Temperature-Compensated Timing Signal Generator With Low-Noise MEMS Sensing
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Solution Overview
Problem
Existing temperature sensors face challenges in achieving low noise performance with high sample rates, low integrated area, and low power operation, particularly in MEMS-based clock applications, where high accuracy and low Allan deviation are required.
Innovation Solution
The use of a switched capacitor network with a digital Sigma-Delta modulator, chopping circuitry, and a pseudo-differential VCO-based analog-to-digital converter to mitigate 1/f noise and circuit offsets, along with a feedback loop that adjusts the Sigma-Delta modulator input based on error data, effectively converts the temperature-dependent resistive element's analog error into a digital code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional temperature sensors are used to achieve high sample rates, then measurement speed is improved, but noise performance deteriorates
Solution Approach 1:
The patent implements periodic chopping of the sensor signal at a specific frequency (e.g., 1 kHz) to modulate the temperature signal. This periodic action separates the measurement signal from noise in the frequency domain, allowing high sample rates while maintaining low noise performance through synchronous detection that integrates only at the chopping frequency.
2Measurement precision
If conventional temperature sensors are used to achieve high accuracy, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The sensor operates in a periodic chop mode rather than continuous measurement, activating the sensing element only during measurement windows. This reduces average power consumption while maintaining high accuracy through precise timing and synchronous detection that captures the full signal amplitude during active measurement periods.
Solution Approach 2:
The patent implements a feedback loop that measures the sensor output and adjusts the chopping duty cycle or integration time to optimize the balance between accuracy and power consumption. The system adapts measurement parameters based on detected signal levels, reducing power when high accuracy is not required while maintaining precision when needed.
3Measurement precision
If conventional temperature sensors are used to achieve low noise performance, then noise is reduced, but integrated area increases
Solution Approach 1:
The patent replaces traditional analog filtering and averaging circuits with digital signal processing techniques. The chopping frequency and synchronous detection are implemented in the digital domain, eliminating the need for large analog capacitors and complex analog filtering networks, thereby reducing integrated area while achieving equivalent or superior noise performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a temperature sensor with improved noise performance, higher sensitivity, and reduced power consumption, enabling accurate temperature measurement across a wide range of temperatures with compact and efficient design.
Implementation Method 1
temperature dependent characteristics (and/or changes therein) of a temperature sensitive device (for example, a micromachined thermistor structure)... the temperature dependent characteristics (and/or changes therein) of the temperature sensitive device is resistance or change in resistance
Data Source
AI summary
The temperature-dependent resistance of a MEMS structure is compared with an effective resistance of a switched CMOS capacitive element to implement a high performance temperature sensor.