MEMS Resonator Clock Generation Without External Quartz
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Solution Overview
Problem
MEMS devices face challenges in generating an accurate clock signal without external quartz crystals, as existing oscillator circuits, such as relaxation oscillators, are sensitive to temperature changes and cost constraints prohibit the use of crystal filters in consumer applications.
Innovation Solution
Utilizing the oscillating MEMS structure as a reference signal for a frequency translator circuit like PLL, DLL, or frequency multiplier to generate an accurate clock source, minimizing additional costs and leveraging the stability of MEMS oscillation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a relaxation oscillator circuit is used to generate the clock signal, then the device complexity and cost are reduced, but the frequency accuracy and stability deteriorate due to temperature sensitivity
Solution Approach 1:
The patent replaces the electrical relaxation oscillator circuit with a mechanical resonating MEMS structure as the frequency-determining element. The MEMS resonator uses mechanical vibration at a stable resonant frequency to generate the clock signal, eliminating temperature-sensitive RC components while maintaining integration benefits. This substitution provides frequency stability comparable to quartz crystals without the associated cost and size penalties.
2Measurement precision
If a crystal filter is used to provide an accurate clock signal, then the frequency accuracy is improved, but the cost and device size increase
Solution Approach 1:
The patent makes the MEMS structure serve dual functions: its primary sensing or actuating function plus a secondary function as the frequency-determining oscillating element for the clock signal. By utilizing the inherent mechanical resonance of the MEMS structure itself rather than adding a separate crystal filter, the design achieves accurate timing without increasing device size or cost, as the same MEMS component performs both roles.
3Ease of manufacture
If RC circuit components are used in the oscillator, then the manufacturing simplicity is improved, but the frequency stability over temperature deteriorates
Solution Approach 1:
The patent changes the fundamental parameter used for frequency determination from electrical RC time constants to mechanical resonant frequency. The MEMS resonator's natural mechanical resonance frequency is inherently stable over temperature and process variations, unlike RC circuits where resistor and capacitor values drift with temperature. This parameter change maintains ease of integration while dramatically improving frequency stability.
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 provides a stable and accurate clock signal for MEMS devices, reducing temperature-induced frequency shifts and eliminating the need for external quartz crystals, while maintaining cost-effectiveness and size efficiency.
Implementation Method 1
MEMS devices with a vibrating MEMS structure
Implementation Method 2
the oscillating MEMS structure as a reference signal for a frequency translator circuit such as PLL, DLL or frequency multiplier which generates the timing source
Data Source
AI summary
A system and method is disclosed that provides a technique for generating an accurate time base for MEMS sensors and actuators which has a vibrating MEMS structure. The accurate clock is generated from the MEMS oscillations and converted to the usable range by means of a frequency translation circuit.