Ring Oscillator RNG Circuit With Metastability-Managed Beat Sampling
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Solution Overview
Problem
Existing random number generation circuits based on coherently sampling ring oscillators fail to account for metastabilities in flip-flops, leading to operation deviations from stochastic models and undesirable hardware implementation.
Innovation Solution
Incorporating a metastability management circuit that removes counter output values resulting from metastabilities and resets the counter on each rising or falling edge of the flip-flop output, using a threshold determined by flip-flop setup and hold times, and jitter standard deviations to generate a metastability-free Beat signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coherently sampling ring oscillator random number generation circuits are used, then random number generation is achieved, but operation deviations occur due to unaccounted metastabilities in flip-flops
Solution Approach 1:
The patent converts the harmful metastability phenomenon into a beneficial feature by deliberately designing the flip-flop to operate in metastability and using the resulting random output transitions (0 to 1 or 1 to 0) as the source of true random numbers, rather than treating them as errors to be eliminated
Solution Approach 2:
The patent introduces a D flip-flop as an intermediary element between the ring oscillators that samples the output signal at the beginning of each period, allowing the metastability effect to be captured and converted into usable random number output while isolating the rest of the circuit from direct exposure to the unstable state
2Measurement precision
If flip-flop sampling is used to generate random bits, then entropy extraction is achieved, but measurement accuracy deteriorates due to unaccounted metastability
Solution Approach 1:
The patent incorporates feedback mechanisms that monitor the flip-flop output and use the observed metastability behavior to adjust and validate the stochastic model, ensuring that the model accurately reflects the actual random number generation process including metastability effects
3Productivity
If counter output values are used directly, then random number output is achieved, but reliability decreases due to metastability-affected values
Solution Approach 1:
The patent extracts only the useful random information from the flip-flop output transitions while discarding or ignoring the metastability-corrupted counter values, separating the reliable random bit generation from the unreliable counting function
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
Ensures accurate and reliable random number generation by eliminating counter outputs affected by metastabilities, maintaining validity of stochastic models, and enhancing measurement accuracy.
Implementation Method 1
The measurement of the period T, that is, the duration of the period T, is representative of the jitter of the signal S1
Implementation Method 2
These stochastic models are used to characterize the entropy source 100, and therefore the random number generation device 1
Implementation Method 3
there is a need to take into account, in a coherently sampling ring oscillator random number generation circuit, metastabilities that may occur in the flip-flop sampling an output signal from a first ring oscillator
Data Source
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AI summary
This description concerns a circuit (3). Identical first and second ring oscillators (R1, R0) provide first and second periodic signals (S1, S0). A flip-flop (102) samples the first signal (S1) at the beginning of each period of the second signal (S0). A counter (COUNTER) is clocked by the second signal (S0). A metastability management circuit (GM) removes output values (N) from the counter resulting from metastabilities of the first flip-flop (102), and resets the counter (COUNTER) on each rising and/or falling edge of an output (Beat) of the first flip-flop (102).