AOZ1210 [AOS]

EZBuck⑩ 2A Simple Buck Regulator; EZBuck ™ 2A简单的降压稳压器
AOZ1210
型号: AOZ1210
厂家: ALPHA & OMEGA SEMICONDUCTORS    ALPHA & OMEGA SEMICONDUCTORS
描述:

EZBuck⑩ 2A Simple Buck Regulator
EZBuck ™ 2A简单的降压稳压器

稳压器
文件: 总14页 (文件大小:576K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
AOZ1210  
EZBuck™ 2A Simple Buck Regulator  
General Description  
Features  
The AOZ1210 is a high efficiency, simple to use, 2A buck  
regulator flexible enough to be optimized for a variety of  
applications. The AOZ1210 works from a 4.5V to 27V  
input voltage range, and provides up to 2A of continuous  
output current on each buck regulator output. The output  
voltage is adjustable down to 0.8V.  
4.5V to 27V operating input voltage range  
70minternal NFET, efficiency: up to 95%  
Internal soft start  
Output voltage adjustable down to 0.8V  
2A continuous output current  
Fixed 370kHz PWM operation  
Cycle-by-cycle current limit  
Short-circuit protection  
Thermal shutdown  
Small size SO-8 packages  
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  
C7  
VIN  
C1  
22µF  
VIN  
EN  
BS  
L1  
6.8µH  
VOUT  
LX  
FB  
AOZ1210  
R1  
R2  
C4, C6  
22µF  
VBIAS  
C4  
GND  
COMP  
RC  
CC  
Figure 1. 3.3V/2A Buck Regulator  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 1 of 14  
AOZ1210  
Ordering Information  
Part Number  
Ambient Temperature Range  
Package  
Environmental  
AOZ1210AI  
-40°C to +85°C  
SO-8  
RoHS  
All AOS Products are offering in packaging with Pb-free plating and compliant to RoHS standards.  
Please visit www.aosmd.com/web/quality/rohs_compliant.jsp for additional information.  
Pin Configuration  
1
2
3
4
8
7
6
5
LX  
BST  
GND  
FB  
VBIAS  
VIN  
EN  
COMP  
SO-8  
(Top View)  
Pin Description  
Pin Number Pin Name  
Pin Function  
1
LX  
PWM output connection to inductor. LX pin needs to be connected externally. Thermal connection  
for output stage.  
2
BST  
Bootstrap voltage input. High side driver supply. Connected to 0.1µF capacitor between BST and  
LX.  
3
4
GND  
FB  
Ground.  
Feedback input. It is regulated to 0.8V. The FB pin is used to determine the PWM output voltage  
via a resistor divider between the output and GND.  
5
6
7
8
COMP  
EN  
External loop compensation. Output of internal error amplifier. Connect a series RC network to  
GND for control loop compensation.  
Enable pin. The enable pin is active HIGH. Connect EN pin to V if not used. Do not leave the EN  
IN  
pin floating.  
V
Supply voltage input. Range from 4.5V to 27V. When V rises above the UVLO threshold the  
IN  
IN  
device starts up. All V pins need to be connected externally.  
IN  
VBIAS  
Compensation pin of internal linear regulator. Place put a 1µF capacitor between this pin and  
ground.  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 2 of 14  
AOZ1210  
Block Diagram  
VIN  
+5V  
VBIAS  
EN  
UVLO  
& POR  
5V LDO  
Regulator  
OTP  
+
ISen  
Reference  
& Bias  
Softstart  
BST  
LX  
ILimit  
Q1  
+
+
GM = 200µA/V  
EAmp  
+
PWM  
Control  
Logic  
0.8V  
PWM  
Comp  
FB  
COMP  
Q2  
370kHz/24kHz  
Oscillator  
Frequency  
Foldback  
Comparator  
+
0.2V  
GND  
Absolute Maximum Ratings  
Exceeding the Absolute Maximum Ratings may damage the device.  
Recommend Operating Ratings  
The device is not guaranteed to operate beyond the Maximum  
Operating Ratings.  
Parameter  
Rating  
Parameter  
Rating  
Supply Voltage (V )  
30V  
-0.7V to V +0.3V  
IN  
Supply Voltage (V )  
4.5V to 27V  
LX to GND  
IN  
IN  
EN to GND  
-0.3V to V +0.3V  
Output Voltage Range  
0.8V to V  
IN  
IN  
FB to GND  
-0.3V to 6V  
-0.3V to 6V  
Ambient Temperature (T )  
-40°C to +85°C  
105°C/W  
A
COMP to GND  
BST to GND  
VBIAS to GND  
Package Thermal Resistance SO-8  
)
(2  
(Θ  
)
V
+6V  
JA  
LX  
-0.3V to 6V  
+150°C  
Note:  
2. The value of ΘJA is measured with the device mounted on 1-in  
2
Junction Temperature (T )  
J
FR-4 board with 2oz. Copper, in a still air environment with T = 25°C.  
The value in any given application depends on the user's specific  
board design.  
A
Storage Temperature (T )  
-65°C to +150°C  
2kV  
S
(1)  
ESD Rating: Human Body Model  
Note:  
1. Devices are inherently ESD sensitive, handling precautions are  
required. Human body model rating: 1.5kin series with 100pF.  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 3 of 14  
AOZ1210  
Electrical Characteristics  
)
(3  
T = 25°C, V = V = 12V, V = 3.3V unless otherwise specified  
OUT  
A
IN  
EN  
Symbol  
Parameter  
Conditions  
Min.  
4.5  
Typ. Max. Units  
V
Supply Voltage  
27  
V
V
IN  
V
Input Under-Voltage Lockout Threshold  
V
V
Rising  
Falling  
4.3  
4.1  
UVLO  
IN  
IN  
I
Supply Current (Quiescent)  
Shutdown Supply Current  
Feedback Voltage  
I
= 0, V = 1.2V, V > 2V  
2
3
3
mA  
µA  
IN  
OUT  
FB  
EN  
I
V
= 0V  
20  
OFF  
EN  
V
0.782  
0.8  
0.5  
0.08  
0.818  
V
FB  
Load Regulation  
%
Line Regulation  
% / V  
nA  
I
Feedback Voltage Input Current  
200  
FB  
ENABLE  
V
EN Input Threshold  
EN Input Hysteresis  
Off Threshold  
On Threshold  
0.6  
EN  
V
2.5  
V
200  
mV  
HYS  
MODULATOR  
f
Frequency  
315  
85  
370  
425  
6
kHz  
%
O
D
Maximum Duty Cycle  
Minimum Duty Cycle  
Error Amplifier Voltage Gain  
Error Amplifier Transconductance  
MAX  
D
G
%
MIN  
VEA  
500  
200  
V / V  
µA /V  
G
EA  
PROTECTION  
I
Current Limit  
3.5  
5.0  
A
LIM  
Over-Temperature Shutdown Limit  
T Rising  
145  
100  
J
°C  
T Falling  
J
f
Short Circuit Hiccup Frequency  
Soft Start Interval  
V
= 0V  
24  
4
kHz  
ms  
SC  
FB  
t
SS  
PWM OUTPUT STAGE  
R
High-Side Switch On-Resistance  
High-Side Switch Leakage  
70  
100  
10  
mΩ  
DS(ON)  
V
= 0V, V = 0V  
µA  
EN  
LX  
Note:  
3. Specification in BOLD indicate an ambient temperature range of -40°C to +85°C. These specifications are guaranteed by design.  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 4 of 14  
AOZ1210  
Typical Performance Characteristics  
Circuit of Figure 1. T = 25°C, V = V = 24V, V = 3.3V unless otherwise specified.  
OUT  
A
IN  
EN  
Light Load (DCM) Operation  
Full Load (CCM) Operation  
Vin ripple  
0.1V/div  
Vin ripple  
0.1V/div  
Vo ripple  
20mV/div  
Vo ripple  
20mV/div  
IL  
1A/div  
IL  
1A/div  
VLX  
20V/div  
VLX  
20V/div  
1µs/div  
1µs/div  
Startup to Full Load  
Short Circuit Protection  
Vo  
2V/div  
Vo  
2V/div  
lin  
0.5A/div  
lL  
2A/div  
2ms/div  
200µs/div  
50% to 100% Load Transient  
Short Circuit Recovery  
Vo  
2V/div  
Vo Ripple  
200mV/div  
lo  
1A/div  
IL  
2A/div  
200µs/div  
2ms/div  
Rev. 1.3 December 2007  
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Page 5 of 14  
AOZ1210  
Efficiency Curves  
Efficiency  
Efficiency  
IN  
V
= 5V  
V
= 12V  
IN  
100  
95  
90  
85  
80  
75  
100  
95  
90  
85  
80  
75  
8.0V OUTPUT  
3.3V OUTPUT  
1.8V OUTPUT  
5.0V OUTPUT  
3.3V OUTPUT  
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2  
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2  
Current (A)  
Current (A)  
Efficiency  
V
= 24V  
IN  
100  
95  
90  
85  
80  
75  
8.0V OUTPUT  
5.0V OUTPUT  
3.3V OUTPUT  
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2  
Current (A)  
Rev. 1.3 December 2007  
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Page 6 of 14  
AOZ1210  
Detailed Description  
The AOZ1210 is a current-mode step down regulator with  
integrated high side NMOS switch. It operates from a  
4.5V to 27V input voltage range and supplies up to 2A of  
load current. The duty cycle can be adjusted from 6% to  
85% allowing a wide range of output voltages. Features  
include; enable control, Power-On Reset, input under  
voltage lockout, fixed internal soft-start and thermal shut  
down.  
high-side switch is off. The inductor current is freewheel-  
ing through the Schottky diode to the output.  
Switching Frequency  
The AOZ1210 switching frequency is fixed and set by  
an internal oscillator. The switching frequency is set to  
370kHz.  
The AOZ1210 is available in SO-8 package.  
Output Voltage Programming  
Output voltage can be set by feeding back the output to  
the FB pin with a resistor divider network. In the applica-  
tion circuit shown in Figure 1. The resistor divider  
Enable and Soft Start  
The AOZ1210 has an internal soft start feature to limit  
in-rush current and ensure the output voltage ramps up  
smoothly to the regulation voltage. A soft start process  
begins when the input voltage rises to 4.1V and voltage  
on EN pin is HIGH. In the soft start process, the output  
voltage is typically ramped to regulation voltage in 4 ms.  
The 4.0 ms soft start time is set internally.  
network includes R and R . Typically, a design is started  
1
2
by picking a fixed R value and calculating the required  
2
R value with equation below.  
1
R
1
V
= 0.8 × 1 +  
------  
O
R
2
If the enable function is not used, connect the EN pin to  
Some standard values for R and R for the most  
commonly used output voltages are listed in Table 1.  
V . Pulling EN to ground will disable the AOZ1210. Do  
1
2
IN  
not leave EN open. The voltage on the EN pin must be  
above 2.5 V to enable the AOZ1210. When voltage on  
EN pin falls below 0.6V, the AOZ1210 is disabled. If an  
application circuit requires the AOZ1210 to be disabled,  
an open drain or open collector circuit should be used to  
interface with the EN pin.  
Table 1.  
V (V)  
R (k)  
R (k)  
2
O
1
0.8  
1.2  
1.5  
1.8  
2.5  
3.3  
5.0  
1.0  
Open  
4.99  
10  
10  
11.5  
10.2  
10  
Steady-State Operation  
12.7  
21.5  
31.6  
52.3  
Under steady-state conditions, the converter operates in  
fixed frequency and Continuous-Conduction Mode  
(CCM).  
10  
The AOZ1210 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. Since the N-MOSFET requires a  
gate voltage higher than the input voltage, a boost  
capacitor connected between the LX and BST pins drives  
the gate. The boost capacitor is charged while LX is low.  
An internal 10switch from LX to GND is used to ensure  
that LX is pulled to GND even in the light load. 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, which shows on the  
COMP pin, is compared against the current signal. The  
current signal is the sum of inductor current signal and  
ramp compensation signal, at the 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  
10  
The combination of R and R should be large enough to  
avoid drawing excessive current from the output, which  
will cause power loss.  
1
2
Protection Features  
The AOZ1210 has multiple protection features to prevent  
system circuit damage under abnormal conditions.  
Over Current Protection (OCP)  
The sensed inductor current signal is also used for over  
current protection. Since the AOZ1210 employs peak  
current mode control, the COMP pin voltage is propor-  
tional to the peak inductor current.The COMP pin voltage  
is limited to be between 0.4V and 2.5V internally. The  
peak inductor current is automatically limited cycle by  
cycle.  
Rev. 1.3 December 2007  
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Page 7 of 14  
AOZ1210  
The cycle-by-cycle current limit threshold is internally set.  
When the load current reaches the current limit thresh-  
old, the cycle-by-cycle current limit circuit turns off the  
high side switch immediately to terminate the current  
duty cycle. The inductor current stops rising. The cycle-  
by-cycle current limit protection directly limits inductor  
peak current.The average inductor current is also limited  
due to the limitation on the peak inductor current. When  
cycle-by-cycle current limit circuit is triggered, the output  
voltage drops as the duty cycle decreases.  
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:  
V
V
O
O
I
= I  
×
O
1 –  
----------  
----------  
CIN_RMS  
V
V
IN  
IN  
if let m equal the conversion ratio:  
The AOZ1210 has internal short circuit protection to  
protect itself from catastrophic failure under output short  
circuit conditions. The FB pin voltage is proportional to  
the output voltage. Whenever the FB pin voltage is below  
0.2V, the short circuit protection circuit is triggered. To  
prevent current limit running away when the comp pin  
voltage is higher than 2.1V, the short circuit protection is  
also triggered. As a result, the converter is shut down  
and hiccups at a frequency equals to 1/16 of normal  
switching frequency. The converter will start up via a soft  
start once the short circuit condition is resolved. In short  
circuit protection mode, the inductor average current is  
greatly reduced because of the low hiccup frequency.  
V
O
= m  
----------  
V
IN  
The relationship between the input capacitor RMS  
current and voltage conversion ratio is calculated and  
shown in Figure 2. It can be seen that when V is half of  
O
V , C is under the worst current stress. The worst  
IN  
IN  
current stress on CIN is 0.5 x I .  
O
0.5  
0.4  
0.3  
ICIN_RMS(m)  
Power-On Reset (POR)  
IO  
A power-on reset circuit monitors the input voltage.  
When the input voltage exceeds 4.3V, the converter  
starts operation. When input voltage falls below 4.1V,  
the converter will stop switching.  
0.2  
0.1  
0
0
0.5  
1
Thermal Protection  
m
An internal temperature sensor monitors the junction  
temperature. It shuts down the internal control circuit and  
high side NMOS if the junction temperature exceeds  
145°C. The regulator will restart automatically under the  
control of soft-start circuit when the junction temperature  
decreases to 100°C.  
Figure 2. I  
vs. Voltage Conversion Ratio  
CIN  
For reliable operation and best performance, the input  
capacitors must have a current rating higher than  
I
at the worst operating conditions. Ceramic  
CIN_RMS  
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.  
Application Information  
The basic AOZ1210 application circuit is shown in  
Figure 1. Component selection is explained below.  
Input Capacitor  
The input capacitor (C in Figure 1) must be connected to  
1
the V pin and GND pin of the AOZ1210 to maintain  
IN  
steady input voltage and filter out the pulsing input  
current. The voltage rating of the input capacitor must be  
greater than maximum input voltage + ripple voltage.  
Inductor  
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,  
The input ripple voltage can be approximated by equation  
below:  
I
V
V
O
O
O
V
V
O
V  
=
× 1 –  
×
------------------  
----------  
----------  
O
IN  
I  
=
× 1 –  
-----------  
f × L  
----------  
V
f × C  
V
L
IN  
IN  
IN  
V
IN  
Rev. 1.3 December 2007  
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Page 8 of 14  
AOZ1210  
The peak inductor current is:  
If the impedance of ESR at switching frequency  
I  
L
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:  
I
= I  
+
O
--------  
Lpeak  
2
High inductance gives low inductor ripple current but  
requires 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.  
V = I × ESR  
CO  
O
L
For lower output ripple voltage across the entire operat-  
ing temperature range, X5R or X7R dielectric type of  
ceramic, or other low ESR tantalum capacitor or  
aluminum electrolytic capacitor may also be used as out-  
put capacitors.  
When selecting the inductor, make sure it is able to  
handle the peak current without saturation even at the  
highest operating temperature.  
In a buck converter, output capacitor current is continu-  
ous. The RMS current of output capacitor is decided by  
the peak to peak inductor ripple current. It can be calcu-  
lated by:  
The inductor takes the highest current in a buck circuit.  
The conduction loss on inductor needs to be checked for  
thermal and efficiency requirements.  
Surface mount inductors in different shape and styles are  
available from Coilcraft, Elytone and Murata. Shielded  
inductors are small and radiate less EMI noise. But they  
cost more than unshielded inductors. The choice  
depends on EMI requirement, price and size.  
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 induc-  
tor ripple current is high, output capacitor could be over-  
stressed.  
Output Capacitor  
The output capacitor is selected based on the DC output  
voltage rating, output ripple voltage specification and  
ripple current rating.  
Schottky Diode Selection  
The selected output capacitor must have a higher rated  
voltage specification than the maximum desired output  
voltage including ripple. De-rating needs to be consid-  
ered for long term reliability.  
The external freewheeling diode supplies the current to  
the inductor when the high side NMOS switch is off. To  
reduce the losses due to the forward voltage drop and  
recovery of diode, a Schottky diode is recommended.  
The maximum reverse voltage rating of the chosen  
Schottky diode should be greater than the maximum  
input voltage, and the current rating should be greater  
than the maximum load current.  
Output ripple voltage specification is another important  
factor for selecting the output capacitor. In a buck con-  
verter circuit, output ripple voltage is determined by  
inductor value, switching frequency, output capacitor  
value and ESR. It can be calculated by the equation  
below:  
Loop Compensation  
1
The AOZ1210 employs peak current mode control for  
easy use and fast transient response. Peak current mode  
control eliminates the double pole effect of the output  
L&C filter. It greatly simplifies the compensation loop  
design.  
V = I × ESR  
+
--------------------------  
O
L
CO  
8 × f × C  
O
where;  
C
is output capacitor value and  
O
ESR is the Equivalent Series Resistor of output capacitor.  
With peak current mode control, the buck power stage  
can be simplified to be a one-pole and one-zero system  
in frequency domain. The pole is the dominant pole and  
can be calculated by:  
CO  
When 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:  
1
f
=
-----------------------------------  
p1  
2π × C × R  
O
L
1
V = I ×  
--------------------------  
O
L
8 × f × C  
O
Rev. 1.3 December 2007  
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Page 9 of 14  
AOZ1210  
The zero is a ESR zero due to output capacitor and its  
ESR. It is can be calculated by:  
The strategy for choosing R and C is to set the cross  
C C  
over frequency with R and set the compensator zero  
C
with C . Using selected crossover frequency, f , to  
C
C
1
calculate R :  
f
=
-------------------------------------------------  
C
Z 1  
2π × C × ESR  
O
CO  
V
2π × C  
O
O
R
= f  
×
C
×
where;  
is the output filter capacitor,  
----------- -----------------------------  
C
V
G
EA  
× G  
FB  
CS  
C
O
where;  
f is desired crossover frequency,  
R is load resistor value, and  
L
C
ESR is the equivalent series resistance of output capacitor.  
CO  
V
is 0.8V,  
FB  
The compensation design is actually to shape the  
converter close loop transfer function to get desired gain  
and phase. Several different types of compensation  
network can be used for AOZ1210. For most cases, a  
series capacitor and resistor network connected to the  
COMP pin sets the pole-zero and is adequate for a stable  
high-bandwidth control loop.  
-6  
G
is the error amplifier transconductance, which is 200x10  
EA  
A/V, and  
G
is the current sense circuit transconductance, which is  
CS  
5.64 A/V  
The compensation capacitor C and resistor R together  
make a zero. This zero is put somewhere close to the  
dominate pole fp1 but lower than 1/5 of the selected  
C
C
In the AOZ1210, FB pin and COMP pin are the inverting  
input and the output of internal transconductance error  
amplifier. A series R and C compensation network  
connected to COMP provides one pole and one zero.  
The pole is:  
crossover frequency. C can is selected by:  
C
1.5  
C
=
------------------------------------  
C
2π × R × f  
C
p1  
G
EA  
The equation above can also be simplified to:  
f
=
-------------------------------------------  
p2  
2π × C × G  
C
VEA  
C
× R  
L
O
C
=
----------------------  
where;  
C
R
C
-6  
G
is the error amplifier transconductance, which is 200 x 10  
EA  
A/V,  
An easy-to-use application software which helps to  
design and simulate the compensation loop can be found  
at www.aosmd.com.  
G
is the error amplifier voltage  
VEA  
The zero given by the external compensation network,  
capacitor C (C5 in Figure 1) and resistor R (R1 in  
Figure 1), is located at:  
Thermal Management and Layout  
Consideration  
C
C
In the AOZ1210 buck regulator circuit, high pulsing  
current flows through two circuit loops. The first loop  
1
f
=
------------------------------------  
Z 2  
2π × C × R  
C
C
starts from the input capacitors, to the V pin, to the LX  
IN  
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 inductor, to the  
output capacitors and load, to the GND pin of the  
AOZ1210, to the LX pins of the AZO1210. Current flows  
in the second loop when the low side diode is on.  
To design the compensation circuit, a target crossover  
frequency f for close loop must be selected.The system  
C
crossover frequency is where the control loop has unity  
gain. The crossover frequency is also called the  
converter bandwidth. Generally a higher bandwidth  
means faster response to load transient. However, the  
bandwidth should not be too high due to system stability  
concern. When designing the compensation loop,  
converter stability under all line and load condition must  
be considered.  
In PCB layout, minimizing the two loops area reduces the  
noise of this circuit and improves efficiency. A ground  
plane is recommended to connect input capacitor, output  
capacitor, and GND pin of the AOZ1210.  
Usually, it is recommended to set the bandwidth to be  
less than 1/10 of switching frequency. It is recommended  
to choose a crossover frequency less than 30kHz.  
In the AOZ1210 buck regulator circuit, the three major  
power dissipating components are the AOZ1210,  
external diode and output inductor. The total power  
f
= 30kHz  
C
Rev. 1.3 December 2007  
www.aosmd.com  
Page 10 of 14  
AOZ1210  
dissipation of converter circuit can be measured by input  
power minus output power.  
The thermal performance of the AOZ1210 is strongly  
affected by the PCB layout. Care should be taken by  
users during design process to ensure that the IC will  
operate under the recommended environmental  
conditions.  
P
= V × I V × I  
IN IN O O  
total_loss  
The power dissipation of inductor can be approximately  
calculated by output current and DCR of the inductor.  
Several layout tips are listed below for the best electric  
and thermal performance. Figure 3 is a layout example.  
2
P
= I × R  
× 1.1  
inductor  
inductor _loss  
O
1. Do not use thermal relief connection to the V and  
IN  
the GND pin. Pour a maximized copper area to the  
The power dissipation of the diode is:  
GND pin and the V pin to help thermal dissipation.  
IN  
V
O
2. Input capacitor should be connected as close as  
P
= I × V × 1 –  
----------  
diode_loss  
O
F
possible to the V and GND pins.  
V
IN  
IN  
3. Make the current trace from LX pins to L to C to  
O
GND as short as possible.  
The actual AOZ1210 junction temperature can be  
calculated with power dissipation in the AOZ1210 and  
thermal impedance from junction to ambient.  
4. Pour copper plane on all unused board area and  
connect it to stable DC nodes, like V , GND or V  
.
IN  
OUT  
T
= (P  
P  
) × Θ  
inductor _loss  
5. Keep sensitive signal traces such as the trace  
connecting FB and COMP pins away from the  
LX pins.  
junction  
total_loss  
JA  
+ T  
ambient  
The maximum junction temperature of AOZ1210 is  
145°C, which limits the maximum load current capability.  
Rc  
Cc  
5 COMP  
6 EN  
4 FB  
AOZ1210 /2  
3 GND  
7 Vin  
2 BST  
8 VBIAS  
1 LX  
L1  
Vo  
C
C2  
2
Figure 3. Layout Example of the AOZ1210  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 11 of 14  
AOZ1210  
Package Dimensions  
D
e
Gauge Plane  
Seating Plane  
0.25  
8
L
E
E1  
h x 45°  
1
C
θ
7° (4x)  
A2  
A
0.1  
A1  
b
Dimensions in millimeters  
Dimensions in inches  
Symbols Min. Nom. Max.  
Symbols Min.  
Nom. Max.  
0.053 0.065 0.069  
0.004 0.010  
0.049 0.059 0.065  
2.20  
A
A1  
A2  
b
1.35  
0.10  
1.25  
0.31  
0.17  
4.80  
3.80  
1.65  
1.75  
0.25  
1.65  
0.51  
0.25  
5.00  
4.00  
A
A1  
A2  
b
1.50  
0.012  
0.007  
0.020  
0.010  
c
c
5.74  
D
E1  
e
4.90  
3.90  
1.27 BSC  
6.00  
D
E1  
e
0.189 0.193 0.197  
0.150 0.154 0.157  
0.050 BSC  
1.27  
E
5.80  
0.25  
0.40  
0°  
6.20  
0.50  
1.27  
8°  
E
0.228 0.236 0.244  
h
h
0.010  
0.016  
0°  
0.020  
0.050  
8°  
L
L
0.80  
θ
θ
Unit: mm  
Notes:  
1. All dimensions are in millimeters.  
2. Dimensions are inclusive of plating  
3. Package body sizes exclude mold flash and gate burrs. Mold flash at the non-lead sides should be less than 6 mils.  
4. Dimension L is measured in gauge plane.  
5. Controlling dimension is millimeter, converted inch dimensions are not necessarily exact.  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 12 of 14  
AOZ1210  
Tape and Reel Dimensions  
SO-8 Carrier Tape  
P1  
P2  
See Note 3  
D1  
T
See Note 5  
E1  
E2  
E
See Note 3  
B0  
K0  
D0  
P0  
A0  
Feeding Direction  
Unit: mm  
Package  
A0  
B0  
K0  
D0  
1.60  
D1  
E
E1  
E2  
P0  
P1  
P2  
T
SO-8  
6.40  
5.20  
2.10  
1.50  
12.00 1.75  
5.50  
8.00  
4.00  
2.00  
0.25  
(12mm) ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10 ±0.10  
SO-8 Reel  
W1  
S
G
V
N
K
M
R
H
W
Tape Size Reel Size  
M
N
W
W1  
ø330.00 ø97.00 13.00 17.40  
H
K
S
G
R
V
ø13.00  
10.60  
2.00  
12mm  
ø330  
±0.50  
±0.10 ±0.30 ±1.00  
+0.50/-0.20  
±0.50  
SO-8 Tape  
Leader/Trailer  
& Orientation  
Trailer Tape  
300mm min. or  
75 empty pockets  
Components Tape  
Orientation in Pocket  
Leader Tape  
500mm min. or  
125 empty pockets  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 13 of 14  
AOZ1210  
AOZ1210 Package Marking  
Z1210AI  
FAYWLT  
Part Number  
Assembly Lot Code  
Fab & Assembly Location  
Year & Week Code  
This datasheet contains preliminary data; supplementary data may be published at a later date.  
Alpha & Omega Semiconductor reserves the right to make changes at any time without notice.  
LIFE SUPPORT POLICY  
ALPHA & 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.  
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.  
Rev. 1.3 December 2007  
www.aosmd.com  
Page 14 of 14  

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