Diodes Incorporated

AP3581B (Obsolete)

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The1AP3581A/B/C1is1a1compact1synchronous-rect ified buck controller specifically designed to operate from 5V/12V supply and deliver high-quality output voltage as low as 0.6V (AP3581A) or 0.8V (AP3581B/C). The AP3581A/B/C operates at fixed frequency of 300kHz (AP3581A/B) or 200kHz (AP3581C) and provides an optimal level of integration to reduce size and cost of the power supply. This controller integrates internal MOSFET drivers that support 12V+12V bootstrapped voltage for highefficiency power conversion. The bootstrap diode is built-in to simplify the circuit design and minimize external part count. This controller provides single feedback loop, voltage-mode control with fast transient response. The error amplifier features a 10MHz gain-bandwidth product and 6V/μs slew rate which enables high converter bandwidth for fast transient performance. Other features include internal soft-start, under voltage protection, over current protection and shutdown function. With afore-mentioned functions, this part provides customers a compact, high efficiency, well-protected and cost-effective solutions.


  • Supply Voltage: 5V/12V
  • VIN Input Range: 3.0V to 13.2V
  • 0.6V/0.8V to 80% of VIN Output Range
  • Internal Reference: 0.6V/0.8V
  • Simple Single-loop Control
  • Voltage-mode PWM Control
  • Duty Cycle: 0% to 80%
  • Fast Transient Response
  • 10MHz High-bandwidth Error Amplifier with 6V/μs Slew Rate
  • Fixed Oscillator Frequency: 300kHz/200kHz
  • Lossless, Programmable Over Current Protection (Uses Lower MOSFET RDS(ON) )
  • Start-up into Pre-biased Output
  • Built-in Thermal Shutdown
  • Built-in Soft-start
  • Over Current/Voltage Protection
  • Under Voltage Protection
  • Integrated Boot Diode


  • Power Supplies for Microprocessors/Peripherals
  • PCs, Embedded Controllers, Memory Supplies
  • DSP and Core Communications Processor Supplies
  • Subsystem Power Supplies
  • PCI, AGP, Graphics Cards, Digital TV
  • SSTL-2 and DDR/2/3 SDRAM Bus Termination Supply
  • Cable Modems, Set Top Boxes, and DSL Modems
  • Industrial Power Supplies and General Purpose Supplies
  • 5V/12V Input DC-DC Regulators
  • Low-voltage Distributed Power Supplies

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