AOZ1280
EZBuck™ 1.2 A Simple Buck Regulator
General Description
The AOZ1280 is a high efficiency, simple to use, 1.2 A
buck regulator which is flexible enough to be optimized
for a variety of applications. The AOZ1280 operates from
a 3 V to 26 V input voltage range, and provides up to
1.2 A of continuous output current. The output voltage is
adjustable down to 0.8 V. The fixed 1.5 MHz PWM
switching frequency reduces inductor size.
The AOZ1280 comes in a SOT23-6L package and is
rated over a -40 °C to +85 °C operating ambient
temperature range.
Features
3 V to 26 V operating input voltage range
240 mΩ internal NMOS
High efficiency: up to 95 %
Internal compensation
1.2 A continuous output current
Fixed 1.5 MHz PWM operation
Internal soft start
Output voltage adjustable down to 0.8 V
Cycle-by-cycle current limit
Short-circuit protection
Thermal shutdown
Small size SOT23-6L
Applications
Point of load DC/DC conversion
Set top boxes
DVD drives and HDD
LCD Monitors & TVs
Cable modems
Telecom/Networking/Datacom equipment
Typical Application
VIN
C1
4.7µF
C3
VIN
EN
L1 2.2µH
AOZ1280
GND
LX
R1
VOUT
FB
R2
C2
10µF
Figure 1. 1.2 A Buck Regulator
Rev. 1.1 August 2011
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Page 1 of 13
AOZ1280
Ordering Information
Part Number
AOZ1280CI
Ambient Temperature Range
-40 °C to +85 °C
Package
SOT23-6L
Environmental
Green Product
RoHS Compliant
AOS Green Products use reduced levels of Halogens, and are also RoHS compliant.
Please visit
www.aosmd.com/media/AOSGreenPolicy.pdf
for additional information.
Pin Configuration
BST
GND
FB
1
2
3
6
5
4
LX
VIN
EN
SOT23-6L
(Top View)
Pin Description
Pin Number
1
2
3
4
5
6
Pin Name
BST
GND
FB
EN
VIN
LX
Pin Function
Bootstrap voltage input. High side driver supply. Connected to 10 nF capacitor between
BST and LX.
Ground.
Feedback input. It is regulated to 0.8 V. The FB pin is used to determine the PWM output
voltage via a resistor divider between the output and GND.
Enable pin. The enable pin is active high. Connect EN pin to VIN through current limiting
resistor. Do not leave the EN pin floating.
Supply voltage input. Input range from 3 V to 26 V. When VIN rises above the UVLO
threshold the device starts up.
PWM output connection to inductor.
Rev. 1.1 August 2011
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Page 2 of 13
AOZ1280
Absolute Maximum Ratings
Exceeding the Absolute Maximum Ratings may damage the
device.
Recommended Operating Conditions
The device is not guaranteed to operate beyond the
Recommended Operating Conditions.
Parameter
Supply Voltage (V
IN
)
LX to GND
EN to GND
FB to GND
BST to AGND
Junction Temperature (T
J
)
ESD Rating
(1)
Storage Temperature (T
S
)
Rating
30 V
-0.7 V to V
VIN
+ 2 V
-0.3 V to 26 V
-0.3 V to 6 V
V
LX
+ 6 V
+150 °C
-65 °C to +150 °C
2 kV
Parameter
Supply Voltage (V
IN
)
Output Voltage Range
Ambient Temperature (T
A
)
Package Thermal Resistance (
JA
)
SOT23-6L
Rating
3.0 V to 26 V
0.8 V to V
VIN
-40 °C to +85 °C
220 °C/W
Note:
1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5 k
Ω
in series with 100 pF.
Electrical Characteristics
T
A
= 25 °C, V
VIN
= V
EN
= 12 V. Specifications in
BOLD
indicate a temperature range of -40 °C to +85 °C. These specifications are
guaranteed by design.
Symbol
V
VIN
V
UVLO
Parameter
Supply Voltage
Input Under-Voltage Lockout Threshold
UVLO Hysteresis
Conditions
V
VIN
Rising
V
VIN
Falling
I
OUT
= 0, V
FB
= 1 V, V
EN
> 1.2 V
V
EN
= 0 V
T
A
= 25 ºC
120 mA < Load < 1.08 A
Load = 600 mA
V
FB
= 800 mV
Off Threshold
On Threshold
Min.
3
2.3
Typ.
Max.
26
2.9
Units
V
V
V
mV
mA
A
mV
%
%/V
nA
200
1
784
800
0.5
0.03
500
0.4
1.2
200
3
1.2
1.5
87
100
1.5
T
J
Rising
T
J
Falling
2
150
110
400
V
IN
= 12 V
V
IN
= 3.3 V
V
EN
= 0 V, V
LX
= 0 V
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240
380
10
1.8
1.5
8
816
I
VIN
I
OFF
V
FB
V
FB_LINE
I
FB
ENABLE
V
EN_OFF
V
EN_ON
V
EN_HYS
I
EN
f
O
D
MAX
T
ON_MIN
I
LIM
Supply Current (Quiescent)
Shutdown Supply Current
Feedback Voltage
Line Regulation
Feedback Voltage Input Current
EN Input Threshold
EN Input Hysteresis
Enable Input Current
Frequency
Maximum Duty Cycle
Minimum On Time
Current Limit
Over-Temperature Shutdown Limit
V
FB_LOAD
Load Regulation
V
V
mV
A
MHz
%
ns
A
°C
°C
s
mΩ
mΩ
A
MODULATOR
T
SS
R
DS(ON)
R
DS(ON)
I
LEAKAGE
Soft Start Interval
NMOS On-Resistance
NMOS On-Resistance
NMOS Leakage
POWER STATE OUTPUT
Rev. 1.1 August 2011
Page 3 of 13
AOZ1280
Block Diagram
VIN
Regulator
+
EN
Enable
Detect
Softstart
Ramp
Generator
Current
Sense
BST
LDO
BST
OC
OSC
CLK
PWM
Logic
Driver
FB
0.8V
–
–
+
Error
Amplifier
+
PWM
Comparator
LX
GND
Rev. 1.1 August 2011
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Page 4 of 13
AOZ1280
Typical Performance Characteristics
Circuit of Figure 1. V
IN
= 12 V, V
OUT
= 3.3 V, L = 4.7
H,
C1 = 10
F,
C2 = 22
F,
T
A
= 25 °C, unless otherwise specified.
Load Transient Test
(I
OUT
= 0.2A to 0.8A)
Steady State Test
(I
OUT
= 0.5A)
Vo ripple
50mV/div
IL
1A/div
Io
1A/div
Vo ripple
20V/div
Vlx
10V/div
IL
500mA/div
200μs/div
500ns/div
Short Circuit Protection
Vlx
10V/div
Short Circuit Recovery
Vlx
10V/div
Vo
1V/div
Vo
1V/div
lL
1A/div
lL
1A/div
2ms/div
2ms/div
Start-up Through Enable No Load
Ven
5V/div
Start-up Through Enable with I
OUT
= 1A
Resistive Load
Ven
5V/div
Vo
2/div
Vlx
10V/div
IL
1A/div
Vo
2V/div
Vlx
10V/div
IL
1A/div
1ms/div
1ms/div
Rev. 1.1 August 2011
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Page 5 of 13
