From project conception to completion, there are many different factors to consider that influence power. Omitting for a moment all other constraints (functionality, performance, cost, and time to market), power related tasks can be sorted into two separate classes.
- Physical domain
- Enclosure, board shape, power supply and power distribution network (PDN), thermal power dissipation system.
- Functional domain
- Area, performance, I/O interfaces signal integrity.
The next chapters demonstrate the inter-dependencies between these two classes. These classes differ in that the physical domain involves hardware decisions, while the functional domain mostly involves design creation. Typically, hardware selection and sizing occurs very early in the design flow to allow time to build prototype boards. The effect of a device functionality on power consumption can be estimated early on, then refined as more and more of the design logic is completed. The following figure illustrates a typical system design process, and highlights power-related decision points. The figure demonstrates that, at the time you select your device and associated cooling parts, the device logic is not yet available. Therefore, a careful methodology to estimate the device logic power requirements is needed. Methodologies are discussed in:
The following sections provide methodologies to analyze and reduce power consumption throughout the design process.