Wide Vin 4.5-28V, 8A, COT Synchronous Step-Down Converter, External Bias Needed

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Product Description

The NB639 is a fully integrated, high frequency synchronous rectified step-down switch mode converter. It offers a very compact solution to achieve 8A continuous output current over a wide input supply range with excellent load and line regulation. The NB639 operates at high efficiency over a wide output current load range. To further optimize efficiency at light load, this device’s VCC supply is designed to be biased externally. Constant-On-Time (COT) control mode provides fast transient response and eases loop stabilization. Full protection features include SCP, OCP, OVP, UVP and thermal shutdown. The NB639 requires a minimum number of readily available standard external components and is available in a space-saving 3mm x 4mm 20-pin QFN package.


Product Features

  • Wide 4.5V to 28V Operating Input Range
  • 8A Output Current
  • Internal 30mΩ High-Side, 12mΩ Low-Side Power MOSFETs
  • Proprietary Switching Loss Reduction Technique
  • 1% Reference Voltage
  • Programmable Soft Start Time
  • Soft Shutdown
  • Programmable Switching Frequency
  • SCP, OCP, OVP, UVP Protection and Thermal Shutdown
  • Output Adjustable from 0.8V to 13V
  • Available in a 20-pin 3x4mm QFN Package


  • fsw (max) (kHz)0
  • Vin (min) (V)4.5
  • Vin (max) (V)28
  • Iout (max) (A)8
  • Isw Limit (typ) (A)16.5
  • Vfb (typ) (V)0.815
  • Iq (typ) (mA)0.04
  • Regulated Outputs1
  • Vout (max) (V)13
  • Vout (min) (V)0.815
  • GradeCatalog
  • PackageQFN-20 (3x4)
  • Control ModeCOT
  • Common FeaturesExternal Soft Start, Light-Load Efficiency, Power Good, Synchronous Rectification
  • Special FeaturesProgrammable Frequency, Soft Stop