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MAX1818EUT25#TG16

P1-P3P4-P6P7-P9
MAX1818
500mA Low-Dropout
Linear Regulator in SOT23
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(V
IN
= (V
OUT
+ 500mV) or +2.5V, whichever is greater; SHDN = IN, C
IN
= 1µF, C
OUT
= 3.3µF, T
A
= +25°C, unless otherwise noted.)
0
60
30
120
90
150
180
0 0.20.1 0.3 0.4 0.5
MAX1818 toc04
LOAD CURRENT (A)
DROPOUT VOLTAGE (mV)
V
OUT
= 3.3V
DROPOUT VOLTAGE
vs. LOAD CURRENT
T
A
= +85
°
C
T
A
= +25
°
C
T
A
= -40
°
C
-3.0
-2.0
-2.5
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
MAX1818 toc05
LOAD CURRENT (A)
OUTPUT VOLTAGE ACCURACY (%)
0 0.2 0.3 0.40.1 0.5 0.6 0.7 0.90.8 1.0
OUTPUT VOLTAGE ACCURACY
vs. LOAD CURRENT
3.3V OUTPUT
2.5V OUTPUT
1.8V OUTPUT
-3.0
-2.0
-2.5
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
-40 -15 10 35 60 85
MAX1818 toc06
TEMPERATURE (°C)
OUTPUT VOLTAGE ACCURACY (%)
OUTPUT VOLTAGE ACCURACY
vs. TEMPERATURE
V
OUT
= 1.5V TO 5.0V
I
LOAD
= 150mA
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX1818 toc07
80
0
20
10
PSRR (dB)
40
30
50
60
70
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
C
OUT
= 3.3
μ
F
V
OUT
= 3.3V
R
LOAD
= 100
Ω
LOAD-TRANSIENT RESPONSE
MAX1818 toc09
I
OUT
V
OUT
500mA
100mA
20mV/div
40
μ
s/div
V
IN
= 3.3V
V
OUT
= 2.5V
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX1818 toc10
V
OUT
100mV/div
200mA
0
I
OUT
10μs/div
V
IN
= V
OUT
+ 100mV
V
OUT
= 3.3V
POWER-ON RESET
MAX1818 toc11
V
IN
V
POK
V
OUT
0
0
0
2V/div
10ms/div
MAX1818
500mA Low-Dropout
Linear Regulator in SOT23
_______________________________________________________________________________________ 5
SHUTDOWN WAVEFORM
MAX1818 toc12
POK
SHUTDOWN
VOLTAGE
V
OUT
0
0
2V/div
0
200μs/div
1.00
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
1.09
1.10
1.11
2.5 3.0 3.5 4.0 4.5 5.0 5.5
SHORT-CIRCUIT CURRENT LIMIT
vs. SUPPLY VOLTAGE
MAX1818 toc13
SUPPLY VOLTAGE (V)
SHORT-CIRCUIT CURRENT LIMIT (A)
V
OUT(NOM)
= +2V
Detailed Description
The MAX1818 is a low-dropout, low-quiescent-current
linear regulator designed primarily for battery-powered
applications. The device supplies loads up to 500mA
and is available with preset output voltages. As illustrat-
ed in Figure 1, the MAX1818 consists of a 1.25V refer-
ence, error amplifier, P-channel pass transistor, and
internal feedback voltage-divider.
The 1.25V reference is connected to the error amplifier,
which compares this reference with the feedback volt-
age and amplifies the difference. If the feedback volt-
age is lower than the reference voltage, the
pass-transistor gate is pulled lower, which allows more
current to pass to the output and increases the output
voltage. If the feedback voltage is too high, the pass-
transistor gate is pulled up, allowing less current to
pass to the output.
The output voltage is fed back through either an inter-
nal resistive divider connected to OUT or an external
resistor network connected to SET. The Dual Mode
comparator examines V
SET
and selects the feedback
path. If V
SET
is below 50mV, the internal feedback path
is used and the output is regulated to the factory-preset
voltage.
Pin Description
PIN NAME FUNCTION
1IN
Regulator Input. Supply voltage can range from 2.5V to 5.5V. Bypass with a 1μF capacitor to GND (see
Capacitor Selection and Regulator Stability).
2 POK
Open-Drain POK Output. POK remains low while the output voltage (V
OUT
) is below the POK threshold.
Connect a 100kΩ pull-up resistor from POK to OUT to obtain an output voltage.
3 SHDN
Active-Low Shutdown Input. A logic low reduces supply current below 15μA. In shutdown, the POK output is
low, and OUT is high impedance. Connect to IN for normal operation.
4 GND Ground
5 SET
Voltage-Setting Input. Connect to GND for preset output. Connect to a resistive voltage-divider between
OUT and GND to set the output voltage between 1.25V and 5.0V.
6 OUT
Regulator Output. Sources up to 500mA. Bypass with a 3.3μF low-ESR capacitor to GND. Use a 4.7μF
capacitor for output voltages below 2V.
Typical Operating Characteristics (continued)
(V
IN
= (V
OUT
+ 500mV) or +2.5V, whichever is greater; SHDN = IN, C
IN
= 1µF, C
OUT
= 3.3µF, T
A
= +25°C, unless otherwise noted.)
MAX1818
500mA Low-Dropout
Linear Regulator in SOT23
6 _______________________________________________________________________________________
Additional blocks include an output current limiter, ther-
mal sensor, and shutdown logic.
Internal P-Channel Pass Transistor
The MAX1818 features a 0.25Ω P-channel MOSFET
pass transistor. Unlike similar designs using PNP pass
transistors, P-channel MOSFETs require no base drive,
which reduces quiescent current. PNP-based regula-
tors also waste considerable current in dropout when
the pass transistor saturates, and use high base-drive
currents under large loads. The MAX1818 does not suf-
fer from these problems and consumes only 125µA of
quiescent current under heavy loads as well as in
dropout.
Output Voltage Selection
The MAX1818’s Dual Mode operation allows operation
in either a preset voltage mode or an adjustable mode.
Connect SET to GND to select the preset output volt-
age. The two-digit part number suffix identifies the out-
put voltage (see
Selector Guide)
. For example, the
MAX1818EUT33 has a preset 3.3V output voltage.
The output voltage may also be adjusted by connecting
a voltage-divider from OUT to SET to GND (Figure 2).
Select R2 in the 25kΩ to 100kΩ range. Calculate R1
with the following equation:
R1 = R2 [(V
OUT
/ V
SET
) – 1]
where V
SET
= 1.25V, and V
OUT
may range from 1.25V
to 5.0V.
Shutdown
Pull SHDN low to enter shutdown. During shutdown, the
output is disconnected from the input and supply cur-
rent drops to 0.1µA. When in shutdown, POK pulls low
and OUT is high impedance. The capacitance and load
at OUT determine the rate at which V
OUT
decays.
SHDN can be pulled as high as 6V, regardless of the
input and output voltage.
100mV
SHDN
IN
POK
ON
OFF
C
IN
1μF
V
IN
= 2.5V TO 5.5V
OUT
V
OUT
= 1.25V TO 5.0V
C
OUT
3.3μF
THERMAL
SENSOR
SET
MOSFET
DRIVER WITH
I
LIM
SHUTDOWN
LOGIC
V
REF
1.25V
ERROR
AMPLIFIER
GND
R1
R2
R
POK
100k
LOGIC SUPPLY
VOLTAGE (V
OUT
)
93% V
REF
TO
μC
5k
MAX1818
Figure 1. Functional Diagram
P1-P3P4-P6P7-P9

MAX1818EUT25#TG16

Mfr. #:
Buy MAX1818EUT25#TG16
Manufacturer:
Maxim Integrated
Description:
LDO Voltage Regulators 500mA
Lifecycle:
New from this manufacturer.
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