3.3V-Input to Regulated 5V-Output
Charge Pumps
MAX682/MAX683/MAX684
Table 2. Recommended Capacitor Values
for Quiescent Current (Skip Mode)
V
OUT
C
OUT
(µF)
OUTPUT C
IN
C
X
PART
RIPPLE
(mA)
(µF) (µF)
TANTALUM CERAMIC
(mV)
MAX682
MAX683
250
100
2.2
1
1
0.47
47
22
10
4.7
100
100
OFF
ON V
ON
IN
R
EXT
CXP
2
3
1
C
IN
SHDN
IN
SKIP
GND
4
PGND
5
7
6
8
C
X
MAX682
MAX683
MAX684
CXN
OUT
OUT
C
OUT
MAX684
50
0.47 0.22
10
2.2
100
Figure 5. Standard Operating Circuit
5V/500mA
Table 3. Recommended Capacitor Values
for Smallest Size (Constant-Frequency
Mode, I
SHDN
= 22µA, 1MHz)
PART
OUTPUT
(mA)
250
100
C
IN
(µF)
1
0.47
C
X
(µF)
0.47
0.22
CERAMIC
C
OUT
(µF)
2.2
1
V
OUT
RIPPLE
(mV)
3.3V
IN
IN
SKIP
100k
1µF
OUT
IN
SKIP
100k
1µF
OUT
MAX682
SHDN
CXP
MAX682
SHDN
CXP
4.7µF
MAX682
MAX683
80
80
0.47µF
CXN
GND
PGND
0.47µF
CXN
GND
PGND
MAX684
50
0.22
0.1
0.47
80
Figure 6. Paralleling Two MAX682s
Table 4. Recommended Capacitor
Manufacturers
VALUE
DESCRIPTION MANUFACTURER
PHONE
NUMBER
47µF to
10µF
47µF to
10µF
0.1µF to
2.2µF
595D-series
tantalum
surface mount
TPS-series
surface mount
Ceramic
surface mount
Sprague
(603) 224-1961
AVX
TDK
(803) 946-0690
(847) 390-4373
where ESR
COUT
is the ESR of the output filter capaci-
tance, and R
TX
is the open-loop output transfer resist-
ance of the IC. R
TX
is typically 0.8Ω for the MAX682,
1.6Ω for the MAX683, and 3Ω for the MAX684. In con-
stant-frequency mode, output ripple is dominated by
C
OUT
and is approximately:
V
RIPPLE(const-freq)
≅
I
OUT
/ (2 x f
OSC
x C
OUT
)
All capacitors must maintain a low (<100mΩ) equiva-
lent series resistance (ESR). Table 4 lists the manufac-
turers of recommended capacitors. Surface-mount
tantalum capacitors will work well for most applications.
Ceramic capacitors will provide the lowest ripple due to
their typically lower ESR.
If the source impedance or inductance of the input sup-
ply is large, additional input bypassing (2.2µF to 22µF)
may be needed. This additional capacitance need not
be a low-ESR type.
In addition, the following two equations approximate
output ripple for each mode. In skip mode, output rip-
ple is dominated by ESR, and is approximately:
V
RIPPLE(SKIP)
≅
(2V
IN
- V
OUT
)ESR
COUT
/ R
TX
8
_______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
