19-1247; Rev 0; 7/97
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
_______________General Description
The MAX1680/MAX1681 inductorless switched-capaci-
tor voltage converters either invert an input voltage of
+2.0V to +5.5V or double it while supplying up to
125mA output current. They have a selectable-frequen-
cy option that allows the use of small capacitors: 4.7µF
(MAX1680), 1µF (MAX1681). With their high output cur-
rent capability, these charge-pump devices are suit-
able replacements for inductor-based regulators, which
require more expensive external components and addi-
tional board space.
The devices’ equivalent output resistance (typically
3.5Ω) allows them to deliver as much as 125mA with
only a 440mV drop. A shutdown feature reduces quies-
cent current to less than 1µA. The MAX1680/MAX1681
are available in 8-pin SO packages. For devices that
deliver up to 50mA in smaller µMAX packages, refer to
the MAX860/MAX861 data sheet.
____________________________Features
o
Selectable Switching Frequencies:
125kHz/250kHz (MAX1680)
500kHz/1MHz (MAX1681)
o
Allow Use of Small Capacitors
(1µF for the MAX1681)
o
125mA Output Current
o
3.5Ω Output Impedance
o
1µA Logic-Controlled Shutdown
o
Configurable as Voltage Inverters or Doublers
o
+2.0V to +5.5V Input Voltage Range
o
Available in 8-Pin SO Packages
o
90% Efficiency
MAX1680/MAX1681
________________________Applications
Local Negative Supplies
Interface Power Supplies
Op-Amp Power Supplies
MOSFET Bias
______________Ordering Information
PART
MAX1680C/D
MAX1680ESA
MAX1681C/D
MAX1681ESA
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
Dice*
8 SO
Dice*
8 SO
*Contact
factory for dice specifications.
Pin Configuration appears at end of data sheet.
__________________________________________________Typical Operating Circuits
+V
INPUT
+3V TO +5.5V
1µF
CAP+
SHDN
C1
1µF
+V
INPUT
+4V TO +5.5V
1µF
CAP+
SHDN
DOUBLED
OUTPUT
VOLTAGE
FSEL
IN
FSEL
IN
C2
1µF
C1
1µF
MAX1681
LV
GND
INVERTED
OUTPUT
VOLTAGE
MAX1681
LV
GND
CAP-
OUT
CAP-
OUT
C2
1µF
INVERTER CONFIGURATION
NOTE: USE 4.7µF CAPACITORS FOR MAX1680
INPUT VOLTAGE RANGE: +2.0V TO +5.5V.
DOUBLER CONFIGURATION
NOTE: USE 4.7µF CAPACITORS FOR MAX1680
INPUT VOLTAGE RANGE: +2.5V TO +5.5V.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
MAX1680/MAX1681
ABSOLUTE MAXIMUM RATINGS
IN ..............................................................................-0.3V to +6V
LV....................................................(V
OUT
- 0.3V) to (V
IN
+ 0.3V)
CAP+ ...........................................................-0.3V to (V
IN
+ 0.3V)
SHDN, FSEL ......................................(V
LV
- 0.3V) to (V
IN
+ 0.3V)
OUT, CAP- ..................................................................-6V to 0.3V
Continuous Output Current ..............................................135mA
Output Short-Circuit Duration to GND (Note 1) ...................1sec
Continuous Power Dissipation (T
A
= +70°C)
SO (derate 5.88mW/°C above +70°C) ..........................471mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1:
Shorting OUT to IN may damage the device and should be avoided.
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 Circuits
(inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF
(MAX1681),
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
Inverter configuration,
R
L
= 1kΩ, LV = GND
Doubler configuration,
R
L
= 1kΩ, LV = OUT
FSEL = IN
(125kHz)
MAX1680
FSEL = LV
(250kHz)
Supply Current
I+
FSEL = IN
(500kHz)
MAX1681
FSEL = LV
(1MHz)
Output Voltage Under Load
(Note 2)
Output Resistance (Note 2)
Output Resistance to Ground
in Shutdown
Shutdown Current
Input Bias Current (SHDN)
Input Bias Current (FSEL)
Shutdown, FSEL Thresholds
V
LOAD
R
OUT
R
OUT(SHUT)
I+
SHDN
I
SHDN
I
FSEL
V
IL
V
IH
LV = GND (Note 3)
FSEL = LV
MAX1680
FSEL = IN
Switching Frequency
f
OSC
FSEL = LV
MAX1681
FSEL = IN
T
A
= +25°C
T
A
= +25°C
T
A
= +25°C
T
A
= +25°C
I
LOAD
= 125mA
FSEL = IN or LV
SHDN = IN
OUT = GND, SHDN = IN
-1
-1
4
187
157
94
79
750
570
375
285
500
1000
125
250
313
348
156
174
1250
1490
625
745
kHz
MAX1680
MAX1681
MAX1680
MAX1681
T
A
= +25°C
T
A
= +25°C
T
A
= +25°C
T
A
= +25°C
MIN
2.0
3.0
2.5
4.0
2.5
5
10
20
TYP
MAX
5.5
5.5
5.5
5.5
4.5
5.4
9
10.8
18
21.6
36
43.2
-3.75
-4.56
3.5
1
10
5
1
1
1
1
V
Ω
Ω
µA
µA
µA
V
mA
V
V
UNITS
Input Voltage Range
V
IN
2
_______________________________________________________________________________________
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
ELECTRICAL CHARACTERISTICS (continued)
(Typical
Operating Circuits
(inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF
(MAX1681),
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Power Efficiency
SYMBOL
CONDITIONS
R
L
= 100Ω to GND, FSEL = IN
MAX1680
MAX1681
MIN
TYP
90
80
MAX
UNITS
%
MAX1680/MAX1681
ELECTRICAL CHARACTERISTICS
(Typical
Operating Circuits
(inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF
(MAX1681),
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
SYMBOL
CONDITIONS
Inverter configuration,
R
L
= 1kΩ, LV = GND
Doubler configuration,
R
L
= 1kΩ, LV = OUT
MAX1680
MAX1681
MAX1680
MAX1681
FSEL = IN
(125kHz)
MAX1680
FSEL = LV
(250kHz)
Supply Current
I+
FSEL = IN
(500kHz)
MAX1681
FSEL = LV
(1MHz)
Output Voltage Under Load
(Note 2)
Output Resistance (Note 2)
Output Resistance in
Shutdown
Shutdown Current
Input Bias Current (SHDN)
Input Bias Current (FSEL)
Shutdown, FSEL Thresholds
V
LOAD
R
OUT
R
OUT(SHUT)
I+
SHDN
I
SHDN
I
FSEL
V
IL
V
IH
LV = GND (Note 3)
MAX1680
Switching Frequency
f
OSC
MAX1681
FSEL = LV
FSEL = IN
FSEL = LV
FSEL = IN
-1
-1
4
157
79
570
285
348
174
1490
745
kHz
I
LOAD
= 125mA
FSEL = IN or LV
SHDN = IN
OUT = GND, SHDN = IN
-3.75
10
5
1
1
1
1
43.2
V
Ω
Ω
µA
µA
µA
V
21.6
10.8
mA
MIN
2.0
3.0
2.5
4.0
TYP
MAX
5.5
5.5
5.5
5.5
5.4
mA
V
UNITS
Input Voltage Range
V
IN
Note 2:
C1 and C2 are low-ESR (<0.2Ω) capacitors. Capacitor ESR adds to the circuit’s output resistance. Using capacitors with
higher ESR reduces output voltage and efficiency. The specified output resistance includes the C1 and C2 0.2Ω ESR.
Note 3:
The typical threshold for V
INPUT
other than +5V is 0.35V
INPUT
(V
IL
= V
IH
).
Note 4:
Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
MAX1680/MAX1681
__________________________________________Typical Operating Characteristics
(All curves generated using the inverter configuration shown in the
Typical Operating Circuits
with LV = GND, FSEL = IN or LV,
C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), and T
A
= +25°C, unless otherwise noted. Test results are also valid for
the doubler configuration with LV = OUT and T
A
= +25°C.)
OUTPUT VOLTAGE DROP
vs. LOAD CURRENT
MAX1680/81TOC01
OSCILLATOR FREQUENCY CHANGE
vs. SUPPLY VOLTAGE
MAX1680/81TOC02
OSCILLATOR FREQUENCY CHANGE
vs. TEMPERATURE
OSCILLATOR FREQUENCY CHANGE (%)
8
6
4
2
0
-2
-4
-6
-8
-10
-40
-20
0
20
40
60
80
100
MAX1680
MAX1681
MAX1680/81TOC03
800
700
OUTPUT VOLTAGE DROP (mV)
600
V
INPUT
= 3V
500
400
300
200
100
0
0
20
40
60
80
100
120
V
INPUT
= 5V
2
OSCILLATOR FREQUENCY CHANGE (%)
0
-2
-4
-6
-8
MAX1681
-10
-12
-14
2.0
2.5
3.0
3.5
4.0
4.5
5.0
MAX1680
10
140
5.5
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
OUTPUT SOURCE RESISTANCE
vs. SUPPLY VOLTAGE
MAX1680/81TOC04
OUTPUT SOURCE RESISTANCE vs.
TEMPERATURE
V
INPUT
= 3V
OUTPUT SOURCE RESISTANCE (Ω)
5
4
V
INPUT
= 5V
3
2
1
0
20
MAX1680/81TOC05
MAX1680 EFFICIENCY vs.
LOAD CURRENT (INVERTER CONFIGURATION)
MAX1680/81TOC06
8.5
OUTPUT SOURCE RESISTANCE (Ω)
7.5
6.5
5.5
4.5
3.5
2.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
6
100
80
EFFICIENCY (%)
60
V
INPUT
= 3V
V
INPUT
= 4V
V
INPUT
= 5.5V
40
FSEL = IN
0
-40
-20
0
20
40
60
80
100
1
10
100
1000
TEMPERATURE (°C)
LOAD CURRENT (mA)
5.5
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
____________________________Typical Operating Characteristics (continued)
(All curves generated using the inverter configuration shown in the
Typical Operating Circuits
with LV = GND, FSEL = IN or LV,
C1 = C2 = 10µF (MAX1680), C1 = C2 = 2.2µF (MAX1681), and T
A
= +25°C, unless otherwise noted. Test results are also valid for
the doubler configuration with LV = OUT and T
A
= +25°C.)
MAX1681 EFFICIENCY vs.
LOAD CURRENT (DOUBLER CONFIGURATION)
MAX1680/81TOC07
MAX1680/MAX1681
MAX1680 SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX1680/81TOC08
MAX1681 SUPPLY CURRENT vs.
SUPPLY VOLTAGE
DOUBLER MODE
FSEL = LV
MAX1680/81TOC09
100
9
8
SUPPLY CURRENT (mA)
7
6
5
4
3
2
1
INVERTER MODE
FSEL = IN
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
DOUBLER MODE
FSEL = IN
INVERTER MODE
FSEL = LV
DOUBLER MODE
FSEL = LV
30
25
SUPPLY CURRENT (mA)
20
15
10
5
0
INVERTER MODE
FSEL = IN
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INVERTER MODE
FSEL = LV
DOUBLER MODE
FSEL = IN
80
EFFICIENCY (%)
60
V
INPUT
= 3V
V
INPUT
= 4V
40
20
V
INPUT
= 5.5V
FSEL = IN
0
1
10
100
1000
LOAD CURRENT (mA)
0
6.0
SUPPLY VOLTAGE (V)
6.0
SUPPLY VOLTAGE (V)
MAX1680 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (INVERTER CONFIGURATION)
MAX1680/81TOC10
MAX1680 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (DOUBLER CONFIGURATION)
V
INPUT
= 3V, FSEL = LV
OUTPUT SOURCE RESISTANCE (Ω)
9
8
7
6
5
4
3
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 3V, FSEL = IN
MAX1680/81TOC11
MAX1680/81TOC13
10
OUTPUT SOURCE RESISTANCE (Ω)
9
8
7
6
5
4
3
0
2
4
6
8
V
INPUT
= 3V, FSEL = IN
V
INPUT
= 5V, FSEL = IN
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 5V, FSEL = LV
10
V
INPUT
= 5V, FSEL = IN
10 12 14 16 18 20
0
2
4
6
8
10 12 14 16 18 20
CAPACITANCE (µF)
CAPACITANCE (µF)
MAX1681 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (INVERTER CONFIGURATION)
MAX1680/81TOC12
MAX1681 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (DOUBLER CONFIGURATION)
10
OUTPUT SOURCE RESISTANCE (Ω)
9
8
7
6
5
4
3
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 5V, FSEL = IN
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 3V, FSEL = IN
10
OUTPUT SOURCE RESISTANCE (Ω)
9
8
7
6
5
V
INPUT
= 5V, FSEL = LV
4
V
INPUT
= 5V, FSEL = IN
3
0
2
4
6
8
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 3V, FSEL = IN
10 12 14 16 18 20
0
2
4
6
8
10 12 14 16 18 20
CAPACITANCE (µF)
CAPACITANCE (µF)
_______________________________________________________________________________________
5
