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PhD Defense: Low Power Reliable Design using Pulsed Latch Circuits

Name: Wael Mahmoud Elsharkasy

Date: February 15, 2017

Time: 11:00 AM

Location: Engineering Hall 3206

Committee: Prof. Fadi J. Kurdahi, Prof. Ahmed Eltawil, Rainer Doemer


System-on-Chip (SoC) faced lots of challenges over the past decade. With nowadays applications centered around Internet-of-Everything (IoE), these challenges are expected to be more critical. Among these challenges are the reduction of power consumption for better energy efficiency, the overcoming of different sources of variations to ensure reliable operation and the reduction of design area to reduce the cost and increase the integration. As a result, chip designers find themselves facing lots of problems, trying to build reliable systems that integrate complex level of functionality, on a minimum die size and with a limited power budgets. Among different circuit components in every chip, memory components are of great concern. They consume the majority of the chip area and power, in addition to affecting the entire chip performance and reliability. These include large memory arrays, caches, register files and different sequential elements in the logic paths. Sequential elements play an important and critical role in modern synchronous CMOS circuits. Indeed, they can represent up to 50% of the standard cells used in a chip. In addition, the power consumption of the clock tree, including these elements can be more than half of the total chip power. In addition, they come in the second place after memory to be affected by different sources of variation. Hence, efficient implementation of these elements is of great importance for the design of energy efficient and reliable integrated circuits. Pulsed latches have been proposed as efficient replacement of flip-flops in the implementation of sequential element. They can achieve higher performance when compared to traditional flip-flop, and can be designed to be smaller in area and more power efficient. However, the operation of pulsed latch is more sensitive to process, voltage and temperature (PVT) variations. In this thesis, we are proposing a methodology to study the reliability of pulsed latches and we have used it to evaluate the effect of PVT variations on their behavior. In addition, novel approaches to enhance the reliability of pulsed latches without significant degradation in performance, area or power are presented. Also, since sequential elements can be used to build small size register files, pulsed latch implementation of register files are discussed and compared to other traditional implementations, including SRAM and flip-flops. In addition, since multiport register files are very beneficial for quite few applications, novel implementations of multiport register files are also presented. The proposed implementation is proved to highly reduce the significant overhead in area, power and latency associated with the traditional way of designing multiport register files.