The first step for low power design is to develop a low power strategy. There are typically different levels of run, idle and stop modes available in most MCUs. In order to determine the low power strategy the user must be aware of the different run modes in addition to the low power modes the MCU is capable of entering. Also, what modes the peripherals are capable of operating in must be considered.  For example, can the ADC referenced earlier run while the CPU is off? All of these factors enter into the overall strategy. It is necessary to define what is meant by active and inactive modes. When in the active mode the CPU is ON and running the required task, typically this is the maximum amount of current draw the system will see at any given time. The inactive mode is entered when the CPU is put into a sleep mode. This means the clock to the CPU is OFF and thus a reduction in current is observed. An example of an active mode is the idle mode, which is considered an “active” mode because the clock is still running. Sleep mode is an example of an inactive mode since all of the clocks are typically turned OFF and any internal regulators are OFF or loosely regulated.