SmartSwitch
TM
AAT3237
300mA MicroPowerTM LDO with PowerOK
3237.2006.01.1.4
1
General Description
The AAT3237 MicroPower low dropout (LDO) lin-
ear regulator is ideally suited for portable applica-
tions where low noise, extended battery life, and
small size are critical. The AAT3237 has been
specifically designed for low output noise perform-
ance, fast transient response, and high power sup-
ply rejection ratio (PSRR).
Other features include low quiescent current, typi-
cally 70A, and low dropout voltage, typically less
than 400mV at full output current. The device is
output short-circuit protected and has a thermal
shutdown circuit for additional protection under
extreme conditions.
The AAT3237 also features a low-power shutdown
mode for extended battery life. A Power-OK open-
drain output signals when V
OUT
is in regulation.
The AAT3237 is available in a Pb-free, space-sav-
ing 6-pin SOT23 or 8-pin SC70JW package in 13
factory-programmed voltages: 1.2V, 1.5V, 1.8V,
2.0V, 2.3V, 2.5V, 2.7V, 2.8V, 2.85V, 2.9V, 3.0V,
3.3V, or 3.5V.
Features
Low Dropout: 400mV at 300mA
Guaranteed 300mA Output
High Accuracy 1.5%
70A Quiescent Current
High Power Supply Ripple Rejection
Power-OK (POK) Output
Fast Line and Load Transient Response
Short-Circuit Protection
Over-Temperature Protection
Uses Low Equivalent Series Resistance
(ESR) Ceramic Capacitors
Shutdown Mode for Longer Battery Life
Low Temperature Coefficient
13 Factory-Programmed Output Voltages
SOT23 6-Pin or SC70JW 8-Pin Package
Applications
Cellular Phones
Desktop Computers
Digital Cameras
Notebook Computers
Personal Portable Electronics
Portable Communication Devices
Typical Application
AAT3237
EN
IN
OUT
POK
GND
ON/OFF
1
F
2.2
F
V
IN
GND
GND
V
OUT
POK
PowerLinear
TM
AAT3237
300mA MicroPowerTM LDO with PowerOK
2
3237.2006.01.1.4
Pin Descriptions
Pin Configuration
SOT23-6
SC70JW-8
(Top View)
(Top View)
OUT
OUT
OUT
GND
EN
IN
IN
POK
1
2
3
4
5
6
7
8
GND
OUT
GND
POK
EN
IN
1
2
3
4
5
6
Pin #
Symbol
Function
SOT23-6
SC70JW-8
1
5, 6
IN
Input voltage pin; should be decoupled with 1F or greater
capacitor.
2, 5
8
GND
Ground connection pin.
3
7
EN
Enable pin; this pin should not be left floating. When pulled
low, the PMOS pass transistor turns off and all internal circuitry
enters low-power mode, consuming less than 1A.
4
1
POK
Power-OK output. This open-drain output is low when OUT is
out of regulation. Connect a pull-up resistor from POK to OUT.
6
2, 3, 4
OUT
Output pin; should be decoupled with 2.2F ceramic capacitor.
Absolute Maximum Ratings
1
T
A
= 25C, unless otherwise noted.
Thermal Information
2
Recommended Operating Conditions
Symbol
Description
Rating
Units
V
IN
Input Voltage
3
(V
OUT
+ V
DO
) to 5.5
V
T
Ambient Temperature Range
-40 to +85
C
Symbol
Description
Rating
Units
JA
Maximum Thermal Resistance (SOT23-6, SC70JW-8)
150
C/W
P
D
Maximum Power Dissipation (SOT23-6, SC70JW-8)
667
mW
Symbol
Description
Value
Units
V
IN,
POK
Input Voltage, POK
6
V
V
ENIN(MAX)
Maximum EN to Input Voltage
0.3
V
I
OUT
DC Output Current
P
D
/(V
IN
- V
O
)
mA
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT3237
300mA MicroPowerTM LDO with PowerOK
3237.2006.01.1.4
3
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on a demo board.
3. To calculate minimum input voltage, use the following equation: V
IN(MIN)
= V
OUT(MAX)
+ V
DO(MAX)
as long as V
IN
2.5V.
Electrical Characteristics
V
IN
= V
OUT(NOM)
+ 1V for V
OUT
options greater than 1.5V. V
IN
= 2.5V for V
OUT
1.5V. I
OUT
= 1mA, C
OUT
= 2.2F,
C
IN
= 1F, T
A
= -40C to +85C, unless otherwise noted. Typical values are T
A
= 25C.
Symbol
Description
Conditions
Min Typ Max
Units
V
OUT
Output Voltage Tolerance
I
OUT
= 1mA to 300mA
T
A
= 25C
-1.5
1.5
%
T
A
= -40 to 85C -2.5
2.5
I
OUT
Output Current
V
OUT
> 1.2V
300
mA
V
DO
Dropout Voltage
1, 2
I
OUT
= 300mA
400
600
mV
I
SC
Short-Circuit Current
V
OUT
< 0.4V
600
mA
I
Q
Ground Current
V
IN
= 5V, No Load, EN = V
IN
70
125
A
I
SD
Shutdown Current
V
IN
= 5V, EN = 0V
1
A
V
OUT
/
Line Regulation
3
V
IN
= V
OUT
+ 1 to 5.0V
0.09
%/V
V
OUT
*
V
IN
V
OUT
(line)
Dynamic Line Regulation
V
IN
= V
OUT
+ 1V to V
OUT
+ 2V,
5
mV
I
OUT
= 300mA, T
R
/T
F
= 2s
V
OUT
(load)
Dynamic Load Regulation
I
OUT
= 1mA to 300mA, T
R
<5s
60
mV
V
EN(L)
Enable Threshold Low
0.6
V
V
EN(H)
Enable Threshold High
1.5
V
I
EN
Leakage Current on Enable Pin
V
EN
= 5V
1
A
V
POK
POK Trip Threshold
V
OUT
Rising, T
A
= 25C
90
94
98
% of V
OUT
V
POKHYS
POK Hysteresis
1
% of V
OUT
V
POK(OL)
POK Output Voltage Low
I
SINK
= 1mA
0.4
V
I
POK
POK Output Leakage Current
V
POK
< 5.5V, V
OUT
in Regulation
1
A
1kHz
65
PSRR
Power Supply Rejection Ratio
I
OUT
= 10mA
10kHz
45
dB
1MHz
42
T
SD
Over-Temperature Shutdown
145
C
Threshold
T
HYS
Over-Temperature Shutdown
12
C
Hysteresis
e
N
Output Noise
250
Vrms
TC
Output Voltage Temperature
22
ppm/C
Coefficient
AAT3237
300mA MicroPowerTM LDO with PowerOK
4
3237.2006.01.1.4
1. V
DO
is defined as V
IN
- V
OUT
when V
OUT
is 98% of nominal.
2. For V
OUT
< 2.1V, V
DO
= 2.5V - V
OUT
.
3. C
IN
= 10F.
AAT3237
300mA MicroPowerTM LDO with PowerOK
3237.2006.01.1.4
5
Typical Characteristics
Unless otherwise noted, V
IN
= 5V, T
A
= 25C.
Output Voltage vs. Temperature
1.196
1.197
1.198
1.199
1.200
1.201
1.202
1.203
-40 -30 -20 -10 0
10 20 30
40
50 60
70 80 90 100
Temperature (
C)
Output Voltage (V)
Quiescent Current vs. Temperature
0
10
20
30
40
50
60
70
80
90
100
-40 -30 -20 -10 0
10 20 30 40 50 60 70 80 90 100 110 120
Temperature (
C)
Quiescent Current (
A)
Ground Current vs. Input Voltage
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
2
2.5
3
3.5
4.5
4
5
Input Voltage (V)
Ground Current (
A)
I
OUT
= 0mA
I
OUT
= 10mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 300mA
Dropout Voltage vs. Output Current
0
50
100
150
200
250
300
350
400
450
500
0
50
100
150
200
250
300
Output Current (mA)
Dropout Voltage (mV)
85
C
25
C
-40
C
Dropout Characteristics
2.00
2.20
2.40
2.60
2.80
3.00
3.20
2.70
2.80
2.90
3.00
3.10
3.20
3.30
Input Voltage (V)
Output Voltage (V)
I
OUT
= 300mA
I
OUT
= 150mA
I
OUT
= 100mA
I
OUT
= 50mA
I
OUT
= 10mA
I
OUT
= 0mA
Dropout Voltage vs. Temperature
0
60
120
180
240
300
360
420
480
540
-40 -30 -20 -10 0
10 20 30 40 50 60 70 80 90 100 110 120
Temperature (
C)
Dropout Voltage (mV)
I
L
= 300mA
I
L
= 150mA
I
L
= 100mA
I
L
= 50mA
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