FPGA Interconnect Delay Measurement via Line Swapping
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Solution Overview
Problem
Existing methods for determining signal propagation delay in programmable logic devices, such as FPGAs, have resolution limitations, making it difficult to characterize delays at a finer scale than what is achievable with ring oscillators, which is insufficient for certain applications.
Innovation Solution
A method involving the formation of multiple signal paths using programmable interconnects in FPGAs, where incremental differences in propagation delay are measured by swapping specific conductive lines, allowing for a sub-ring oscillator resolution of propagation delay characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ring oscillators are used to measure propagation delay, then measurement capability is provided, but measurement precision is limited to ring oscillator resolution
Solution Approach 1:
The patent segments the propagation delay measurement into multiple components by creating separate signal paths that can be independently measured. Instead of measuring total delay through a ring oscillator, the invention divides the measurement into incremental segments by swapping individual conductive lines, allowing each segment's delay to be characterized separately and summed for higher precision overall measurement
Solution Approach 2:
The patent transitions from temporal measurement (ring oscillator frequency) to spatial measurement by creating multiple parallel signal paths with different conductive line configurations. This dimensional shift allows comparison of propagation delays across different physical routes, enabling sub-ring oscillator resolution through differential measurement
2Measurement precision
If sub-ring oscillator resolution is implemented, then propagation delay measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent creates a universal measurement framework where a single ring oscillator structure serves multiple measurement purposes. The same basic circuit topology is reused across different signal path configurations, allowing the system to measure various conductive line delays without requiring separate dedicated measurement circuits for each line, thus reducing overall device complexity
Solution Approach 2:
The patent uses copying by creating duplicate signal paths that mirror each other with one key difference (swapped conductive lines). These copied paths allow differential measurement where the incremental delay difference can be extracted by comparing identical structures, reducing the need for entirely new measurement circuits
Data Source
AI summary
A method for determining propagation delay differences for conductive lines of an integrated circuit is described. A first path is formed by coupling a first portion of conductive lines together. The first portion is associated with a first region of the integrated circuit. The first path is coupled in a ring oscillator, and a first delay is determined. A second path is formed by coupling a second portion of the conductive lines together. The second portion is the first portion except for at least a first conductive line in the first portion of the conductive lines being swapped for a second conductive line. The second conductive line is associated with a second region of the integrated circuit. The second path is coupled in the ring oscillator circuit. A second delay is determined, and an incremental difference between the first delay and the second delay may be determined.