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Diodes Pericom: A product line of Diodes Incorporated
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The AP3591 is a synchronous adaptive on-time buck controller providing high efficiency, excellent transient response and high DC output accuracy for low voltage regulation in notebook application.
The constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and features small external component count and fast transient response.
The operation mode is selectable by EN voltage. A Diode Emulation Mode (DEM) is activated for increasing efficiency at light loads, while PWM mode is activated only for low noise operation. The AP3591 also integrates internal Soft-start, UVLO, OVP, OTP, and programmable OCP to protect the circuit. A Power Good signal is employed to monitor the output voltage.
The AP3591 is available in U-QFN3535-14 package.


  • Notebook Computer, AIO PC
  • Low-voltage Distribute Power
  • I/O Supplies


  • Fixed Frequency Constant On-time Control; Resistor Programmable Frequency Adjustable from 100kHz to 700kHz
  • Good Stability Independent of the Output Capacitor ESR
  • Quick Load Step Response
  • Input Voltage Range: 4.5V to 26V
  • Output Voltage Range: 0.75V to 5.5V
  • CCM/DEM Mode Selection
  • Integrated Bootstrap Diode
  • Resistor Programmable Current Limit by Low-side RDSON Sense
  • Integrated Negative Over Current Limit
  • Integrated OVP/UVP and Over Thermal Shutdown Function
  • Power Good Indicator
  • Internal Soft-start
  • Integrate Output Discharge (Soft-stop)
  • Safe Start-up into Pre-biased Loads
  • Totally Lead-Free & Fully RoHS Compliant 
  • Halogen and Antimony Free. “Green” Device

Product Specifications

Product Specs

Type Buck
Minimum Input Voltage 4.5
Maximum Input Voltage 26
Output Voltage 0.75 to 5.5
Frequency 100K to 700K
Efficiency 93

Quality & Reliability