/C above +70C) ....................330mW CERDIP (derate 8.00mW/C above +70C) .................640mW Note 1: Operating Temperature Ranges MAX86_I_A ......................................................-25C to +85C MAX86_ESA.....................................................-40C to +85C MAX86_MJA ..................................................-55C to +125C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
OUT may be shorted to GND for 1sec without damage, but shorting OUT to VDD may damage the device and should be avoided. Also, for temperatures above +85C, OUT must not be shorted to GND or VDD, even instantaneously, or device damage may result.
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.
---- --- - (Typical Operating Circuit (Inverter), VDD = +5V, SHDN = VDD, FC = LV = GND, C1 = C2 = 10F (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Supply Voltage SYMBOL VDD RL = 1k CONDITIONS Inverter, LV = GND Doubler, LV = OUT FC = VDD = 5V MAX860I/E FC = VDD = 3V FC = GND FC = OUT FC = VDD MAX860M No-Load Supply Current IDD MAX861I/E FC = GND FC = OUT FC = VDD FC = GND FC = OUT FC = VDD MAX861M FC = GND FC = OUT VDD = 5V, VOUT more negative than -3.75V Output Current IOUT VDD = 3V, VOUT more negative than -2.5V Output Resistance (Note 3) ROUT IL = 50mA IL = 10mA, VDD = 2V 10 30 12 20 25 35 50 100 mA 0.3 1.1 2.5 MIN 1.5 2.5 0.2 0.07 0.6 1.4 1.0 2.5 0.4 1.3 3.3 0.4 2.0 5.0 0.5 2.6 6.5 mA TYP MAX 5.5 5.5 0.3 UNITS V
ELECTRICAL CHARACTERISTICS
2
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
ELECTRICAL CHARACTERISTICS (continued)
PARAMETER SYMBOL MAX860 Switching Frequency (Note 4) fS MAX861 FC Current (from VDD) IFC FC < 4V MAX860, FC = VDD RL = 2k from VDD to OUT RL = 1k from OUT to GND RL = 2k from VDD to OUT RL = 1k from OUT to GND 93 90 93 88
MAX860/MAX861
---- --- - (Typical Operating Circuit (Inverter), VDD = +5V, SHDN = VDD, FC = LV = GND, C1 = C2 = 10F (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) CONDITIONS FC = VDD FC = GND FC = OUT FC = VDD FC = GND FC = OUT MIN 3 30 80 8 60 160 TYP 6 50 130 13 100 250 -2 96 93 96 92 87 99 1.2 0.3 -- - ----- S H D N < 0.3V No load, VOUT = -4V MAX86_I/E MAX86_M 500 1 10 99.9 % V A s % -4 A kHz MAX UNITS
Power Efficiency (Note 5) MAX861, FC = VDD
MAX860/MAX861, FC = VDD, IL = 50mA to GND, C1 = C2 = 68F Voltage-Conversion Efficiency ---- --- - SHDN Threshold Shutdown Supply Current Time to Exit Shutdown Note 2: Note 3: Note 4: Note 5: VIH VIL No load LV = GND
C1 and C2 are low-ESR (<0.2) aluminum electrolytics. Capacitor ESR adds to the circuit's output resistance. Using capacitors with higher ESR may reduce output voltage and efficiency. Specified output resistance includes the effect of the 0.2 ESR of the test circuit's capacitors. The switches are driven directly at the oscillator frequency, without any division. At lowest frequencies, using 10F capacitors gives worse efficiency figures than using the recommended capacitor values in Table 3, due to larger 1 (fs x C1) term in ROUT.
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
__________________________________________Typical Operating Characteristics
(All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GND and TA = +25C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and TA = +25C. All capacitor values used are those recommended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is RO in the equation for ROUT shown in the Capacitor Selection section.)
OUTPUT VOLTAGE DROP FROM SUPPLY VOLTAGE vs. LOAD CURRENT
MAX860-01
PERCENTAGE FREQUENCY CHANGE (%) (FROM FREQUENCY MEASURED WITH VDD = +5V)
OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
MAX860-02
OUTPUT SOURCE RESISTANCE (RO) vs. SUPPLY VOLTAGE
OUTPUT SOURCE RESISTANCE () 18 16 14 12 10 8 6 4 2 0 ALL FREQUENCIES 0 1 2 3 4 5
MAX860-03
0.8 0.7 0.6 VOUT DROP (V) 0.5 0.4 0.3 0.2 0.1 0 0
2 0 -2 -4 -6 -8
ALL FREQUENCIES VDD = +1.5V VDD = +2.5V
20
VDD = +3.5V VDD = +4.5V, +5.0V VDD = +5.5V 10 20 30 40 50
-10 -12
ALL FREQUENCIES, LV CONNECTED TO GND (INVERTER) OR OUT (DOUBLER)
-14
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
OUTPUT SOURCE RESISTANCE (RO) vs. TEMPERATURE
OUTPUT SOURCE RESISTANCE () ALL FREQUENCIES 28 24 20 16 12 8 4 0 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) VDD = +5V VDD = +1.5V VDD = +3V EFFICIENCY (%)
MAX860-04
MAX860 EFFICIENCY vs. LOAD CURRENT
MAX860-05
MAX860 SUPPLY CURRENT vs. SUPPLY VOLTAGE
FC = VDD 400 DOUBLER, LV = OUT SUPPLY CURRENT (A)
MAX860-06
32
100 90 80 70 60 50 40 30 20 10 0 0.01 0.1 1 10 INVERTER FC = VDD VDD = +1.5V VDD = +3V VDD = +5V
500
300 INVERTER, LV = GND (VDD > 3V)
200
100
0 100 0 1 2 3 4 5 6 LOAD CURRENT (mA) SUPPLY VOLTAGE (V)
MAX861 SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX860-07
MAX860 OUTPUT CURRENT vs. CAPACITANCE HIGH-FREQUENCY MODE
MAX860-08
MAX860 OUTPUT CURRENT vs. CAPACITANCE MEDIUM-FREQUENCY MODE
70 OUTPUT CURRENT (mA) 60 50 40 30 VIN = +4.5V, VOUT = -4V 20 10 0 VIN = +3V, VOUT = -2.7V fOSC = 50kHz FC = GND LV = GND INVERTER MODE VIN = +4.5V, VOUT = -3.5V VIN = +3V, VOUT = -2.4V
MAX860-09
500 FC = VDD 400 SUPPLY CURRENT (A) DOUBLER, LV = OUT
70 60 OUTPUT CURRENT (mA) 50 40 30 20 10 0
300 INVERTER, LV = GND 200
fOSC = 130kHz FC = OUT LV = GND INVERTER MODE VIN = +4.5V, VOUT = -3.5V VIN = +4.5V, VOUT = -4V
80
VIN = +3V, VOUT = -2.4V
100
VIN = +3V, VOUT = -2.7V
0 0 1 2 3 4 5 6 SUPPLY VOLTAGE (V)
0.33
1
2.2
4.7
10
22
0.33
1
2.2
4.7
10
22
CAPACITANCE (F)
CAPACITANCE (F)
4
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
____________________________Typical Operating Characteristics (continued)
(All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GND and TA = +25C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and TA = +25C. All capacitor values used are those recommended in Table 3, unless otherwise noted. The output resistance curves represent the resistance of the device itself, which is RO in the equation for ROUT shown in the Capacitor Selection section.)
MAX861 OUTPUT CURRENT vs. CAPACITANCE HIGH-FREQUENCY MODE
MAX860-10
MAX860/MAX861
MAX861 OUTPUT CURRENT vs. CAPACITANCE MEDIUM-FREQUENCY MODE
70 OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 VIN = +3V, VOUT = -2.7V VIN = +3V, VOUT = -2.4V VIN = +4.5V, VOUT = -4V fOSC = 100kHz FC = GND LV = GND INVERTER MODE VIN = +4.5V, VOUT = -3.5V
MAX860-11
90 80 OUTPUT CURRENT (mA) 70 60 50 40 30 20 10 0 0.33 1 2.2 4.7 10 VIN = +3V, VOUT = -2.7V VIN = +4.5V, VOUT = -4V VIN = +3V, VOUT = -2.4V fOSC = 250kHz FC = OUT LV = GND INVERTER MODE
80
VIN = +4.5V, VOUT = -3.5V
22
0.33
1
2.2
4.7
10
22
CAPACITANCE (F)
CAPACITANCE (F)
______________________________________________________________Pin Description
FUNCTION PIN 1 2 3 4 5 6 7 8 NAME INVERTER FC C1+ GND C1OUT LV ---- --- - SHDN VDD Frequency Control, see Table 1 Flying-Capacitor Positive Terminal Ground Flying-Capacitor Negative Terminal Negative Output Low-Voltage-Operation Input. Connect to GND. Active-Low Shutdown Input. Connect to VDD if not used. Connect to GND to disable the charge pump. Positive Input Supply DOUBLER Frequency Control, see Table 1 Flying-Capacitor Positive Terminal Positive Input Supply Flying-Capacitor Negative Terminal Ground Low-Voltage-Operation Input. Connect to OUT. Active-Low Shutdown Input. Connect to GND pin if not used. Connect to OUT to disable the charge pump. Doubled Positive Output
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
_______________Detailed Description
The MAX860/MAX861 capacitive charge pumps either invert or double the voltage applied to their inputs. For highest performance, use low equivalent series resistance (ESR) capacitors. See the Capacitor Selection section for more details. The frequency-control (FC) pin allows you to choose one of three switching frequencies; these three selectable frequencies are different for each device. When shut down, MAX860/MAX861 current consumption reduces to less than 1A. is not used. When the device is shut down, all active circuitry is turned off. In the inverting configuration, loads connected from OUT to GND are not powered in shutdown mode. However, a reverse-current path exists through two diodes between OUT and GND; therefore, loads connected from VDD to OUT draw current from the input supply. In the doubling configuration, loads connected from the VDD pin to the GND pin are not powered in shutdown mode. Loads connected from the VDD pin to the OUT pin draw current from the input supply through a path similar to that of the inverting configuration (described above).
Common Applications
Voltage Inverter The most common application for these devices is a charge-pump voltage inverter (see Typical Operating Circuits). This application requires only two external components--capacitors C1 and C2--plus a bypass capacitor if necessary (see Bypass Capacitor section). Refer to the Capacitor Selection section for suggested capacitor types and values.
Even though the MAX860/MAX861's output is not actively regulated, it is fairly insensitive to load-current changes. A circuit output source resistance of 12 (calculated using the formula given in the Capacitor Selection section) means that, with a +5V input, the output voltage is -5V under no load and decreases to -4.4V with a 50mA load. The MAX860/MAX861 output source resistance (used to calculate the circuit output source resistance) vs. temperature and supply voltage are shown in the Typical Operating Characteristics graphs. Calculate the output ripple voltage using the formula given in the Capacitor Selection section.
Frequency Control
Charge-pump frequency for both devices can be set to one of three values. Each device has a unique set of three available frequencies, as indicated in Table 1. The oscillator and charge-pump frequencies are the same (i.e., the charge-pump frequency is not half the oscillator frequency, as it is on the MAX660, MAX665, and ICL7660).
Table 1. Nominal Switching Frequencies*
FREQUENCY (kHz) FC CONNECTION MAX860 FC = VDD or open FC = GND FC = OUT 6 50 130 MAX861 13 100 250
Positive Voltage Doubler The MAX860/MAX861 can also operate as positive voltage doublers (see Typical Operating Circuits). This application requires only two external components, capacitors C1 and C2. The no-load output is twice the input voltage. The electrical specifications in the doubler mode are very similar to those of the inverter mode except for the Supply Voltage Range (see Electrical Characteristics table) and No-Load Supply Current (see graph in Typical Operating Characteristics). The circuit output source resistance and output ripple voltage are calculated using the formulas in the Capacitor Selection section.
When driven low, the SHDN input -- - --shuts down the --- device. In inverter mode, connect SHDN - VDD if it is - -- to ---- not used. In doubler mode, connect SHDN to GND if it
*See the Electrical Characteristics for detailed switchingfrequency specifications.
A higher switching frequency minimizes capacitor size for the same performance and increases the supply current (Table 2). The lowest fundamental frequency of the switching noise is equal to the minimum specified switching frequency (e.g., 3kHz for the MAX860 with FC open). The spectrum of noise frequencies extends above this value because of harmonics in the switching waveform. To get best noise performance, choose the device and FC connection to select a minimum switching frequency that lies above your sensitive bandwidth.
Active-Low Shutdown Input --- - ----
Low-Voltage-Operation Input LV should be connected to GND for inverting operation. To enhance compatibility with the MAX660, MAX665, and ICL7660, you may float LV if the input voltage exceeds 3V. In doubling mode, LV must be connected to OUT for all input voltages.
6
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
Table 2. Switching-Frequency Trade-Offs
ATTRIBUTE Output Ripple C1, C2 Values Supply Current LOWER FREQUENCY Larger Larger Smaller HIGHER FREQUENCY Smaller Smaller Larger
__________Applications Information
Capacitor Selection
The MAX860/MAX861 are tested using 10F capacitors for both C1 and C2, although smaller or larger values can be used (Table 3). Smaller C1 values increase the output resistance; larger values reduce the output resistance. Above a certain point, increasing the capacitance of C1 has a negligible effect (because the output resistance becomes dominated by the internal switch resistance and the capacitor ESR). Low-ESR capacitors provide the lowest output resistance and ripple voltage. The output resistance of the entire circuit (inverter or doubler) is approximately: ROUT = RO + 4 x ESRC1 + ESRC2 + 1 / (fS x C1) where R O (the effective resistance of the MAX860/ MAX861's internal switches) is approximately 8 and fS is the switching frequency. ROUT is typically 12 when using capacitors with 0.2 ESR and fS, C1, and C2 values suggested in Table 3. When C1 and C2 are so large (or the switching frequency is so high) that the internal switch resistance dominates the output resistance, estimate the output resistance as follows: ROUT = RO + 4 x ESRC1 + ESRC2
A typical design procedure is as follows: 1) Choose C1 and C2 to be the same, for convenience. 2) Select fS: a) If you want to avoid a specific noise frequency, choose fS appropriately. b) If you want to minimize capacitor cost and size, choose a high fS. c) If you want to minimize current consumption, choose a low fS. 3) Choose a capacitor based on Table 3, although higher or lower values can be used to optimize performance. Table 4 lists manufacturers who provide low-ESR capacitors.
MAX860/MAX861
Table 3. Suggested Capacitor Values*
NOMINAL FREQUENCY (kHz) 6 13 50 100 130 250 C1, C2 (F) 68 47 10 4.7 4.7 2.2
*In addition to Table 3, four graphs in the Typical Operating Characteristics section show typical output current for C1 and C2 capacitances ranging from 0.33F to 22F. Output current is plotted for inputs of 4.5V (5V - 10%) and 3.0V (3.3V - 10%), and also for 10% and 20% output droop from the ideal -VIN value.
Table 4. Low-ESR Capacitor Manufacturers
MANUFACTURER-Series AVX TPS Series AVX TAG Series Matsuo 267 Series Sprague 595 Series Sanyo MV-GX Series Sanyo CV-GX Series Nichicon PL Series United Chemicon (Marcon) TDK PHONE (803) 946-0629 (803) 946-0629 (714) 969-2491 (603) 224-1961 (619) 661-6835 (619) 661-6835 (847) 843-7500 (847) 696-2000 (847) 390-4461 FAX (803) 626-3123 (803) 626-3123 (714) 960-6492 (613) 224-1430 (619) 661-1055 (619) 661-1055 (847) 843-2798 (847) 696-9278 (847) 390-4405 COMMENTS Low-ESR tantalum, SMT Low-cost tantalum, SMT Low-cost tantalum, SMT Low-ESR tantalum, SMT Aluminum electrolytic, through hole Aluminum electrolytic, SMT Aluminum electrolytic, through hole Ceramic SMT Ceramic SMT 7
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
Flying Capacitor, C1 Increasing the size of the flying capacitor reduces the output resistance. Output Capacitor, C2 Increasing the size of the output capacitor reduces the output ripple voltage. Decreasing its ESR reduces both output resistance and ripple. Smaller capacitance values can be used if one of the higher switching frequencies is selected, if less than the maximum rated output current (50mA) is required, or if higher ripple can be tolerated. The following equation for peak-to-peak ripple applies to both the inverter and doubler circuits.
IOUT VRIPPLE = ---------------- + 2 x IOUT x ESRC2 2 x fS x C2 unloaded output voltage is nominally -2 x VIN, but this is reduced slightly by the output resistance of the first device multiplied by the quiescent current of the second. The output resistance of the complete circuit is approximately five times the output resistance of a single MAX860/MAX861. Three or more devices can be cascaded in this way, but output resistance rises dramatically, and a better solution is offered by inductive switching regulators (such as the MAX755, MAX759, MAX764, or MAX774). Connect LV as with a standard inverter circuit (see Pin Description).
Paralleling Devices
Paralleling multiple MAX860s or MAX861s reduces the output resistance. As illustrated in Figure 2, each device requires its own pump capacitor (C1), but the reservoir capacitor (C2) serves all devices. C2's value should be increased by a factor of n, where n is the number of devices. Figure 2 shows the equation for calculating output resistance. An alternative solution is to use the MAX660 or MAX665, which are capable of supplying up to 100mA of load current. Connect LV as with a standard inverter circuit (see Pin Description).
Bypass Capacitor Bypass the incoming supply to reduce its AC impedance and the impact of the MAX860/MAX861's switching noise. The recommended bypassing depends on the circuit configuration and where the load is connected.
When the inverter is loaded from OUT to GND or the doubler is loaded from VDD to GND, current from the supply switches between 2 x IOUT and zero. Therefore, use a large bypass capacitor (e.g., equal to the value of C1) if the supply has a high AC impedance. When the inverter and doubler are loaded from VDD to OUT, the circuit draws 2 x IOUT constantly, except for short switching spikes. A 0.1F bypass capacitor is sufficient.
Combined Doubler/Inverter
In the circuit of Figure 3, 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 towards GND. Make sure the sum of the currents drawn from the two outputs does not exceed 60mA. Connect LV as with a standard inverter circuit (see Pin Description).
Cascading Devices
Two devices can be cascaded to produce an even larger negative voltage, as shown in Figure 1. The
...
8 2 C1 3 4 7 +VIN 2 C1 5 3 4 8 7 8 2 5 VOUT C2 C1 3 4 7
ROUT OF SINGLE DEVICE ROUT = NUMBER OF DEVICES +VIN
...
8 2 7
MAX860 MAX861 "1"
MAX860 MAX861 "n"
...
C2 VOUT = -nVIN
MAX860 MAX861 "1"
C1 5
3 4
MAX860 MAX861 "n"
5
VOUT
...
VOUT = -VIN C2
Figure 1. Cascading MAX860s or MAX861s to Increase Output Voltage
8
Figure 2. Paralleling MAX860s or MAX861s to Reduce Output Resistance
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50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
Table 5. Product Selection Guide
+VIN 8 2 C1 3 4 7 D1, D2 = 1N4148 D1 5 C2 D2 C3 C4 VOUT = (2VIN) (VFD1) - (VFD2) VOUT = -VIN
MAX860/MAX861
PART NUMBER MAX660 MAX665 MAX860 MAX861 ICL7660
OUTPUT CURRENT (mA) 100 100 50 50 10
OUTPUT SWITCHING RESISTANCE FREQUENCY () (kHz) 6.5 6.5 12 12 55 5/40 5/40 6/50/130 13/100/250 5
MAX860 MAX861
Figure 3. Combined Doubler and Inverter
Compatibility with MAX660/MAX665/ICL7660
The MAX860/MAX861 can be used in sockets designed for the MAX660, MAX665, and ICL7660 with a minimum of one wiring change. This section gives advice on installing a MAX860/MAX861 into a socket designed for one of the earlier devices. The MAX660, -- - --MAX665, and ICL7660 have an OSC pin --- instead of SHDN. MAX660, MAX665, and ICL7660 normal operation is with OSC floating (although - - -- OSC can ---- be overdriven). If OSC is floating, pin 7 (SHDN ) should be jumpered to VDD to enable the MAX860/MAX861 --- - ---- permanently. Do not leave SHDN on the MAX860/ MAX861 floating. The MAX860/MAX861 operate with FC either floating or connected to V DD , OUT, or GND; each connection defines the oscillator frequency. Thus, any of the normal MAX660, MAX665, or ICL7660 connections to pin 1 will work with the MAX860/MAX861, without modifications. Changes to the FC connection are only required if you want to adjust the operating frequency.
___________________Chip Topography
FC V DD
C1+ GND
0.084" (2.13mm)
SHDN C1LV
OUT
0.058" (1.47mm)
TRANSISTOR COUNT: 101 SUBSTRATE CONNECTED TO VDD
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9
50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
________________________________________________________Package Information
CDIPS.EPS
10
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SOICN.EPS
50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters
___________________________________________Package Information (continued)
8LUMAXD.EPS
MAX860/MAX861
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11
50mA, Frequency-Selectable, Switched-Capacitor Voltage Converters MAX860/MAX861
NOTES
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.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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