Circuit synchrone | EPFL Graph Search

Un circuit synchrone est un circuit électronique numérique qui fonctionne à un rythme dicté par une horloge. Cette horloge interne au processeur donne à intervalles réguliers une impulsion électrique simultanée (en première approximation) à tous les composants du processeur. Sa fréquence peut atteindre quelques gigahertz (GHz) pour des processeurs récents. Les ordinateurs personnels usuels sont munis de processeurs synchrones. Composants Un circuit numérique, comme un processeur, est composé de multiples composants comme les mémoires, additionneurs, multiplexeurs, soustracteurs, diviseurs, multiplicateurs). Ces composants fonctionnent de manière binaire suivant le niveau de tension qu'ils reçoivent en entrée et rendent un niveau de tension haut ou bas en sortie (en binaire, 0 ou 1). L’impulsion électrique sur le composant l'autorise à utiliser les données reçues en entrée, ce qui peut le faire passer d’un état à un autre (tension de sortie haute ou basse) en passant par

Signaling in 3-D integrated circuits, benefits and challenges

Somayyeh Rahimian Omam

Three-dimensional (3-D) or vertical integration is a design and packaging paradigm that can mitigate many of the increasing challenges related to the design of modern integrated systems. 3-D circuits have recently been at the spotlight, since these circuits provide a potent approach to enhance the performance and integrate diverse functions within amulti-plane stack. Clock networks consume a great portion of the power dissipated in a circuit. Therefore, designing a low-power clock network in synchronous circuits is an important task. This requirement is stricter for 3-D circuits due to the increased power densities. Synchronization issues can be more challenging for 3-D circuits since a clock path can spread across several planes with different physical and electrical characteristics. Consequently, designing low power clock networks for 3-D circuits is an important issue. Resonant clock networks are considered efficient low-power alternatives to conventional clock distribution schemes. These networks utilize additional inductive circuits to reduce power while delivering a full swing clock signal to the sink nodes. In this research, a design method to apply resonant clocking to synthesized clock trees is proposed. Manufacturing processes for 3-D circuits include some additional steps as compared to standard CMOS processes which makes 3-D circuits more susceptible to manufacturing defects and lowers the overall yield of the bonded 3-D stack. Testing is another complicated task for 3-D ICs, where pre-bond test is a prerequisite. Pre-bond testability, in turn, presents new challenges to 3-D clock network design primarily due to the incomplete clock distribution networks prior to the bonding of the planes. A design methodology of resonant 3-D clock networks that support wireless pre-bond testing is introduced. To efficiently address this issue, inductive links are exploited to wirelessly transmit the clock signal to the disjoint resonant clock networks. The inductors comprising the LC tanks are used as the receiver circuit for the links, essentially eliminating the need for additional circuits and/or interconnect resources during pre-bond test. Recent FPGAs are quite complex circuits which provide reconfigurablity at the cost of lower performance and higher power consumption as compared to ASIC circuits. Exploiting a large number of programmable switches, routing structures are mainly responsible for performance degradation in FPAGs. Employing 3-D technology can providemore efficient switches which drastically improve the performance and reduce the power consumption of the FPGA. RRAM switches are one of the most promising candidates to improve the FPGA routing architecture thanks to their low on-resistance and non-volatility. Along with the configurable switches, buffers are the other important element of the FPGAs routing structure. Different characteristics of RRAM switches change the properties of signal paths in RRAM-based FPGAs. The on resistance of RRAMswitches is considerably lower than CMOS pass gate switches which results in lower RC delay for RRAM-based routing paths. This different nature in critical path and signal delay in turn affect the need for intermediate buffers. Thus the buffer allocation should be reconsidered. In the last part of this research, the effect of intermediate buffers on signal propagation delay is studied and a modified buffer allocation scheme for RRAM-based FPGA routing path is proposed.

EPFL2015

Low-power clock distribution networks for 3-D ICs

Giovanni De Micheli, Vasileios Pavlidis, Somayyeh Rahimian Omam

Designing a low power clock network in synchronous circuits is an important task. This requirement is stricter for 3-D circuits due to the increased power densities. Resonant clock networks are considered efficient low-power alternatives to conventional clock distribution schemes. These networks utilize additional inductive circuits to reduce the power consumption while delivering a full swing clock signal to the sink nodes. Test is another complex task for 3-D ICs, where pre-bond test is a prerequisite. This paper, consequently, introduces a design methodology for resonant 3-D clock networks that lowers the power of the clock networks while supporting pre-bond test. Several 3-D clock network topologies are explored in a 0.18 μm CMOS technology. Simulation results indicate 43% reduction in the power consumed by the resonant 3-D clock network as compared to a conventional buffered clock network. By properly distributing the inductance within the layers of the 3-D stack, resonance is ensured both in pre-bond test and normal operation. The important aspects of this approach are introduced in this paper.

2012

Signaling in 3-D integrated circuits, benefits and challenges

Somayyeh Rahimian Omam

EPFL2015