AOZ2237QI-01
28V/8A Synchronous EZBuckTM Regulator
Not Recommended For New Designs
General Description
Features
The AOZ2237-01 is a high-efficiency, easy-to-use DC/DC
synchronous buck regulator that operates up to 28V.
The device is capable of supplying 8A of continuous
output current with an output voltage adjustable down to
0.8V (±1.0%).
Wide input voltage range
s
ig
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Output voltage adjustable down to 0.8V (±1.0%)
– 35m high-side
es
Low RDS(ON) internal NFETs
– 12m low-side SRFET™
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Constant On-Time with input feed-forward
Programmable frequency up to 1MHz
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Selectable PFM light load operation
Ceramic capacitor stable
Adjustable soft start
Power Good output
Integrated bootstrap diode
Fo
r
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 programmed up to 1MHz.
8A continuous output current
N
The AOZ2237-01 integrates an internal linear regulator
to generate 5.3V VCC from input. If input voltage is lower
than 5.3V, the linear regulator operates at low dropoutput mode, which allows the VCC voltage is equal to
input voltage minus the drop-output voltage of the
internal linear regulator.
– 2.7V to 28V
Cycle-by-cycle current limit
Short-circuit protection
Thermal shutdown
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The device features multiple protection functions such as
VCC under-voltage lockout, cycle-by-cycle current limit,
output over-voltage protection, short-circuit protection, as
well as thermal shutdown.
Thermally enhanced 4mm x 4mm QFN-23L package
Applications
No Replacement
Servers
Portable computers
Compact desktop PCs
Graphics cards
Set-top boxes
LCD TVs
Cable modems
Point-of-load DC/DC converters
Telecom/Networking/Datacom equipment
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The AOZ2237-01 is available in a 4mm x 4mm QFN-23L
package and is rated over a -40°C to +85°C ambient
temperature range.
Rev. 2.0 February 2014
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Page 1 of 16
AOZ2237QI-01
Typical Application
RTON
C4
1μF
Power Good
VCC
C5
0.1μF
AOZ2237-01
LX
PGOOD
Off On
L1
1μH
FB
R1
25kΩ
1%
AGND
R2
80kΩ
1%
EN
PFM
SS
C3
88μF
es
PGND
Output
1.05V, 8A
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CSS
C2
20μF
ig
n
R3
100kΩ
BST
Input
6.5V to 28V
s
IN
TON
Fo
r
N
External VCC Bias
RTON
TON
IN
AIN
C4
1μF
VCC
PGOOD
Off On
om
m
EN
PFM
SS
LX
L1
1μH
FB
AGND
R1
25kΩ
1%
R2
80kΩ
1%
Output
1.05V, 8A
C3
88μF
PGND
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CSS
C2
20μF
AOZ2237-01
en
Power Good
C5
0.1μF
d
R3
100kΩ
de
5V
BST
Input
2.7V to 28V
Rev. 2.0 February 2014
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Page 2 of 16
AOZ2237QI-01
Ordering Information
Part Number
Ambient Temperature Range
Package
Environmental
AOZ2237QI-01
-40°C to +85°C
23-Pin 4mm x 4mm QFN
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.
BST
PGND
LX
21
20
19
18
ig
n
VCC
22
1
17
LX
EN
2
16
LX
PFM
3
AGND
4
FB
5
TON
6
ew
PGOOD
LX
15
PGND
14
PGND
PGND
12
PGND
11
LX
Fo
r
10
LX
IN
9
13
d
8
IN
7
AIN
N
IN
es
IN
23
D
SS
s
Pin Configuration
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23-Pin 4mm x 4mm QFN
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(Top View)
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Page 3 of 16
AOZ2237QI-01
Pin Description
Pin Name
Pin Function
1
PGOOD
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 15% 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.
2
EN
3
PFM
4
AGND
5
FB
6
TON
On-Time Setting Input. Connect a resistor between VIN and TON to set the on time.
7
AIN
Supply Input for analog functions.
8, 9, 22
IN
12, 13, 14, 15, 19
PGND
Power Ground.
10, 11, 16, 17, 18
LX
Switching Node.
20
BST
Bootstrap Capacitor Connection. The AOZ2237-01 includes an internal bootstrap diode.
Connect an external capacitor between BST and LX as shown in the Typical Application
diagrams.
21
VCC
Supply Input for analog functions. Bypass VCC to AGND with a 1µF ceramic capacitor.
Place the capacitor close to VCC pin.
23
SS
Enable Input. The AOZ2237-01 is enabled when EN is pulled high. The device shuts
down when EN is pulled low.
s
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.
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Analog Ground.
D
es
Feedback Input. Adjust the output voltage with a resistive voltage-divider between the
regulator’s output and AGND.
Fo
r
N
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Supply Input. IN is the regulator input. All IN pins must be connected together.
d
Soft-Start Time Setting Pin. Connect a capacitor between SS and AGND to set the
soft-start time.
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Pin Number
Rev. 2.0 February 2014
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Page 4 of 16
AOZ2237QI-01
Absolute Maximum Ratings
Maximum Operating Ratings
Exceeding the Absolute Maximum Ratings may damage the
device.
Rating
Parameter
-0.3V to 30V
LX to AGND
Output Voltage Range
-0.3V to 40V
SS, PGOOD, FB, EN, VCC, PFM to AGND
+150°C
Storage Temperature (TS)
-65°C to +150°C
ESD Rating(1)
(θJA)
(θJC)
Note:
40°C/W
4.5°C/W
3. Connect VCC to external 5V for VIN = 2.7V ~ 6.5V application.
es
2kV
-40°C to +85°C
Package Thermal Resistance
-0.3V to +0.3V
Junction Temperature (TJ)
0.8V to 0.85*VIN
Ambient Temperature (TA)
-0.3V to 6V
PGND to AGND
2.7V(3) to 28V
Supply Voltage (VIN)
-2V to 30V
BST to AGND
Rating
s
IN, AIN, TON to AGND
ig
n
Parameter
The device is not guaranteed to operate beyond the
Maximum Operating ratings.
Note:
D
1. Devices are inherently ESD sensitive, handling precautions are
required. Human body model rating: 1.5k in series with 100pF.
ew
2. LX to PGND Transient (t 2V
2
3
mA
VEN = 0V
1
20
A
0.800
0.800
0.808
0.812
V
AIN rising
AIN falling
en
Under-Voltage Lockout Threshold
Max
d
VIN
Parameter
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Symbol
Fo
r
TA = 25°C, VIN = 12V, VCC = 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of
-40°C to +85°C.
TA = 25°C
TA = 0°C to 85°C
Min.
Typ.
2.7
3.2
0.792
0.788
Load Regulation
0.5
%
Line Regulation
1
%
FB Input Bias Current
ec
IFB
R
Enable
EN Input Threshold
VEN_HYS
EN Input Hysteresis
Off threshold
On threshold
0.5
2.5
200
ot
VEN
200
nA
V
mV
N
PFM Control
VPFM
PFM Input Threshold
VPFMHYS
PFM Input Hysteresis
PFM Mode threshold
Force PWM threshold
0.5
2.5
100
V
mV
Modulator
TON
On Time
RTON = 100k, VIN = 12V
RTON = 100k, VIN = 28V
200
250
150
300
ns
TON_MIN
Minimum On Time
100
ns
TOFF_MIN
Minimum Off Time
250
ns
Rev. 2.0 February 2014
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Page 5 of 16
AOZ2237QI-01
Electrical Characteristics (Continued)
TA = 25°C, VIN = 12V, VCC = 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of
-40°C to +85°C.
Symbol
Parameter
Conditions
Min.
Typ.
Max
Units
7
10
15
A
0.5
V
Soft-Start
ISS_OUT
SS Source Current
VSS = 0
CSS = 0.001F to 0.1F
Power Good Signal
IOL = 1mA
s
PGOOD Low Voltage
PGOOD Leakage Current
PGOOD Threshold
(Low Level to High Level)
VPGL
PGOOD Threshold
(High Level to Low Level)
FB rising
FB falling
87
109
112
82
D
PGOOD Threshold Hysteresis
ew
PGOOD Fault Delay Time (FB falling)
TPG_L
±1
A
90
112
93
115
%
115
85
118
88
%
es
VPGH
ig
n
VPG_LOW
Under Voltage and Over Voltage Protection
50
s
Under Voltage Delay Time
VPH
Over Voltage Threshold
FB rising
Under Voltage Shutdown Blanking Time
VIN = 12V, VEN = 0V, VCC = 5V
20
VIN = 12V, VCC = 5V
35
Low-Side NFET Leakage
Valley Current Limit
om
m
ILIM
Fo
r
VLX = 12V, VCC = 5V
en
Low-Side NFET On-Resistance
Over-current and Thermal Protection
115
VEN = 0V, VLX = 0V
High-Side NFET Leakage
RDS(ON)
112
d
High-Side NFET On-Resistance
85
TJ rising
TJ falling
8
%
s
118
%
ms
45
m
10
A
15
m
10
A
A
145
100
°C
N
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Thermal Shutdown Threshold
12
VEN = 0V
VCC = 5V
88
128
de
RDS(ON)
N
Under Voltage Threshold
TPL
Power Stage Output
82
%
VPL
TUV_LX
FB falling
3
Rev. 2.0 February 2014
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Page 6 of 16
AOZ2237QI-01
Functional Block Diagram
IN
BST AIN
PGood
LDO
VCC
UVLO
Reference
& Bias
TOFF_MIN
Q
Timer
Error Comp
0.8V
SS
FB
Decode
ig
n
S
Q
R
ILIM Comp
ILIM_VALLEY
Current
Information
Processing
OTP
D
ISENSE
Vcc
ISENSE
ISENSE (AC)
ew
TON
Timer
PFM
N
Q
LX
es
FB
ISENCE
(AC)
PG Logic
s
EN
EN
TON
ISENSE
PGND
AGND
N
ot
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d
Light Load
Threshold
Light Load
Comp
Fo
r
TON
Generator
Rev. 2.0 February 2014
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Page 7 of 16
AOZ2237QI-01
Typical Performance Characteristics
Circuit of Typical Application. TA = 25°C, VIN = 19V, VOUT = 1.05V, fs = 450kHz unless otherwise specified.
Load Transient 0.8A to 7.2A
Normal Operation
VLX
20V/div
VLX
10V/div
ILX
2A/div
ig
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s
ILX
2A/div
Vo ripple
50mV/div
es
Vo ripple
20mV/div
1ms/div
Full Load Start-up
Short Circuit Protection
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5μs/div
N
VLX
20V/div
lLX
5A/div
Vo
500mV/div
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Vo
1V/div
ILX
5A/div
Fo
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EN
2V/div
50μs/div
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500μs/div
LX
10V/div
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Page 8 of 16
AOZ2237QI-01
Detailed Description
The AOZ2237-01 is a high-efficiency, easy-to-use,
synchronous buck regulator optimized for notebook
computers. The regulator is capable of supplying 8A of
continuous output current with an output voltage
adjustable down to 0.8V. The programmable operating
frequency range of 200kHz to 1MHz enables optimizing
the configuration for PCB area and efficiency.
Constant-On-Time PWM Control with Input
Feed-Forward
The control algorithm of AOZ2237-01 is constant-on-time
PWM Control with input feed-forward.
The simplified control schematic is shown in Figure 1.
s
–
ig
n
Programmable
One-Shot
Comp
+
0.8V
es
PWM
FB Voltage/
AC Current
Information
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Figure 1. Simplified Control Schematic of AOZ2237-01
ew
The high-side switch on-time is determined solely by a
one-shot whose pulse width can be programmed by one
external resistor and is inversely proportional to input
voltage (IN). The one-shot is triggered when the internal
0.8V is lower than the combined information of FB
voltage and the AC current information of inductor, which
is processed and obtained through the sensed lower-side
MOSFET current once it turns on. The added AC current
information can help the stability of constant-on time
control even with pure ceramic output capacitors, which
have very low ESR. The AC current information has no
DC offset, which does not cause offset with output load
change, which is fundamentally different from other V2
constant-on time control schemes.
Fo
r
The AOZ2237-01 is available in 23-pin 4mm x 4mm QFN
package.
IN
N
The input voltage of AOZ2237-01 can be as low as 2.7V.
The highest input voltage of AOZ2237-01 can be 28V.
Constant on-time PWM with input feed-forward control
scheme results in ultra-fast transient response while
maintaining relatively constant switching frequency over
the entire input range. True AC current mode control
scheme guarantees the regulator can be stable with a
ceramic output capacitor. The switching frequency can
be externally programmed up to 1MHz. Protection
features include VCC under-voltage lockout, valley
current limit, output over voltage and under voltage
protection, short-circuit protection, and thermal
shutdown.
Input Power Architecture
Enable and Soft Start
om
m
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d
The AOZ2237-01 integrates an internal linear regulator
to generate 5.3V (±5%) VCC from input. If input voltage is
lower than 5.3V, the linear regulator operates at low
drop-output mode; the VCC voltage is equal to input
voltage minus the drop-output voltage of internal linear
regulator.
N
ot
R
ec
The AOZ2237-01 has external soft start feature to limit
in-rush current and ensure the output voltage ramps up
smoothly to regulation voltage. A soft start process
begins when VCC rises to 4.1V and voltage on EN pin is
HIGH. An internal current source charges the external
soft-start capacitor; the FB voltage follows the voltage of
soft-start pin (VSS) when it is lower than 0.8V. When VSS
is higher than 0.8V, the FB voltage is regulated by
internal precise band-gap voltage (0.8V). The soft-start
time can be calculated by the following formula:
TSS(s) = 330 x CSS(nF)
The constant-on-time PWM control architecture is a
pseudo-fixed frequency with input voltage feed-forward.
The internal circuit of AOZ2237-01 sets the on-time of
high-side switch inversely proportional to the IN.
– 12
26.3 10
R TON
T ON = ---------------------------------------------------------------V IN V
(1)
To achieve the flux balance of inductor, the buck
converter has the equation:
V OUT
F SW = --------------------------V IN T ON
(2)
If CSS is 1nF, the soft-start time will be 330µs; if CSS is
10nF, the soft-start time will be 3.3ms.
Rev. 2.0 February 2014
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Page 9 of 16
AOZ2237QI-01
12
V OUT 10
F SW = --------------------------------26.3 R TON
(3)
A further simplified equation will be:
38000 V OUT V
F SW kHz = ----------------------------------------------R TON k
Inductor
Current
(4)
s
An external resistor between the IN and TON pin sets the
switching frequency according to the following equation:
characteristic and maximum load capability are a
function of the inductor value as well as input and output
voltages. The current limit will keep the low-side
MOSFET ON and will not allow another high-side ontime, until the current in the low-side MOSFET reduces
below the current limit. Figure 2 shows the inductor
current during the current limit.
ig
n
Once the product of VIN x TON is constant, the switching
frequency keeps constant and is independent with input
voltage.
Ilim
es
Time
If VOUT is 1.8V, RTON is 137k, the switching frequency
will be 500kHz.
D
Figure 2. Inductor Current
After 128s (typical), the AOZ2237-01 considers this is a
true failed condition and therefore, turns-off both highside and low-side MOSFETs and latches off. When
triggered, only the enable can restart the AOZ2237-01
again.
N
ew
This algorithm results in a nearly constant switching
frequency despite the lack of a fixed-frequency clock
generator.
True Current Mode Control
Output Voltage Under-Voltage Protection
Fo
r
The constant-on-time control scheme is intrinsically
unstable if output capacitor’s ESR is not large enough as
an effective current-sense resistor. Ceramic capacitors
usually cannot be used as output capacitor.
d
If the output voltage is lower than 15% by over-current or
short circuit, the AOZ2237-01 will wait for 128s (typical)
and turns-off both high-side and low-side MOSFETs and
latches off. When triggered, only the enable can restart
the AOZ2237-01 again.
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om
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The AOZ2237-01 senses the low-side MOSFET current
and processes it into DC and AC current information
using AOS proprietary technique. The AC current
information is decoded and added on the FB pin on
phase. With AC current information, the stability of
constant-on-time control is significantly improved even
without the help of output capacitor’s ESR, and thus the
pure ceramic capacitor solution can be applicable. The
pure ceramic capacitor solution can significantly reduce
the output ripple (no ESR caused overshoot and
undershoot) and less board area design.
R
Valley Current-Limit Protection
N
ot
The AOZ2237-01 uses the valley current-limit protection
by using RDSON of the lower MOSFET current sensing.
To detect real current information, a minimum constantoff (150ns typical) is implemented after a constant-on
time. If the current exceeds the valley current-limit
threshold, the PWM controller is not allowed to initiate a
new cycle. The actual peak current is greater than the
valley current-limit threshold by an amount equal to the
inductor ripple current. Therefore, the exact current-limit
Rev. 2.0 February 2014
Output Voltage Over-Voltage Protection
The threshold of OVP is set 15% higher than 800mV.
When the VFB voltage exceeds the OVP threshold, highside MOSFET is turned-off and low-side MOSFETs is
turned-on until VFB voltage is lower than 800mV.
Power Good Output
The power good (PGOOD) output, which is an open
drain output, requires the pull-up resistor. When the
output voltage is 15% below than the nominal regulation
voltage for 50s (typical), the PGOOD is pulled low.
When the output voltage is 15% higher than the nominal
regulation voltage, the PGOOD is also pulled low.
When combined with the under-voltage-protection circuit,
this current limit method is effective in almost every
circumstance. In forced-PWM mode, the AOZ2237-01
also implements a negative current limit to prevent
excessive reverse inductor currents when VOUT is
sinking current.
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Page 10 of 16
AOZ2237QI-01
Application Information
The input ripple voltage can be approximated by
equation below:
Inductor
de
en
if let m equal the conversion ratio:
om
m
R
ec
The relation between the input capacitor RMS current
and voltage conversion ratio is calculated and shown in
Figure 3. 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.
ew
N
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 30% to
50% 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.
ot
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.
N
0.4
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.
ICIN_RMS(m) 0.3
IO
0.2
0.1
0
The peak inductor current is:
d
VO
VO
I CIN_RMS = I O --------- 1 – ---------
V IN
V IN
0
VO
VO
I L = ----------- 1 – ---------
V IN
fL
Fo
r
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:
0.5
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:
D
VO VO
IO
V IN = ----------------- 1 – --------- --------V IN V IN
f C IN
VO
-------- = m
V IN
s
The input capacitor must be connected to the IN pins and
PGND pin of the AOZ2237-01 to maintain steady input
voltage and filter out the pulsing input current. A small
decoupling capacitor, usually 1F, should be connected
to the VCC pin and AGND pin for stable operation of the
AOZ2237-01. The voltage rating of input capacitor must
be greater than maximum input voltage plus ripple
voltage.
ig
n
Input Capacitor
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.
es
The basic AOZ2237-01 application circuit is shown in
page 2. Component selection is explained below.
0.5
m
1
Figure 3. ICIN vs. Voltage Conversion Ratio
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Page 11 of 16
AOZ2237QI-01
Output Capacitor
The output capacitor is selected based on the DC output
voltage rating, output ripple voltage specification and
ripple current rating.
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.
In the AOZ2237-01 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
pins, to the filter inductor, to the output capacitor and
load, and then returns to the input capacitor through
ground. Current flows in the first loop when the high side
switch is on. The second loop starts from the inductor, to
the output capacitors and load, to the low side switch.
Current flows in the second loop when the low side
switch is on.
ig
n
s
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:
Thermal Management and Layout
Consideration
es
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 the input
capacitor, output capacitor and PGND pin of the
AOZ2237-01.
D
1
V O = I L ESR CO + -------------------------
8fC
O
In the AOZ2237-01 buck regulator circuit, the major
power dissipating components are the AOZ2237-01 and
output inductor. The total power dissipation of the converter circuit can be measured by input power minus output power.
CO is output capacitor value and
ESRCO is the Equivalent Series Resistor of output capacitor.
Fo
r
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:
N
ew
where,
The power dissipation of inductor can be approximately
calculated by output current and DCR of inductor and
output current.
d
de
1
V O = I L ------------------------8fC
en
O
om
m
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
P total_loss = V IN I IN – V O I O
P inductor_loss = IO2 R inductor 1.1
The actual junction temperature can be calculated with
power dissipation in the AOZ2237-01 and thermal
impedance from junction to ambient.
T junction = P total_loss – P inductor_loss JA
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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.
N
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:
The maximum junction temperature of AOZ2237-01 is
150ºC, which limits the maximum load current capability.
The thermal performance of the AOZ2237-01 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.
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.
Rev. 2.0 February 2014
www.aosmd.com
Page 12 of 16
AOZ2237QI-01
Layout Considerations
Several layout tips are listed below for the best electric
and thermal performance.
1. The LX pins and pad are connected to internal low
side switch drain. They are low resistance thermal
conduction path and most noisy switching node.
Connect a large copper plane to LX pin to help
thermal dissipation.
4. Decoupling capacitor CVCC should be connected to
VCC and AGND as close as possible.
5. Voltage divider R1 and R2 should be placed as close
as possible to FB and AGND.
6. RTON should be put on the PCB reverse side of the
feedback network or away from the FB pin and FB
feedback resistors to avoid contact, which may short
the TON pin and FB together to ground and cause an
abnormal operation.
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2. The IN pins and pad are connected to internal high
side switch drain. They are also low resistance
thermal conduction path. Connect a large copper
plane to IN pins to help thermal dissipation.
3. Input capacitors should be connected to the IN pin
and the PGND pin as close as possible to reduce the
switching spikes.
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7. A ground plane is preferred; Pin 19 (PGND) must be
connected to the ground plane through via.
D
8. Keep sensitive signal traces such as feedback trace
far away from the LX pins.
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9. Pour copper plane on all unused board area and
connect it to stable DC nodes, like VIN, GND or
VOUT.
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Rev. 2.0 February 2014
www.aosmd.com
Page 13 of 16
AOZ2237QI-01
Package Dimensions, QFN 4x4, 23 Lead EP2_S
D
D2
Pin #1 Dot
By Marking
D3
L1
L
e
E
E2
E3
b
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s
E1
L3
L2
D1
D1
es
TOP VIEW
D
BOTTOM VIEW
A1
ew
A
N
A2
Fo
r
SIDE VIEW
0.22
Symbols
Min.
Typ.
Max.
Symbols
Min.
Typ.
Max.
A
A1
A2
E
E1
E2
E3
D
D1
D2
D3
L
L1
L2
L3
b
e
0.80
0.00
0.90
—
0.2 REF
4.00
3.05
2.66
3.05
4.00
0.75
0.95
1.34
0.40
0.62
0.28
0.62
0.25
0.50 BSC
1.00
0.05
A
A1
A2
E
E1
E2
E3
D
D1
D2
D3
L
L1
L2
L3
b
e
0.031
0.000
0.035
—
0.008 REF
0.157
0.120
0.105
0.120
0.157
0.030
0.037
0.053
0.016
0.024
0.011
0.024
0.010
0.020 BSC
0.039
0.002
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en
0.45
2.71
3.10
3.43
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3.10
0.50
0.25
d
0.37
0.25
0.37
0.75
0.95
UNIT: MM
3.90
2.95
2.56
2.95
3.90
0.65
0.85
1.24
0.35
0.57
0.23
0.57
0.20
4.10
3.15
2.76
3.15
4.10
0.85
1.05
1.44
0.45
0.67
0.33
0.67
0.30
0.154
0.116
0.101
0.116
0.154
0.026
0.033
0.049
0.014
0.022
0.009
0.022
0.008
0.141
0.124
0.109
0.124
0.141
0.033
0.041
0.057
0.018
0.026
0.013
0.026
0.012
N
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R
0.26
0.75
1.34
Dimensions in inches
Dimensions in millimeters
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RECOMMENDED LAND PATTERN
Notes:
1. Controlling dimensions are in millimeters. Converted inch dimensions are not necessarily exact.
2. Tolerance: ± 0.05 unless otherwise specified.
3. Radius on all corners is 0.152 max., unless otherwise specified.
4. Package wrapage: 0.012 max.
5. No plastic flash allowed on the top and bottom lead surface.
6. Pad planarity: ± 0.102
7. Crack between plastic body and lead is not allowed.
Rev. 2.0 February 2014
www.aosmd.com
Page 14 of 16
AOZ2237QI-01
Tape and Reel Dimensions, QFN 4x4, 23 Lead EP2_S
Carrier Tape
P1
P2
D1
T
E1
E2
E
D0
A0
UNIT: mm
A0
B0
K0
D0
QFN 4x4
(12mm)
4.35
±0.10
4.35
±0.10
1.10
±0.10
1.50
Min.
D1
E
1.50
+0.10/-0
12.00
±0.30
Reel
E1
E2
1.75
±0.10
5.50
±0.05
P0
P1
P2
T
8.00
±0.10
4.00
±0.10
2.00
±0.05
0.30
±0.05
ew
Package
Feeding Direction
es
P0
D
K0
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s
B0
Fo
r
N
W1
G
N
UNIT: mm
om
m
M
ø330.0
±2.0
N
ø79.0
±1.0
W
12.4
+2.0/-0.0
H
W
W1
17.0
+2.6/-1.2
H
ø13.0
±0.5
K
10.5
±0.2
S
2.0
±0.5
G
—
R
—
V
—
ec
Tape Size Reel Size
12mm
ø330
K
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R
d
M
V
S
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Leader/Trailer and Orientation
Trailer Tape
300mm min.
or 75 Empty Pockets
Rev. 2.0 February 2014
Components Tape
Orientation in Pocket
www.aosmd.com
Leader Tape
500mm min.
or 125 Empty Pockets
Page 15 of 16
AOZ2237QI-01
Part Marking
AOZ2237QI-01
Z2237QI1
Part Number Code
es
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FAYWLT
s
(QFN4x4)
ew
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d
Fo
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N
Year & Week Code
D
Assembly Lot Code
Fab & Assembly Location
en
LEGAL DISCLAIMER
om
m
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.
R
ec
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
ot
LIFE SUPPORT POLICY
N
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. 2.0 February 2014
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.
www.aosmd.com
Page 16 of 16
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