Maxim MAX861IUA 50ma, frequency-selectable, switched-capacitor voltage converter Datasheet

MAX860/MAX861
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 200µA (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 1µA. 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 µMAX® and
SO packages.
________________________Applications
Portable Computers
Medical Instruments
Interface Power Supplies
Hand-Held Instruments
Operational-Amplifier Power Supplies
__________Typical Operating Circuit
1
2
3
C1 10μF 4
FC
INPUT
VOLTAGE
+1.5V TO +5.5V
8
MAX860
MAX861 VDD
C1+
SHDN
GND
LV
C1-
OUT
7
6
5
INVERTED
NEGATIVE
OUTPUT
10μF
C2
____________________________Features
o 8-Pin, 1.11mm High µMAX 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 200µA Quiescent Current (MAX860)
o 1µA Shutdown Supply Current
o 600mV Voltage Drop at 50mA Load
o 12Ω Output Resistance
______________Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX860ISA
-25°C to +85°C
8 SO
MAX860IUA
-25°C to +85°C
8 µMAX
MAX860C/D
0°C to +70°C
Dice*
MAX860ESA
-40°C to +85°C
8 SO
MAX860MJA
-55°C to +125°C
8 CERDIP†
MAX860MSA/PR3
-55°C to +125°C
8 SO
MAX861ISA
-25°C to +85°C
8 SO
MAX861IUA
-25°C to +85°C
8 µMAX
MAX861C/D
0°C to +70°C
Dice*
MAX861ESA
-40°C to +85°C
8 SO
MAX861MJA
-55°C to +125°C
8 CERDIP†
*Dice are tested at TA = +25°C, DC parameters only.
†Contact factory for availability.
__________________Pin Configuration
TOP VIEW
VOLTAGE INVERTER
INPUT
VOLTAGE
+2.5V TO +5.5V
+
1
2
3
C1
10μF 4
FC MAX860 VDD
MAX861
C1+
SHDN
GND
LV
C1-
OUT
8
7
6
DOUBLED
POSITIVE
OUTPUT
10μF
C2
8
VDD
7
SHDN
GND 3
6
LV
C1- 4
5
OUT
FC 1
C1+ 2
MAX860
MAX861
5
POSITIVE VOLTAGE DOUBLER
SO/μMAX
µMAX is a registered trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-0239; Rev 3; 8/13
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
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).......................................1s
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
µMAX (derate 4.2mW/°C above +70°C) ......................362mW
CERDIP (derate 8.00mW/°C above +70°C) .................640mW
Note 1:
Operating Temperature Ranges
MAX86_I_A ......................................................-25°C to +85°C
MAX86_ESA.....................................................-40°C to +85°C
MAX86_M_A ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+240°C
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 +85°C, 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.
ELECTRICAL CHARACTERISTICS
–———–
(Typical Operating Circuit (Inverter), VDD = +5V, SHDN = VDD, FC = LV = GND, C1 = C2 = 10µF (Note 2), TA = TMIN to TMAX, unless
otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Supply Voltage
SYMBOL
VDD
CONDITIONS
RL = 1kΩ
MAX860I/E
MAX860M
No-Load Supply Current
(Note 3)
IDD
MAX861M
Doubler, LV = OUT
2.5
5.5
FC = VDD = 5V
0.2
FC = VDD = 3V
0.07
FC = GND
0.6
1.0
FC = OUT
1.4
2.5
0.4
FC = GND
1.3
3.3
FC = VDD
0.3
0.4
FC = GND
1.1
2.0
FC = OUT
2.5
5.0
FC = VDD
0.5
FC = GND
2.6
FC = OUT
6.5
50
V
mA
100
IOUT
ROUT
UNITS
0.3
FC = VDD
mA
VDD = 3V, VOUT more negative than -2.5V
2
MAX
5.5
VDD = 5V, VOUT more negative than -3.75V
Output Resistance
(Note 4)
TYP
1.5
FC = OUT
MAX861I/E
Output Current
MIN
Inverter, LV = GND
10
30
IL = 50mA
12
25
IL = 10mA, VDD = 2V
20
35
Ω
Maxim Integrated
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
ELECTRICAL CHARACTERISTICS (continued)
–———–
(Typical Operating Circuit (Inverter), VDD = +5V, SHDN = VDD, FC = LV = GND, C1 = C2 = 10µF (Note 2), TA = TMIN to TMAX, unless
otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MAX860
Switching Frequency
(Note 5)
fS
MAX861
FC Current (from VDD)
IFC
MIN
FC = VDD
3
6
FC = GND
30
50
FC = OUT
80
130
FC = VDD
8
13
FC = GND
60
100
FC = OUT
160
250
FC < 4V
MAX860,
FC = VDD
Power Efficiency (Note 6)
MAX861,
FC = VDD
-2
RL = 2kΩ from VDD
to OUT
93
96
RL = 1kΩ from OUT
to GND
90
93
RL = 2kΩ from VDD
to OUT
93
96
RL = 1kΩ from OUT
to GND
88
92
MAX860/MAX861, FC = VDD,
IL = 50mA to GND, C1 = C2 = 68µF
Voltage-Conversion Efficiency
–———–
SHDN Threshold
VIH
99
LV = GND
1.2
No load, VOUT = -4V
Note 4:
Note 5:
Note 6:
-4
µA
%
%
0.3
Time to Exit Shutdown
UNITS
kHz
99.9
VIL
–———–
S H D N < 0.3V
Note 3:
MAX
87
No load
Shutdown Supply Current
Note 2:
TYP
MAX86_I/E
1
MAX86_M
10
500
V
µA
µs
C1 and C2 are low-ESR (<0.2Ω) aluminum electrolytics. Capacitor ESR adds to the circuit’s output resistance. Using
capacitors with higher ESR may reduce output voltage and efficiency.
MAX860/MAX861 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.
Specified output resistance includes the effect of the 0.2Ω ESR of the test circuit’s capacitors.
The switches are driven directly at the oscillator frequency, without any division.
At lowest frequencies, using 10µF capacitors gives worse efficiency figures than using the recommended capacitor
values in Table 3, due to larger 1 ⁄ (fs x C1) term in ROUT.
Maxim Integrated
3
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
__________________________________________Typical Operating Characteristics
(All curves generated using the inverter circuit shown in the Typical Operating Circuits with LV = GND and TA = +25°C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and TA = +25°C. 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.)
0.4
0.3
VDD = +3.5V
0.2
VDD = +4.5V, +5.0V
VDD = +5.5V
0.1
0
10
20
30
-10
ALL FREQUENCIES,
LV CONNECTED TO GND
(INVERTER) OR OUT (DOUBLER)
-12
-14
OUTPUT SOURCE RESISTANCE (RO) vs.
TEMPERATURE
MAX860
EFFICIENCY vs. LOAD CURRENT
MAX860-04
VDD = +3V
12
90
VDD = +1.5V
60
VDD = +3V
50
VDD = +5V
40
0
0
MAX860-03
INVERTER, LV = GND
(VDD > 3V)
200
1
0.1
100
10
0
1
2
3
4
5
6
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
MAX861 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX860 OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
MAX860 OUTPUT CURRENT vs. CAPACITANC
MEDIUM-FREQUENCY MODE
400
OUTPUT CURRENT (mA)
DOUBLER, LV = OUT
60
300
INVERTER, LV = GND
200
100
fOSC = 130kHz
FC = OUT
LV = GND
INVERTER MODE
50
VIN = +4.5V, VOUT = -3.5V
VIN = +4.5V, VOUT = -4V
40
30
VIN = +3V, VOUT = -2.4V
20
VIN = +3V, VOUT = -2.7V
10
1
2
3
4
SUPPLY VOLTAGE (V)
5
6
70
60
fOSC = 50kHz
FC = GND
LV = GND
INVERTER MODE
VIN = +4.5V, VOUT = -3.5V
50
40
VIN = +3V, VOUT = -2.4V
30
VIN = +4.5V, VOUT = -4V
20
VIN = +3V, VOUT = -2.7V
10
0
0
0
80
OUTPUT CURRENT (mA)
70
MAX860-07
FC = VDD
MAX860-09
TEMPERATURE (°C)
500
0
300
0
0.01
20 40 60 80 100 120 140
DOUBLER, LV = OUT
100
INVERTER
FC = VDD
10
5
4
FC = VDD
400
70
3
2
500
20
4
ALL FREQUENCIES
1
MAX860 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
30
VDD = +5V
-60 -40 -20 0
6
4
0
SUPPLY CURRENT (μA)
VDD = +1.5V
8
8
2
80
16
10
SUPPLY VOLTAGE (V)
100
24
20
12
0
SUPPLY VOLTAGE (V)
28
14
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
EFFICIENCY (%)
OUTPUT SOURCE RESISTANCE (Ω)
-8
LOAD CURRENT (mA)
ALL FREQUENCIES
SUPPLY CURRENT (μA)
-6
50
40
32
4
-4
MAX860-05
0
-2
18
16
MAX860-06
0.5
20
MAX860-08
VOUT DROP (V)
0.6
VDD = +2.5V
0
OUTPUT SOURCE RESISTANCE (Ω)
VDD = +1.5V
2
OUTPUT SOURCE RESISTANCE (RO) vs.
SUPPLY VOLTAGE
MAX860-02
ALL FREQUENCIES
0.7
PERCENTAGE FREQUENCY CHANGE (%)
(FROM FREQUENCY MEASURED WITH VDD = +5V)
0.8
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGE
MAX860-01
OUTPUT VOLTAGE DROP FROM
SUPPLY VOLTAGE vs. LOAD CURRENT
0.33
1
2.2
4.7
CAPACITANCE (μF)
10
22
0.33
1
2.2
4.7
10
22
CAPACITANCE (μF)
Maxim Integrated
MAX860/MAX861
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 = +25°C, unless otherwise noted. Test results also valid for doubler mode with LV = OUT and TA = +25°C. 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.)
70
fOSC = 250kHz
FC = OUT
LV = GND
INVERTER MODE
60
80
VIN = +4.5V,
VOUT = -3.5V
50
VIN = +4.5V, VOUT = -4V
40
30
VIN = +3V, VOUT = -2.4V
20
60
0
VIN = +4.5V,
VOUT = -3.5V
50
VIN = +3V,
VOUT = -2.4V
40
VIN = +4.5V,
VOUT = -4V
30
20
VIN = +3V, VOUT = -2.7V
10
VIN = +3V, VOUT = -2.7V
10
fOSC = 100kHz
FC = GND
LV = GND
INVERTER MODE
70
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
80
MAX860-10
90
MAX861
OUTPUT CURRENT vs. CAPACITANCE
MEDIUM-FREQUENCY MODE
MAX860-11
MAX861
OUTPUT CURRENT vs. CAPACITANCE
HIGH-FREQUENCY MODE
0
0.33
1
2.2
4.7
10
0.33
22
CAPACITANCE (μF)
1
2.2
4.7
10
22
CAPACITANCE (μF)
______________________________________________________________Pin Description
FUNCTION
PIN
NAME
INVERTER
DOUBLER
Frequency Control, see Table 1
Frequency Control, see Table 1
1
FC
2
C1+
Flying-Capacitor Positive Terminal
Flying-Capacitor Positive Terminal
3
GND
Ground
Positive Input Supply
4
C1-
Flying-Capacitor Negative Terminal
Flying-Capacitor Negative Terminal
5
OUT
Negative Output
Ground
6
LV
Low-Voltage-Operation Input. Connect to GND.
Low-Voltage-Operation Input. Connect to OUT.
7
–———–
SHDN
Active-Low Shutdown Input. Connect to VDD if not
used. Connect to GND to disable the charge pump.
Active-Low Shutdown Input. Connect to GND pin if not
used. Connect to OUT to disable the charge pump.
8
VDD
Positive Input Supply
Doubled Positive Output
Maxim Integrated
5
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
_______________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 1µA.
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 12Ω (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.
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.
Active-Low
Shutdown Input
–———–
When driven low, the SHDN input
shuts
down the
–———
–
device. In inverter mode, connect SH–—
D—
N—–to VDD if it is
not used. In doubler mode, connect SHDN to GND if it
6
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).
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
MAX861
FC = VDD or open
6
13
FC = GND
50
100
FC = OUT
130
250
*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.
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.
Maxim Integrated
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Table 2. Switching-Frequency Trade-Offs
LOWER
FREQUENCY
Larger
HIGHER
FREQUENCY
Smaller
C1, C2 Values
Larger
Smaller
Supply Current
Smaller
Larger
ATTRIBUTE
Output Ripple
__________Applications Information
Capacitor Selection
The MAX860/MAX861 are tested using 10µF 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 8Ω and fS
is the switching frequency. ROUT is typically 12Ω when
using capacitors with 0.2Ω 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.
Table 3. Suggested Capacitor Values*
NOMINAL FREQUENCY (kHz)
C1, C2 (μF)
6
68
13
47
50
10
100
4.7
130
4.7
250
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
0.33µF to 22µF. 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
PHONE
FAX
COMMENTS
AVX TPS Series
(803) 946-0629
(803) 626-3123
Low-ESR tantalum, SMT
AVX TAG Series
(803) 946-0629
(803) 626-3123
Low-cost tantalum, SMT
Matsuo 267 Series
(714) 969-2491
(714) 960-6492
Low-cost tantalum, SMT
Sprague 595 Series
(603) 224-1961
(613) 224-1430
Low-ESR tantalum, SMT
Sanyo MV-GX Series
(619) 661-6835
(619) 661-1055
Aluminum electrolytic, through hole
Sanyo CV-GX Series
(619) 661-6835
(619) 661-1055
Aluminum electrolytic, SMT
Nichicon PL Series
(847) 843-7500
(847) 843-2798
Aluminum electrolytic, through hole
United Chemicon (Marcon)
(847) 696-2000
(847) 696-9278
Ceramic SMT
TDK
(847) 390-4461
(847) 390-4405
Ceramic SMT
Maxim Integrated
7
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
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
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 0.1µF bypass capacitor is
sufficient.
Cascading Devices
Two devices can be cascaded to produce an even
larger negative voltage, as shown in Figure 1. The
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).
The maximum load current and startup current of nth
cascaded circuit must not exceed the maximum output
current capability of (n-1)th circuit to ensure proper
startup.
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).
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
ROUT OF SINGLE DEVICE
ROUT = NUMBER OF DEVICES
…
8
2
C1
3
4
MAX860
MAX861
“1”
+VIN
+VIN
8
2
7
3
C1
5
MAX860
MAX861
“n”
8
7
5
4
…
2
VOUT
C1
3
4
C2
C2
…
MAX860
MAX861
“1”
8
2
7
3
C1
5
7
MAX860
MAX861
“n”
5
4
VOUT
…
VOUT = -VIN
C2
VOUT = -nVIN
Figure 1. Cascading MAX860s or MAX861s to Increase
Output Voltage
8
Figure 2. Paralleling MAX860s or MAX861s to Reduce Output
Resistance
Maxim Integrated
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Table 5. Product Selection Guide
+VIN
8
2
C1
3
MAX860
MAX861
4
7
PART
NUMBER
OUTPUT
CURRENT
(mA)
MAX660
100
6.5
5/40
MAX665
100
6.5
5/40
MAX860
50
12
6/50/130
MAX861
50
12
13/100/250
ICL7660
10
55
5
D1, D2 = 1N4148
D1
5
OUTPUT
SWITCHING
RESISTANCE FREQUENCY
(Ω)
(kHz)
VOUT = -VIN
C2
D2
C3
C4
VOUT = (2VIN) (VFD1) - (VFD2)
Figure 3. Combined Doubler and Inverter
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).
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
the
be jumpered to VDD to enable
–——
—– 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.
Maxim Integrated
___________________Chip Topography
V DD
FC
0.084"
(2.13mm)
C1+
GND
SHDN
C1-
LV
OUT
0.058"
(1.47mm)
PROCESS: BiCMOS
SUBSTRATE CONNECTED TO VDD
9
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.
10
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND
PATTERN NO.
8 SO
S8-4
21-0041
90-0096
8 CDIP
J8-2
21-0045
—
8 µMAX
U8-1
21-0036
90-0092
Maxim Integrated
MAX860/MAX861
50mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
Revision History
PAGES
CHANGED
REVISION
NUMBER
REVISION
DATE
0
7/94
Initial release
2
4/03
Updated Electrical Characteristics and Cascading Devices section.
3, 8
3
8/13
Added MAX860MSA/PR3 to data sheet and revised Absolute Maximum
Ratings.
1, 2
DESCRIPTION
—
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 ________________________________ 11
© 2013 Maxim Integrated Products, Inc.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.