Work Takes Energy
It takes energy to perform work, whether it is physical work, such as digging a ditch, or electrical work like playing an MP3 file. The tools may be different for physical work as compared to electrical work, but the idea is that the tools will allow the work to be done more efficiently using the least amount of energy. For instance, you could dig a ditch using a teaspoon, but it would take a lot more energy than if you used a shovel. The tools used to do electrical work are circuits. Some circuits are designed to be more efficient than others, even though they may perform the same function. We are interested in designing circuits that are energy efficient when performing the necessary work.
Working Efficiently
There are multiple ways to design efficient circuits, but it boils down to controlling active currents, static currents and leakage currents. Active current is frequency dependent, leakage current is temperature dependent and static current tends not to be either frequency or temperature dependent. There are several techniques to address each one of these types of currents, including, but not limited to:Active currents:
- Reduced voltage
- Dynamic voltage and frequency scaling
- Accelerators
- Asynchronous circuits
Static currents:
- Reduced voltage
- Better bias current circuits
- Power gating
Leakage:
- Reduced voltage
- State retention power gating
- Save and restore power gating
- Basic power gating
When selecting a component for your system, identifying and understanding the power control techniques implemented on the component will help you make the right selection for your end product. Each of these techniques will be described in future posts to help you understand what they are and how they may (or may not) impact your end system. Please let me know if there are other topics that interest you.
– Chris
