28V/4A Synchronous EZBuck
TM
Regulator
AOZ1231-01
General Description
The AOZ1231-01 is high-efficiency, easy-to-use DC/DC
synchronous buck regulator that operates up to 28V.
The device is capable of supplying 4A of continuous
output current with an output voltage adjustable down to
0.8V (±1.0%).
The AOZ1231-01 integrates an internal linear regulator
to generate 5.3V V
CC
from the input source. If the input
voltage is lower than 5.3V, the linear regulator operates
in low drop-output mode and the V
CC
voltage is equal to
input voltage minus the drop-output voltage of the
internal linear regulator.
A proprietary constant on-time PWM control with input
feed-forward results in ultra-fast transient response while
maintaining relatively constant switching frequency over
the entire input voltage range. The switching frequency
can be externally set up to 1MHz.
The devices feature multiple protection functions such
as V
CC
under-voltage lockout, cycle-by-current limit,
output over-voltage protection, short-circuit protection,
and thermal shutdown.
The AOZ1231-01 is available in a 5mm × 5mm
QFN-30L package and is rated over a -40°C to +85°C
ambient temperature range.
Features
Wide input voltage range:
–
4.5V to 28V (internal V
CC
)
–
2.7V to 28V (external V
CC
)
4A continuous output current
Output voltage adjustable to 0.8V (±1.0%)
Low R
DS(ON)
internal NFETs
–
40m high-side
–
25m low-side
Constant On-time with input feed-forward
Programmable frequency up to 1MHz
Internal 5.3V, 20mA linear regulator
Ceramic capacitor stable
Adjustable soft start
Power Good output
Over voltage protection
Integrated bootstrap diode
Cycle-by-cycle current limit
Short-circuit protection
Thermal shutdown
Thermally enhanced 5mm × 5mm QFN-30L package
Applications
Portable computers
Compact desktop PCs
Servers
Graphics cards
Set top boxes
LCD TVs
Cable modems
Point of load DC/DC converters
Telecom/Networking/Datacom equipment
Rev. 1.1 June 2012
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Page 1 of 17
AOZ1231-01
Typical Application for V
IN
= 12V or above
Input = 12V or above
IN
C2
22μF
AIN
VCC
R3
100kΩ
Power Good
C4
1μF
TON
BST
C5
0.1μF
Output
1.05V, 4A
R1
FB
EN
R2
SS
C
SS
PGND
Analog Ground
Power Ground
AGND
C3
100μF
R
TON
AOZ1231-01
LX
PGOOD
L1 2.2μH
Off On
Typical Application for V
IN
= 5V
Input = 5V
IN
C2
22μF
AIN
VCC
R3
100kΩ
Power Good
C4
1μF
TON
BST
C5
0.1μF
Output
1.05V, 4A
R1
FB
EN
R2
SS
C
SS
PGND
Analog Ground
Power Ground
AGND
C3
100μF
R
TON
AOZ1231-01
LX
PGOOD
L1 2.2μH
Off On
Rev. 1.1 June 2012
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Page 2 of 17
AOZ1231-01
Typical Application for High Light Load Efficiency Requirement or V
IN
= 3.3V
Input
IN
C2
22μF
5V
R3
100kΩ
Power Good
C4
1μF
AIN
VCC
TON
BST
C5
0.1μF
Output
1.05V, 4A
R1
FB
EN
R2
PFM
SS
C
SS
PGND
AGND
C3
100μF
R
TON
AOZ1231-01
LX
PGOOD
L1 2.2μH
Off On
Analog Ground
Power Ground
Ordering Information
Part Number
AOZ1231QI-01
Ambient Temperature Range
-40°C to +85°C
Package
30-Pin 5mm x 5mm QFN
Environmental
Green Product
AOS Green Products use reduced levels of Halogens, and are also RoHS compliant.
Please visit
www.aosmd.com/media/AOSGreenPolicy.pdf
for additional information.
Rev. 1.1 June 2012
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Page 3 of 17
AOZ1231-01
Pin Configuration
AGND
PGND
VCC
BST
SS
LX
LX
24
30
29
28
27
26
25
PGOOD
EN
PFM
AGND
FB
LX
23
1
2
3
4
5
22
21
LX
LX
LX
PGND
PGND
PGND
PGND
PGND
AGND
LX
20
19
18
17
TON
AIN
6
7
8
9
IN
16
15
10
11
12
13
14
PGND
PGND
30-pin 5mm x 5mm QFN
(Top View)
Pin Description
Pin Number
1
Pin Name
PGOOD
Pin Function
Power Good Signal Output. PGOOD is an open-drain output used to indicate the status
of the output voltage. It is internally pulled low when the output voltage is 10% lower than
the nominal regulation voltage for 50µs (typical time) or 15% higher than the nominal
regulation voltage. PGOOD is pulled low during soft-start and shut down.
Enable Input. The AOZ1231-01 is enabled when EN is pulled high. The device shuts
down when EN is pulled low.
PFM Selection Input. Connect PFM pin to VCC/VIN for forced PWM operation. Connect
PFM pin to ground for PFM operation to improve light load efficiency.
Analog Ground.
Feedback Input. Adjust the output voltage with a resistive voltage-divider between the
regulator’s output and AGND.
On-Time Setting Input. Connect a resistor between VIN and TON to set the on time.
Supply Input for analog functions.
Supply Input. IN is the regulator input. All IN pins must be connected together.
Power Ground.
Switching Node.
Bootstrap Capacitor Connection. The AOZ1231-01 includes an internal bootstrap diode.
Connect an external capacitor between BST and LX as shown in the Typical Application
diagrams.
Output for internal linear regulator. Bypass VCC to AGND with a 1µF ceramic capacitor.
Place the capacitor close to VCC pin.
Soft-Start Time Setting Pin. Connect a capacitor between SS and AGND to set the
soft-start time.
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2
3
4, 29
5
6
7
8, 9, 10, 11
12, 13, 14, 15, 16,
17, 18, 19, 26
20, 21, 22, 23,
24, 25
27
28
30
Rev. 1.1 June 2012
EN
PFM
AGND
FB
TON
AIN
IN
PGND
LX
BST
VCC
SS
PGND
IN
IN
IN
IN
AOZ1231-01
Absolute Maximum Ratings
Exceeding the Absolute Maximum Ratings may damage the
device.
Maximum Operating Ratings
The device is not guaranteed to operate beyond the
Maximum Operating ratings.
Parameter
IN, AIN, TON, PFM to AGND
LX to AGND
BST to AGND
SS, PGOOD, FB, EN to AGND
PGND to AGND
Junction Temperature (T
J
)
Storage Temperature (T
S
)
ESD Rating
Note:
(1)
Rating
-0.3V to 30V
-2V to 30V
-0.3V to 36V
-0.3V to 6V
-0.3V to +0.3V
+150°C
-65°C to +150°C
2kV
Parameter
Supply Voltage (V
IN
)
Output Voltage Range
Ambient Temperature (T
A
)
Package Thermal Resistance
HS MOSFET
LS MOSFET
PWM Controller
Rating
4.5V to 28V
0.8V to 0.85*V
IN
-40°C to +85°C
25°C/W
20°C/W
50°C/W
1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5k
in series with 100pF.
2. LX to PGND Transient (t<20ns) ------ -7V to V
IN
+ 7V.
Electrical Characteristics
T
A
= 25°C, V
IN
= 12V, EN = 5V, unless otherwise specified. Specifications in
BOLD
indicate a temperature range of -40°C to +85°C.
Symbol
V
IN
V
UVLO
I
q
I
OFF
V
FB
Parameter
IN Supply Voltage
Under-Voltage Lockout Threshold of V
cc
Quiescent Supply Current of V
cc
Shutdown Supply Current
Feedback Voltage
Load Regulation
Line Regulation
V
cc
rising
V
cc
falling
Conditions
Min.
4.5
3.2
Typ.
4.0
3.7
2
1
Max
28
4.4
3
20
0.808
0.812
Units
V
V
mA
A
V
%
%
I
OUT
= 0, V
FB
= 1.0V, V
EN
> 2V
V
EN
= 0V
T
A
= 25°C
T
A
= 0°C to 85°C
0.792
0.788
0.800
0.800
0.5
1
I
FB
Enable
V
EN
V
EN_HYS
FB Input Bias Current
Off threshold
On threshold
200
0.5
2.5
100
PFM Mode threshold
Force PWM threshold
0.5
2.5
100
R
TON
= 100k, V
IN
= 12V
R
TON
= 100k, V
IN
= 24V
200
250
150
100
250
300
nA
EN Input Threshold
EN Input Hysteresis
V
mV
PFM Control
Input Threshold
Input Hysteresis
Modulator
T
ON
T
ON
_
MIN
T
OFF
_
MIN
On Time
Minimum On Time
Minimum Off Time
ns
ns
ns
V
mV
Rev. 1.1 June 2012
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Page 5 of 17
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