Multiplexer Ring Oscillator for Select-to-Output Delay Measurement
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Solution Overview
Problem
Existing ring oscillator designs struggle to accurately measure signal propagation delay through specific components like multiplexers, particularly the select-to-output delay, which is crucial for assessing integrated circuit performance and timing in communications and data processing applications.
Innovation Solution
A ring oscillator circuit incorporating two or more multiplexer elements with specific logic level orientations on their data input leads, allowing the oscillating signal to pass through the select input of each multiplexer, enabling the determination of signal propagation delay and select-to-output delay, which varies with supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ring oscillators with active logic elements (inverters, flip-flops, gates) are used, then the circuit can generate oscillation, but the measurement precision of select-to-output delay through multiplexer is insufficient because the total delay includes multiple components
Solution Approach 1:
The patent extracts and removes active logic elements (inverters, flip-flops, gates) from the ring oscillator circuit, retaining only the multiplexer elements. This extraction isolates the select-to-output delay measurement by eliminating other delay-contributing components, thereby improving measurement precision while reducing device complexity
Solution Approach 2:
The patent segments the ring oscillator into discrete multiplexer elements connected in a ring configuration, where each multiplexer contributes only its select-to-output delay. This segmentation allows the total oscillation period to represent exactly N times the select-to-output delay, enabling precise measurement through frequency calculation
2Device complexity
If a ring oscillator includes an even number of ring elements, then the circuit structure is simplified, but conventional wisdom states it cannot oscillate because the output voltage level of the last element equals the input voltage level of the first element
Solution Approach 1:
The patent inverts the conventional approach by using multiplexer elements instead of active logic elements like inverters. Multiplexers can transfer voltage levels without inversion, allowing an even number of elements to oscillate by maintaining proper logic level orientation between adjacent elements, thus achieving both structural simplicity and reliable oscillation
3Speed
If the supply voltage is increased to reduce signal propagation delay, then the switching speed improves, but the power consumption increases
Solution Approach 1:
The patent uses periodic oscillation to continuously monitor select-to-output delay at different supply voltages. By measuring frequency at various voltage levels, the system identifies the minimum voltage required for proper operation, enabling dynamic voltage adjustment that reduces power consumption while maintaining adequate switching speed through periodic characterization
Data Source
AI summary
The frequency of an oscillating signal generated by a ring oscillator is used to determine the select-to-output delay of standard cell multiplexers. The ring oscillator has no active logic elements other than an odd or even number of standard cell multiplexers. The signal path of the oscillating signal passes through the select input leads of the multiplexers of the ring oscillator. The ring oscillator can be used to characterize how signal propagation delay varies depending on the voltage supplied to the multiplexers. The lowest supply voltage at which a signal can continue to travel through the most critical circuit path of a test circuit can be modeled. In addition, the ring oscillator can be built into operational circuits to monitor timing and signal propagation delay in real time. Real time monitoring of delay enhances the benefits of adaptive voltage scaling, which is used in signal processing circuits in cell phones.