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MAX1682EUK+T

P1-P3P4-P6P7-P9
MAX1682/MAX1683
Switched-Capacitor Voltage Doublers
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Typical Operating Circuit, V
IN
= +5V, C1 = C2 = 10µF for the MAX1682 and 3.3µF for the MAX1683, T
A
= +25°C, unless otherwise
noted.)
11.0
11.5
12.0
12.5
-40 0 20-20 406080
MAX1682 OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX1682/83 TOC10
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (kHz)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
28
32
30
36
34
38
40
-40 0 20-20 406080
MAX1683 OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX1682/83 TOC11
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (kHz)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
0
2
1
4
3
6
5
7
9
8
10
0 1015205 253035 4540 50
MAX1682 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1682/83 TOC12
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
0
2
1
4
3
6
5
7
9
8
10
0 1015205 253035 4540 50
MAX1683 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1682/83 TOC13
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
20μs/div
V
OUT
20mV/div
I
LOAD
= 5mA, V
IN
= 5V, C1 = C2 = 10μF
MAX1682
OUTPUT RIPPLE
MAX1682toc16
80
86
84
82
88
90
92
94
96
98
100
0105 15202530
MAX1682 EFFICIENCY vs.
LOAD CURRENT
MAX1682/83 TOC14
LOAD CURRENT (mA)
EFFICIENCY (%)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
80
86
84
82
88
90
92
94
96
98
100
0105 15202530
MAX1683 EFFICIENCY vs.
LOAD CURRENT
MAX1682/83 TOC15
LOAD CURRENT (mA)
EFFICIENCY (%)
V
IN
= 5V
V
IN
= 3.3V
V
IN
= 2V
MAX1683
OUTPUT RIPPLE
MAX1682toc17
I
LOAD
= 5mA, V
IN
= 5V, C1 = 3.3μF, C2 = 10μF
20μs/div
V
OUT
20mV/div
0
0.5
1.0
1.5
2.0
2.5
700 30 10100 70300 7 3 1 0.7 0.3
START-UP VOLTAGE
vs. RESISTIVE LOAD
MAX1682toc18
R
LOAD
(kΩ)
V
START
(V)
MAX1682
MAX1683
_______________Detailed Description
The MAX1682/MAX1683 capacitive charge pumps
double the voltage applied to their input. Figure 1
shows a simplified functional diagram of an ideal volt-
age doubler. During the first half-cycle, switches S1
and S2 close, and capacitor C1 charges to V
IN
. During
the second half cycle, S1 and S2 open, S3 and S4
close, and C1 is level shifted upward by V
IN
volts. This
connects C1 to the reservoir capacitor C2, allowing
energy to be delivered to the output as necessary. The
actual voltage is slightly lower than 2 x V
IN
, since
switches S1–S4 have resistance and the load drains
charge from C2.
Charge-Pump Output
The MAX1682/MAX1683 have a finite output resistance
of about 20Ω (Table 2). As the load current increases,
the devices’ output voltage (V
OUT
) droops. The droop
equals the current drawn from V
OUT
times the circuit’s
output impedance (R
S
), as follows:
V
DROOP
= I
OUT
x R
S
V
OUT
= 2 x V
IN
- V
DROOP
Efficiency Considerations
The power efficiency of a switched-capacitor voltage
converter is affected by three factors: the internal losses
in the converter IC, the resistive losses of the capacitors,
and the conversion losses during charge transfer
between the capacitors. The total power loss is:
The internal losses are associated with the IC’s internal
functions, such as driving the switches, oscillator, etc.
These losses are affected by operating conditions such
as input voltage, temperature, and frequency.
The next two losses are associated with the voltage
converter circuit’s output resistance. Switch losses
occur because of the on-resistance of the MOSFET
switches in the IC. Charge-pump capacitor losses
occur because of their ESR. The relationship between
these losses and the output resistance is as follows:
where f
OSC
is the oscillator frequency. The first term is
the effective resistance from an ideal switched-
capacitor circuit (Figures 2a and 2b).
PP
IxR
R
fxC
R ESR
ESR
PUMP CAPACITOR LOSSES SWITCH LOSSES
OUT OUT
OUT
OSC
SWITCHES C
C
+=
≅
()
++
+
2
1
2
1
1
24
ΣPP
P
P
LOSS INTERNAL LOSSES
PUMP CAPACITOR LOSSES
CONVERSION LOSSES
=
+
+
MAX1682/MAX1683
Switched-Capacitor Voltage Doublers
_______________________________________________________________________________________ 5
_____________________Pin Description
NAME FUNCTION
1 GND Ground
2 OUT
Doubled Output Voltage. Connect C2
between OUT and GND.
PIN
3 C1-
Negative Terminal of the Flying
Capacitor
4 IN Input Supply
5 C1+
Positive Terminal of the Flying
Capacitor
Figure 2a. Switched-Capacitor Model
V+
C1
f
C2 R
L
V
OUT
Figure 1. Simplified Functional Diagram of Ideal Voltage
Doubler
S1
V
IN
S3
S2
V
IN
V
OUT
S4
C1
C2
Figure 2b. Equivalent Circuit
R
EQUIV
=
R
EQUIV
V
OUT
R
L
1
V+
f × C1
C2
MAX1682/MAX1683
Conversion losses occur during the charge transfer
between C1 and C2 when there is a voltage difference
between them. The power loss is:
where V
RIPPLE
is the peak-to-peak output voltage ripple
determined by the output capacitor and load current
(see Output Capacitor section). Choose capacitor val-
ues that decrease the output resistance (see Flying
Capacitor section).
Applications Information
Flying Capacitor (C1)
To maintain the lowest output resistance, use capaci-
tors with low ESR. Suitable capacitor manufacturers are
listed in Table 1. The charge-pump output resistance is
a function of C1 and C2’s ESR and the internal switch
resistance, as shown in the equation for R
OUT
in the
Efficiency Considerations section.
Minimizing the charge-pump capacitor’s ESR mini-
mizes the total resistance. Suggested values are listed
in Tables 2 and 3.
Using a larger flying capacitor reduces the output
impedance and improves efficiency (see the Efficiency
Considerations section). Above a certain point, increas-
ing C1’s capacitance has a negligible effect because
the output resistance becomes dominated by the inter-
nal switch resistance and capacitor ESR (see the
Output Resistance vs. Capacitance graph in the
Typical Operating Characteristics). Table 2 lists the
most desirable capacitor values—those that produce a
low output resistance. But when space is a constraint, it
may be necessary to sacrifice low output resistance for
the sake of small capacitor size. Table 3 demonstrates
how the capacitor affects output resistance.
Output Capacitor (C2)
Increasing the output capacitance reduces the output
ripple voltage. Decreasing its ESR reduces both output
resistance and ripple. Smaller capacitance values can
be used with light loads. Use the following equation to
calculate the peak-to-peak ripple:
V
RIPPLE
= I
OUT
/ (f
OSC
x C2) + 2 x I
OUT
x ESR
C2
Input Bypass Capacitor
Bypass the incoming supply to reduce its AC imped-
ance and the impact of the MAX1682/MAX1683’s
switching noise. When loaded, the circuit draws a con-
tinuous current of 2 x I
OUT
. A 0.1µF bypass capacitor is
sufficient.
P / C1 4V V
/ C2 2V V V x f
CONVERSION LOSS
1
2IN
2
OUT
2
1
2 OUT RIPPLE
2
RIPPLE
OSC
=−
⎛
⎝
⎜
⎞
⎠
⎟
+
⎡
⎣
⎢
⎢
−
⎛
⎝
⎜
⎞
⎠
⎟
⎤
⎦
⎥
Switched-Capacitor Voltage Doublers
6 _______________________________________________________________________________________
Table 1. Recommended Capacitor Manufacturers
Table 2. Suggested Capacitor Values for
Low Output Resistance
Table 3. Suggested Capacitor Values for
Minimum Size
MANUFACTURER
AVX
PRODUCTION METHOD SERIES
TPS
PHONE FAX
803-946-0690 803-448-2170
Matsuo 267 714-969-2491 714-960-6492Surface-Mount Tantalum
Sprague 593D, 595D 603-224-1961 603-224-1430
AVX X7R 803-946-0590 803-626-3123
Surface-Mount Ceramic
Matsuo X7R 714-969-2491 714-960-6492
PART
FREQUENCY
(kHz)
MAX1682 12
MAX1683 35
CAPACITOR
VALUE (µF)
10
3.3
TYPICAL
R
OUT
(Ω)
20
20
PART
FREQUENCY
(kHz)
CAPACITOR
VALUE (µF)
MAX1682 12 3.3
1
TYPICAL
R
OUT
(Ω)
35
35MAX1683 35
P1-P3P4-P6P7-P9

MAX1682EUK+T

Mfr. #:
Buy MAX1682EUK+T
Manufacturer:
Maxim Integrated
Description:
Switching Voltage Regulators Switched-Capacitor Voltage Doublers
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