30GHz Operation of Single-Flux-Quantum Arithmetic Logic Unit Implemented by Using Dynamically Reconfigurable Gates


IEICE TRANSACTIONS on Electronics   Vol.E99-C   No.6   pp.692-696
Publication Date: 2016/06/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.692
Type of Manuscript: Special Section PAPER (Special Section on Cutting-Edge Technologies of Superconducting Electronics)
SFQ circuit,  shielding,  arithmetic logic unit,  reconfigurable logic device,  

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A single-flux-quantum (SFQ) arithmetic logic unit (ALU) was designed and tested to evaluate the effectiveness of introducing dynamically reconfigurable logic gates in the design of a superconducting logic circuit. We designed and tested a bit-serial SFQ ALU that can perform six arithmetic/logic functions by using a dynamically reconfigurable AND/OR gate. To ensure stable operation of the ALU, we improved the operating margin of the SFQ AND/OR gate by employing a partially shielded structure where the circuit is partially surrounded by under- and over-ground layers to reduce parasitic inductances. Owing to the introduction of the partially shielded structure, the operating margin of the dynamically reconfigurable AND/OR gate can be improved without increasing the circuit area. This ALU can be designed with a smaller circuit area compared with the conventional ALU by using the dynamically reconfigurable AND/OR gate. We implemented the SFQ ALU using the AIST 2.5kA/cm2 Nb standard process 2. We confirmed high-speed operation and correct reconfiguration of the SFQ ALU by a high-speed test. The measured maximum operation frequency was 30GHz.