VOICE OF THE ENGINEER - ElectronicsAndBooks

DISCOVERINGTHE LASTUNREALIZEDPOWER REDUCTIONPOWER-OPTIMIZED ARCHITECTURES HELP ENGINEERS DESIGNING CHIPS WITH BLOCKS THAT CANPOWER DOWN OR OPERATE AT REDUCED FREQUENCIES AND VOLTAGES.BY JAY CHIANG • SYNOPSYSPower has become one of the most importantdesign criteria for almost all design projects,and the industry, in response, has invested alot of effort to address this challenge. Consequently,we have seen a plethora of lowpowerdesign techniques and new technologiesemerge. Some of these techniques arerelatively easy to adopt. For example, clockgating and multiple-threshold-voltage cellshave become mainstream design practices because they are effective.In addition, EDA tools can automate their implementation.Some techniques, on the other hand, require more planning.For example, design engineers can group SOC (system-onchip)circuits into multiple blocks so that they can power downsome blocks or operate them at reduced frequencies or voltageswhen operating conditions allow it. Although these more advancedtechniques take more deliberate effort to implement,design engineers are increasingly employing them to meet themore stringent power requirements in next-generation chips.When applying low-power designtechniques, design engineers typicallyconcentrate on only the few modules,such as embedded processors andon-chip memories, that consume morepower than the other blocks. Althoughthis focus is necessary, it is incomplete.Engineers may often overlook thefact that many low-power-consumingblocks frequently have a greater impacton energy consumption than their power-consumptionnumber suggests. If youcorrectly plan a chip’s power-managementstrategy, the power-consumptionprofile and energy-consumption profileshould not correlate closely. You shouldkeep the active period of the high-power-consumingmodules as short as possible.The modules that remain poweredfor a long time should not consume toomuch power. Even though these modulesconsume less power than otherblocks, they consume a higher propor-24 EDN | SEPTEMBER 9, 2010