Development Background

The proliferation of hybrid and electric vehicles in response to the growing need to curb CO₂ emissions on a global scale has brought attention (particularly in Europe) to mild hybrid vehicles that provide better cost performance than full hybrids. Mild hybrid systems utilize a 48V lithium ion battery to deliver greater efficiency over conventional 12V power supplies. However, the many ECUs used in many vehicle systems demand lower drive voltages, typically 3.3V but as low as 2.5V.
To convert 48V to 3.3V at 2MHz (to prevent interference with the AM radio band) conventional solutions employ 2 stages (2 chips), the first to step-down to an intermediate voltage such as 12V. In 48V systems it is also necessary support step-down operation from a maximum voltage of 60V to 2.5V, requiring an extremely high step-down ratio of 24:1 when using a single chip.

Technology Development and Commercialization

At ROHM, we challenged ourselves with the extremely high goal of developing ultra-high-speed pulse control technology (Nano Pulse Control) for monolithic (single-chip) DC/DC converters. As a result, we were able to reduce the switching ON time to an unprecedented 9ns, the smallest in the world and a breakthrough accomplishment considering that the typical ON time is around 120ns. Another major benefit of this technology is stable control at extremely narrow pulse widths.
Development involved breaking from convention by leveraging proprietary analog design technology and power supply process expertise along with our vertically integrated production system. As a result, step-down operation from 60V to 2.5V is achieved through the BD9V100MUF monolithic buck DC/DC converter with integrated MOSFET.

A world of possibilities

Developing a DC/DC capable of stepping down from 60V to 2.5V on a single chip significantly reduces the number of parts compared to conventional 2-chip systems. In particular, at higher frequencies it becomes possible to greatly reduce the size of the coil.

This will allow users to simplify system design, reduce application size, and at the same time decrease costs. For example, minimizing the size and costs of 48V power supply systems used for mild hybrid cars, industrial robots, and base station sub-power supplies is expected to contribute to the advancement of society.

In addition to the BD9V100MUF, ROHM will continue to develop products incorporating Nano Pulse Control to meet customer demands.

Development Background

In the electronic equipment field, in addition to the increasing functionality of smartphones and widespread use of wearables, the introduction of IoT devices that can operate and communicate wirelessly between devices without human intervention is attracting attention. In many cases these devices are driven by batteries, making it necessary to reduce power consumption. And although improving design and securing space for integrating new functions are progressing, miniaturization is also an important factor, leading to smaller drive batteries, but there is a large number of devices where maintenance (i.e. changing batteries) cannot be carried out regularly, especially in the IoT field, driving the demand to enable long-term operation (10 years) on a single coin battery.
In response to these market trends and themes, ROHM began developing technologies to significantly reduce IC power consumption. At the start, the lowest current consumption in the industry for power supply ICs was 360nA. This provided a baseline for our efforts.

Technology Development and Commercialization

When simply considering reducing current consumption, the first option is to raise the resistance value of the circuit, but this can lead to problems such as element current leakage, increased sensitivity to noise, and reduced response speed. In response, ROHM developed Nano Energy, a breakthrough technology that decreases current consumption during ultra-light loads while minimizing the ensuing trade-off. The result is a current consumption of 180nA, the smallest in the world*.

This technology was used to develop the BD70522GUL DC/DC converter, which delivers twice the battery drive time of conventional products at no-load (standby). In addition, high 90% power efficiency is enabled in the widest current range in the industry: 10uA to 500mA. ROHM was able to achieve these characteristics by leveraging proprietary circuit design, layout, and process technologies with its original vertically integrated production system.

A world of possibilities

Dramatic reductions in the power consumption of power supply ICs in the IoT field has brought about a demand to achieve 10-year drive on a single coin battery. This allows for a reduction in the amount of labor and costs required for device maintenance by enabling long-term drive with small batteries even in wearables that are becoming increasingly compact and multifunctional.

In addition, it will be possible to continue operation even in extremely low-power environments, such as energy harvesting systems that generate small amounts of electricity from light, heat, and vibration (which is expected to see increased adoption in a variety of fields).
At ROHM, Nano Energy will be used as a core technology to expand its lineup of power supply ICs to meet a range of customer requirements. At the same time, we plan on promoting the use of PMICs (Power Management ICs).

Development Background

ROHM is committed to further enhancing the development of Nano Cap™ technology to completely eliminate the need for capacitors while expanding the use of this technology not only to linear regulators, but Op amps, LED drivers, and other analog ICs as well, which contribute to society through the effective use of resources that minimizes environmental load.

Details of Technology

Nano Cap provides stable control of linear regulator output by improving response in analog circuits while minimizing parasitic factors related to wiring and amplifiers, making it possible to reduce the output capacitance to less than 1/10th over conventional solutions.

As a result, circuits composed of a linear regulator and MCU which usually require a 1uF capacitor at the output of the linear regulator and a 100nF at the input of the MCU as mentioned above, ROHM’s Nano Cap™ linear regulator technology achieve stable operation using just one 100nF capacitor at the MCU side.

Given an industry requirement for output voltage fluctuation of ±5.0% max. (in case focusing on just fluctuation) with respect to 50mA load current fluctuation with 100nF capacitance, Nano Cap™ equipped chips achieve a stable operation of ±3.6% in the evaluations, compared with conventional linear regulators whose output voltage can vary by as much as ±15.6%.