Ring Oscillator Frequency Control with Wide Linear Tuning
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Solution Overview
Problem
Existing resistor-capacitor (RC) oscillators face challenges in achieving wide tuning ranges with fine frequency steps and linear frequency control, leading to nonlinearity and sensitivity to process, voltage, and temperature variations.
Innovation Solution
The oscillator circuit employs a ring oscillator, current source, amplifier, RC network, and bias circuit with a coarse and fine adjustment mechanism, allowing for a wide tuning range with small, linear frequency steps through selective resistance and capacitance adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a ring oscillator with current source control is used, then frequency tuning range is extended, but frequency control linearity deteriorates
Solution Approach 1:
The frequency control is segmented into two independent ranges: a first frequency range controlled by a first control signal and a second frequency range controlled by a second control signal. This segmentation allows each control range to be optimized independently, maintaining linearity within each segment while achieving a wide overall tuning range across both segments.
2Device complexity
If RC oscillators are used for integration, then circuit complexity is reduced, but frequency accuracy deteriorates
Solution Approach 1:
An amplifier is configured to control the current source based on feedback from the ring oscillator output, enabling automatic adjustment and stabilization of the oscillation frequency. This feedback mechanism compensates for component tolerances and environmental variations, achieving high frequency accuracy while maintaining the integration advantages of RC oscillators.
3Adaptability or versatility
If frequency tuning range is widened, then adaptability is improved, but frequency step linearity worsens
Solution Approach 1:
The overall frequency tuning range is divided into multiple segments (first frequency range and second frequency range), each with its own control signal and optimization. This allows frequency steps to be made linear within each segment while the combined segments provide the wide overall tuning range required for adaptability.
Data Source
AI summary
A circuit includes a ring oscillator, a current source, an amplifier, a resistor-capacitor (RC) network, and a bias circuit. The current source is configured to power the ring oscillator. The amplifier is configured to control the current source. The amplifier has a first amplifier input and a second amplifier input. The RC network is coupled to the first amplifier input. The bias circuit is coupled to the second amplifier input. The bias circuit is configured to selectably set a frequency range of the ring oscillator, and selectably set a frequency of the ring oscillator within the frequency range.