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MAX684EUA+

P1-P3P4-P6P7-P9P10-P12
MAX682/MAX683/MAX684
3.3V-Input to Regulated 5V-Output
Charge Pumps
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 5, V
IN
= 3.3V, component values from Tables 2 and 3, T
A
= +25°C, unless otherwise noted.)
100
0
1 10 100 1000
MAX682 EFFICIENCY
vs. LOAD CURRENT (SKIP = HIGH)
20
10
MAX682 TOC13
LOAD CURRENT (mA)
EFFICIENCY (%)
50
70
60
40
30
80
90
V
IN
= 5.0V
V
IN
= 3.3V
V
IN
= 3.0V
I
SHDN
= 22µA
100
0
1 10 100 1000
MAX683 EFFICIENCY
vs. LOAD CURRENT (SKIP = HIGH)
20
10
MAX682 TOC14
LOAD CURRENT (mA)
EFFICIENCY (%)
50
70
60
40
30
80
90
V
IN
= 5.0V
V
IN
= 3.3V
V
IN
= 3.0V
I
SHDN
= 22µA
90
0
1 10 100
MAX684 EFFICIENCY
vs. LOAD CURRENT (SKIP = HIGH)
20
10
MAX682 TOC15
LOAD CURRENT (mA)
EFFICIENCY (%)
40
30
50
60
70
80
V
IN
= 3.0V
V
IN
= 3.3V
V
IN
= 5.0V
I
SHDN
= 22µA
200ns/div
OUTPUT WAVEFORM
(SKIP = HIGH)
MAX682 TOC16
50mV/div
SKIP = HIGH, I
SHDN
= 22µA, I
LOAD
= 250mA, MAX682
100
0
0.1 1 10 100 1000
MAX682 EFFICIENCY
vs. LOAD CURRENT (SKIP = LOW)
20
10
MAX682 TOC10
LOAD CURRENT (mA)
EFFICIENCY (%)
50
70
60
40
30
80
90
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 3.0V
100
0
0.1 1 10 100 1000
MAX683 EFFICIENCY
vs. LOAD CURRENT (SKIP = LOW)
20
10
MAX682 TOC11
LOAD CURRENT (mA)
EFFICIENCY (%)
50
70
60
40
30
80
90
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 3.0V
100
0
0.1 1 10 100
MAX684 EFFICIENCY
vs. LOAD CURRENT (SKIP = LOW)
20
10
MAX682 TOC12
LOAD CURRENT (mA)
EFFICIENCY (%)
50
70
60
40
30
80
90
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 3.0V
MAX682/MAX683/MAX684
3.3V-Input to Regulated 5V-Output
Charge Pumps
_______________________________________________________________________________________ 5
2ms/div
LOAD-TRANSIENT RESPONSE
MAX682 TOC19
A
B
A: LOAD CURRENT: I
LOAD
= 5mA TO 250mA, 500mA/div
B: OUTPUT VOLTAGE: SKIP = HIGH, I
SHDN
= 22µA,
100mV/div, MAX682
100µs/div
SHUTDOWN TIMING
MAX682 TOC18
A
B
A: OUTPUT VOLTAGE: SKIP = HIGH, R
L
= 5V / I
MAX
, 2V/div
B: SHDN VOLTAGE: 1V/div
2ms/div
LINE-TRANSIENT RESPONSE
MAX682 TOC20
A
B
A: INPUT VOLTAGE: V
IN
= 3.1V TO 3.6V, 500mV/div
B: OUTPUT VOLTAGE: SKIP = HIGH, I
SHDN
= 22µA,
I
LOAD
= 250mA, 50mV/div, MAX682
Typical Operating Characteristics (continued)
(Circuit of Figure 5, V
IN
= 3.3V, component values from Tables 2 and 3, T
A
= +25°C, unless otherwise noted.)
Pin Description
NAME FUNCTION
1
SKIP
When SKIP = low, the regulator operates in low-quiescent-current skip mode. When SKIP = high, the
regulator operates in constant-frequency mode, minimizing output ripple and noise. SKIP must be tied
high for input voltages above 3.6V.
2
SHDN
Shutdown Input. Drive SHDN through an external resistor. When SHDN = low, the device turns off. When
current is sourced into SHDN through R
EXT
, the device activates, and the SHDN pin input current sets the
oscillator’s switching frequency. R
EXT
(kΩ) = 45000 (V
IN
- 0.69V) / f
OSC
(kHz).
PIN
3 IN
Input Supply Pin. Can range from 2.7V to 5.5V for SKIP = high, and 2.7V to 3.6V for SKIP = low. Bypass to
PGND with a suitable value capacitor (see
Capacitor Selection
section).
4 GND Ground Pin. Connect to PGND through a short trace.
8 OUT Fixed 5V Power Output. Bypass to PGND with output filter capacitor.
7 CXP Positive Terminal of the Charge-Pump Transfer Capacitor
6 CXN Negative Terminal of the Charge-Pump Transfer Capacitor
5 PGND Power Ground Pin
MAX682/MAX683/MAX684
3.3V-Input to Regulated 5V-Output
Charge Pumps
6 _______________________________________________________________________________________
Detailed Description
The MAX682/MAX683/MAX684 charge pumps provide
a regulated 5V output from a 2.7V to 5.5V input. They
deliver a maximum of 250mA, 100mA, or 50mA load
current, respectively. Designed specifically for com-
pact applications, a complete regulator circuit requires
only three small external capacitors and one resistor.
An externally adjustable switching frequency and inno-
vative control scheme allow the circuit to be optimized
for efficiency, size, or output noise. The devices also
contain a shutdown feature.
The MAX682/MAX683/MAX684 consist of an error
amplifier, a 1.23V bandgap reference, an internal resis-
tive feedback network, an oscillator, high-current MOS-
FET switches, and shutdown and control logic (Figure
1). Figure 2 shows an idealized unregulated charge-
pump voltage doubler. The oscillator runs at a 50%
duty cycle. During one half of the period, the transfer
capacitor (C
X
) charges to the input voltage. During the
other half, the doubler stacks the voltage across C
X
and the input voltage, and transfers the sum of the two
voltages to the output filter capacitor (C
OUT
). Rather
than simply doubling the input voltage, the
MAX682/MAX683/MAX684 provide a regulated fixed
output voltage (5V) using either skip mode or constant-
frequency mode. Skip mode and constant-frequency
mode are externally selected via the SKIP input pin.
Skip Mode
In skip mode (SKIP = low), the error amplifier disables
switching when it detects an output higher than 5V. The
device then skips switching cycles until the output volt-
age drops. Then the error amplifier reactivates the
oscillator. Figure 3 illustrates the regulation scheme.
This regulation method minimizes operating current
because the device does not switch continuously. SKIP
is a logic input and should not remain floating.
Constant-Frequency Mode
When SKIP is high, the charge pump runs continuously
at the selected frequency. Figure 4 shows a block dia-
gram of the device in constant-frequency mode. The
error amplifier controls the charge on C
X
by driving the
gate of the N-channel FET. When the output voltage
falls, the gate drive increases, resulting in a larger volt-
age across C
X
. This regulation scheme minimizes out-
put ripple. Since the device switches continuously, the
CXP
OUT
1.23V
EN
SHDN
PGND
SWITCHES
CONTROL
LOGIC
CXN
SHDN
SKIP
IN
OSC
IN
S1
S2
C
IN
C
OUT
OUT
C
X
OSC
Figure 2. Unregulated Voltage Doubler
IN
S1
S2
C
IN
C
X
OUT
OSCILLATOR
EN
Figure 3. Skip-Mode Regulation
Figure 1. Functional Block Diagram
P1-P3P4-P6P7-P9P10-P12

MAX684EUA+

Mfr. #:
Buy MAX684EUA+
Manufacturer:
Maxim Integrated
Description:
IC REG CHARGE PUMP 5V 50MA 8UMAX
Lifecycle:
New from this manufacturer.
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