_______________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: 4.7F
(MAX1680), 1F (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
3.5
) allows them to deliver as much as 125mA with
only a 440mV drop. A shutdown feature reduces quies-
cent current to less than 1A. The MAX1680/MAX1681
are available in 8-pin SO packages. For devices that
deliver up to 50mA in smaller MAX packages, refer to
the MAX860/MAX861 data sheet.
________________________Applications
Local Negative Supplies
Interface Power Supplies
Op-Amp Power Supplies
MOSFET Bias
____________________________Features
o
Selectable Switching Frequencies:
125kHz/250kHz (MAX1680)
500kHz/1MHz (MAX1681)
o
Allow Use of Small Capacitors
(1F for the MAX1681)
o
125mA Output Current
o
3.5
Output Impedance
o
1A 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
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
________________________________________________________________
Maxim Integrated Products
1
MAX1681
FSEL
IN
CAP+
SHDN
GND
C1
1
F
+V
INPUT
+3V TO +5.5V
INVERTED
OUTPUT
VOLTAGE
C2
1
F
1
F
LV
CAP-
INVERTER CONFIGURATION
OUT
MAX1681
FSEL
IN
CAP+
SHDN
GND
C1
1
F
C2
1
F
DOUBLED
OUTPUT
VOLTAGE
+V
INPUT
+4V TO +5.5V
NOTE: USE 4.7
F CAPACITORS FOR MAX1680
INPUT VOLTAGE RANGE: +2.5V TO +5.5V.
NOTE: USE 4.7
F CAPACITORS FOR MAX1680
INPUT VOLTAGE RANGE: +2.0V TO +5.5V.
1
F
LV
CAP-
DOUBLER CONFIGURATION
OUT
__________________________________________________Typical Operating Circuits
19-1247; Rev 0; 7/97
PART
MAX1680
C/D
MAX1680ESA
MAX1681
C/D
0C to +70C
-40C to +85C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
Dice*
8 SO
Dice*
______________Ordering Information
*
Contact factory for dice specifications.
Pin Configuration appears at end of data sheet.
MAX1681ESA
-40C to +85C
8 SO
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.
V
MAX1680/MAX1681
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(
Typical Operating Circuits (inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10F (MAX1680), C1 = C2 = 2.2F
(MAX1681),
T
A
= 0C to +85C
, unless otherwise noted. Typical values are at T
A
= +25C.)
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.
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
= +70C)
SO (derate 5.88mW/C above +70C) ..........................471mW
Operating Temperature Range ...........................-40C to +85C
Junction Temperature ......................................................+150C
Storage Temperature Range .............................-65C to +160C
Lead Temperature (soldering, 10sec) .............................+300C
I
LOAD
= 125mA
Inverter configuration,
R
L
= 1k
, LV = GND
LV = GND (Note 3)
FSEL = IN or LV
SHDN = IN
OUT = GND, SHDN = IN
CONDITIONS
375
500
625
750
1000
1250
94
125
156
187
250
313
4
V
IH
V
-3.75
-4.56
V
LOAD
Output Voltage Under Load
(Note 2)
V
3.0
5.5
2.0
5.5
V
1
V
IL
Shutdown, FSEL Thresholds
A
-1
1
I
FSEL
Input Bias Current (FSEL)
3.5
10
R
OUT
Output Resistance (Note 2)
1
5
R
OUT(SHUT)
Output Resistance to Ground
in Shutdown
A
1
I+
SHDN
Shutdown Current
A
-1
1
I
SHDN
Input Bias Current (SHDN)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Doubler configuration,
R
L
= 1k
, LV = OUT
4.0
5.5
V
IN
2.5
5.5
Input Voltage Range
MAX1680
5.4
mA
10.8
FSEL = IN
(125kHz)
FSEL = LV
(250kHz)
MAX1681
21.6
43.2
I+
FSEL = IN
(500kHz)
Supply Current
FSEL = LV
(1MHz)
Note 1:
Shorting OUT to IN may damage the device and should be avoided.
T
A
= +25C
T
A
= +25C
T
A
= +25C
T
A
= +25C
MAX1681
MAX1680
MAX1681
MAX1680
T
A
= +25C
T
A
= +25C
T
A
= +25C
T
A
= +25C
2.5
4.5
5
9
10
18
20
36
FSEL = LV
157
348
FSEL = IN
MAX1680
79
174
FSEL = LV
570
1490
kHz
FSEL = IN
MAX1681
f
OSC
Switching Frequency
285
745
mA
ELECTRICAL CHARACTERISTICS
(
Typical Operating Circuits (inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10F (MAX1680), C1 = C2 = 2.2F
(MAX1681),
T
A
= -40C to +85C
, unless otherwise noted.) (Note 4)
MAX1680/MAX1681
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
_______________________________________________________________________________________
3
FSEL = IN
FSEL = LV
MAX1681
I
LOAD
= 125mA
21.6
mA
Inverter configuration,
R
L
= 1k
, LV = GND
43.2
Doubler configuration,
R
L
= 1k
, LV = OUT
MAX1681
FSEL = LV
FSEL = IN
MAX1680
LV = GND (Note 3)
FSEL = IN or LV
SHDN = IN
OUT = GND, SHDN = IN
CONDITIONS
I+
FSEL = IN
(500kHz)
Supply Current
FSEL = LV
(1MHz)
kHz
285
745
f
OSC
570
1490
79
174
157
348
Switching Frequency
4
V
IH
V
-3.75
V
LOAD
Output Voltage Under Load
(Note 2)
3.0
5.5
V
2.0
5.5
4.0
5.5
V
IN
V
-1
1
V
IL
Shutdown, FSEL Thresholds
A
-1
1
I
FSEL
Input Bias Current (FSEL)
10
R
OUT
Output Resistance (Note 2)
5
R
OUT(SHUT)
Output Resistance in
Shutdown
A
1
I+
SHDN
Shutdown Current
A
1
I
SHDN
Input Bias Current (SHDN)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
MAX1681
MAX1680
2.5
5.5
Input Voltage Range
MAX1681
MAX1680
MAX1680
5.4
10.8
FSEL = IN
(125kHz)
FSEL = LV
(250kHz)
ELECTRICAL CHARACTERISTICS (continued)
(
Typical Operating Circuits (inverter configuration), FSEL = LV = GND, V
IN
= 5V, C1 = C2 = 10F (MAX1680), C1 = C2 = 2.2F
(MAX1681),
T
A
= 0C to +85C
, unless otherwise noted. Typical values are at T
A
= +25C.)
Note 2:
C1 and C2 are low-ESR (<0.2
) 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 0.2
ESR.
Note 3:
The typical threshold for V
INPUT
other than +5V is 0.35V
INPUT
(V
IL
= V
IH
).
Note 4:
Specifications to -40C are guaranteed by design, not production tested.
R
L
= 100
to GND, FSEL = IN
MAX1680
MAX1681
%
80
90
Power Efficiency
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
CONDITIONS
MAX1680/MAX1681
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
4
_______________________________________________________________________________________
__________________________________________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 = 10F (MAX1680), C1 = C2 = 2.2F (MAX1681), and T
A
= +25C, unless otherwise noted. Test results are also valid for
the doubler configuration with LV = OUT and T
A
= +25C.)
2.5
3.5
5.5
4.5
7.5
6.5
8.5
2.5
2.0
3.0
3.5
4.0
4.5
5.0
5.5
OUTPUT SOURCE RESISTANCE
vs. SUPPLY VOLTAGE
MAX1680/81TOC04
SUPPLY VOLTAGE (V)
OUTPUT SOURCE RESISTANCE (
)
0
1
3
2
5
4
6
-20
-40
0
20
40
60
80
100
OUTPUT SOURCE RESISTANCE vs.
TEMPERATURE
MAX1680/81TOC05
TEMPERATURE (C)
OUTPUT SOURCE RESISTANCE (
)
V
INPUT
= 3V
V
INPUT
= 5V
100
0
1
100
1000
MAX1680 EFFICIENCY vs.
LOAD CURRENT (INVERTER CONFIGURATION)
20
40
60
80
MAX1680/81TOC06
LOAD CURRENT (mA)
EFFICIENCY (%)
10
V
INPUT
= 5.5V
V
INPUT
= 4V
V
INPUT
= 3V
FSEL = IN
0
200
100
500
400
300
700
600
800
0
60
80
20
40
100
120
140
OUTPUT VOLTAGE DROP
vs. LOAD CURRENT
MAX1680/81TOC01
LOAD CURRENT (mA)
OUTPUT VOLTAGE DROP (mV)
V
INPUT
= 3V
V
INPUT
= 5V
-14
-10
-12
-4
-6
-8
0
-2
2
2.0
3.5
4.0
2.5
3.0
4.5
5.0
5.5
OSCILLATOR FREQUENCY CHANGE
vs. SUPPLY VOLTAGE
MAX1680/81TOC02
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY CHANGE (%)
MAX1680
MAX1681
-10
-6
-8
-2
-4
2
0
4
8
6
10
-40
0
20
-20
40
60
80
100
OSCILLATOR FREQUENCY CHANGE
vs. TEMPERATURE
MAX1680/81TOC03
TEMPERATURE (C)
OSCILLATOR FREQUENCY CHANGE (%)
MAX1680
MAX1681
MAX1680/MAX1681
125mA, Frequency-Selectable,
Switched-Capacitor Voltage Converters
_______________________________________________________________________________________
5
100
0
1
100
1000
MAX1681 EFFICIENCY vs.
LOAD CURRENT (DOUBLER CONFIGURATION)
20
40
60
80
MAX1680/81TOC07
LOAD CURRENT (mA)
EFFICIENCY (%)
10
V
INPUT
= 5.5V
V
INPUT
= 4V
V
INPUT
= 3V
FSEL = IN
1
0
3
2
6
5
4
8
7
9
2.0
3.5
4.0
2.5
3.0
4.5
5.0
5.5
6.0
MAX1680 SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX1680/81TOC08
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
DOUBLER MODE
FSEL = LV
INVERTER MODE
FSEL = IN
INVERTER MODE
FSEL = LV
DOUBLER MODE
FSEL = IN
0
5
15
10
25
20
30
3.0
2.5
3.5
4.0
4.5
5.0
5.5
6.0
MAX1681 SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX1680/81TOC09
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
DOUBLER MODE
FSEL = LV
INVERTER MODE
FSEL = IN
INVERTER MODE
FSEL = LV
DOUBLER MODE
FSEL = IN
3
4
6
5
7
8
9
10
0
4
6
8
2
10
12
14
18
16
20
MAX1680 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (INVERTER CONFIGURATION)
MAX1680/81TOC10
CAPACITANCE (
F)
OUTPUT SOURCE RESISTANCE (
)
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 3V, FSEL = IN
V
INPUT
= 5V, FSEL = IN
3
4
6
5
7
8
9
10
0
4
6
8
2
10
12
14
18
16
20
MAX1681 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (DOUBLER CONFIGURATION)
MAX1680/81TOC13
CAPACITANCE (
F)
OUTPUT SOURCE RESISTANCE (
)
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 5V, FSEL = IN
V
INPUT
= 3V, FSEL = IN
3
4
6
5
7
8
9
10
0
4
6
8
2
10
12
14
18
16
20
MAX1680 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (DOUBLER CONFIGURATION)
MAX1680/81TOC11
CAPACITANCE (
F)
OUTPUT SOURCE RESISTANCE (
)
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 5V, FSEL = IN
V
INPUT
= 3V, FSEL = IN
3
4
6
5
7
8
9
10
0
4
6
8
2
10
12
14
18
16
20
MAX1681 OUTPUT SOURCE RESISTANCE vs.
CAPACITANCE (INVERTER CONFIGURATION)
MAX1680/81TOC12
CAPACITANCE (
F)
OUTPUT SOURCE RESISTANCE (
)
V
INPUT
= 3V, FSEL = LV
V
INPUT
= 5V, FSEL = LV
V
INPUT
= 5V, FSEL = IN
V
INPUT
= 3V, FSEL = IN
____________________________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 = 10F (MAX1680), C1 = C2 = 2.2F (MAX1681), and T
A
= +25C, unless otherwise noted. Test results are also valid for
the doubler configuration with LV = OUT and T
A
= +25C.)
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