AOZ6622DI
EZBuckTM 2A Synchronous Buck Regulator
General Description
Features
The AOZ6622DI is a high efficiency, easy to use, 2A
synchronous buck regulator. The AOZ6622DI works from
4.5V to 18V input voltage range, and provides up to 2A of
continuous output current with an output voltage
adjustable down to 0.8V.
4.5V to 18V operating input voltage range
The AOZ6622DI comes in a DFN 3mm x 3mm package
and is rated over a -40°C to +85°C operating ambient
temperature range.
Synchronous Buck: 150mΩ internal high-side switch
and 90mΩ internal low-side switch
Up to 95% efficiency
Pulse energy mode for high light load efficiency
(Vin=12V, Vo=5V, 83% @10mA)
Output voltage adjustable to 0.8V
Adjacent pin short protection
2A continuous output current
550kHz PWM operation
Cycle-by-cycle current limit
Pre-bias start-up
Short-circuit protection
Thermal shutdown
Applications
Point of load DC/DC converters
LCD TV
Set top boxes
DVD / Blu-ray players/recorders
Cable modems
Typical Application
VIN
CIN
10µF
VIN
BST
CBST
EN
EN
AOZ6622DI
VOUT
LX
L1
4.7µH
R1
FB
GND
C2,C3
22µF
RT
R2
Figure 1. 3.3V 2ASynchronous Buck Regulator, Fs = 550kHz
Rev. 1.1 July 2016
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Page 1 of 15
AOZ6622DI
Ordering Information
Part Number
Ambient Temperature Range
Package
Environmental
AOZ6622DI
-40°C to +85°C
8-Pin 3mm x 3mm DFN
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.
Pin Configuration
GND
1
LX
2
LX
VIN
8
BST
7
EN
3
6
NC
4
5
FB
Thermal
PAD (9)
8-Pin 3mm x 3mm DFN
(Top View)
Pin Description
Pin Number
Pin Name
1
GND
2, 3
LX
Switching output.
4
VIN
Supply voltage input. When VIN rises above the UVLO threshold and EN is logic high, the
device starts up.
5
FB
Feedback input. The FB pin is used to set the output voltage via a resistive voltage divider
between the output and GND.
6
NC
No connection.
7
EN
Enable pin. Pull EN to logic high to enable the device. Pull EN to logic low to disable the
device. If on/off control in not needed, connect it to VIN and do not leave it open.
8
BST
Bootstrap.
9
Thermal PAD
Rev. 1.1 July 2016
Pin Function
System ground.
GND pin must be connected to the exposed pad for proper operation.
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Page 2 of 15
AOZ6622DI
Absolute Maximum Ratings(1)
Maximum Operating Ratings(3)
Exceeding the Absolute Maximum Ratings may damage the
device.
The device is not guaranteed to operate beyond the
Maximum Operating ratings.
Parameter
Rating
Parameter
Supply Voltage (VIN)
20V
-0.7V to VIN+0.3V
LX to GND
LX to GND (20ns)
-5V to 22V
-0.3V to VIN+0.3V
EN to GND
BST to GND
26V
BST to LX
6V
Junction Temperature (TJ)
+150°C
Storage Temperature (TS)
-65°C to +150°C
ESD Rating
(2)
2kV
Notes:
Rating
Supply Voltage (VIN)
4.5V to 18V
Output Voltage Range
0.8V to 0.85*VIN
Ambient Temperature (TA)
-40°C to +85°C
Package Thermal Resistance
(θJA)(4)
50°C/W
Notes:
3. The device is not guaranteed to operate beyond the Maximum
Operating ratings.
4. The value of θJA is measured with the device mounted on a 1-in2
FR-4 four layer board with 2oz copper and Vias, in a still air environment with TA = 25°C. The value in any given application depends on
the user’s specification board design.
1. Exceeding the Absolute Maximum ratings may damage the device.
2. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5k in series with 100pF.
Electrical Characteristics
TA = 25°C, VIN = VEN = 12V, VOUT = 3.3V, unless otherwise specified(5).
Symbol
VIN
VUVLO
Parameter
Conditions
Supply Voltage
Input Under-Voltage Lockout Threshold
VIN rising
VIN falling
IOUT = 0V, VFB = 1.2V,
VEN > 2V
IOFF
Shutdown Supply Current
VEN = 0V
VFB
Feedback Voltage
TA = 25°C
RO
Load Regulation
PWM mode
500mA < ILoad < 2A
SV
Line Regulation
4.5V < VIN < 18V
IFB
Feedback Voltage Input Current
VEN
EN Input Threshold
VHYS
EN Input Hysteresis
IEN
EN Input Current
tSS
SS Time
Typ.
4.5
Supply Current (Quiescent)
IIN
Min.
Off threshold
On threshold
3.4
4.1
3.7
Max
Units
18
V
4.35
V
V
0.55
0.784
mA
1
3
A
0.800
0.816
V
0.5
%
1
%
100
nA
0.6
V
V
2
mV
300
VEN = 5V
3
A
5
1.5
ms
Modulator
Frequency
400
DMAX
Maximum Duty Cycle
88
DMIN
Controllable Minimum Duty Cycle
fO
550
660
kHz
7.5
%
%
Protection
ILIM
TOTP
Current Limit
Over Temperature Shutdown Limit
Rev. 1.1 July 2016
3.0
TJ rising
TJ falling
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3.5
A
150
100
°C
°C
Page 3 of 15
AOZ6622DI
Electrical Characteristics
TA = 25°C, VIN = VEN = 12V, VOUT = 3.3V, unless otherwise specified(5).
Symbol
Parameter
Conditions
Min.
Typ.
Max
Units
Output Stage
RH
High-Side Switch On-Resistance
VBST-LX = 5V
150
m
RL
Low-Side Switch On-Resistance
VCC = 5V
90
m
Note:
5. The device is not guaranteed to operate beyond the Maximum Operating Ratings. Specifications in Bold indicate an ambient temperature range
of -40°C to +85°C. These specifications are guaranteed by design.
Rev. 1.1 July 2016
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Page 4 of 15
AOZ6622DI
Functional Block Diagram
BST
UVLO
& POR
EN
VIN
LDO
Regulator
HS
BSTUVLO
Soft Start
ISEN
LX
Reference
& Bias
Q1
ILIMIT
PWM
COMP
EAMP
PWM
Control
Logic
FB
HS
DRV
LX
VCC
500kHz
Oscillator
0.96V
Q2
LS
DRV
OVP
OTP
PEM
Logic
NCD
GND
Rev. 1.1 July 2016
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Page 5 of 15
AOZ6622DI
Typical Characteristics
Efficiency
Efficiency vs. Load Current (VIN=5V)
100
100
95
95
90
90
85
85
80
80
Efficiency (%)
Efficiency (%)
Efficiency vs. Load Current (VIN=12V)
75
70
65
60
55
50
45
40
0.01
12V to 5.0V, EN=VIN, L=6.8µH
12V to 3.3V, EN=VIN, L=4.7µH
12V to 2.5V, EN=VIN, L=4.7µH
12V to 1.8V, EN=VIN, L=2.2µH
12V to 1.2V, EN=VIN, L=2.2µH
0.1
1
75
70
65
60
55
50
45
10
40
0.01
IO (A)
Rev. 1.1 July 2016
5V to 3.3V, EN=VIN, L=4.7µH
5V to 2.5V, EN=VIN, L=4.7µH
5V to 1.8V, EN=VIN, L=2.2µH
5V to 1.2V, EN=VIN, L=2.2µH
0.1
1
10
IO (A)
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Page 6 of 15
AOZ6622DI
Typical Characteristics
Circuit of Typical Application. TA = 25°C, VIN = VEN = 12V, VOUT = 3.3V, unless otherwise specified.
Figure 2. Light Load Operation
Figure 3. Full Load Operation
Figure 4. PEM to PWM Operation
Figure 5. PWM to PEM Operation
Figure 6. Short Circuit Protection
Figure 7. Short Circuit Recovery
Rev. 1.1 July 2016
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Page 7 of 15
AOZ6622DI
Typical Characteristics (continued)
Circuit of Typical Application. TA = 25°C, VIN = VEN = 12V, VOUT = 3.3V, unless otherwise specified.
Figure 8. Full Load Startup
Rev. 1.1 July 2016
Figure 9. 50% to 100% Load Transient
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Page 8 of 15
AOZ6622DI
Detailed Description
Steady-State Operation
The AOZ6622DI is a current-mode step down regulator
with integrated high-side NMOS switch and low-side
NMOS switch. It operates from a 4.5V to 18V input
voltage range and supplies up to 2A of load current.
Features include, enable control, Power-On Reset, input
under voltage lockout, output over voltage protection,
internal soft-start and thermal shut down.
Under heavy load steady-state conditions, the converter
operates in fixed frequency and Continuous-Conduction
Mode (CCM).
The AOZ6622DI is available in 8-pin 3mm x 3mm DFN
package.
Enable and Soft Start
The AOZ6622DI has internal soft start feature to limit inrush current and ensure the output voltage ramps up
smoothly to regulation voltage. A soft start process
begins when the input voltage rises to 4.1V and voltage
on EN pin is HIGH. In soft start process, the output
voltage is typically ramped to regulation voltage in 1.5ms.
The 1.5ms soft start time is set internally.
The EN pin of the AOZ6622DI is active high. Connect the
EN pin to VIN if enable function is not used. Pull it to
ground will disable the AOZ6622DI. Do not leave it open.
The voltage on EN pin must be above 2 V to enable the
AOZ6622DI. When voltage on EN pin falls below 0.6V,
the AOZ6622DI is disabled. The Figure 10 shows the EN
input current vs. voltage.
4
EN Input Current (µA)
Comparing with regulators using freewheeling Schottky
diodes, the AOZ6622DI uses freewheeling NMOSFET to
realize synchronous rectification. It greatly improves the
converter efficiency and reduces power loss in the lowside switch.
The AOZ6622DI uses a N-Channel MOSFET as the
high-side switch. Since the NMOSFET requires a gate
voltage higher than the input voltage, a boost capacitor is
needed between LX pin and BST pin to drive the gate.
The boost capacitor is charged while LX is low.
3.5
2.5
2
Output Voltage Programming
1.5
1
0.5
0
The AOZ6622DI integrates an internal N-MOSFET as
the high-side switch. Inductor current is sensed by
amplifying the voltage drop across the drain to source of
the high side power MOSFET. Output voltage is divided
down by the external voltage divider at the FB pin. The
difference of the FB pin voltage and reference is
amplified by the internal transconductance error
amplifier. The error voltage is compared against the
current signal, which is sum of inductor current signal
and ramp compensation signal, at PWM comparator
input. If the current signal is less than the error voltage,
the internal high-side switch is on. The inductor current
flows from the input through the inductor to the output.
When the current signal exceeds the error voltage, the
high-side switch is off. The inductor current is
freewheeling through the internal low-side N-MOSFET
switch to output. The internal adaptive FET driver
guarantees no turn on overlap of both high-side and lowside switch.
0
2
4
6
8
10
12
14
Output voltage can be set by feeding back the output to
the FB pin by using a resistor divider network. In the
application circuit shown in Figure 1. The resistor divider
network includes R1 and R2. Usually, a design is started
by picking a fixed R2 value and calculating the required
R1 with equation below.
EN Voltage (V)
R 1
V O = 0.8 1 + -------
R 2
Figure 10. EN Input Current vs. EN Voltage
Light Load and PWM Operation
Under low output current settings, the AOZ6622DI will
operate with pulse energy mode to obtain high efficiency.
In pulse energy mode, the PWM will not turn off until the
inductor current reaches to 800 mA and the current
signal exceeds the error voltage.
Rev. 1.1 July 2016
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Page 9 of 15
AOZ6622DI
Some standard value of R1, R2 and most used output
voltage values are listed in Table 1.
VO (V)
R1 (kΩ)
R2 (kΩ)
0.8
1.0
Open
1.2
4.99
10
1.5
10
11.5
1.8
12.7
10.2
2.5
21.5
10
3.3
31.1
10
5.0
52.3
10
Application Information
The basic AOZ6622DI application circuit is shown in
Figure 1. Component selection is explained below.
Input Capacitor
The input capacitor must be connected to the VIN pin
and GND pin of the AOZ6622DI to maintain steady input
voltage and filter out the pulsing input current. The
voltage rating of input capacitor must be greater than
maximum input voltage plus ripple voltage.
The input ripple voltage can be approximated by
equation below:
VO VO
IO
V IN = ----------------- 1 – --------- --------V IN V IN
f C IN
Table 1.
Combination of R1 and R2 should be large enough to
avoid drawing excessive current from the output, which
will cause power loss.
Protection Features
The AOZ6622DI has multiple protection features to
prevent system circuit damage under abnormal
conditions.
Since the input current is discontinuous in a buck
converter, the current stress on the input capacitor is
another concern when selecting the capacitor. For a buck
circuit, the RMS value of input capacitor current can be
calculated by:
VO
VO
I CIN_RMS = I O --------- 1 – ---------
V IN
V IN
Over Current Protection (OCP)
The sensed inductor current signal is also used for over
current protection. Since the AOZ6622DI employs peak
current mode control, during over current conditions. The
peak inductor current is automatically limited to cycle-bycycle, and if output is shorted to GND, then the
AOZ6622DI will shutdown and auto restart approximately
every 25ms.
Power-On Reset (POR)
A power-on reset circuit monitors the VCC voltage. When
the VCC voltage exceeds 4.1V, the converter starts
operation. When VCC voltage falls below 3.7V, the
converter will be shut down.
if let m equal the conversion ratio:
VO
-------- = m
V IN
The relation between the input capacitor RMS current
and voltage conversion ratio is calculated and shown in
Figure 11 below. It can be seen that when VO is half of
VIN, CIN it is under the worst current stress. The worst
current stress on CIN is 0.5 x IO.
0.5
Thermal Protection
0.4
An internal temperature sensor monitors the junction
temperature. It shuts down the internal control circuit and
high side NMOS if the junction temperature exceeds
150°C. The regulator will restart automatically under the
control of soft-start circuit when the junction temperature
decreases to 100°C.
ICIN_RMS(m) 0.3
IO
0.2
0.1
0
0
0.5
m
1
Figure 11. ICIN vs. Voltage Conversion Ratio
Rev. 1.1 July 2016
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Page 10 of 15
AOZ6622DI
For reliable operation and best performance, the input
capacitors must have current rating higher than ICIN-RMS
at worst operating conditions. Ceramic capacitors are
preferred for input capacitors because of their low ESR
and high ripple current rating. Depending on the
application circuits, other low ESR tantalum capacitor or
aluminum electrolytic capacitor may also be used. When
selecting ceramic capacitors, X5R or X7R type dielectric
ceramic capacitors are preferred for their better
temperature and voltage characteristics. Note that the
ripple current rating from capacitor manufactures is
based on certain amount of life time. Further de-rating
may be necessary for practical design requirement.
The selected output capacitor must have a higher rated
voltage specification than the maximum desired output
voltage including ripple. De-rating needs to be
considered for long term reliability.
Inductor
where,
The inductor is used to supply constant current to output
when it is driven by a switching voltage. For given input
and output voltage, inductance and switching frequency
together decide the inductor ripple current, which is:
CO is output capacitor value and ESRCO is the
Equivalent Series Resistor of output capacitor. When a
low ESR ceramic capacitor is used as output capacitor,
the impedance of the capacitor at the switching
frequency dominates. Output ripple is mainly caused by
capacitor value and inductor ripple current. The output
ripple voltage calculation can be simplified to:
VO
VO
I L = ----------- 1 – ---------
V IN
fL
Output ripple voltage specification is another important
factor for selecting the output capacitor. In a buck
converter circuit, output ripple voltage is determined by
inductor value, switching frequency, output capacitor
value and ESR. It can be calculated by the equation
below:
1
V O = I L ESR CO + -------------------------
8fC
O
1
V O = I L ------------------------8fC
The peak inductor current is:
O
I L
I Lpeak = I O + -------2
High inductance gives low inductor ripple current but
requires a larger size inductor to avoid saturation. Low
ripple current reduces inductor core losses. It also
reduces RMS current through inductor and switches,
which results in less conduction loss. Usually, peak to
peak ripple current on inductor is designed to be 20% to
40% of output current.
When selecting the inductor, make sure it is able to
handle the peak current without saturation even at the
highest operating temperature.
The inductor takes the highest current in a buck circuit.
The conduction loss on the inductor needs to be checked
for thermal and efficiency requirements.
Surface mount inductors in different shapes and styles
are available from Coilcraft, Elytone and Murata.
Shielded inductors are small and radiate less EMI noise,
but they do cost more than unshielded inductors. The
choice depends on EMI requirement, price and size.
Output Capacitor
If the impedance of ESR at switching frequency
dominates, the output ripple voltage is mainly decided by
capacitor ESR and inductor ripple current. The output
ripple voltage calculation can be further simplified to:
V O = I L ESR CO
For lower output ripple voltage across the entire
operating temperature range, X5R or X7R dielectric type
of ceramic, or other low ESR tantalum are recommended
to be used as output capacitors.
In a buck converter, output capacitor current is
continuous. The RMS current of output capacitor is
decided by the peak to peak inductor ripple current.
It can be calculated by:
I L
I CO_RMS = ---------12
Usually, the ripple current rating of the output capacitor is
a smaller issue because of the low current stress. When
the buck inductor is selected to be very small and
inductor ripple current is high, the output capacitor could
be overstressed.
The output capacitor is selected based on the DC output
voltage rating, output ripple voltage specification and
ripple current rating.
Rev. 1.1 July 2016
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Page 11 of 15
AOZ6622DI
Thermal Management and Layout
Consideration
In the AOZ6622DI buck regulator circuit, high pulsing
current flows through two circuit loops. The first loop
starts from the input capacitors, to the VIN pin, to the LX
pad, to the filter inductor, to the output capacitor and
load, and then return to the input capacitor through
ground. Current flows in the first loop when the high side
switch is on. The second loop starts from inductor, to the
output capacitors and load, to the low side NMOSFET.
Current flows in the second loop when the low side
NMOSFET is on.
The thermal performance of the AOZ6622DI is strongly
affected by the PCB layout. Extra care should be taken
by users during design process to ensure that the IC will
operate under the recommended environmental
conditions.
The AOZ6622DI is an exposed pad DFN3X3 package.
Several layout tips are listed below for the best electric
and thermal performance.
1. The exposed thermal pad has to connect to ground
by PCB externally. Connect a large copper plane to
exposed thermal pad to help thermal dissipation.
In PCB layout, minimizing the two loops area reduces the
noise of this circuit and improves efficiency. A ground
plane is strongly recommended to connect input
capacitor, output capacitor, and GND pin of the
AOZ6622DI.
2. Do not use thermal relief connection to the VIN and
the GND pin. Pour a maximized copper area to the
GND pin and the VIN pin to help thermal dissipation.
In the AOZ6622DI buck regulator circuit, the major power
dissipating components are the AOZ6622DI and output
inductor. The total power dissipation of the converter
circuit can be measured by input power minus output
power.
4. Make the current trace from LX pins to L to Co to the
GND as short as possible.
P total_loss = V IN I IN – V O I O
6. Keep sensitive signal trace far away from the LX pad.
3. Input capacitor should be connected to the VIN pin
and the GND pin as close as possible.
5. Pour copper plane on all unused board area and
connect it to stable DC nodes, like VIN, GND or
VOUT.
The power dissipation of inductor can be approximately
calculated by output current and DCR of inductor.
P inductor_loss = IO2 R inductor 1.1
The actual junction temperature can be calculated with
power dissipation in the AOZ6622DI and thermal
impedance from junction to ambient.
T junction = P total_loss – P inductor_loss JA
The maximum junction temperature of AOZ6622DI is
150ºC, which limits the maximum load current capability.
Rev. 1.1 July 2016
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Page 12 of 15
AOZ6622DI
Package Dimensions, DFN 3x3B, 8 Lead EP1_P
θ
RECOMMENDED LAND PATTERN
SYMBOLS
A
A1
b
c
D
D1
E
E1
E2
e
K
L
L1
θ1
DIMENSIONS IN MILLIMETERS
MIN
NOM
−−−
MAX
DIMENSIONS IN INCHES
MIN
NOM
−−−
MAX
NOTE
1. PAKCAGE BODY SIZES EXCLUDE MOLD FLASH AND GATE BURRS.
MOLD FLASH AT THE NON-LEAD SIDES SHOULD BE LESS THAN 6 MILS EACH.
2. CONTROLLING DIMENSION IS MILLIMETER.
CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT.
Rev. 1.1 July 2016
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Page 13 of 15
AOZ6622DI
Tape and Reel Dimensions, DFN 3x3, EP
Carrier Tape
D0
P1
D1
A-A
E1
K0
E2
E
B0
T
P0
P2
A0
Feeding Direction
UNIT: mm
Package
A0
B0
K0
D0
DFN 3x3 EP
3.40
±0.10
3.35
±0.10
1.10
±0.10
1.50
+0.10/-0
D1
1.50
+0.10/-0
E
12.00
±0.30
E1
E2
P0
P1
P2
T
1.75
±0.10
5.50
±0.05
8.00
±0.10
4.00
±0.10
2.00
±0.05
0.30
±0.05
Reel
W1
N
S
G
K
M
V
R
H
W
UNIT: mm
Tape Size Reel Size
12mm
ø330
M
ø330.0
±0.50
N
ø97.0
±1.0
W
13.0
±0.30
W1
17.4
±1.0
H
ø13.0
+0.5/-0.2
K
10.6
S
2.0
±0.5
G
—
R
—
V
—
Leader/Trailer and Orientation
Unit Per Reel:
5000pcs
Trailer Tape
300mm min.
Rev. 1.1 July 2016
Components Tape
Orientation in Pocket
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Leader Tape
500mm min.
Page 14 of 15
AOZ6622DI
Part Marking
AOZ6622DI
(3x3 DFN-8)
6622
Industrial Temperature Range
No Option
I 0 A W
LT
Part Number Code
Week (Year code is embedded
by using upper dot, on “W”)
Assembly Location
Assembly Lot Number
LEGAL DISCLAIMER
Applications or uses as critical components in life support devices or systems are not authorized. AOS does not
assume any liability arising out of such applications or uses of its products. AOS reserves the right to make
changes to product specifications without notice. It is the responsibility of the customer to evaluate suitability of the
product for their intended application. Customer shall comply with applicable legal requirements, including all
applicable export control rules, regulations and limitations.
AOS' products are provided subject to AOS' terms and conditions of sale which are set forth at:
http://www.aosmd.com/terms_and_conditions_of_sale
LIFE SUPPORT POLICY
ALPHA AND OMEGA SEMICONDUCTOR PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL
COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS.
As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant into
the body or (b) support or sustain life, and (c) whose
failure to perform when properly used in accordance
with instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of
the user.
Rev. 1.1 July 2016
2. A critical component in any component of a life
support, device, or system whose failure to perform can
be reasonably expected to cause the failure of the life
support device or system, or to affect its safety or
effectiveness.
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Page 15 of 15
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