Please note that JavaScript and style sheet are used in this website,
Due to unadaptability of the style sheet with the browser used in your computer, pages may not look as original.
Even in such a case, however, the contents can be used safely.
Volume 76 (Mar 26, 2008)
The V850ES/Jx3-L™ 32-bit All Flash™ microcontroller: The untold story behind the quest to achieve class-leading power performance
Amidst the increasing importance of extended battery operation and low power consumption in devices for all sorts of products ranging from consumer electronics to industrial devices and automobiles, demand has begun to rise for even greater reduction of power consumption in microcontrollers. NEC Electronics has developed a 32-bit microcontroller capable of achieving the class-leading power consumption that is 50% lower than existing products. Behind this achievement was a development team that faced its challenges head-on.
Developing the world's top microcontroller
Customers often make comments such as, "It's really hard to pass up the high performance of 32-bit microcontrollers, but when it comes to power consumption..." The tradeoff between performance and power consumption not only affects microcontrollers, it is also a never-ending issue faced by both customers and semiconductor manufacturers. NEC Electronics' 32-bit microcontroller development team confronted this issue head-on.
In the spring of 2005, an order to "develop the world's top 32-bit microcontroller" was handed down by the head of the microcontroller division. Upon receiving this order, the development team immediately set about considering what features this next-generation 32-bit microcontroller should have and how to go about making it the best in the world. Those in charge—including Mamoru Ikeda from Product Planning, Kazunari Shimohara from System Design and Masaki Furuchi from Circuit Design—came together in Kyushu, Japan, the home of NEC Microsystems, to attend a training camp and discuss at length the task at hand. Among those in attendance, several team members brought up the theme of "low power consumption."
Up until then, 32-bit V850 microcontrollers had been used in products for markets that did not take advantage of their performance. The team therefore narrowed down its target to high-end systems and focused its development efforts on high performance. However, what the development team members actually had in mind was the "development of a simple chip with the lowest power consumption possible." It was with the goal of "achieving the performance of a 32-bit chip with the power consumption of a 16-bit chip" that development aimed at creating the world's lowest-power-consuming 32-bit microcontroller began (Figure 1).
Complete analysis of power dissipation in existing products by circuit and consideration of measures
Embarking on development with a vague objective like "low power consumption" would certainly not bring about the desired results. This is why a specific target value of 1 mW/MIPS was set. To achieve this value, which would be the highest in the world for 16- and 32-bit microcontrollers, it would be necessary to reduce power consumption to less than half that of existing products (in other words, below 2.1 mW/MIPS). The team began by analyzing existing products in detail to find out how much electrical current is consumed by each circuit and whether any of the circuits consume more electrical current than is necessary. The team also involved people in charge of design environments, circuit design, and components such as memory and timers and used their various perspectives to consider what could be done to achieve the ultimate goal of decreasing electrical current. As a result, with the help of various departments, including the software macro and hardware macro departments, the team was able to decide on and begin executing a design plan.
First, we set the objective of reducing the scale of the drive circuit to one-third for the clock line, which had the highest power dissipation at software macro, and then carried out a thorough optimization. A low-drive cell with low power dissipation was also used and, as a result, we were able to cut power dissipation by a total of more than 50% at software macro.
Meanwhile, we set our sights on the flash macro, which had the highest power dissipation at hardware macro. Then we studied the ON/OFF control system while power was turned off (HALT mode), when the CPU did not require the flash macro. Although the setting of timing proved to be anything but a simple task, the team did find a way to achieve it and was thus able to realize a drastic reduction in power consumption. And by taking measures for other issues one by one, we reduced power consumption by more than 40% at the hardware macro. In the end, we were able to go beyond the initial target value of 1 mW/MIPS to achieve 0.9 mW/MIPS (Figure 2).
Collaboration from the get-go brings about significant results
According to Ikeda and Furuchi, "If we had followed the typical development pattern without involving the planning, system design and circuit design teams from the get-go, there is no way we would have achieved the results we did. We truly feel that bringing together the disparate groups to form a development team and collaborating from the very beginning was what led to these significant results." And now, even after completion of this project, the team members continue to travel back and forth between Kyushu and Tokyo to work together on their next project.
Shimohara adds, "One of the biggest factors behind our success was the establishment of a product concept and target value from the very beginning. Because we spoke with engineers from various other departments about what they could do to help us achieve our objective, we were able to narrow down possible measures. From the standpoint of specifications, I was particularly pleased with the collaborative consideration of the optimal balance of frequency and built-in functions for the power performance ratio by related departments."
If the measures taken to reduce power consumption in this development project can be standardized, they could be applied to reducing power consumption in other products as well. It can be said that there is no limit to what can be done to meet the increasing demand for reduced power consumption in devices. NEC Electronics remains committed to the development of microcontrollers aimed at lowering power consumption even further.
Experiencing ultra-low power consumption through a demonstration
Demonstration by a engineerA demonstration introducing the ultra-low power consumption of V850ES/Jx3-L™ 32-bit All Flash™ microcontrollers was conducted in November at Embedded Technology 2007 in Japan.
"The V850ES/Jx3-L is capable of conducting relatively heavy processing tasks such as display control for electronic billboards and speech synthesis with a power supply comparable to that of a solar battery."
180KB)Links
- Product Information:
- Press Release (NEC Electronics Europe):
