19-1860; Rev 1; 3/01
500mA Low-Dropout
Linear Regulator in SOT23
General Description
The MAX1818 low-dropout linear regulator operates
from a +2.5V to +5.5V supply and delivers a guaran-
teed 500mA load current with low 120mV dropout. The
high-accuracy (±1%) output voltage is preset at an
internally trimmed voltage (see
Selector Guide)
or can
be adjusted from 1.25V to 5.0V with an external resis-
tive divider.
An internal PMOS pass transistor allows the low 125µA
supply current to remain independent of load, making
this device ideal for portable battery-operated equip-
ment such as personal digital assistants (PDAs), cellu-
lar phones, cordless phones, base stations, and
notebook computers.
Other features include an active-low open-drain reset
output that indicates when the output is out of regula-
tion, a 0.1µA shutdown, short-circuit protection, and
thermal shutdown protection. The device is available in
a miniature 800mW 6-pin SOT23 package.
o
Guaranteed 500mA Output Current
o
Low 120mV Dropout at 500mA
o
±1% Output Voltage Accuracy
Preset at 1.5V, 1.8V, 2.0V, 2.5V, 3.3V, 5V
Adjustable from 1.25V to 5.0V
o
Power OK Output
o
Low 125µA Ground Current
o
0.1µA Shutdown Current
o
Thermal Overload Protection
o
Output Current Limit
o
Tiny 800mW 6-Pin SOT23 Package
Features
MAX1818
Ordering Information
PART*
MAX1818EUAT_ _
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
6 SOT23-6
Applications
Notebook Computers
Cellular and Cordless Telephones
Personal Digital Assistants (PDAs)
Palmtop Computers
Base Stations
USB Hubs
Docking Stations
*Insert the desired two-digit suffix (see Selector Guide) into the
blanks to complete the part number.
Note:
The MAX1818 requires a special solder temperature
profile described in the Absolute Maximum Ratings section.
Selector Guide
PART AND
SUFFIX
MAX1818EUT15
MAX1818EUT18
MAX1818EUT20
MAX1818EUT25
MAX1818EUT33
MAX1818EUT50
V
OUT
1.5V or Adj
1.8V or Adj
2.0V or Adj
2.5V or Adj
3.3V or Adj
5.0V or Adj
SOT23
TOP MARK
AASO
AANU
AANV
AANF
AANG
AANH
Pin Configuration
TOP VIEW
IN
1
6
OUT
V
IN
= 2.5V TO 5.5V
Typical Operating Circuit
IN
NC
C
IN
1µF
OUT
V
OUT
C
OUT
3.3µF
POK
2
MAX1818
MAX1818
5
SET
ON
SHDN
OFF
POK
R
POK
100k
TO
µC
SHDN
3
4
GND
SOT23
SET
GND
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
500mA Low-Dropout
Linear Regulator in SOT23
MAX1818
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
POK, SET to GND ...................................-0.3V to +6V
OUT to GND ................................................-0.3V to (V
IN
+ 0.3V)
Output Short-Circuit Duration ...............................................1min
Continuous Power Dissipation (T
A
= +70°C) (Note 1)
6-Pin SOT23 (derate 10mW/°C above +70°C)..............800mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) (Note 2) ...................+300°C
Note 1:
Thermal properties are specified with product mounted on PC board with one square-inch of copper area and still air. With
minimal copper, the SOT23 package dissipates 712mW at +70°C. With a quarter square inch of copper, it will dissipate
790mW at +70°C. Copper should be equally shared between the IN, OUT, and GND pins.
Note 2:
This device is constructed using a unique set of packaging techniques that imposes a limit on the thermal profile to which
the device can be exposed during board-level solder attach and rework. The limit permits only the use of the solder profiles
recommended in the industry standard specification, IPC JEDEC-J-STD-020A, paragraph 7.6, Table 3 for the IR/VPR and
convection reflow. Preheating is required. Hand or wave soldering is not allowed.
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.
ELECTRICAL CHARACTERISTICS
(V
IN
= V
OUT
+ 500mV or V
IN
= +2.5V, whichever is greater;
SHDN
= IN, T
A
= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 3)
PARAMETER
Input Voltage
Input Undervoltage Lock-Out
SYMBOL
V
IN
V
UVLO
Rising, 75mV hysteresis
I
OUT
= 100mA, T
A
= +25°C, V
OUT
≥
2.0V
Output Voltage Accuracy
(Preset Mode)
I
OUT
= 100mA, V
OUT
< 2.0V
V
OUT
I
OUT
= 100mA, T
A
= -40°C to +85°C
I
OUT
= 1mA to 500mA, V
IN
> V
OUT
+ 0.5V,
T
A
= -40°C to +85°C
Adjustable Output Voltage
Range
SET Voltage Threshold
(Adjustable Mode)
Guaranteed Output Current
(RMS)
Short-Circuit Current Limit
In-Regulation Current Limit
SET Dual Mode™ Threshold
SET Input Bias Current
Ground-Pin Current
I
SET
I
Q
V
SET
= 1.25V
I
OUT
= 100µA
I
OUT
= 500mA
V
OUT
= 5V
Dropout Voltage (Note 4)
V
IN
- V
OUT
I
OUT
= 500mA
V
OUT
= 3.3V
V
OUT
= 2.5V
Line Regulation
∆V
LNR
V
IN
from (V
OUT
+ 100mV) to 5.5V,
I
LOAD
= 5mA
-0.15
V
SET
V
IN
= 2.7V,
I
OUT
= 100mA,
V
OUT
set to 2.0V
V
IN
≥
2.7V
V
OUT
= 0, V
IN
≥
2.7V
V
OUT
> 96% of nominal value, V
IN
≥
2.7V
50
-100
125
140
100
120
210
0
220
215
360
+0.15
%/V
mV
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
CONDITIONS
MIN
2.5
2.0
-1
-1.5
-2.5
-3
1.25
1.225
1.213
500
0.55
0.8
1.6
100
150
+100
250
1.8
1.250
2.15
TYP
MAX
5.5
2.3
+1
+1.5
+2.5
+3
5
1.275
V
1.288
mA
A
A
mV
nA
µA
V
%
UNITS
V
V
I
OUT
I
LIM
Dual Mode is a trademark of Maxim Integrated Products
2
_______________________________________________________________________________________
500mA Low-Dropout
Linear Regulator in SOT23
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
OUT
+ 500mV or V
IN
= +2.5V, whichever is greater;
SHDN
= IN, T
A
= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 3)
PARAMETER
Load Regulation
Output Voltage Noise
SHUTDOWN
Shutdown Supply Current
SHDN
Input Threshold
SHDN
Input Bias Current
POK OUTPUT
POK Output Low Voltage
Operating Voltage Range for
Valid POK
POK Output High Leakage
Current
POK Threshold
THERMAL PROTECTION
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
T
SHDN
∆T
SHDN
170
20
°C
°C
V
OL
POK sinking 1mA
POK sinking 100µA
POK = 5.5V, T
A
= +25°C
T
A
= +85°C
Rising edge, referred to V
OUT(NOMINAL)
90
1.0
1
5
93
96
0.01
0.1
5.5
25
V
V
nA
%
I
OFF
V
IH
V
IL
I
SHDN
SHDN
= GND, V
IN
= 5.5V
2.5V < V
IN
< 5.5V
2.5V < V
IN
< 5.5V
SHDN
= IN or GND, T
A
= +25°C
T
A
= +85°C
1
5
1.6
0.6
25
0.1
15
µA
V
nA
SYMBOL
∆V
LDR
CONDITIONS
I
OUT
= 1mA to 500mA
10Hz to 1MHz, C
OUT
= 3.3µF (ESR < 0.1Ω)
MIN
TYP
0.4
115
MAX
1.0
UNITS
%
µV
RMS
MAX1818
Note 3:
All devices are 100% production tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by
design.
Note 4:
The Dropout Voltage is defined as V
IN
- V
OUT
, when V
OUT
is 100mV below the value of V
OUT
measured for V
IN
= V
OUT(NOM)
+ 500mV. Since the minimum input voltage is 2.5V, this specification is only meaningful when V
OUT(NOM)
> 2.5V. For
V
OUT(NOM)
between 2.5V and 3.5V, use the following equations: Typical Dropout = -93mV/V
✕
V
OUT(NOM)
+ 445mV;
Guaranteed Maximum Dropout = -137mV/V
✕
V
OUT(NOM)
+7004mV. For V
OUT(NOM)
> 3.5V, Typical Dropout = 120mV;
Maximum Dropout = 220mV.
Typical Operating Characteristics
(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.)
GROUND PIN CURRENT
vs. INPUT VOLTAGE
MAX1818 toc01
GROUND PIN CURRENT
vs. LOAD CURRENT
MAX1818 toc02
GROUND PIN CURRENT
vs. TEMPERATURE
I
LOAD
= 150mA
GROUND PIN CURRENT (µA)
160
150
140
1.5V OUTPUT
130
120
110
5.0V OUTPUT
MAX1818 toc03
250
225
GROUND PIN CURRENT (µA)
200
175
150
125
100
75
50
25
0
1.8V OUTPUT
3.3V OUTPUT
I
LOAD
= 150mA
160
145
GROUND PIN CURRENT (µA)
130
115
100
85
70
55
40
1.8V OUTPUT
2.5V OUTPUT
3.3V OUTPUT
170
2.5V OUTPUT
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
3
500mA Low-Dropout
Linear Regulator in SOT23
MAX1818
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.)
DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX1818 toc04
OUTPUT VOLTAGE ACCURACY
vs. LOAD CURRENT
3.0
2.5
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
0
3.0
2.5
2.0
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-40
MAX1818 toc05
OUTPUT VOLTAGE ACCURACY
vs. TEMPERATURE
V
OUT
= 1.5V TO 5.0V
I
LOAD
= 150mA
MAX1818 toc06
180
V
OUT
= 3.3V
150
DROPOUT VOLTAGE (mV)
120
90
60
T
A
= -40°C
30
0
0
0.1
0.2
0.3
0.4
T
A
= +85°C
OUTPUT VOLTAGE ACCURACY (%)
3.3V OUTPUT
2.5V OUTPUT
T
A
= +25°C
1.8V OUTPUT
0.5
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)
OUTPUT VOLTAGE ACCURACY (%)
-15
10
35
60
85
LOAD CURRENT (A)
TEMPERATURE (°C)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX1818 toc07
LINE TRANSIENT
MAX1818 toc08
LOAD-TRANSIENT RESPONSE
MAX1818 toc09
80
70
60
PSRR (dB)
50
40
C
OUT
= 3.3µF
V
OUT
= 3.3V
R
LOAD
= 100Ω
V
OUT
2.5V
10mV/div
V
IN
= 3.3V
V
OUT
= 2.5V
I
OUT
500mA
100mA
3.5V
500mV/div
30
20
10
0
0.01
0.1
1
10
100
1000
100µs/div
V
IN
V
OUT
40µs/div
FREQUENCY (kHz)
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX1818 toc10
POWER-ON RESET
MAX1818 toc11
V
OUT
100mV/div
V
IN
= V
OUT
+ 100mV
V
OUT
= 3.3V
V
POK
0
V
OUT
2V/div
200mA
I
OUT
V
IN
0
0
0
10µs/div
10ms/div
4
_______________________________________________________________________________________
20mV/div
500mA Low-Dropout
Linear Regulator in SOT23
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.)
SHUTDOWN WAVEFORM
MAX1818 toc12
MAX1818
SHORT-CIRCUIT CURRENT LIMIT
vs. SUPPLY VOLTAGE
SHORT-CIRCUIT CURRENT LIMIT (A)
1.10
1.09
1.08
1.07
1.06
1.05
1.04
1.03
1.02
1.01
1.00
2.5
3.0
3.5
4.0
4.5
5.0
5.5
V
OUT(NOM)
= +2V
MAX1818 toc13
1.11
SHUTDOWN
VOLTAGE
0
V
OUT
0
2V/div
POK
0
200µs/div
SUPPLY VOLTAGE (V)
Pin Description
PIN
1
2
3
4
5
6
NAME
IN
POK
SHDN
GND
SET
OUT
FUNCTION
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).
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.
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.
Ground
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.
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.
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.
_______________________________________________________________________________________
5
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