BD9V100MUF-C：A DC-DC Converter with the Industry’s Highest Step-Down Ratio : The Advantage of a 24:1 Step-Down Ratio at 2 MHz

In June 2017, ROHM began sample shipments of the BD9V100MUF-C DC-DC converter IC with the industry’s highest step-down ratio, achieved with switching at 2 MHz, and in December 2017 announced that it would begin volume production.

Engineering samples of the BD9V100MUF-C were demonstrated at exhibits such as CEATEC in 2016, and the development had already been announced. Due to the high level of interest expressed, this device was immediately addressed in an “Ask Direct to Engineers” column (Japanese) of TECH INFO on ROHM’s Tech Web, with the title ” DC-DC Converter IC Capable of Direct Step-Down from 48 V to 3.3 V”, consisting of two articles: Part 1: Is Direct Step-Down from 48 V to 3.3 V Possible? and Part 2: Simplifying the Power Supplies of 48 V Hybrid Systems to Cut Losses.

In this article, we shall go over the features and specifications of the BD9V100MUF-C that have been formally released. There are generally no changes to the basic functions and features described in the article mentioned above, but the specifications and ratings for the product were provisional at that time, and there have been some changes. The initial edition of the data sheet has also been released, and should be consulted for further details.

The Advantage of a 24:1 Step-Down Ratio at 2 MHz

The BD9V100MUF-C is a MOSFET-based synchronous rectification step-down DC-DC converter IC. Through an ultra-high-speed pulse control technology ‘Nano Pulse ControlR’ developed uniquely by ROHM, high input voltages up to a maximum 60 V can be stepped down to a minimum 2.5 V at a switching frequency of 2 MHz. The step-down ratio is 24:1, making it the industry’s highest* step-down ratio. (*According to a 7/27/2017 survey by ROHM)

The BD9V100MUF-C is a DC-DC converter that also merits study for industrial use, but it was primarily intended for installation in automotive equipment in particular. The 2 MHz switching frequency means smaller peripheral components can be used, contributing to more compact power supply circuits, and at the same time, this frequency is a standard requirement for automotive systems to avoid interference with the AM radio band.

Moreover, for automotive systems that are driven by 48 V power supplies such as those in modern mild hybrid vehicles, 60 V input is actually sought in consideration of the fluctuations attending 48 V input, and so stepping down from 60 V to the system voltage of 5 V or 3.3 V becomes necessary. However, there had been no conventional power supply ICs capable of such high step-down ratios at a switching frequency of 2 MHz, and therefore two-step step-down designs requiring two step-down converters, for example to step down from 60 V to 12 V and then from 12 V to 5.5/3 V, were generally used.

The BD9V100MUF-C is capable of stepping down with ratios up to 24:1, and so can step down from 60 V to 2.5 V in one step. In other words, one DC-DC converter can be omitted, reducing space requirements and simplifying the power supply system.

In this way, the BD9V100MUF-C achieves a high step-down ratio under 2 MHz operation, and so represents a solution to such urgent problems in automotive subsystems as miniaturization and avoidance of AM radio interference (through 2 MHz operation), as well as power supply circuit simplification and reduction of space requirements (by stepping down from 60 V/48 V to low voltages in one step).