Ring Oscillator Bias Circuit for Stable Frequency in Small ICs
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Solution Overview
Problem
Integrated circuit (IC) oscillators with limited layout area face challenges in maintaining accurate frequency output due to voltage supply and temperature variations without an accurate voltage and current reference.
Innovation Solution
The design incorporates a voltage supply variation reduction circuit, a bias generation circuit, and a temperature-compensation circuit, utilizing transistors and resistors with specific temperature coefficients to regulate current and generate a stable frequency waveform, eliminating the need for an accurate voltage and current reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an accurate voltage and current reference is added to the IC oscillator design, then the frequency output accuracy is improved, but the layout area increases
Solution Approach 1:
The patent extracts and eliminates the need for accurate voltage and current reference circuits from the oscillator design. By using a voltage supply variation reduction circuit that generates a regulated current directly from the voltage source, and a temperature-compensation circuit that adjusts for environmental variations, the design achieves accurate frequency output without requiring separate reference circuits, thereby reducing layout area while maintaining precision
Solution Approach 2:
The oscillator circuit serves its own reference needs through self-regulation mechanisms. The voltage supply variation reduction circuit automatically regulates current based on voltage source variations, and the temperature-compensation circuit automatically adjusts for temperature effects, eliminating the need for external reference circuits and reducing overall circuit complexity and area
2Area of stationary object
If voltage supply and temperature variations are large without accurate reference, then the layout area is reduced, but the frequency output accuracy deteriorates
Solution Approach 1:
The patent implements feedback mechanisms through the voltage supply variation reduction circuit and temperature-compensation circuit. These circuits continuously monitor voltage source variations and temperature changes, and automatically adjust the current supplied to the oscillator to maintain stable frequency output, achieving both area reduction and precision maintenance through self-regulating feedback control
Solution Approach 2:
The patent changes the operating parameters of the oscillator circuit dynamically. The voltage supply variation reduction circuit adjusts current parameters in response to voltage variations, and the temperature-compensation circuit modifies circuit parameters to counteract temperature effects, enabling the circuit to maintain accurate frequency output across varying conditions without requiring large layout area
3Device complexity
If voltage supply variations are not compensated, then the circuit complexity is reduced, but the frequency stability deteriorates
Solution Approach 1:
The patent segments the oscillator system into functional modules: a voltage supply variation reduction circuit that handles voltage stabilization, a temperature-compensation circuit that handles thermal variations, and the core oscillator circuitry. This segmentation allows each module to perform its specific function efficiently, achieving frequency stability through coordinated operation of specialized sub-circuits while keeping overall complexity manageable
Data Source
AI summary
Electronic oscillator designs and methods that do not require an accurate voltage and current reference to be provided, and which output an accurate frequency waveform over a range of voltage supply and temperature variations. Embodiments of the present invention are particularly well-suited for IC designs with very limited layout area and a tight oscillator frequency spread requirement. An embodiment uses a current subtraction technique that provides an essentially constant through a bias generation circuit when the voltage of the voltage source exceeds a selected value. An embodiment includes a temperature-compensation circuit, coupled to the bias generation circuit, that includes at least one NFET and at least one negative temperature coefficient resistor and is configured to pass a temperature-compensated current through the at least one NFET. An embodiment includes a ring oscillator that uses paired negative temperature coefficient resistors to provide temperature compensation for at least one ring oscillator stage.