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AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 1 - DESCRIPTION FEATURES The A7322 is a fully integrat ed, synchronous rectified step-down converter that provides wide 4.2V to 28V input voltage range and 2A continuous load current capability. The A7322 can operate at PFM mode to achieve high efficiency and reduce power loss at light load. In shutdown mode, the Max supply current is about 3μA. The A7322 protection function includes cycle-by-cycle current limit, UVLO and thermal shutdown. Besides, internal soft-start prevents inrush current at fast power- on. This device uses slope compensated current mode control which provides fast load transient response. Internal loop compensation function reduces the external compensator components and simplifies the design process. The A7322 is available in PSOP8 package.
ORDERING INFORMATION
SPQ: 2,500pcs/Reel MP8 A7322MP8R A7322MP8VR Note V: Halogen free Package R: Tape & Reel AiT provides all RoHS products Wide input voltage range: 4.2V to 28V 2A output current 0.8V reference voltage Low R DS(ON) integrated power MOSFET (180/110mΩ) 3μA(Max) shutdown current Integrated internal compensation High efficiency at light load Internal 1ms soft-start Cycle-by-cycle current limit Over-temperature protection with auto recovery Under voltage lockout(UVLO) Hiccup short circuit protection Available in PSOP8 package APPLICATION Distributed power system Flat panel television and monitors STB (set-top-box) Networking, XDSL modem TYPICAL APPLICATION 1. CIN & COUT use ceramic capacitors application circuit 2. L= AiT Semi’s # WSI05030E-4R7M
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 2 - PIN DESCRIPTION Top View Pin # Symbol Description 1 BST High side power transistor gate drive boost input. 2 V IN Power input. Bypass with a 22uF ceramic capacitor to GND. 3 SW Power switching node to connect inductor.
4 GND Ground
5 FB Feedback input with refe rence voltage set to 0.8V.
6 NC No connection
7 EN Enable input. Set this pin to high level to enable the part, low level to disable.
8 NC No connection
Ground. The exposed pad must be soldered to a large PCB area an d connected to GND for maximum power dissipation.
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 3 - ABSOLUTE MAXIMUM RATINGS VIN, Supply Voltage -0.3V ~ 30V VSW, Switch Node Voltage -0.3V ~ (V IN+0.5V) VBST, Boost Voltage V SW-0.3V ~ VSW+5V VEN, Enable Voltage -0.3V ~ 12V The Others Pins -0.3V ~ 6V Operating Temperature Range -40°C ~ 85℃ Storage Temperature Range -65°C ~ 150℃ Lead Temperature (soldering, 10s) 300℃ Stress beyond above listed “Absolut e Maximum Ratings” may lead permanent damage to the device. These are stress ratings only a nd operations of the device at these or any other conditions beyond those indicated in the operati onal sections of the specificat ions are not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED WORK CONDITIONS Parameter Symbol Conditions Min Typ Max Unit Supply Voltage V IN 4.2 - 28 V Ambient Temperature -40 - 85 ℃
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 4 -
ELECTRICAL CHARACTERISTICS
VIN=12V, TA=25℃, unless otherwise stated Parameter Conditions Min Typ Max Unit Input Voltage Range 4.2 - 28 V UVLO Threshold V IN rising - 3.8 - V UVLO Hysteresis V IN falling - 200 - mV Supply Current in Operation V EN = 5V, VFB = 1V - 150 - uA Supply Current in Shutdown V EN = 0V - 1 - uA Regulated Feedback Voltage 3.8V ≤ V IN ≤ 28V 0.784 0.8 0.816 V High-side Switch on Resistance V BST-SW = 5V - 180 - mΩ Low-side Switch on Resistance V IN = 5V - 110 - mΩ High-side Switch Leakage Current V EN = 0V, VSW = 0V - 0.1 10 uA Upper Switch Current Limit Minimum duty cycle 3 - - A Oscillation Frequency - 500 - kHz Maximum Duty Cycle - 93 - % Minimum on Time - 100 - ns EN Input Voltage “H” 1.5 - - V EN Input Voltage “L” - - 0.6 V Thermal Shutdown - 160 - °C
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 5 - TYPICAL PERFORMANCE CHARACTERISTICS
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 6 - 7. Steady State Waveform VIN=12V, VOUT=3.3V, CIN=COUT=10μF*2, L=4.7μH, IOUT=0A Ch1—VIN, Ch2—VOUT, Ch3—VSW, Ch4—ISW 8. Steady State Waveform VIN=12V, VOUT=3.3V, CIN=COUT=10μF*2, L=4.7μH, IOUT=2A Ch1—VIN, Ch2—VOUT, Ch3—VSW, Ch4—ISW 9. Load Transient VIN=12V, VOUT=3.3V, IOUT=0.01~1A Ch2—VOUT, Ch4—IL 10. Load Transient VIN=12V, VOUT=3.3V, IOUT=1~2A Ch2—VOUT, Ch4—IL
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 7 - BLOCK DIAGRAM
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 8 - DETAILED INFORMATION The A7322 is a wide input range, high-efficiency, DC-to-DC step -down switching regulator, capable of delivering up to 2A of output current, integrated with a 180/110mΩ synchronous MOSFET pair, eliminating the need for external diode. It uses a PWM current-mode control sch eme. An error amplifier integrates error between the FB signal and the internal reference voltage. The output of the integrator is then compared to the sum of a current-sense signal and the slope compensation ramp. This operation generates a PWM signal that modulates the duty cycle of the power MOSFETs to achieve regulation for output voltage. Internal soft-start The soft-start is important for many applications because it el iminates 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 A7322 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 u ntil FB falls below the Under-Voltage (UV) threshold (typically 300mV) to trigger a UV event, the A7322 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 t o protect the regulator. The A7322 exits hiccup mode once the overcurrent condition is removed. Light load operation Traditionally, a fixed constant frequency PWM DC-DC regulator always switches even when the output load is small. When energy is shuffling back and forth through the powe r MOSFETs, power is lost due to the finite RDSONs of the MOSFETs and parasitic capacitances. At light load , this loss is prominent and efficiency is therefore very low. A7322 employs a proprietary control scheme that improves efficiency in this situation by enabling the device into a power save mode during light load, t hereby extending the range of high efficiency operation. 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 volt age 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 d own. The floating driver is not subject to this shutdown command.
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 9 -
APPLICATION INFORMATION
The external resistor divider is used to set the output voltage. The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. R2 is then given by: R 2 = R1 VOUT / VFB -1 Selecting the inductor Use a 2.2μH-to-6.8μH inductor with a DC current rating of at least 25% higher than the maximum load current for most applications. For most designs, derive the inductance value from the following equation: L= VOUT x (VIN - VOUT ) VIN x ΔIL x 𝑓OSC Where ΔIL is the inductor ripple current. Choose an inductor current approximately 30% of the maximum load current. The maximum inductor peak current is: ILሺMAXሻ = ILOAD+ ΔIL Under light-load conditions (below 100mA), use a larger inductor to improve efficiency. Selecting the output capacitor The output capacitor maintains t he DC output voltage. Use ceram ic, tantalum, or low-ESR electrolytic capacitors. Use low ESR capacitors to limit the output voltage ripple. Estimate the output voltage ripple with: ΔV OUT = VOUT 𝑓S x L x 1- VOUT VIN ൨ x RESR + 1 8 x 𝑓S x C2 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 = VOUT 8 x 𝑓ௌ ଶ x L x C2 x 1- VOUT VIN
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 10 - For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with: ΔVOUT = VOUT 𝑓ௌ x L x 1- VOUT VIN ൨ x RESR The characteristics of the output capacitor also affect the stability of the regulation system. The A7322 can be optimized for a wide range of capacitance and ESR values. Selecting the external boost diode It is recommended to add an external Boost Diode to improve efficiency and stability in these situations when the input voltage is fixed at 5.0V.Any a readily and cheap diod e can meet the need of these application such as AiT Semi’s 1N4148.
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 11 - TYPICAL APPLICATION Fig 11. CIN & COUT use ceramic capacitors application circuit Fig 12. CIN & COUT use electrolytic capacitors application circuit NOTE: If the input voltage is below 12V, R1 can be set to 0K and R2 can be removed. Table1. Recommended component values VIN=24V, the recommended BOM list is shows as below. VOUT C1 C2 L R3 R4 C4 Fig 11. 10uF MLCC 10uF MLCC 3.3uH-6.8uH, WSI06030E-3R3M~6R8M 68K 13K 22uF MLCC 3.3V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 47K 15K 2.8V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 30K 12K 2.5V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 39K 18K 1.8V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 15K 12K 1.2V 2.2uH-3.3uH, WSI06030E-2R2M~3R3M 7.5K 15K Fig 12. 100uF/35V ECL 0.1uF MLCC 3.3uH-6.8uH, WSI06030E-3R3M~6R8M 68K 13K 220uF/6.3V ECL 3.3V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 47K 15K 2.8V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 30K 12K 2.5V 2.2uH-4.7uH, WSI06030E-2R2M~4R7M 39K 18K 1.8V 2.2uH-3.3uH, WSI06030E-2R2M~3R3M 15K 12K 1.2V 2.2uH-3.3uH, WSI06030E-2R2M~3R3M 7.5K 15K
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 12 -
PACKAGE INFORMATION
Dimension in PSOP8 Package (Unit: mm) Symbol Millimeters Min Max A 1.350 1.70 A1 0.0 0.120 A2 1.350 1.550 b 0.330 0.510 c 0.170 0.250 D 4.700 5.100 D1 3.202 3.402 E 3.800 4.000 E1 5.800 6.200 E2 2.313 2.513 e 1.270(BSC) L 0.400 1.270 θ 0° 8°
AiT Semiconductor Inc. www.ait-ic.com A7322 DC-DC CONVERTER BUCK (STEP-DOWN) 28V, 2A, 500kHZ SYNCHRONOUS REV1.1 - MAY 2020 RELEASED – AUG 2022 UPDATED - - 13 - IMPORTANT NOTICE AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to discontinue any integrated circu it product or service without n otice, and advises its customers to obtain the latest version of relevant information to verify, before placin g orders, that the information being relied on is current. AiT Semiconductor Inc.'s integrat ed circuit products are not de signed, intended, authorized, or warranted to be suitable for use in life support applications, devices or sy stems 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 servere 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.