Picture Perfect

Displays continue to take up the lion’s share of battery power. The savings need to come elsewhere.

popularity

For the past five years power/energy efficiency has been a growing concern in the IC world, as well as in the OEM world that has to compete based on battery life. The days when you could plug a phone into the wall at night and be assured you could use it for three days or more without worrying about finding another plug ended with the advent of great displays and more functionality.

Since then there have been steady predictions that display resolution had maxed out. Those predictions were proved wrong because companies figured out how to power down those displays quickly enough to be able to prolong battery life sufficiently. And while the display still is estimated to consume half the battery, battery times continue to grow along with display quality.

There are some tricks being used, of course. Granularity allows displays to control pixels better than in the past. Backlighting can be improved with LEDs to limit the overall energy consumption. And streaming doesn’t require the same quality display as a photograph.

Still, these tricks can only go so far. More megapixels in cameras, better graphics in games and smoother motion all require more battery life, which means that what is lost in one place has to be made up in another. This is where things get interesting. If battery technology is relatively fixed and display technology isn’t decreasing, then the next targets are logic, transport fabrics and architectures, and memory.

The only way to make significant dents here are to rethink how processors are used, what runs on top of them—the entire software stack—and how chips are packaged together. This is an architecture issue, and the next likely solutions are more reliance on the GPU and other application-specific processors, shorter distances through stacking die, faster pipelines with wide I/O, and more rational usage of memory tied to more specific processor applications.

The direction is clear. To be competitive you need better display resolution, clearer sound and at least reasonable video quality, and to do that you have to make up the efficiency somewhere else. With battery technology improving only about 3% per year, that puts the onus on SoC engineering teams to come up with some significant improvements.

This is a big opportunity as well as a major challenge, and it’s one that likely will reshape the IC industry for the next decade. It’s also one that should provide huge growth for tools vendors that can support this next inflection point.