Low energy has become such a buzz word, but there is so much that goes into a low-power project and many factors to consider when selecting the best microcontroller for a project. The first thing to look at is the energy efficiency; what is recieved in return for the energy invested into the microcontroller? The next thing to take a look at is the power figures for the various operating modes; both for active mode, idle and in sleep modes. All these figures will contribute to the lowest overall power consumption to extended the battery life of the application. Another very important factor is the fast wake-up. For many low-power applications, extended amounts of time is spent in sleep modes and the microcontroller wakes up on message reception or for instance an RTC interrupt. With a fast wake-up, the time wasted in getting the system back into action upon waking from a sleep modes is reduced to achieve the lowest overall power consumption. One thing that is sometimes overlooked is the performance. High performance is important as it allows the job or computation to completed sooner and thus allowing the application to go to sleep sooner. In addition, a high level of integration and advanved power management allows the system to shut down parts of the system that is not currently in use and efficiently manage the power consumption at a system level. Many low-power applications interact directly with the user, so having a broad range of user interface capabilities is important. Having this on chip allows the system to minimize the overall system power. Speaking of integration; having a wide range peripherals and features embedded into the microcontroller lowers the total BOM cost and reduces real estate needed. This applies to communication peripherals, regulators, BOD, POR and the like. This will make any solution more cost effective, more power efficient and use less space. Of course it all has to be easy to use. Often this is over looked; but what is a feature worth if it cannot be used? Also, being able to utilize features easily reduced the time-to-market and allows the designer to spend time on the parts that differentate the product from a competitor’s product.