Selector-Based Random Number Generator Bias Self-Calibration
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Solution Overview
Problem
Existing random number generators using selector-based oscillators face challenges in maintaining proper bias voltage across the selector due to process-voltage-temperature (PVT) variations, leading to impaired oscillation and biased random number generation.
Innovation Solution
A random number generator is designed with an oscillation circuit, control circuit, oscillation detection circuit, and latch circuit, where the bias voltage is self-calibrated by sweeping the bias control signal configuration and locking it once oscillation is detected, ensuring robust oscillation and high-quality digitalized random number generation across PVT variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a selector-based oscillator is biased with a fixed voltage between threshold voltage and hold voltage, then oscillation can be generated, but the oscillation is impaired and random number generation is biased due to PVT variation
Solution Approach 1:
The oscillation circuit performs self-calibration by automatically adjusting its own bias voltage through the interaction of the selector device's non-linear characteristics and the capacitor charging/discharging cycle. The circuit uses its operational states (oscillating vs. non-oscillating) to feedback-control the bias voltage, eliminating the need for external calibration mechanisms.
Solution Approach 2:
The bias voltage is dynamically adjusted based on the oscillation state. When oscillation stops (due to PVT variation pushing the bias out of the valid range), the control circuit modifies the bias voltage parameter to restore oscillation, thereby adapting to PVT conditions without requiring fixed predetermined voltage values.
2Reliability
If the bias voltage is manually adjusted to account for PVT variation, then oscillation robustness improves, but the device complexity and calibration difficulty increase
Solution Approach 1:
The circuit employs feedback control where the oscillation detection unit monitors whether oscillation is occurring and feeds this information back to the bias control unit. When oscillation is detected as stopped, the feedback mechanism triggers bias voltage adjustment to restore oscillation, creating a closed-loop system that automatically compensates for PVT variations.
Solution Approach 2:
The capacitor serves as an intermediary element that enables the self-calibration process. By charging and discharging through the selector device, the capacitor creates voltage conditions that allow the circuit to probe and identify the optimal bias voltage point automatically, without requiring external calibration equipment or complex adjustment mechanisms.
3Manufacturing precision
If the bias voltage is set exactly between threshold voltage and hold voltage, then proper oscillation is achieved, but this becomes difficult due to PVT variation
Solution Approach 1:
The bias voltage transitions from a static fixed value to a dynamic adjustable parameter. The control circuit continuously monitors oscillation status and adjusts the bias voltage in real-time based on actual operating conditions, allowing the system to adapt to PVT variations rather than relying on a predetermined fixed voltage setting.
Solution Approach 2:
The circuit performs preliminary calibration actions by systematically adjusting the bias voltage to find the oscillation threshold point before normal operation begins. This preliminary action establishes the correct operating point in advance, ensuring that subsequent random number generation operates from a calibrated state without requiring continuous manual adjustment.
Data Source
AI summary
A random number generator that includes control circuit, an oscillation circuit, an oscillation detection circuit and a latch circuit is introduced. The control circuit sweeps a configuration of a bias control signal among a plurality of configurations. The oscillation circuit generates an oscillation signal based on the configuration of the bias control signal. The oscillation detection circuit detects an onset of the oscillation signal, and outputs a lock signal. The latch circuit latches the oscillation signal according to a trigger signal to output a random number, wherein the trigger signal is asserted after the lock signal is outputted, and the configuration of bias control signal is locked after the lock signal is outputted. A method for generating a random number and an operation method of a random number generator are also introduced.