MEMS Oscillator vs Crystal Oscillator

Both of these oscillator types are electronic oscillators which are used to generate precise and stable clock signals in various electronic devices. They have different structures, working principles and distinct characteristics.

What is MEMS Oscillator ?

It is a type of electronic oscillator which uses micro-electro-mechanical system (MEMS) technology to generate stable and precise clock signals. It is used in wide range of devices to provide accurate timing references.

MEMS Oscillator circuit

The figure-1 depicts SI based MEMS oscillator circuit and its structure. It uses silicon resonator as source of oscillation. It uses PLL circuit in order to correct the frequency mismatches. The frequency variations occur due to tolerences due to manufacturing process and temperature drift.

The working principle of MEMS oscillator is that it utilizes mechanical vibrations of tiny microstructures integrated onto a semiconductor substrate. Microstructures can be in the form of beams, resonators or cantilevers. They are fabricated using microfabrication techniques similar to fabrication of ICs. When electrical signals are applied to these microstructures, they will vibrate at specific resonant frequency which generates oscillating signal.

The manufacturers of MEMS oscillator include SiTime Corporation, Microchip technology, Abracon, IQD Frequency products, Vectron International, Rakon, TXC Corporation etc.

What is Quartz Crystal Oscillator ?

It uses piezoelectric properties of a quartz crystal to generate stable and precise clock signals. It is widely used in various electronic devices such as communication systems, computers, space systems and more to provide accurate timing references.

crystal oscillator structure

The figure-2 depicts crystal oscillator circuit and its structure. As shown it uses simple oscillator circuit with quartz crystal operating in fundamental mode.

The heart of quartz oscillator is the quartz crystal oscillator which works on piezoelectric effect. When voltage is applied across the crystal, it mechanically deforms and generates vibrations. It vibrates at specific resonant frequency which is determined by its dimensions and properties. An electrical signal is applied through metal electrodes attached to the crystal.

The manufacturers of Quartz crystal oscillator are Epson Toyocom, TXC Corporation, Vectron International, Murata Manufacturing Co. Ltd, NDK, Bliley Technologies, CTS Corporation, Citizen Watch Co. Ltd., Abracon etc.

Difference between MEMS Oscillator and Crystal Oscillator

The differences are based on characteristics, structures and working of MEMS and quartz crystal oscillators. Following table mentions difference between MEMS Oscillator and crystal oscillator.

Specifications Quartz Crystal Oscillator MEMS Oscillator
Structure Simple complex (resonator, PLL, temperature compensation part, calibration)
Size and integration Larger size, may not be as integrable Small size, can be integrated onto chips
Aging and drift Very low aging and drift, suitable for precise applications Some drift due to mechanical aging, temperature variations etc.
Cost Higher manufacturing costs due to precision in crystal fabrication Cost effective manufacturing
Frequency determining element Very high Q quartz crystal resonator PLL (Phase Locked Loop)
Frequency flexibility Fixed frequency based on crystal's resonance properties Flexible frequency designs.
Working principle Utilizes piezoelectric effect in quartz crystals to generate oscillations. Utilizes micro-structured mechanical structures to generate oscillations.
Phase Jitter (ps) or phase noise Lower Higher
Power Consumption (mA) Lower Higher
Oscillator start up time Low High
Frequency accuracy and stability Excellent accuracy and long term stability, Exceptionally stable over time, No frequency jumps (i.e. less variation) Good accuracy and stability; may not match crystal, Frequency jumps observed (i.e. more variation)
Efficiency and reliability More Less

Conclusion: Overall, from above comparison between mems vs crystal oscillators we can conclude that MEMS and Quartz crystal oscillators are used in their specific domain areas. MEMS oscillators are used in high volume and low cost clock applications requiring not stringent phase noise. Quartz oscillators are used in space applications, radar, noise sensitive circuits and other RF and microwave applications MEMS oscillators may not provide same level of frequency accuracy and long term stability as offered by quartz crystal oscillators.

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