Superconducting Circuit Timing with Virtual Retime and Anchor Cells
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Solution Overview
Problem
CMOS technology-based digital circuits face limitations in device size and power consumption, especially at high clock speeds, due to ongoing power dissipation even when inactive, and superconducting logic circuits with Josephson junctions complicate timing design.
Innovation Solution
The implementation of a superconducting circuit design using virtual timing elements, including anchor cells and retime cells, which allow for precise control of latency and synchronization in Josephson junction-based logic gates, enabling efficient pipelining and cycle-accurate simulation in wave pipelined logic designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If CMOS technology is used for digital circuits, then device size can be reduced, but power consumption increases due to ongoing power dissipation even when inactive
Solution Approach 1:
The patent replaces CMOS-based digital circuits with superconducting logic circuits that use Josephson junctions. This substitution eliminates the need for continuous power supply to maintain transistor states, as superconducting circuits operate without resistive losses when current flows below the critical current threshold. The Josephson junctions enable logic operations through quantum tunneling effects, providing a fundamentally different operational mechanism that eliminates static power consumption while maintaining computational functionality.
Solution Approach 2:
The patent changes the operating parameters by transitioning from CMOS voltage-based logic to superconducting current-based logic. By operating Josephson junctions in a superconducting state at cryogenic temperatures, the system achieves zero electrical resistance, eliminating I²R power losses. The use of microwave-frequency clock signals (GHz range) instead of lower-frequency CMOS clocks further reduces dynamic power consumption while increasing operational speed.
2Use of energy by moving object
If superconducting logic circuits with Josephson junctions are used, then power consumption is reduced, but timing design becomes more complex due to active transmission elements
Solution Approach 1:
The patent introduces virtual timing elements as intermediary constructs in the timing model. These virtual elements (virtual flip-flops, virtual buffers) serve as abstractions that simplify timing analysis by providing clear synchronization points and latency definitions without requiring detailed analysis of the underlying active transmission elements. The virtual timing model acts as a mediator between the complex physical superconducting circuit and the timing verification process, enabling high-level timing checks without getting lost in the complexity of individual Josephson junction timing characteristics.
Solution Approach 2:
The patent segments the timing path into distinct segments separated by virtual timing elements. Each segment between virtual flip-flops or virtual buffers can be independently analyzed for latency and timing constraints. This segmentation breaks down the complex overall timing problem into manageable sub-problems, where each segment's timing characteristics can be characterized and verified independently, then composited to ensure overall timing correctness of the superconducting circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for reduced power consumption and improved timing accuracy in superconducting circuits, addressing the limitations of CMOS technology and simplifying the design of high-performance digital circuits by enabling efficient latency management and logical equivalence testing.
Implementation Method 1
Many superconducting logic circuits include Josephson junctions, which may be controlled using high speed clocks or microwave signals
Implementation Method 2
a second virtual timing element for adding latency to the at least one timing path
Data Source
AI summary
Superconducting circuit with virtual timing elements and related methods are described. A method includes specifying a superconducting circuit portion including a timing path comprising: (1) at least one logic gate to be implemented using Josephson junctions, (2) a first virtual timing element for defining a synchronization point along the timing path, and (3) a second virtual timing element for adding latency to the timing path. The method further includes synthesizing the superconducting circuit portion, where the synthesizing comprises treating the first virtual timing element as a first flip-flop and the second virtual timing element as a second flip-flop, where the first flip-flop is treated as being fixed in relation to the at least one logic gate along the timing path, but the second flip-flop is treated as being movable in relation to the at least one logic gate along the timing path.