Ring Oscillator RNG With Contention Current for Higher Jitter
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Solution Overview
Problem
Existing random-number generation circuits based on ring oscillators lack sufficient time jitter, which limits the randomness and rate of generated random numbers.
Innovation Solution
The implementation of a contention-current generator in a ring oscillator circuit, where a buffer drives a node with a contention current that opposes and is weaker than the drive current, increasing time jitter and enhancing the randomness of the oscillating signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring oscillator is used for random number generation, then the circuit can generate oscillating signals, but the time jitter is insufficient which limits randomness
Solution Approach 1:
A contention-current generator is introduced as an intermediary component between the ring oscillator and the output. This generator includes a buffer that drives a node with a contention current opposing the drive current, creating additional uncertainty and time jitter in the oscillating signal without disrupting the core ring oscillator operation.
Solution Approach 2:
The invention changes the electrical parameters of the oscillating signal by introducing a contention current with a specific strength ratio (weaker than drive current but significant enough to create jitter). This parameter modification increases time jitter and enhances randomness while maintaining the oscillation frequency and other critical parameters.
2Reliability
If the contention current is made stronger to increase time jitter, then randomness improves, but the oscillation stability deteriorates
Solution Approach 1:
The contention current is designed to be partial rather than equal or excessive. Specifically, it is configured to be weaker than the drive current, providing just enough interference to increase time jitter and randomness while maintaining sufficient drive strength to preserve oscillation stability. This partial action achieves the desired randomness enhancement without compromising system stability.
Data Source
AI summary
An electronic circuit for Random Number Generation (RNG) includes multiple inverters, a contention-current generator, and digitization circuitry. The multiple inverters are connected to one another in a ring and configured to generate an oscillating signal. The contention-current generator is connected to a node at which an output of an inverter of the ring drives an input of a subsequent inverter of the ring with a drive current. The contention-current generator includes at least a buffer configured to drive the node, at least while a voltage at the node transitions between opposite logic states, with a contention current that opposes the drive current and is weaker than the drive current. The digitization circuitry is configured to generate a sequence of random numbers by sampling the oscillating signal generated in the ring.