Integrated MEMS Gyroscope CMOS Drive Loop
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Solution Overview
Problem
Conventional MEMS devices face challenges in increasing performance, reducing size, and decreasing cost, particularly in achieving greater computational power for complex microsystems, which limits their applications.
Innovation Solution
The proposed system architecture for an integrated MEMS gyroscope includes a capacitive sensing element with a drive loop featuring a rectifier, comparator, Proportional-Integral-Derivative (PID) controller, and High Voltage (HV) driver forming an Automatic Gain Control (AGC) loop, along with a charge pump to maintain resonator oscillation at desired frequency and amplitude, and incorporates temperature compensation and quadrature signal measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEMS process technologies are used, then manufacturing simplicity is maintained, but performance improvement and computational power are limited
Solution Approach 1:
The patent combines CMOS circuitry and MEMS structures into a single integrated device, merging the computational capabilities of CMOS with the sensing capabilities of MEMS. This integration allows the device to achieve greater computational power and performance while maintaining a compact form factor, resolving the contradiction between performance improvement and system complexity.
Solution Approach 2:
The integrated device performs multiple functions including sensing, signal processing, and computation within a single structure. The CMOS portion handles computational tasks while the MEMS portion provides sensing capabilities, creating a multi-functional device that overcomes the limitations of conventional single-function MEMS devices.
2Volume of moving object
If MEMS device size is reduced, then integration density increases, but manufacturing precision and performance maintenance become more difficult
Solution Approach 1:
By integrating CMOS and MEMS fabrication processes into a single unified device structure, the patent achieves miniaturization without sacrificing manufacturing precision. The combined structure allows both sensing elements and computational circuitry to be fabricated together using compatible processes, maintaining precision while reducing overall device volume.
3Adaptability or versatility
If computational power is increased for complex microsystems, then application capability improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent creates a universal platform that combines computational CMOS circuitry with MEMS sensing capabilities, enabling the device to handle complex computational tasks while maintaining sensing functions. This multi-functional integration provides the computational power needed for complex microsystem applications without proportionally increasing device complexity.
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 solution enhances the performance of MEMS gyroscope systems by maintaining resonator velocity and amplitude, improving signal quality, and enabling efficient temperature compensation, thereby expanding their applicability in various fields.
Implementation Method 1
The sensing element is shown as capacitive but other sensing elements are also possible
Implementation Method 2
The system includes a rectifier, comparator, Proportional-Integral-Derivative (PID) controller driver
Implementation Method 3
A Coriolis vibration gyroscope (CVG) senses an applied angular rate about a sensitive axis by measuring a reaction force generated by the applied angular rate acting on a resonating drive structure
Data Source
AI summary
A CMOS IC substrate can include sense amplifiers, demodulation circuits and AGC loop circuit coupled to the MEMS gyroscope. The AGC loop acts in a way such that generated desired signal amplitude out of the drive signal maintains MEMS resonator velocity at a desired frequency and amplitude. The system can include charge pumps to create higher voltages as required in the system. The system can incorporate ADC to provide digital outputs that can be read via serial interface such as I2C. The system can also include temperature sensor which can be used to sense and output temperature of the chip and system and can be used to internally or externally compensate the gyroscope sensor measurements for temperature related changes. The CMOS IC substrate can be part of a system which can include a MEMS gyroscope having a MEMS sensor overlying the CMOS IC substrate.