Chopper Relaxation Oscillator for Flicker Noise and Drift Suppression
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Solution Overview
Problem
Relaxation oscillators used in low-cost, single-chip systems are susceptible to device mismatch and flicker noise, which affect their accuracy and reliability.
Innovation Solution
The implementation of a chopper circuit that alternately couples current sources to resistive and capacitive components, using distinct chopper clocks to mitigate frequency drift caused by flicker noise and device mismatch, thereby enhancing the accuracy of the oscillator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If relaxation oscillators are used for low-power operation, then power consumption is reduced, but accuracy deteriorates due to susceptibility to device mismatch and flicker noise
Solution Approach 1:
The patent employs periodic chopping action to alternately connect and disconnect the resistive and capacitive components from the current sources. This periodic switching modulates the flicker noise to higher frequencies where it can be more easily filtered, while maintaining the low-power operation of the relaxation oscillator topology.
Solution Approach 2:
The patent introduces chopper circuits as intermediary components between the current sources and the resonant tank. These chopper circuits act as mediators that periodically switch the connection states, enabling noise suppression without directly modifying the core oscillator structure or significantly increasing power consumption.
2Measurement precision
If chopper circuit is introduced to suppress flicker noise, then oscillator accuracy is improved, but device complexity increases
Solution Approach 1:
The patent divides the oscillator circuit into distinct functional segments: current sources, chopper circuits, resonant tank, and output stage. The chopper circuits themselves are segmented into separate control and switching portions. This segmentation allows for modular design and independent optimization of each component.
Solution Approach 2:
The chopper circuits operate with periodic switching controlled by clock signals, creating a regular temporal pattern that simplifies the control logic. The periodic nature of the chopping action allows for predictable noise modulation and easier synchronization with the oscillator output.
3Object-generated harmful factors
If chopper circuit alternately couples current sources to resistive and capacitive components, then flicker noise is suppressed, but frequency drift increases due to device mismatch
Solution Approach 1:
The patent incorporates feedback mechanisms where the oscillator output is monitored and used to control the chopper circuit timing. This feedback loop allows the system to compensate for frequency drift caused by device mismatch, as the chopping frequency and duty cycle can be adjusted based on the actual oscillator performance.
Solution Approach 2:
The patent dynamically changes operating parameters such as chopping frequency and duty cycle to optimize performance. By adjusting these parameters in response to detected frequency drift, the system can maintain frequency stability while continuing to suppress flicker noise through the chopping action.
Data Source
AI summary
An oscillator includes a first current source, a second current source, a first chopper circuit, a resistive component, a capacitive component, and a processing circuit. The first current source provides a first current. The second current source provides a second current. The first chopper circuit includes a first terminal coupled to the first current source, a second terminal coupled to the second current source, a third terminal coupled to the resistive component, and a fourth terminal coupled to the capacitive component. The processing circuit generates an output clock in response to a first voltage across the resistive component and a second voltage across the capacitive component. The first chopper circuit couples the first terminal and the second terminal to the third terminal and the fourth terminal, respectively and alternately. The resistive component and the capacitive component receive the first current and the second current, respectively and alternately.