Chapter 16: Decoupling Capacitors for Multi-Voltage Power Distribution Systems

Overview

Power dissipation has become a critical design issue in high performance microprocessors as well as battery powered and wireless electronics, multimedia and digital signal processors, and high speed networking. The most effective way to reduce power consumption is to lower the supply voltage. Reducing the supply voltage, however, increases the circuit delay [295], [297], [330]. The increased delay can be compensated by changing the critical paths with behavioral transformations such as parallelization or pipelining [331]. The resulting circuit consumes less power while satisfying global throughput constraints at the cost of increased circuit area.

Recently, the use of multiple on-chip supply voltages has become common practice [310]. This strategy has the advantage of permitting modules along the critical paths to operate with the highest available voltage level (in order to satisfy target timing constraints) while permitting modules along the non-critical paths to use a lower voltage (thereby reducing the energy consumption). A multi-voltage scheme lowers the speed of those circuits operating at a lower power supply voltage without affecting the overall frequency, thereby reducing power without decreasing the system frequency. In this manner, the energy consumption is decreased without affecting circuit speed. This scheme results in a smaller area as compared to parallel architectures. The problem of using multiple supply voltages for reducing the power requirements has been investigated in the area of high level synthesis for low power [306], [327]. While it is possible to provide many supply voltages, in practice such a scenario is expensive. Practically, the availability...