Feedback-Stabilized Ring Oscillator With Parasitic Current Compensation
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Solution Overview
Problem
High frequency RC oscillators are sensitive to process variations, supply voltage fluctuations, and temperature changes, and their comparator delay contributes to frequency instability, requiring either a more power-consuming design or inefficient power usage.
Innovation Solution
A stabilized ring oscillator design incorporating a feedback element and current compensator with a fixed current ratio, independent of parasitic capacitances, to maintain frequency stability across temperature and voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a faster comparator is designed to reduce comparator delay, then oscillation frequency stability is improved, but current consumption increases
Solution Approach 1:
The patent extracts and compensates for the parasitic current component separately from the functional current. By identifying and removing the parasitic current's effect through the compensator circuit, the system achieves frequency stability without requiring a faster comparator, thus avoiding increased power consumption.
Solution Approach 2:
The patent implements a feedback mechanism where the compensator circuit continuously monitors and compensates for parasitic current effects. This feedback loop maintains oscillation frequency stability by dynamically adjusting for parasitic variations, eliminating the need for a high-speed comparator that would consume more power.
2Speed
If RC oscillator time constant is reduced for high frequency operation, then oscillation frequency increases, but sensitivity to process variations and temperature increases
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitance into a measurable and compensatable parameter. By creating a dedicated compensator circuit that mirrors the parasitic current path, the system transforms the previously harmful parasitic effect into a controllable variable that can be actively compensated, enabling high-frequency operation with improved stability.
Solution Approach 2:
The compensator circuit creates a copy of the parasitic current path and characteristics. By replicating the parasitic effects in the compensator, the system can accurately measure and compensate for these effects, thereby stabilizing the oscillation frequency despite process variations and temperature changes.
3Device complexity
If offset compensation is eliminated to simplify the design, then device complexity is reduced, but frequency accuracy deteriorates
Solution Approach 1:
The patent merges the offset compensation function with the existing parasitic current compensation mechanism. By integrating these functions into a unified compensator circuit, the system achieves both offset compensation and parasitic compensation without significantly increasing overall circuit complexity, while maintaining high frequency accuracy.
Data Source
AI summary
A stabilized oscillator which comprises a ring oscillator with an odd number of inverters. The output of an inverter is driving a capacitor and the input of the a next inverter. A feedback element is configured for generating a first and a second current with a fixed current ratio between both, and for applying the same voltage over the ring oscillator as over a resistor which is connected in parallel with a current compensator. The first current goes through the parallel connection, the second current goes through the ring oscillator. The current compensator is configured such that the ratio of the current through the current compensator and a parasitic current component of the second current is substantially equal to the ratio of the first and second current.