ROHM Develops Industry’s First Direct Step-Down (48V to 3.3V) DC/DC Converter IC


Reduces design load and provides greater compactness, improved efficiency, and safer operation in automotive and industrial applications

ROHM has recently announced the development of a DC/DC converter IC featuring the lowest minimum ON time in the industry. This enables stable direct step-down conversion to 3.3V or 5V from a wide input voltage range – including 48V used in the automotive and industrial sectors. Significantly increasing the step-down ratio allows the BD51180TL to eliminate the need for intermediate conversion utilizing a secondary power supply IC, while current mode control makes it possible to simplify phase compensation, lightening design load, improving efficiency, and contributing to end-product miniaturization.

In recent years, there is a growing need to conserve energy in all areas, including in the automotive sector where attention has focused on 48V systems for hybrid vehicles that take safety into account and provide better fuel economy than conventional 12V systems. However, until now there has not been a power supply IC available with a high enough step-down ratio to directly convert 48V to the 3.3V or 5V required to drive control systems and automotive MCUs. Normally, 2 step-down stages are necessary to create an intermediate voltage such as 12V. Moreover, high frequency operation over 2MHz is needed to prevent interference with AM radio bands.

Proprietary technology for controlling pulses in a very short time allowed ROHM to reduce the minimum ON time to an unprecedented 20ns – 6x shorter than conventional solutions – enabling stable step-down operation from 48V to 3.3V at a constant switching frequency of 2MHz. In addition, current mode control provides easy phase compensation required for constant voltage output with fewer external parts, contributing to greater end-product miniaturization while reducing customer design load. And integrating ROHM’s high voltage MOSFET expands the input voltage range to 65V, 4.6x higher than conventional products, ensuring compatibility with a wider range of applications.


Key Features

  1. 02_EBreakthrough minimum ON time provides stable buck operation

Leveraging original technology for controlling pulses in a very short period makes it possible to reduce the minimum ON time to an unprecedented 20ns, 6x shorter than the conventional level. This ensures stable 3.3V output from 48V battery systems for driving various functions and control blocks while enabling 2MHz operation that prevents interference with AM radio band frequencies.

  1. 03_ECurrent mode control simplifies phase compensation

Switching power supplies such as DC/DC converters typically include a feedback circuit and require phase compensation to prevent abnormal oscillation. ROHM’s new IC employs current mode control capable of controlling the current using very short pulse widths, simplifying phase compensation while reducing design load. In addition, only 2 components are required to ensure stable operation over a wide input voltage range.

  1. 04_E1Broad input voltage range supports a wider variety of applications.

Integrating ROHM’s high voltage MOSFET makes it possible to expand the input voltage range by over 4.6x vs conventional products, from 12V to 65V, enabling compatibility with a wider range of applications – including industrial equipment and automotive systems.

  1. Compact package offers superior heat dissipation

Typically, increasing the breakdown voltage requires greater heat dissipation, making it difficult to reduce size. However, ROHM’s VQFN24SV4040 package adopts a backside heat sink that reduces size to a compact 4.0×4.0x1.0mm form factor – 54% smaller than conventional products – by significantly improving heat dissipation.

  1. Multiple protection functions improve safety and reliability

Standard protection circuits are built in to ensure safe operation and provide a greater degree of reliability.

  • AEC-Q100 qualified
  • Overcurrent protection
  • Input undervoltage lockout protection
  • Input overvoltage protection
  • Output overvoltage protection
  • Thermal shutdown
  • Short-circuit protection