Chopper-Based RC Oscillator for Stable Linear Frequency Tuning
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Solution Overview
Problem
Integrated oscillators face challenges in achieving precise frequency tuning over a wide range while minimizing power consumption and chip area, with temperature variations affecting frequency accuracy and linearity, and existing solutions lack flexibility in resistor-based trimming and are sensitive to temperature-dependent components.
Innovation Solution
A transconductance circuit with chopping circuitry and a frequency-controlled current source, coupled with a ring oscillator, uses a segmented capacitor array and a voltage divider to provide a frequency-controlled voltage, allowing for linear frequency tuning and reduced temperature dependence, and includes cross-coupled capacitors to improve loop recovery and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chopping circuitry is used to reduce temperature dependence and improve frequency stability, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The chopping circuitry is implemented by segmenting the oscillator circuit into distinct functional blocks: a ring oscillator stage, a chopping stage with switching elements, and a filtering stage. This segmentation allows the temperature compensation function to be isolated and controlled without redesigning the entire oscillator, managing complexity through modular architecture.
Solution Approach 2:
The chopping circuitry introduces intermediate filtering stages and switching elements that act as mediators between the ring oscillator and the output. These intermediary components process the oscillator signal to eliminate temperature-dependent variations, improving frequency stability while keeping the core oscillator simple.
2Adaptability or versatility
If a wide frequency range is achieved through frequency tuning, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The oscillator employs dynamic frequency tuning mechanisms where capacitor arrays and resistor values can be adjusted during operation to change the oscillation frequency. This dynamic adjustability allows the circuit to cover a wide frequency range (11-53 MHz) while maintaining accuracy through controlled variation of circuit parameters rather than relying on precise fixed component values.
Solution Approach 2:
The invention changes key circuit parameters (capacitance values through capacitor arrays, resistance values) to achieve frequency tuning across a wide range. By systematically varying these parameters, the oscillator achieves both wide adaptability and maintained manufacturing precision, as the parameter changes are controlled and predictable.
3Area of stationary object
If chip area is minimized for integrated circuit integration, then area consumption is reduced, but device complexity increases due to component integration
Solution Approach 1:
The invention merges multiple oscillator functions into a single integrated circuit block. The ring oscillator, chopping circuitry, filtering stages, and frequency tuning elements are combined into one unified structure, minimizing chip area while managing integration complexity through functional consolidation rather than separate discrete components.
Solution Approach 2:
The oscillator circuit employs a nested architecture where the chopping circuitry is nested within the oscillator structure, and filtering elements are nested within the signal path. This nesting allows compact integration of multiple functional layers, reducing overall chip area while organizing complexity in a hierarchical manner.
Data Source
AI summary
Circuitry for providing an oscillating output signal. This circuitry includes a transconductance circuit having a first input, a second input, an output. The transconductance also includes a first transistor, a second transistor, and chopping circuitry. The chopping circuitry is for alternatively connecting, in a first clock cycle phase, a first node to a first terminal of the first transistor and a second node to a first terminal of the second transistor and, in a second clock cycle phase, following the first clock cycle phase, the first node to the first terminal of the second transistor and the second node to a first terminal of the first transistor. An oscillator circuit is also included and coupled to receive voltage from the output of the transconductance circuit, wherein the oscillating output signal is responsive to an output of the oscillator circuit. Further connected to the transconductance circuit are circuitry for providing a first voltage to its first input and a frequency controlled circuit for providing a second voltage to its second input.