This approach applied to complex engineering projects and is now finding its way into low power design. Hierarchical design can be roughly separated into three broad categories: planning, implementation, and assembly. Planning, often called “top-down ” design, is the process of breaking the overall design into blocks that will be implemented individually. Planning is critical, because it sets the baseline for the entire project and must yield a final design that meets the project goals for timing, size, power, and other requirements