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AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 1 - 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. 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. The A7222A is available in SOT-26 package.
ORDERING INFORMATION
SPQ: 3,000pcs/Reel A7222AE6R A7222AE6VR Note V: Halogen free Package R: Tape & Reel AiT provides all RoHS products High Efficiency: Up to 96% 500kHz Frequency Operation 2A Output Current No Schottky Diode Required 4.5V to 16V Input Voltage Range 0.6V Reference Slope Compensated Current Mode Control f or Excellent Line and Load Transient Response Integrated internal compensation Stable with Low ESR Ceramic Output Capacitors Over Current Protection with Hiccup-Mode Thermal Shutdown Inrush Current Limit and Soft Start -40°C to +85°C Temperature Range Available in SOT-26 package. APPLICATION Distributed Power Systems 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.
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 2 - PIN DESCRIPTION Top View Pin # Symbol Function
1 BST
Bootstrap. A capacitor connected between SW and BST pins is required to form a floating supply across the high-side switch driver.
2 GND Ground
Adjustable version feedback input. Connect FB to the center point of the external resistor divider. 4 EN 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.
5 VIN Power supply Pin
6 SW Switching Pin
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 3 - ABSOLUTE MAXIMUM RATINGS VIN, Supply Voltage -0.3V ~ 18V VSW, Switch Node Voltage -0.3V to (VIN+0.5V) VBST, Boost Voltage VSW-0.3V to VSW+5V VEN, Enable Voltage -0.3V ~ 18V All Other Pins -0.3V ~ 6V Operating Temperature Range -40ºC ~ +85ºC Storage Temperature Range -65ºC ~ +150ºC Lead Temperature (Soldering, 10s) 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 Conditions Min Typ Max Unit Input Voltage Range 4.5 - 16 V UVLO Threshold - 4.1 - V Supply Current in Operation VEN = 2.0V, VFB = 0.9V - 0.5 - mA Supply Current in Shutdown VEN = 0V - 5 10 uA Regulated Feedback Voltage 4.5V≤VIN ≤16V 0.588 0.6 0.612 V High-side Switch On Resistance VBST-SW = 5V - 150 - m Ω Low-side Switch On Resistance VIN = 5V - 70 - m Ω High-side Switch Leakage Current VEN = 0V, VSW = 0V - 0 10 uA Upper Switch Current Limit Minimum Duty Cycle - 3 - A Oscillation Frequency 350 500 700 kHz Maximum Duty Cycle VFB = 0.5V - 95 - % Minimum On Time - 100 - ns EN Input Voltage “H” 1.3 - - V EN Input Voltage “L” - - 0.4 V Thermal Shutdown - 170 - °C
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 4 - TYPICAL PERFORMANCE CHARACTERISTICS Tested under, L=4.7uH, TA=25°C, unless otherwise specified
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 5 - 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
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 6 - TYPICAL APPLICATION CIRCUITS 1. 12V VIN, 5V/2A 2. 12V VIN, 3.3V/2A
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 7 - 3. 12V VIN, 2.5V/2A 4. 12V VIN, 1.8V/2A 5. 12V VIN, 1.2V/2A
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 8 - BLOCK DIAGRAM
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 9 - 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 (V FB) 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 appl ications 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 vol tage 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 f irst 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.
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 10 - 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 =
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 11 - 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 V IN 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.
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 12 -
PACKAGE INFORMATION
Dimension in SOT-26 (Unit: mm)
AiT Semiconductor Inc. www.ait-ic.com A7222A DC-DC CONVERTER BUCK (STEP-DOWN) 500kHz, 16V , 2A SYNCHRONOUS REV1.0 - JUN 2018 RELEASED - - 13 - 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 not ice, 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, authori zed, 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 de ath, 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.