A8447 High Voltage Step Down Regulator Discontinued PrNot forLast T New Designime Buyoduct These parts are no longer in production These parts are in production but have been determined to be These parts are in production but have been determined to be The device should not be LASTpurchased for new design applications. Samples are no longer available.NOT FOR NEW TIME BUY DESIGN This classification indicates that the product is This classification indicates that sale of obsolete and notice has been given. Sale of this device is currently this device is currently restricted to existing customer applications. restricted to existing customer applications. The device should not be purchased for new design applications The device should not be purchased for new design applications because of obsolescence in the because obsolescence in the near future is probable. Samples are no near future. Samples are no longer available.longer available. Date of status change: December 1, 2015Date of status change: February 1, 2006 Date of status change: April 2003 Deadline for receipt of LAST TIME BUY orders: April 28, 2006 Recommended Substitutions: For existing customer transition, and for new customers or new appli- cations, refer to the A8498. NOTE: For detailed information on purchasing options, contact your local Allegro field applications engineer or sales representative. Allegro MicroSystems, LLC reserves the right to make, from time to time, revisions to the anticipated product life cycle plan for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no respon- sibility for its use nor for any infringements of patents or other rights of third parties which may result from its use.A8447 High Voltage Step Down Regulator Features and Benefits Description Wide input voltage range: 8 to 50 V The A8447 is a 3 A, high efficiency general-purpose buck Integrated low R DMOS switch regulator designed for a wide variety of applications. The output DS(on) 3 A continuous output current voltage is adjustable from 0.8 to 24 V, based on a resistor divider Adjustable fixed off-time and the 0.8 V 2% reference. External components include an Highly efficient external clamping diode, inductor, and filter capacitor. The off- Adjustable output: 0.8 to 24 V time is determined by an external resistor to ground. It operates Small package with exposed thermal pad in both continuous and discontinuous modes to maintain light load regulation. An internal blanking circuit is used to filter out transients due to the reverse recovery of the external clamp diode. Typical blanking time is 200 ns. This new device is ideal for various end products including applications with 8 to 50 V input voltage range and require up to 3 A output current, such as uninterruptible power supplies, point of sale (POS) applications, and industrial applications with 24 or 36 V bus. Package: 8 pin SOIC with exposed thermal pad (suffix LJ) Applications include: Printer power supplies Office automation equipment POS thermal, laser, photo, and inkjet printers Tape drives Industrial applications Approximate Scale 1:1 Engineering samples available on a limited basis. Contact your local sales or applications support office for additional information. Typical Application +42 V CBOOT Efficiency vs. Output Current 0.01 F CIN1 CIN2 90.0 0.22 F 88.0 BOOT VIN 86.0 D1 84.0 82.0 ENB LX L 1 A8447 V 80.0 OUT 3.3 V 78.0 3 A TSET VBIAS V (V) OUT 76.0 RTSET R1 5 74.0 54 k 2.87 k 3.3 ESR 72.0 GND FB 70.0 COUT CBYP R2 220 F 0 500 1000 1500 2000 2500 3000 0.22 F 910 25 V I (mA) OUT Data is for reference only. Efficiency data from circuit shown in left panel. A8447-DS, Rev. 4 Conceptual Data Sheet Subject to Change Without Notice March 24, 2006 Efficiency %