ROHM Semiconductor : BD9x family – DC-DC converter family supports both synchronous and asynchronous rectification

ROHM Semiconductor’s BD9x family of buck DC-DC converters meets a wide variety of application requirements, supporting input voltages ranging from 2.7V up to 42V, and output currents from 0.5A to 6.0A.

The family includes two devices that implement asynchronous rectification with current-mode control:

• the BD9G101G has an input-voltage range of 6V-42V and a maximum output current of 0.5A. It switches at a frequency of 1.5MHz. The output voltage ranges from 1.0V up to 70% of the supply voltage.
• the BD9E151NUX has an input-voltage range of 6V-28V, and an output current of 1.2A. Its switching frequency is 600kHz.

Synchronous rectification is also supported by the BD9x family, with some devices implementing current-mode control and others implementing on-time control.

This enables users to eliminate the external diode required with the asynchronous method. ROHM supplies various high-efficiency synchronous-rectification converters to cover a broad voltage range.

The current-mode control technique available with the BD9A, BD9E and BD9C series converters offers faster transient responses than the conventional voltage-mode control method. In addition, phase compensation can easily be set and output ripple reduced.

In addition, some ROHM converters use hysteresis control to provide faster transient response than current-mode control; these parts do not require phase compensation.

The BD9B series implements on-time control, and features a light-load mode, with a slower switching frequency to reduce the operating current when the load current decreases, helping to improve efficiency.

The packaging of the BD9x series of converters features an exposed pad for excellent heat dissipation from the back side of the package.


  • 45V/800mΩ internal MOSFET
  • 1.5MHz fixed switching frequency
  • Feedback pin voltage: 0.75V ±1.5%
  • Over-current protection
  • Under-voltage lock-out
  • Thermal shut-down
  • 5μA maximum stand-by current


  • Coin-processing machines
  • Portable data terminals
  • Portable medical equipment
  • Barcode scanners
  • Digital multimeters
  • Digital stethoscopes
  • Single-board computers
  • X-ray security scanners