A7222A [AITSEMI]
DC-DC CONVERTER BUCK (STEP-DOWN) SYNCHRONOUS;
| 型号： | A7222A |
| 厂家： | 
AiT Semiconductor |
| 描述： | DC-DC CONVERTER BUCK (STEP-DOWN) SYNCHRONOUS DC-DC转换器 |
| 文件： | 总13页 (文件大小：803K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
DESCRIPTION
FEATURES
The A7222A is a fully integrated, high-efficiency 2A
synchronous rectified step-down converter. The
A7222A operates at high efficiency over a wide
output current load range.
High Efficiency: Up to 96%
500kHz Frequency Operation
2A Output Current
No Schottky Diode Required
This device offers two operation modes, PWM
control and PFM Mode switching control, which
allows a high efficiency over the wider range of the
load.
4.5V to 16V Input Voltage Range
0.6V Reference
Slope Compensated Current Mode Control for
Excellent Line and Load Transient Response
Integrated internal compensation
Stable with Low ESR Ceramic Output
Capacitors
The A7222A is available in SOT-26 package.
ORDERING INFORMATION
Over Current Protection with Hiccup-Mode
Thermal Shutdown
Package Type
Part Number
A7222AE6R
A7222AE6VR
Inrush Current Limit and Soft Start
-40°C to +85°C Temperature Range
Available in SOT-26 package.
SOT-26
E6
SPQ: 3,000pcs/Reel
V: Halogen free Package
R: Tape & Reel
Note
APPLICATION
Distributed Power Systems
AiT provides all RoHS products
Digital Set Top Boxes
Flat Panel Television and Monitors
Wireless and DSL Modems
Notebook Computer
TYPICAL APPLICATION
NOTE: 1) C1 and C2 recommended using 22uF ceramic capacitors.
If the electrolytic capacitor is used, it is recommended
that the ceramic capacitor in parallel with a capacitance
value of 0.1uF or more.
2) C3 can be valued as 1uF, 0.1uF.
REV1.0
- JUN 2018 RELEASED -
- 1 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
PIN DESCRIPTION
Top View
Pin #
Symbol
BST
Function
Bootstrap. A capacitor connected between SW and BST pins is required to
form a floating supply across the high-side switch driver.
Ground
1
2
3
GND
FB
Adjustable version feedback input. Connect FB to the center point of the
external resistor divider.
Drive this pin to a logic-high to enable the IC. Drive to a logic-low to disable
the IC and enter micro-power shutdown mode.
Power supply Pin
4
EN
5
6
VIN
SW
Switching Pin
REV1.0
- JUN 2018 RELEASED -
- 2 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
ABSOLUTE MAXIMUM RATINGS
VIN, Supply Voltage
-0.3V ~ 18V
-0.3V to (VIN+0.5V)
VSW-0.3V to VSW+5V
-0.3V ~ 18V
VSW, Switch Node Voltage
VBST, Boost Voltage
VEN, Enable Voltage
All Other Pins
-0.3V ~ 6V
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10s)
-40ºC ~ +85ºC
-65ºC ~ +150ºC
300ºC
Stress beyond above listed “Absolute Maximum Ratings” may lead permanent damage to the device. These are stress ratings only and
operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not
implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
VIN=12V, VOUT=5V, TA=25℃, unless otherwise stated
Parameter
Input Voltage Range
Conditions
Min
Typ
-
Max
Unit
V
4.5
16
UVLO Threshold
-
4.1
0.5
5
-
V
Supply Current in Operation
Supply Current in Shutdown
Regulated Feedback Voltage
High-side Switch On Resistance
Low-side Switch On Resistance
High-side Switch Leakage Current
Upper Switch Current Limit
Oscillation Frequency
VEN = 2.0V, VFB = 0.9V
VEN = 0V
-
-
mA
uA
V
-
10
4.5V≤VIN ≤16V
VBST-SW = 5V
0.588
0.6
150
70
0
0.612
-
-
m Ω
m Ω
uA
A
VIN = 5V
-
-
VEN = 0V, VSW = 0V
Minimum Duty Cycle
-
10
-
3
-
350
500
95
100
-
700
kHz
%
Maximum Duty Cycle
VFB = 0.5V
-
-
-
-
Minimum On Time
ns
V
EN Input Voltage “H”
1.3
-
-
EN Input Voltage “L”
-
0.4
-
V
Thermal Shutdown
-
170
°C
REV1.0
- JUN 2018 RELEASED -
- 3 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
TYPICAL PERFORMANCE CHARACTERISTICS
Tested under, L=4.7uH, TA=25°C, unless otherwise specified
1.
3.
5.
Efficiency vs. Iout (Vout=1.2V)
Efficiency vs. Iout (Vout=5.0V)
Vout vs. Iout (Vout=3.3V)
2.
4.
6.
Efficiency vs. Iout (Vout=3.3V)
Vout vs. Iout (Vout=1.2V)
Vout vs. Iout (Vout=5.0V)
REV1.0
- JUN 2018 RELEASED -
- 4 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
7.
Efficiency vs. Vin Iout=1A
8.
Vout vs. Vin Iout=1A
9.
Load Transient
Vin=12V, Vout=3.3V, Iout=0.01~2A
Ch2—Vout, Ch4--IL
10. Load Transient
Vin=12V, Vout=3.3V, Iout=0.5~1A
Ch2—Vout, Ch4--IL
REV1.0
- JUN 2018 RELEASED -
- 5 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
TYPICAL APPLICATION CIRCUITS
1. 12V VIN, 5V/2A
2. 12V VIN, 3.3V/2A
REV1.0
- JUN 2018 RELEASED -
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AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
3. 12V VIN, 2.5V/2A
4. 12V VIN, 1.8V/2A
5. 12V VIN, 1.2V/2A
REV1.0
- JUN 2018 RELEASED -
- 7 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
BLOCK DIAGRAM
REV1.0
- JUN 2018 RELEASED -
- 8 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
DETAILED INFORMATION
Internal Regulator
The A7222A is a current mode step down DC/DC converter that provides excellent transient response with no
extra external compensation components. This device contains an internal, low resistance, high voltage
power MOSFET, and operates at a high 500k operating frequency to ensure a compact, high efficiency
design with excellent AC and DC performance.
Error Amplifier
The error amplifier compares the FB pin voltage with the internal FB reference (VFB) and outputs a current
proportional to the difference between the two. This output current is then used to charge or discharge the
internal compensation network to form the COMP voltage, which is used to control the power MOSFET
current. The optimized internal compensation network minimizes the external component counts and
simplifies the control loop design.
Internal Soft-Start
The soft-start is important for many applications because it eliminates power-up initialization problems. The
controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up
transient events to the input power bus.
Over-Current-Protection and Hiccup
The A7222A has a cycle-by-cycle over-current limit for when the inductor current peak value exceeds the set
current-limit threshold. First, when the output voltage drops until FB falls below the Under-Voltage (UV)
threshold (typically 140mV) to trigger a UV event, the A7222A enters hiccup mode to periodically restart the
part. This protection mode is especially useful when the output is dead-shorted to ground. This greatly
reduces the average short-circuit current to alleviate thermal issues and to protect the regulator. The A7222A
exits hiccup mode once the overcurrent condition is removed.
Startup and Shutdown
If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first,
generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator
provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low
and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault
triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not
subject to this shutdown command.
REV1.0
- JUN 2018 RELEASED -
- 9 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
APPLICATIONS INFORMATION
Setting Output Voltages
The external resistor divider is used to set the output voltage (see Typical Application on page 1). The
feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. R1, R2
is then given by:
Selecting the Inductor
Use a 2.2μH-to-10μH inductor with a DC current rating of at least 25% percent higher than the maximum load
current for most applications. For highest efficiency, select an inductor with a DC resistance less than 15mΩ.
For most designs, derive the inductance value from the following equation.
L =
Where ΔIL is the inductor ripple current. Choose an inductor current approximately 30% of the maximum load
current. The maximum inductor peak current is:
IL(MAX) = ILOAD
+
Under light-load conditions (below 100mA), use a larger inductor to improve efficiency.
Selecting the Output Capacitor
The output capacitor (C2) maintains the DC output voltage. Use ceramic, tantalum, or low-ESR electrolytic
capacitors. Use low ESR capacitors to limit the output voltage ripple. Estimate the output voltage ripple with:
ΔVOUT
=
Where L is the inductor value and RESR is the equivalent series resistance (ESR) of the output capacitor.
For ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes
most of the output voltage ripple. For simplification, estimate the output voltage ripple with:
ΔVOUT
=
REV1.0
- JUN 2018 RELEASED -
- 10 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For
simplification, the output ripple can be approximated with:
ΔVOUT
=
The characteristics of the output capacitor also affect the stability of the regulation system. The A7222A can
be optimized for a wide range of capacitance and ESR values.
PC BOARD LAYOUT
PCB layout is very important to achieve stable operation. For best results, use the following guidelines and
figures as reference.
1) Keep the connection between the input ground and GND pin as short and wide as possible.
2) Keep the connection between the input capacitor and VIN pin as short and wide as possible.
3) Use short and direct feedback connections. Place the feedback resistors and compensation components
as close to the chip as possible.
4) Route SW away from sensitive analog areas such as FB.
REV1.0
- JUN 2018 RELEASED -
- 11 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
PACKAGE INFORMATION
Dimension in SOT-26 (Unit: mm)
REV1.0
- JUN 2018 RELEASED -
- 12 -
AiT Semiconductor Inc.
A7222A
www.ait-ic.com
DC-DC CONVERTER BUCK (STEP-DOWN)
500kHz, 16V, 2A SYNCHRONOUS
IMPORTANT NOTICE
AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to
discontinue any integrated circuit product or service without notice, and advises its customers to obtain the
latest version of relevant information to verify, before placing orders, that the information being relied on is
current.
AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to
be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT
products in such applications is understood to be fully at the risk of the customer. As used herein may involve
potential risks of death, personal injury, or server property, or environmental damage. In order to minimize
risks associated with the customer's applications, the customer should provide adequate design and
operating safeguards.
AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT
warrants the performance of its products of the specifications applicable at the time of sale.
REV1.0
- JUN 2018 RELEASED -
- 13 -
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