BD9V100MUF-C：A DC-DC Converter with the Industry's Highest Step-Down RatioProvision of ROHM’s Unique Nano Pulse Control®

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 datasheet has also been released, and should be consulted for further details.

Nano Pulse Control^®, ROHM’s Original Leading-Edge Power Supply Technology

Nano Pulse Control^®is an ultra-high-speed pulse control technology that combines three advanced ROHM technologies in the circuit design, layout, and process areas. It is a leading-edge technology that contributes to simplification of 48 V power supply systems for mild hybrid vehicles, industrial robots, sub-power supplies of base stations and the like, and also helps to reduce their application sizes.

A new product, the BD9V100MUF-C, is equipped with Nano Pulse Control, consisting of an ultra-high-speed pulse control circuit, optimized pattern layout, and high-voltage BiCDMOS processes. Nano Pulse Control makes possible stable control using the world’s lowest* switching ON time of 9 ns (typ) for a power supply IC, to achieve high-speed switching at up to a maximum 2.3 MHz and an industry-highest 24:1 step-down ratio.   *As of July 27 2017; result of a ROHM survey

Advantages Afforded by Nano Pulse Control

1) A conventional two-step step-down design can be achieved in one step, so that the footprint of the power supply circuitry can be reduced by 50% or more.

The minimum ON time of the BD9V100MUF-C is 9 ns (typ), 20 ns (max). This minimum ON time is made more stable through Nano Pulse Control, so that, for example at a switching frequency of 2 MHz, up to a maximum 60 V can be stepped down directly to a minimum of 2.5 V. The following waveform diagram was actually measured under conditions of a switching frequency of 2.1 MHz, with 60 V input and 3.3 V output. Under these conditions, the ON time is 1/2.1 MHz × (3.3 V/60 V) ? 26.2 ns. The reader should above all note that this short pulse is extremely well-formed and stable. Of course the output is also a well-behaved and stable stepped-down voltage.

Nearly all conventional high-voltage step-down DC-DC converter ICs have been incapable of this level of control, and so in stepping down from higher voltages such as 60 V or 48 V, they have used two steps in which, for example, 60 V is first stepped down to 12 V, and then the 12 V is used to generate 3.3 V or 2.5 V. Of course if the switching frequency is lowered, this kind of control is possible, but in order to avoid interference with AM radio in automotive applications, the switching frequencies in switching power supplies are generally set to 2 MHz or higher.

The advantages of stepping down the voltage in one step rather than two steps are obvious. The power supply circuitry consists of a single circuit instead of two circuits, and the board footprint for the power supply circuitry is roughly halved.

2) Higher switching frequencies mean smaller external components can be used, for approximately a 60% reduction in footprint

As explained above, the BD9V100MUF-C is capable of, for example, stepping down from 60 V or 48 V to 3.3 V or 2.5 V using a switching frequency of 2 MHz. As the switching frequency increases, the values required of the inductors and capacitors that are the external components required in a switching power supply are lowered. This means that component sizes can also be reduced, and so by raising the switching frequency, the footprint required by the circuit can be slashed as well.

The following graphic compares cases for switching frequencies of 300 kHz and 2 MHz. The footprint is cut from 6 mm2 to 2.4 mm2, a reduction of about 60%.

BD9V100MUF-C Key Specifications（For details, refer to the datasheet from the link below.）