Inverter-Based Filter Biasing With Ring Oscillator Supply Regulation
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Solution Overview
Problem
Inverter-based filters face variability in their transfer function due to process, voltage, and temperature (PVT) variations, leading to unstable frequency response without efficient supply regulation.
Innovation Solution
The implementation of a ring oscillator-based supply regulation system, which includes a voltage regulator and a control circuit that adjusts the supply voltage to maintain a stable oscillation frequency, ensuring consistent performance across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inverter-based filters are used to achieve higher speed and better power efficiency, then the filter performance improves, but the transfer function varies beyond acceptable range due to PVT variations
Solution Approach 1:
The patent implements a feedback mechanism where the ring oscillator monitors the supply voltage and generates a control signal to the voltage regulator. The oscillation frequency of the ring oscillator is directly related to the supply voltage level, creating a closed-loop feedback system that automatically adjusts the supply voltage to maintain stable filter operation despite PVT variations.
Solution Approach 2:
The patent dynamically changes the supply voltage parameter to compensate for PVT variations. By adjusting the supply voltage through the voltage regulator based on ring oscillator feedback, the system maintains optimal operating conditions for the inverter-based filter, ensuring stable transfer function while preserving high speed performance.
2Reliability
If supply voltage is increased to maintain stable transfer function, then frequency response stability improves, but power consumption increases
Solution Approach 1:
The patent employs dynamic supply voltage regulation instead of a fixed high voltage. The supply voltage is dynamically adjusted based on actual operating conditions monitored by the ring oscillator, allowing the system to use minimum necessary voltage to maintain stability, thus reducing power consumption while preserving frequency response stability.
Solution Approach 2:
The ring oscillator-based feedback system enables self-regulation of the supply voltage without external intervention. The system automatically detects voltage deviations through oscillation frequency changes and self-corrects by adjusting the voltage regulator, eliminating the need for complex external control circuits and reducing overall power consumption.
3Device complexity
If conventional current-mode circuits are used, then circuit simplicity is maintained, but speed and power efficiency are reduced compared to inverter-based filters
Solution Approach 1:
The patent makes inverter-based filters universally applicable by addressing their main drawback (sensitivity to PVT variations) through the integrated voltage regulation system. The same inverter-based filter topology can now operate reliably across different process, voltage, and temperature conditions, enabling widespread adoption without sacrificing speed or requiring complex circuit redesign.
Data Source
AI summary
An example circuit includes: an inverter-based filter; a voltage regulator having an input and an output, the output of the voltage regulator providing a supply voltage to bias the inverter-based filter; a ring oscillator having a supply input and an output, the supply input of the ring oscillator coupled to the output of the voltage regulator; a control circuit coupled to the output of the ring oscillator and the input of the voltage regulator, the control circuit configured detect an oscillation frequency of the ring oscillator and to adjust the voltage regulator in response to the oscillator frequency.