ASIC Stress Sensing Layout for MEMS Temperature Drift Compensation
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Solution Overview
Problem
Conventional ASIC chips and MEMS devices face challenges in accurately measuring stress due to deformation and temperature-related issues, leading to poor accuracy and stability, while electric toothbrushes with Wheatstone bridges suffer from adhesive overflow affecting stress detection consistency and temperature drift.
Innovation Solution
An ASIC chip with a delay chain array, RC circuit, and microprocessor for stress measurement, combined with an MEMS chip and substrate configuration for consistent stress concentration, and an electric toothbrush design using the ASIC chip for stress detection without a separate analog-to-digital converter, improving accuracy and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Wheatstone bridge is used for stress detection in electric toothbrushes, then stress detection capability is achieved, but welding adhesive overflow affects the proportion relationship between bridge arms, reducing consistency, stability, reliability, sensitivity, and linearity
Solution Approach 1:
The patent replaces the mechanical Wheatstone bridge structure with an ASIC chip-based stress detection system. The ASIC chip integrates delay chains, counters, and control logic to measure stress through time-domain signal processing rather than resistance ratio measurements. This substitution eliminates the need for welding adhesive and bridge arm assemblies, thereby resolving the reliability issues caused by adhesive overflow while maintaining stress detection capability.
Solution Approach 2:
The patent merges the stress detection function with the existing drive circuitry by integrating the detection components directly into the ASIC chip that also serves as the drive controller. This consolidation eliminates separate Wheatstone bridge assemblies and their associated adhesive bonding requirements, improving both reliability and consistency of stress measurements.
2Device complexity
If a separate stress detection component and analog-to-digital converter circuit are used in different temperature fields, then modular design is achieved, but temperature drift compensation accuracy is insufficient
Solution Approach 1:
The patent combines the stress detection circuits and analog-to-digital converter into a single ASIC chip, ensuring they operate in the same temperature field. This integration allows real-time temperature drift compensation by placing reference delay chains and measurement delay chains in identical thermal environments, thereby improving compensation accuracy while maintaining manageable device complexity through unified design.
Solution Approach 2:
The patent introduces temperature compensation delay chains as intermediary elements that mediate between the temperature variations and the stress measurement signals. These reference delay chains experience the same temperature drift as the measurement chains, allowing the system to calculate and compensate for temperature effects through differential measurement, thus improving precision without requiring separate temperature sensing components.
3Ease of manufacture
If conventional ASIC chip internal circuits are used, then standard manufacturing processes are followed, but the circuits cannot be quantified due to deformation, making stress measurement impossible
Solution Approach 1:
The patent replaces conventional voltage-based or resistance-based stress sensing circuits with a time-based delay chain measurement system. The delay chains consist of cascaded logic elements whose propagation delay time changes predictably with stress-induced deformation. This time-domain measurement approach allows precise quantification of stress while using standard CMOS manufacturing processes, as the delay chains are implemented using conventional logic gates and transistors.
Solution Approach 2:
The patent changes the measurement parameter from electrical properties (voltage, resistance) to temporal properties (signal propagation delay). By measuring the time delay of signals traversing stress-sensitive delay chains, the system can quantify mechanical deformation and stress while maintaining compatibility with standard ASIC manufacturing processes. The delay time serves as a direct proxy for stress magnitude.
Data Source
AI summary
An application specific integrated circuit (ASIC) chip is provided. Stress in various directions can be measured by disposing symmetrical “four-corner+middle” delay chain combinations in three dimensions inside the ASIC chip. Two sensors using the ASIC chip are further provided. In one sensor, a micro-electromechanical system (MEMS) chip is stacked with the ASIC chip. In the other sensor, the MEMS chip and the ASIC chip are symmetrically arranged. After being stacked and symmetrically arranged, the MEMS chip and the ASIC chip have highly consistent stress concentration characteristics, which can calibrate stress in various directions and effectively improve accuracy and temperature stability of the MEMS chip. In addition, an electric toothbrush using the ASIC chip is further provided, which can effectively improve consistency, stability, reliability, sensitivity, and linearity of stress detection, and can more accurately compensate for a temperature drift.