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Investigation of High-T c Single Flux Quantum Logic Gates

Kazuo Saitoh, Hiroyuki Fuke

IEICE Transactions on ElectronicsOct 25, 19970 citations

Dynamically Reconfigurable Single Flux Quantum Logic Gates

Yuki Yamanashi, 一朗大河, Yoshikawa Nobuyuki

IEICE Technical Report; IEICE Tech. Rep.Oct 13, 20090 citations

Design and demonstration of fundamental logic circuits based on a single-flux-quantum gate with a resettable latch

Naoki Takeuchi, A. Akahori, N. Mori +4 more

We have confirmed the importance of the tolerance design for obtaining correct operation in larger-scale Single Flux Quantum (SFQ) logic circuit. Experimental results show that the bias margin of SFQ/dc converter is considerably enhanced by employing tolerance design. The primitives of Single-Flux-Quantum-logic with Ressettable Latch (SFQ-RL) are designed to have high tolerance. As a result, relatively complex circuits based on SFQ-RL including 4-bit Shift Register, 3-Input Majority circuits, binary counter operate correctly with sufficient bias margins. These circuits are fabricated in NEC's standard process using 2.5 kA/cm/sup 2/ Nb/AlOx/Nb junction technology.We have confirmed the importance of the tolerance design for obtaining correct operation in larger-scale Single Flux Quantum (SFQ) logic circuit. Experimental results show that the bias margin of SFQ/dc converter is considerably enhanced by employing tolerance design. The primitives of Single-Flux-Quantum-logic with Ressettable Latch (SFQ-RL) are designed to have high tolerance. As a result, relatively complex circuits based on SFQ-RL including 4-bit Shift Register, 3-Input Majority circuits, binary counter operate correctly with sufficient bias margins. These circuits are fabricated in NEC's standard process using 2.5 kA/cm/sup 2/ Nb/AlOx/Nb junction technology.

IEEE Transactions on Applied SuperconductivityMar 1, 20010 citations

Asynchronous Dynamic Single-Flux Quantum Majority Gates

Gleb Krylov, Eby G. Friedman

Among the major issues in modern large-scale rapid single-flux quantum (RSFQ) circuits are the complexity of the clock network, tight timing tolerances, poor applicability of existing CMOS-based design algorithms, and extremely deep pipelines, which reduce the effective clock frequency. In this article, asynchronous dynamic single-flux quantum majority gates are proposed to solve some of these problems. The proposed logic gates exhibit high bias margins and do not require significant area or a large number of Josephson junctions as compared to existing RSFQ logic gates. These gates exhibit a tradeoff among the input skew tolerance, clock frequency, and bias margins. Asynchronous logic gates greatly reduce the complexity of the clock network in large-scale RSFQ circuits, thereby alleviating certain timing issues and reducing the required bias currents. Furthermore, asynchronous logic allows existing design algorithms to utilize CMOS approaches for synthesis, verification, and testability. The adoption of majority logic in complex RSFQ circuits also reduces the pipeline depth, enabling higher clock speeds in very large scale integration RSFQ circuits.Among the major issues in modern large-scale rapid single-flux quantum (RSFQ) circuits are the complexity of the clock network, tight timing tolerances, poor applicability of existing CMOS-based design algorithms, and extremely deep pipelines, which reduce the effective clock frequency. In this article, asynchronous dynamic single-flux quantum majority gates are proposed to solve some of these problems. The proposed logic gates exhibit high bias margins and do not require significant area or a large number of Josephson junctions as compared to existing RSFQ logic gates. These gates exhibit a tradeoff among the input skew tolerance, clock frequency, and bias margins. Asynchronous logic gates greatly reduce the complexity of the clock network in large-scale RSFQ circuits, thereby alleviating certain timing issues and reducing the required bias currents. Furthermore, asynchronous logic allows existing design algorithms to utilize CMOS approaches for synthesis, verification, and testability. The adoption of majority logic in complex RSFQ circuits also reduces the pipeline depth, enabling higher clock speeds in very large scale integration RSFQ circuits.

IEEE Transactions on Applied SuperconductivityMar 4, 202039 citations

Clockless Dynamic SFQ and Gate With High Input Skew Tolerance

Sergey V. Rylov

We have introduced a new class of dc-powered Single Flux Quantum (SFQ) logic that uses dynamic (self-resetting) internal states to achieve completely clock-free gate operation and provide high immunity to input data skew. We call it DSFQ (dynamic SFQ) logic. We have successfully designed and tested a 2-input DSFQ and gate and showed its ability to hold dynamically its internal states for over 25 ps while operating at 10 GHz clock frequency. We also demonstrated picosecond-scale dynamics of DSFQ circuit with an on-chip Josephson sampler, with only low-speed interfaces required.We have introduced a new class of dc-powered Single Flux Quantum (SFQ) logic that uses dynamic (self-resetting) internal states to achieve completely clock-free gate operation and provide high immunity to input data skew. We call it DSFQ (dynamic SFQ) logic. We have successfully designed and tested a 2-input DSFQ and gate and showed its ability to hold dynamically its internal states for over 25 ps while operating at 10 GHz clock frequency. We also demonstrated picosecond-scale dynamics of DSFQ circuit with an on-chip Josephson sampler, with only low-speed interfaces required.

IEEE Transactions on Applied SuperconductivityJan 30, 201944 citations

Rapid Single-Flux-Quantum Logic

K. K. Likharev

Springer eBooksJan 1, 199346 citations

High-Tolerance Uni-Lateral Single-Flux-Quantum Logic Gate

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