MAX680-681 Datasheet by Maxim Integrated

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MAX680IMAX681 +5V to 110V Voltage Converters I’M—\flflflflfl LILILILHJLILI maxim Integrated ,,
General Description
The MAX680/MAX681 are monolithic, CMOS, dual charge-
pump voltage converters that provide ±10V outputs from a
+5V input voltage. The MAX680/MAX681 provide both a
positive step-up charge pump to develop +10V from +5V
input and an inverting charge pump to generate the -10V
output. Both parts have an on-chip, 8kHz oscillator. The
MAX681 has the capacitors internal to the package, and
the MAX680 requires four external capacitors to produce
both positive and negative voltages from a single supply.
The output source impedances are typically 150Ω, provid-
ing useful output currents up to 10mA. The low quiescent
current and high efficiency make this device suitable
for a variety of applications that need both positive and
negative voltages generated from a single supply.
The MAX864/MAX865 are also recommended for new
designs. The MAX864 operates at up to 200kHz and uses
smaller capacitors. The MAX865 comes in the smaller
µMAX package.
Applications
The MAX680/MAX681 can be used wherever a single
positive supply is available and where positive and nega-
tive voltages are required. Common applications include
generating ±6V from a 3V battery and generating ±10V
from the standard +5V logic supply (for use with analog
circuitry). Typical applications include:
Features
95% Voltage-Conversion Efficiency
85% Power-Conversion Efficiency
+2V to +6V Voltage Range
Only Four External Capacitors Required (MAX680)
No Capacitors Required (MAX681)
500µA Supply Current
Monolithic CMOS Design
19-0896; Rev 2; 7/19
±6V from 3V Lithium Cell
Hand-Held Instruments
Data-Acquisition Systems
Panel Meters
±10V from +5V Logic
Supply
Battery-Operated
Equipment
Operational Amplifier
Power Supplies
PART TEMP. RANGE PIN-PACKAGE
MAX680CPA 0°C to +70°C 8 Plastic DIP
MAX680CSA 0°C to +70°C 8 Narrow SO
MAX680C/D 0°C to +70°C Dice
MAX680EPA -40°C to +85°C 8 Plastic DIP
MAX680ESA -40°C to +85°C 8 Narrow SO
MAX680MJA -55°C to +125°C 8 CERDIP
MAX681CPD 0°C to +70°C 14 Plastic DIP
MAX681EPD -40°C to +85°C 14 Plastic DIP
Pin Configurations
Typical Operating Circuits
VCC
C2-
GNDV-
1
2
8
7
V+
C1+C2+
C1-
MAX680
DIP/SO
TOP VIEW
3
4
6
5
14
13
12
11
10
9
8
1
2
3
4
5
6
7
VCC
VCC
VCC
VCC
C2+
C1-
C1-
V+
MAX681
V+
GND
GNDV-
C2-
C2-
DIP
MAX680 +10V
4.7µF
4.7µF
4.7µF
4.7µF -10V
GND
+10V
-10V
GND
FOUR PINS REQUIRED
(MAX681 ONLY)
+5V
GND
GND
+5V
C1-
C2+
V-
V+
C2-
VCC
GND
+5V to ±10V CONVERTER
MAX681
V-
V+
VCC
GND
C1+
Ordering Information
MAX680/MAX681 +5V to ±10V Voltage Converters
Click here for production status of specific part numbers.
VCC ....................................................................................+6.2V
V+ .......................................................................................+12V
V- ........................................................................................ -12V
V- Short-Circuit Duration ..........................................Continuous
V+ Current .........................................................................75mA
VCC ΔV/ΔT ........................................................................1V/µs
Continuous Power Dissipation (TA = +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C). ....727mW
8-Pin Narrow SO (derate 5.88mW/°C above +70°C) .... 471mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C) ........ 640mW
14-Pin Plastic DIP (derate 10.00mW/°C above +70°C) 800mW
Storage Temperature Range ............................-65°C to +160°C
Lead Temperature (soldering, 10sec) ............................ +300°C
(VCC = +5V, test circuit Figure 1, TA = +25°C, unless otherwise noted.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply Current
VCC = 3V, TA = +25°C, RL = 0.5 1
mA
VCC = 5V, TA = +25°C, RL = 1 2
VCC = 5V, 0°C ≤ TA+70°C, RL = 2.5
VCC = 5V, -40°C ≤ TA+85°C, RL = 3
VCC = 5V, -55°C ≤ TA+125°C, RL = 3
Supply-Voltage Range MIN ≤ TAMAX, RL = 10kΩ 2.0 1.5 to 6.0 6.0 V
Positive Charge-Pump
Output Source Resistance
IL+ = 10mA, IL- = 0mA, VCC = 5V, TA = +25°C 150 250
IL+ = 5mA, IL- = 0mA, VCC = 2.8V, TA = +25°C 180 300
IL+ = 10mA,
IL- = 0mA,
VCC = 5V
0°C ≤ TA+70°C 325
-40°C ≤ TA+85°C 350
-55°C ≤ TA+125°C 400
Negative Charge-Pump
Output Source Resistance
IL- = 10mA, IL+ = 0mA, V+ = 10V, TA = +25°C 90 150
IL- = 5mA, IL+ = 0mA, V+ = 5.6V, TA = +25°C 110 175
IL- = 10mA,
IL+ = 0mA,
VCC = 10V
0°C ≤ TA+70°C 200
-40°C ≤ TA+85°C 200
-55°C ≤ TA+125°C 250
Oscillator Frequency 4 8 kHz
Power Efficiency RL = 10kΩ 85 %
Voltage-Conversion
Efficiency
V+, RL = ∞ 95 99 %
V+, RL = ∞ 90 97
Absolute Maximum Ratings
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
MAX680/MAX681 +5V to ±10V Voltage Converters
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(TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
0
2.0
OUTPUT RESISTANCE
vs. SUPPLY VOLTAGE
MAX680/681 toc01
VCC (V)
OUTPUT RESISTANCE ()
50
100
150
200
250
3.0 4.0 5.0 6.0
ROUT-
ROUT+
C1-C4 = 10µF
4
0 1 2 3 4 6 7 8 9
OUTPUT VOLTAGE vs. OUTPUT CURRENT
(FROM V+ TO V-)
MAX680/681 toc04
OUTPUT CURRENT (mA)
|
VOUT
|
(V)
5
6
7
8
9
10
5 10
C1–C4 = 10µF
V-
V+
MAX680, MAX681
4
0
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX680/681 toc02
LOAD CURRENT (mA)
|VOUT| (V)
5
6
7
8
9
10
510 15 20
V+ vs. IL+
IL- = 0
V- vs. IL+
IL- = 0
V+ vs. IL-
IL+ = 0
V- vs. IL-
IL+ = 0
0
-50
OUTPUT SOURCE RESISTANCE
vs. TEMPERATURE
MAX680/681 toc05
TEMPERATURE (°C)
OUTPUT SOURCE RESISTANCE (
)
50
100
150
200
-25 0 25 50 75 100 125
ROUT+
ROUT-
VCC = 5V
0
2.0
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX680/681 toc03
VCC (V)
SUPPLY CURRENT (mA)
0.5
1.0
1.5
2.0
3.0 4.0 5.0 6.0
RL =
0
OUTPUT RIPPLE vs.
OUTPUT CURRENT (IL+ OR IL-)
MAX681/681-TOC6
OUTPUT CURRENT (mA)
OUTPUT RIPPLE (mVp-p)
50
100
150
200
510 15 20
V+ AND V-
V-
V-
MAX681
VCC = 5V
V+
MAX680
C3, C4 = 100µF
MAX680
C3, C4 = 10µF
0
V+
MAX680/MAX681 +5V to ±10V Voltage Converters
Maxim Integrated
3
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Detailed Description
The MAX681 contains all circuitry needed to implement a
dual charge pump. The MAX680 needs only four capac-
itors. These may be inexpensive electrolytic capacitors
with values in the 1µF to 100µF range. The MAX681
contains two 1.5µF capacitors as C1 and C2, and two
2.2µF capacitors as C3 and C4. See Typical Operating
Characteristics.
Figure 2a shows the idealized operation of the positive
voltage converter. The on-chip oscillator generates a 50%
duty-cycle clock signal. During the first half of the cycle,
switches S2 and S4 are open, S1 and S3 are closed, and
capacitor C1 is charged to the input voltage VCC. During
the second half-cycle, S1 and S3 are open, S2 and S4
are closed, and C1 is translated upward by VCC volts.
Assuming ideal switches and no load on C3, charge is
transferred onto C3 from C1 such that the voltage on C3
will be 2VCC, generating the positive supply.
Figure 2b shows the negative converter. The switches
of the negative converter are out of phase from the
positive converter. During the second half of the clock
cycle, S6 and S8 are open and S5 and S7 are closed,
charging C2 from V+ (pumped up to 2VCC by the posi-
tive charge pump) to GND. In the first half of the clock
Figure 2. Idealized Voltage Quadrupler: a) Positive Charge Pump; b) Negative Charge Pump
Figure 1. Test Circuit
VCC
a) b)
S1
S3
8kHz
C1+
C1 C3
C1-
S2
S4
S5 S6
S7 S8
C2-
GND
V-
RL-
RL+
C2+
C4
C2
GNDVCC
IL-
V+
GND
IL+
V+
IL+
RL+
RL-
IL-
MAX680
C1
4.7µF
VCC IN
C3
10µF
V+ OUT
V- OUT
GND
C4
10µF
C2
4.7µF
C1- 8
7
6
5
C2+
V-
V+
1
2
3
4
C1+
VCC
GND
C2-
MAX680/MAX681 +5V to ±10V Voltage Converters
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W H \ fififi H
cycle, S5 and S7 are open, S6 and S8 are closed,
and the charge on C2 is transferred to C4, generat-
ing the negative supply. The eight switches are CMOS
power MOSFETs. S1, S2, S4, and S5 are P-channel
switches, while S3, S6, S7, and S8 are N-channel
switches.
Efficiency Considerations
Theoretically, a charge-pump voltage multiplier can
approach 100% efficiency under the following conditions:
The charge-pump switches have virtually no offset
and extremely low on-resistance
Minimal power is consumed by the drive circuitry
The impedances of the reservoir and pump
capacitors are negligible
For the MAX680/MAX681, the energy loss per clock cycle
is the sum of the energy loss in the positive and negative
converters as below:
LOSSTOT = LOSSPOS + LOSSNEG
= ½ C1 [(V+)2 – (V+)(VCC)] +
½ C2 [(V+)2 – (V-)2]
There will be a substantial voltage difference between
(V+ - VCC) and VCC for the positive pump, and between
V+ and V-, if the impedances of pump capacitors C1 and
C2 are high relative to their respective output loads.
Larger C3 and C4 reservoir capacitor values reduce
output ripple. Larger values of both pump and reservoir
capacitors improve efficiency.
Maximum Operating Limits
The MAX680/MAX681 have on-chip zener diodes that
clamp VCC to approximately 6.2V, V+ to 12.4V, and
V- to -12.4V. Never exceed the maximum supply volt-
age: excessive current may be shunted by these diodes,
potentially damaging the chip. The MAX680/MAX681
operate over the entire operating temperature range with
an input voltage of +2V to +6V.
Applications
Positive and Negative Converter
The most common application of the MAX680/MAX681
is as a dual charge-pump voltage converter that provides
positive and negative outputs of two times a positive
input voltage. For applications where PC board space
is at a premium, the MAX681, with its capacitors inter-
nal to the package, offers the smallest footprint. The
simple circuit shown in Figure 3 performs the same
function using the MAX680 with external capacitors C1
and C3 for the positive pump and C2 and C4 for the
negative pump. In most applications, all four capaci-
tors are low-cost, 10µF or 22µF polarized electrolytics.
When using the MAX680 for low-current applications,
1µF can be used for C1 and C2 charge-pump capac-
itors, and 4.7µF for C3 and C4 reservoir capacitors.
C1 and C3 must be rated at 6V or greater, and C2 and C4
must be rated at 12V or greater.
Figure 3. Positive and Negative Converter
MAX680
C1
22µF
C3
22µF
V+ OUT
V- OUT
VCC IN
GND
C4
22µF
C2
22µF
C1- 8
7
6
5
C2+
V-
V+
1
2
3
4
C1+
VCC
GND
C2-
MAX680/MAX681 +5V to ±10V Voltage Converters
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5
if
The MAX680/MAX681 are not voltage regulators: the
output source resistance of either charge pump is approx-
imately 150Ω at room temperature with VCC at 5V. Under
light load with an input VCC of 5V, V+ will approach +10V
and V- will be at -10V. However both, V+ and V- will droop
toward GND as the current drawn from either V+ or V-
increases, since the negative converter draws its power
from the positive converter’s output. To predict output
voltages, treat the chips as two separate converters and
analyze them separately. First, the droop of the negative
supply (VDROP-) equals the current drawn from V- - (IL-)
times the source resistance of the negative converter
(RS-):
VDROP - = IL- x RS-
Likewise, the positive supply droop (VDROP+) equals the
current drawn from the positive supply (IL+) times the
positive converter’s source resistance (RS+), except that
the current drawn from the positive supply is the sum of
the current drawn by the load on the positive supply (IL+)
plus the current drawn by the negative converter (IL-):
(VDROP+) = IL+ x RS+ = (IL+ + IL-) x RS+
The positive output voltage will be:
V+ = 2VCC – VDROP+
The negative output voltage will be:
V- = (V+ – VDROP) = - (2VCC – VDROP+ – VDROP-)
The positive and negative charge pumps are tested and
specified separately to provide the separate values of
output source resistance for use in the above formulas.
When the positive charge pump is tested, the negative
charge pump is unloaded. When the negative charge
pump is tested, the positive supply V+ is from an external
source, isolating the negative charge pump.
Calculate the ripple voltage on either output by noting
that the current drawn from the output is supplied by the
reservoir capacitor alone during one half-cycle of the
clock. This results in a ripple of:
VRIPPLE = ½ IOUT (1/fPUMP)(1/CR)
For the nominal fPUMP of 8kHz with 10µF reservoir
capacitors, the ripple will be 30mV with IOUT at 5mA.
Remember that in most applications, the positive charge
pump’s IOUT is the load current plus the current taken by
the negative charge pump.
Figure 4. Paralleling MAX680s For Lower Source Resistance
MAX680
22µF
22µF
C1- 8
7
6
5
C2+
V-
V+
1
2
3
4
C1+
VCC
GND
C2-
MAX680
22µF
22µF
22µF
V+ OUT
V- OUT
VCC IN
GND
22µF
C1- 8
7
6
5
C2+
V-
V+
1
2
3
4
C1+
VCC
GND
C2-
MAX680/MAX681 +5V to ±10V Voltage Converters
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Paralleling Devices
Paralleling multiple MAX680/MAX681s reduces the output
resistance of both the positive and negative converters.
The effective output resistance is the output resistance
of a single device divided by the number of devices. As
Figure 4 shows, each MAX680 requires separate pump
capacitors C1 and C2, but all can share a single set of
reservoir capacitors.
±5V Regulated Supplies from
a Single 3V Battery
Figure 5 shows a complete ±5V power supply using
one 3V battery. The MAX680/MAX681 provide +6V at
V+, which is regulated to +5V by the MAX666, and -6V,
which is regulated to -5V by the MAX664. The MAX666
and MAX664 are pretrimmed at wafer sort and require
no external setting resistors, minimizing part count. The
combined quiescent current of the MAX680/MAX681,
MAX663, and MAX664 is less than 500µA, while the
output current capability is 5mA. The MAX680/MAX681
input can vary from 3V to 6V without affecting regulation
appreciably. With higher input voltage, more current can
be drawn from the MAX680/MAX681 outputs. With 5V at
VCC, 10mA can be drawn from both regulated outputs
simultaneously. Assuming 150Ω source resistance for
both converters, with (IL+ + IL-) = 20mA, the positive
charge pump will droop 3V, providing +7V for the nega-
tive charge pump. The negative charge pump will droop
another 1.5V due to its 10mA load, leaving -5.5V at V-
sufficient to maintain regulation for the MAX664 at this
current.
Figure 5. Regulated +5V and -5V from a Single Battery
MAX680
100µF 10µF
0.1µF
100µF
100µF
+12V TO +6V
-12V TO -6V
0.1µF
10µF
100µF
C1+
GND
VCC
C1-
C2-
V+
LBI
LOW-BATTERY
WARNING AT 3.5V
SENSE
VOUTVIN
6V TO 3V
2M
1.2M
+5V
-5V
GND
LBO
SDNGND VSET
V-
C2+
MAX666
VIN
VOUT1
VOUT2
SENSE
SDNGND VSET
MAX664
MAX680/MAX681 +5V to ±10V Voltage Converters
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Chip Topography
VCC
C1+
0.72"
(1.83mm)
0.116"
(2.95mm)
C2+
C2-
V- GND
C1- V+
MAX680/MAX681 +5V to ±10V Voltage Converters
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8
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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.
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 and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX680/MAX681 +5V to ±10V Voltage Converters
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