A4402 ALLEGRO [Allegro MicroSystems], A4402 Datasheet
A4402
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A4402 Summary of contents
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... Constant On-Time Buck Converter with Integrated Linear Regulator Description The A4402 is a power management IC that combines a 2% constant on-time buck regulator and a 2% linear regulator. Ideal for applications that require two regulated voltages. The buck regulator output supplies the adjustable linear regulator to reduce power dissipation and increase overall efficiency ...
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... A4402 Selection Guide Part Number A4402ELPTR-T 4000 pieces per 13-in. reel Absolute Maximum Ratings Characteristic VIN1 Pin VIN2 Pin LX Pin ISEN Pin ENB Pin VO2 Pin WDI Pin TON Pin FB1 and FB2 Pins NPOR Ambient Operating Temperature Junction Temperature Storage Temperature Range ...
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... A4402 C TSET TSET 0.15 μF WDI C POR POR 0.33 μF ENB kΩ NPOR WDI 4.7 kΩ Constant On-Time Buck Converter with Integrated Linear Regulator Functional Block Diagram V REF Soft Start Boot Ramp Generator Charge Watchdog Timer Switch PWM Control V FB2 Switch Disable ...
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... A4402 ELECTRICAL CHARACTERISTICS Characteristics Symbol Input Voltage Supply 1 Input Voltage Supply 2 Supply Quiescent Current ENB Logic Input Voltage ENB Hysteresis V ENB Logic Input Current Linear Regulator Output Voltage Range Feedback Voltage V Undervoltage Lockout O2 V Threshold V Undervoltage Lockout O2 V O2UVHYS Hysteresis Feedback Input Bias Current ...
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... A4402 ELECTRICAL CHARACTERISTICS Characteristics Symbol Protection Circuitry NPOR Output Voltage V NPOR Leakage Current NPOR Reset V NPORRESET Thermal Shutdown Threshold Thermal Shutdown Hysteresis T Timing Circuitry TSET Current, Watchdog Mode I TSETWDI TSET Valley Voltage, Watchdog Mode TSET Reset Voltage, Watchdog V Mode WDI Frequency ...
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... A4402 Power-Up and Power-Down Timing Diagrams Using ENB ENB VIN1 LIN NPOR Using VIN1 VIN1 LIN NPOR VPOR VCTSET Constant On-Time Buck Converter with Integrated Linear Regulator t ss UVLO Rising UVLO Falling t por t ss UVLO Rising t por UVLO Rising ...
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... A4402 ENB VO2 NPOR WDI V TSET Constant On-Time Buck Converter with Integrated Linear Regulator Watchdog Timing Diagram UVLO Rising t por t wait V reset t por t wait V trip Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 ...
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... A4402 Basic Operation The A4402 contains a fixed on-time, adjust- able voltage buck switching regulator with valley sensing current mode control, and an adjustable linear regulator designed to run off the buck regulator output. The constant on-time converter maintains a constant output frequency because the on-time is inversely proportional to the supply voltage ...
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... A4402 TSET The TSET pin serves a dual function by controlling the timing for both the soft start ramp and the WDI input. The current sourced from the TSET pin is dependant on the state of NPOR. There are two formulas for calculating the time constants. C must be selected so that both the WDI frequency and soft start requirements are met ...
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... Thermal Shutdown When the device junction temperature sensed thermal shutdown circuit disables the JTSD regulator output, protecting the A4402 from damage. Power-on Reset Delay The POR function monitors the V voltage and provides a signal that can be used to reset a DSP or microcontroller. A POR event is triggered by either of the follow- ing conditions: • ...
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... A4402 Switcher On-Time and Switching Frequency In order for the switcher to maintain regulation, the energy that is transferred to the inductor during the on-time must be transferred to the capacitor during the off-time. Because of this relationship, the load current, IR drops, as well as input and output voltages, affect the on-time of the converter ...
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... A4402 Worst-case ripple current occurs at maximum supply voltage. After calculating the duty cycle, DC, for this condition, the ripple current can be calculated. First to calculate DC × SENSE (max IN1 f SENSE Using the duty cycle, a ripple current can be calculated using the ...
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... ENB C2 VIN1 R1 GND BOOT D1 ISEN POR R2 C4 FB1 R3 VIN1 GND Solder A4402 Trace (2 oz.) PCB Thermal Vias Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com Star Ground Signal (1 oz.) Ground (1 oz.) Thermal (2 oz.) 13 ...
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... A4402 Power Terminals GND GND V IN1 BOOT GND V IN2 VO2 GND Constant On-Time Buck Converter with Integrated Linear Regulator Pin Circuit Diagrams V IN1 TON GND VIN1 54 V GND Logic Terminals VIN2 FB1 FB2 WDI 7 V TSET NPOR POR ...
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... A4402 5.00 ±0. 3.00 16X 0.10 C +0.05 0.65 0.25 –0.06 Copyright ©2008-2009, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products ...