理解高效MCU設計的功耗和性能權衡

　　單片機作為主控單元，在每一個可以想象的應用。它們的力量和靈活性使它們成為大多數設計的核心部件。使用MCU往往依賴于智能權衡功耗和性能之間建立高效的設計的關鍵。許多微控制器提供供電的單片機，單片機的時鐘速率，從而限制了幾個選項，其性能。了解工作電壓和工作時鐘頻率之間的共同關系可能是至關重要的，以獲得您的下一個MCU設計最。

　　本文將回顧一些驅動MCU通用選項和討論造成的限制，可能會導致性能。在運行時修改的工作電壓，以獲得最佳的性能和功率效率的最佳組合的共同技術將探討，以幫助您選擇和實施您的下一個基于MCU的設計。

　　Frequency vs. operating voltage – a key performance consideration

　　One of the most fundamental relationships between performance and power is the voltage at which the MCU operates. Operating power is directly related to operating voltage （by definition since power equals voltage times current）， so clearly the operating power needs to be a key consideration when deciding on the MCU you will use for your design. You might think that this means you should always use the lowest power MCU， but if performance is at all an issue in your design you will need to consider the operating frequency as a key element as well， and an MCU’s operating frequency is often limited by its operating voltage.

　　Many MCU manufacturers understand the importance of the relationship between operating voltage， frequency of operation， MCU performance， and MCU operating power and they provide different levels of operating power and operating frequency to make it easier to optimize the design for a best fit to your system requirements. As an example， the Renesas RL78 MCU has four different operating voltage ranges， each supporting a different operating frequency， as illustrated in Figure 1 below. Between 1.6 V and 1.8 V， the RL78 can run anywhere between 1 MHz and 4 MHz. Between 2.7 V and 5.5 V， it can run at a maximum of 20 MHz. Thus， the RL78 can operate five times faster if it uses 2.7 V instead of 1.8 V， only a 50% increase in the operating voltage.