Design Methods for Low-Energy-Consumption System LSIs : Approaches from System Design

低消費エネルギー化はシステムLSI設計における重要な技術課題である.発熱に起因する回路の性能や信頼性の低下を防ぎ,微細加工技術のもたらす集積度を向上の恩恵を受けるために,低消費エネルギー化は必須の技術である.さらに,携帯情報機器等のバッテリー駆動機器へ搭載されるシステムLSIにおいては,バッテリーの容量(機器の重量や大きさに大きな影響を与える)の削減や充電頻度の削減による利便性の向上と関係し,低消費エネルギー化の成否が機器の商品価値を決定することも少なくない.地球規模での環境問題が重要視される中,低消費エネルギー化技術は,半導体や情報機器の市場規模そのものを規定する要因ともなりうる.本稿では,システム設計レベルでの低消費エネルギー化技術の基本方針を議論し,具体的な手法をいくつか紹介する.Reduction of energy consumption is one of the most important technical issues in System-on-a-Chip (SoC or System LSI) design. For preventing the decrease of system performance and reliability caused by heating and for enjoying the increase of the number of transistors on a chip by the progress of fabrication technology, the reduction of energy consumption is very important. In mobile information terminal devices, which are driven by batteries, the energy consumption of SoCs on the devices strongly influences the frequency of battery charge and the weight and the size of the batteries, which are directly involved with the commercial value of the devices. Since the global environment problem is argued as a large political problem in the 21st century, the low-energy design technology for SoC may be a significant factor to determine the size of the market of semiconductors and information technology. In this article, basic concepts of the energy reduction technology for SoC in the system design level are discussed, and several examples of energy reduction techniques are presented