Keith Odland, Silicon Laboratories
EDN (November 28, 2012)
Low-energy system design requires attention to nontraditional factors ranging from the silicon process technology to the software that runs on microcontroller-based embedded platforms. Closer examination at the system level reveals three key parameters that determine the energy efficiency of a microcontroller: active-mode power consumption; standby power consumption; and the duty cycle, which determines the ratio of time spent in either state and is itself determined by the behavior of the software.
A low-energy standby state can make an MCU seem extremely energy efficient, but its true performance is evident only after taking into account all of the factors governing active power consumption. For this and other reasons, trade-offs among process technology, IC architecture, and software construction are some of the many decisions with subtle and sometimes unexpected outcomes. The manner in which functional blocks on an MCU are combined has a dramatic impact on overall energy efficiency. Even seemingly small and subtle changes to the hardware implementation can result in large swings in overall energy consumption over a system’s lifetime.
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