Synthesis & Testing for Low Power

Abstract

In recent years, power dissipation has emerged as the key issue not only for portable computers and mobile communication devices, but also for high-end systems. Reducing power dissipation is of primary importance in achieving longer battery life in portable devices. On the other hand, for high-end systems the cooling and packaging requirements are pushing the chip designers for low power alternatives. As a consequence, apart from the size, cost and performance, now-adays power is also considered as one of the most important constraints. This has led to vigorous research in the synthesis of low-power and high-performance circuits and systems. Moreover, aggressive device size scaling used to achieve high-performance leads to increased variability due to short-channel and other effects. This, in turn, leads to variations in process parameters such as, Leff, Nch, W, Tox, Vt, etc. Performance parameters such as power and delay are significantly affected due to the variations in process parameters and environmental/operational (Vdd, temperature, input values, etc.) conditions. Due to variability, the design methodology in the future nanometer VLSI circuits will essentially require a paradigm shift from deterministic to probabilistic and statistical design approach. The tight constraint on power dissipation has also created new challenges for testing low power VLSI circuits, as the traditional test techniques do not account for power dissipation during test application. It is now an accepted truth that test power is often much higher than the power consumed in normal operation, due to voluminous test data, test parallelization and the low correlation between successive test patterns. The objective of this tutorial is to provide an overview of different aspects of low power circuit synthesis at various levels of design hierarchy. It will introduce techniques to optimize the performance and power in the presence of process variations. Low power testing techniques will also be discussed.