Technical Information Site of Power Supply Design

Product Key Points

BD9227F: Step-down DC/DC Converter to Drive DC Fan Motor

Integrated Discrete Components for Higher Precision, Efficiency and Smaller Size

  • Component integration
  • DC fan motor
  • Incorporate a MOSFET
  • High-precision control
  • Enhanced efficiency
  • Fewer components
  • Faster operation

As with other electronic equipment, in recent years there have been mounting demands for intelligent, compact, and highly efficient motors. Nearly 50% of the world consumption of electric power is used to drive motors, and there is an urgent need to respond to these demands.

The BD9227F is the industry's first* power supply IC capable of controlling the rotational speed of DC fan motors with the high precision that would be difficult using conventional discrete components, achieved by linear control of the output voltage according to a PWM signal generated by the MCU. Through control optimization achieved by component integration, efficiency is dramatically improved, the number of components is decreased and faster switching is possible to enable miniaturization of peripheral components, so that the footprint can be reduced drastically. (*ROHM survey as of Nov. 18, 2016)

The BD9227F is a non-synchronous (diode) rectifying PWM-control step-down converter with 20 V input and 1 A output, optimized for DC fan motor power supplies. It incorporates a high-side power MOSFET, and the operating frequency is fixed at 1 MHz. Phase compensation is simplified by current-mode control and there are few external components; a ceramic output capacitor can be used. It is also equipped with overcurrent and overvoltage protection, thermal shutdown, and undervoltage lockout functions, and uses a compact SOP8 package. Its main features are as follows.



  • ・Wide operating input range (Vcc): 6 V to 20 V
  • ・Output voltage range: Vcc×0.25 to Vcc
  • ・20V/200mΩ internal Power MOSFET
  • ・Operating frequency: 1MHz (typ.) fixed
  • ・High-precision reference: ±1.0% (Ta=25℃)
     ±2.0% (over temperature)
  • ・Max output current: 1 A(max.)
  • ・Current mode
  • ・Overcurrent Hiccup protection
  • ・Undervoltage lockout (UVLO), Overvoltage
     Protection (OVP), Thermal shutdown (TSD)
  • ・Operating temperature range: –40℃ to +85℃


  • ・DC fan motor
  • ・Home appliance, etc.


  •  Compact SOP8 package: 5.00 mm × 6.20 mm
     × 1.71 mm



Discrete Components Integrated into IC

Conventional power supplies for DC fan motors, installed in refrigerators and other products, have mainly been configured using discrete components. By integrating these components into ICs, it has been possible to achieve high-precision control, enhanced efficiency, and more compact peripherals, resulting from fewer components and faster operation. Compared with discrete-component designs, efficiency has been increased by 19%, and footprint has been slashed by 75%.


Power Supply Design Technical Materials Free Download

Power Supply Design Technical Materials Free Download

This website uses cookies.


By continuing to browse this website without changing your web-browser cookie settings, you are agreeing to our use of cookies.