A4447 ALLEGRO [Allegro MicroSystems], A4447 Datasheet
A4447
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A4447 Summary of contents
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... Data is for reference only. Efficiency data from circuit shown in left panel. A4447-DS, Rev. 1 High Voltage Step Down Regulator Description The A4447 high efficiency general-purpose buck regulator designed for a wide variety of applications. The output voltage is adjustable from 0 based on a resistor divider and the 0.8 V ± reference. External components include an external clamping diode, inductor, and filter capacitor ...
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... T Package Thermal Characteristics* R θJA Package (°C/ Additional information is available on the Allegro website. Ordering Information Use the following complete part numbers when ordering: Part Number A4447SLJTR-T High Voltage Step Down Regulator Symbol Conditions BIAS ENB ...
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... A4447 BOOT V IN ENB μC TSET GND VBB UVLO TSD High Voltage Step Down Regulator Functional Block Diagram Boot Charge – Switch PWM Control Switch Disable Clamp + – – I_Peak I_Demand Error COMP Soft Start Ramp Generation VIN LX L1 ESR D1 COUT ...
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... A4447 ELECTRICAL CHARACTERISTICS Characteristics VIN Quiescent Current 3 VBIAS Input Current Buck Switch On Resistance Fixed Off-Time Proportion Feedback Voltage Output Voltage Regulation Feedback Input Bias Current Soft Start Time Buck Switch Current Limit ENB Open Circuit Voltage ENB Input Voltage Threshold ENB Input Current ...
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... VOUT when the V target level is between 3.3 and OUT the output voltage is less than 3.3 V, then the A4447 can operate with an internal supply and pay a penalty in efficiency, as the bias current will come from the high voltage supply, VIN. VBIAS can also be supplied with an external voltage source. No power-up sequencing is required for normal operation ...
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... A4447 L1. The inductor must be rated to handle the total load current. The value should be chosen to keep the ripple current to a reason- able value. The ripple current, I RIPPLE = V × RIPPLE L(OFF) OFF L(OFF) OUT L(AV) f Example: Given 0. ...
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... A4447 RTSET Selection. Correct selection of RTSET values will ensure that minimum on time of the switcher is not violated and prevent the switcher from cycle skipping. For a given ratio, R must be greater than or equal to the value OUT TSET defined by the curve in the RTEST Value Selection graph below. ...
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... VOUT node to be located as close as practical to the A4447 (U1). Thermal conduction from the A4447 is enhanced by direct contact of its exposed thermal pad to the smaller ground area under the A4447. This area is connected by thermal vias to the large copper ground plane on the unpopulated side of the PCB. ...
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... A4447 4.90 ±0.10 8 2.41 NOM 3.30 NOM 8X 0.10 C 0.51 0.31 1.27 BSC Pin Out Diagram BOOT 1 ENB 2 Pad TSET 3 GND 4 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 ...