A4447 High Voltage Step Down Regulator Features and Benefits Description Wide input voltage range: 8 to 50 V The A4447 is a 2 A, high efficiency general-purpose buck Integrated low R DMOS switch regulator designed for a wide variety of applications. The output DS(on) 2 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 Highly efficient an external clamping diode, inductor, and filter capacitor. Adjustable output: 0.8 to 24 V The off-time is determined by an external resistor to ground. Small package with exposed thermal pad It operates 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 2 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 Typical Application +42 V CBOOT Efficiency vs. Output Current 0.01 F CIN1 CIN2 90 0.22 F 5 BOOT VIN 85 3.3 D1 80 ENB LX L1 A4447 V OUT 75 1.8 3.3 V 2 A TSET VBIAS 70 RTSET R1 1.5 54 k7 2.87 k7 65 ESR V (V) GND FB OUT R3 A 60 COUT R2 C BYP 10 k7 220 F 0 500 1000 1500 2000 910 7 0.22 F 25 V A R3 required when C connected I (mA) BYP OUT Data is for reference only. Efficiency data from circuit shown in left panel. A4447-DS, Rev. 2 Efficiency %A4447 High Voltage Step Down Regulator Absolute Maximum Ratings Characteristic Symbol Conditions Min. Typ. Max. Units VIN Supply Voltage V 50 V IN VBIAS Input Voltage V 0.3 7 V BIAS SW Switching Voltage V 1 V S ENB Input Voltage Range V 0.3 7 V ENB Operating Ambient Temperature Range T 2085C A Junction Temperature T (max) 150 C J Storage Temperature T 55 150 C stg *Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current ratings, or a junction temperature, T , of 150C. J Thermal Characteristics*may require derating at maximum conditions, see application section for optimization Characteristic Symbol Test Conditions* Value Unit On 4-layer PCB based on JEDEC standard 35 C/W Package Thermal Resistance R JA (Junction to Ambient) 2 On 2-layer generic test PCB with 0.8 in. of copper area each side 62 C/W Package Thermal Resistance R 2 C/W JP (Junction to Pad) *Additional thermal information available on the Allegro website. Ordering Information Use the following complete part numbers when ordering: Part Number Packing Description LJ package, SOIC surface mount with A4447SLJTR-T 13-in. reel, 3000 pieces/reel exposed thermal pad leadframe plating 100% matte tin. Allegro MicroSystems, LLC 2 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000 www.allegromicro.com