ROHM Semiconductor's General-Purpose Automotive MCU System Power Supplies for Start Stop Systems

Advanced design ensures optimum MCU performance even during cranking


KYOTO, Japan and SANTA CLARA, Calif., October 21, 2014 – ROHM Semiconductor has recently announced the development of system power supplies optimized for high-performance microcontrollers in a variety of automotive systems, from electronic power steering to fuel injection, including HEVs and EVs.


The newly developed BD39001EKV-C utilizes a proprietary boost-buck switching method that ensures stable voltage supply, even when the battery voltage drops during start–stop operation, while improving power conversion efficiency by up to 5% vs. conventional products. And in response to the continued standardization and advancements in the automotive industry a startup sequence setting function is included that can adapt to a variety of MCU specifications and requirements.

With the continuing trend towards platform standardization in the automotive industry comes a push to promote the use of common parts worldwide. This is expected to increase demand for versatile products that can suit a variety of requirements and support microcontrollers of all types – as well as high-performance devices and solutions optimized for customized dedicated power supplies and specific applications.

In addition, the need to minimize fuel consumption has led to the adoption of start-stop systems that stop the engine during idling and other brief stops in order to prevent wasteful fuel consumption. However, this requires countermeasures to prevent MCU malfunction due to battery voltage fluctuations caused by cranking when the engine is started again.

In response, ROHM quickly developed a versatile, standardized power supply IC capable of providing stable voltage after idling stop operation. The BD39001EKV-C utilizes leading-edge 0.35um BiCDMOS power processes and takes advantage of ROHM's analog design expertise to achieve a breakdown voltage of 40V with an ultra-low drive voltage of 4V, providing a wide input voltage range

ROHM's Original Boost-Buck Switching Method

And to ensure compatibility with start-stop systems, ROHM adopted a new boost-buck automatic switching control method that provides stable voltage to the MCU, even when the battery voltage fluctuates below 5V, while increasing power conversion efficiency by 5%.

Besides providing continuous, stable power supply for I/O (5V LDO) and the MCU core (3.3V DC/DC) based on a variable primary power supply, a number of surveillance functions are built in, including a watchdog timer that monitors MCU operation, improving reliability. The products also feature a compact form factor that contributes to end-product miniaturization.

Pricing: $5.26 ea
Availability: Now (Samples), Dec. 2014 (OEM Quantities)

Key Features

1. New boost-buck automatic switching control ensures stable operation even during cranking and increases energy savings by up to 5% over conventional products.
2. Startup sequence setting function compatible with virtually any MCU.
3. Watchdog timer function improves reliability.

Startup settings adjustable based on MCU


Product Lineup

Product Lineup


  • HEV / EV Inverters
  • Electronic Power Steering (EPS)
  • Fuel Injection (FI)
  • ADAS (Advanced Driver Assist Systems)
  • Other devices and systems utilizing high-performance 16bit/32bit MCUs



· LDOs and DC/DC Converters
DC/DC converters are normally preferred over LDOs when driving more sophisticated, high-performance microcontrollers (i.e. higher powered 16bit/32bit MCUs) in automotive applications.