Ring Oscillator Test Structure with Scan Flip-Flop Control
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Solution Overview
Problem
The high cost and resource-intensive nature of system-level testing for microcontrollers, which requires numerous ring oscillators to accurately measure performance under various conditions, leads to significant routing overhead and increased test costs.
Innovation Solution
Implementing self-activating functional ring oscillators within integrated circuits, where each ring oscillator circuit is assigned a unique scan flip-flop group, allowing for decentralized activation and reduced routing overhead through the use of an input multiplexer controlled by scan flip-flops, eliminating the need for a central control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If numerous ring oscillators are implemented to accurately measure performance under various conditions, then measurement precision is improved, but device complexity and routing overhead increase
Solution Approach 1:
The scan flip-flops serve dual purposes: their primary function for normal circuit operation and their secondary function for controlling ring oscillator activation during performance testing. This eliminates the need for separate control circuits, reducing routing overhead while maintaining the capability to activate multiple ring oscillators independently for accurate performance measurement.
2Ease of operation
If a central control signal is used to activate ring oscillators, then ease of operation is improved, but device complexity and routing overhead increase
Solution Approach 1:
The control mechanism is segmented from a centralized control signal into distributed control elements. Each ring oscillator group has its own dedicated scan flip-flop that independently controls activation. This segmentation eliminates extensive routing for central control signals while maintaining ease of operation through the existing scan flip-flop control structure.
3Measurement precision
If comprehensive system-level testing is performed to test each application case, then measurement precision is improved, but loss of time and test costs increase
Solution Approach 1:
The testing approach changes from comprehensive system-level testing to parameter-based indirect measurement. By measuring ring oscillator frequencies (a physical parameter) and correlating them to performance metrics, the test duration is significantly reduced while maintaining measurement precision. The ring oscillator frequency directly reflects the maximum clock frequency under worst-case conditions without requiring exhaustive application testing.
Data Source
AI summary
One exemplary embodiment describes an integrated circuit, comprising a multiplicity of scan flip-flops, a multiplicity of ring oscillator circuits, wherein each ring oscillator circuit comprises a chain of logic gates comprising a plurality of logic gates connected in succession, an input multiplexer for the chain, and a feedback line from an output connection of the last logic gate of the chain to a data input connection of the input multiplexer. Each ring oscillator circuit is assigned a scan flip-flop group that contains at least one of the multiplicity of scan flip-flops. The input multiplexer of the ring oscillator circuit is controlled depending on a control bit stored by the at least one scan flip-flop of the scan flip-flop group assigned to the ring oscillator circuit such that the input multiplexer outputs an output bit fed back via the feedback line to the first logic gate of the chain or that the input multiplexer outputs a input bit that is to be processed by the chain to the first logic gate of the chain. The ring oscillator circuits are assigned different scan flip-flop groups.