MEMS frequency synthesiser rivals quartz

NXP has unveiled a new ultra-compact high-precision MEMS-based frequency synthesiser at CES.
The company’s MEMS replaces a quartz crystal with a bare silicon die that is more than 20 times smaller than the smallest crystal available today. The MEMS die does not require any dedicated, quartz-like, ceramic or metal-can hermetic package. Instead, it can be merged with other ICs into a standardised, low-cost plastic package.

Picture: NXP

NXP says its proprietary resonator technology for MEMS-based timing devices features higher frequency stability, lower timing jitter and lower temperature drift compared to other CMOS oscillators. The first prototype currently released for production enables a highly stable clock reference that is ideal for communications equipment using Gigabit Ethernet, USB, PCI-Express and S-ATA, plus CPU timing, memory and control in consumer electronics devices. According to the company the device’s high level of system integration and very small form factor make it a compact, robust and highly cost-effective alternative to quartz crystal-based timing devices.
Key features of NXP MEMS resonator technology include:
•         Higher frequency stability. The resonator exhibits very low motion damping and hence a very high quality factor (Q-factor), allowing for high frequency stability and low close-to-carrier noise levels of the oscillator. Low damping is achieved using a mono-crystalline silicon resonator that is placed under reduced atmospheric pressure in a low-cost, on-wafer processed hermetic cavity. The resonator shows no significant ageing, even after accelerated lifetimes such as HTOL, HAST and TMCL.
•         Lower timing jitter. NXP’s MEMS resonator uses a unique piezo-resistive concept combining strong electro-mechanical coupling with a high resonance frequency. The high oscillation frequency that is made possible with this concept enables very low timing jitter. By using the piezo-resistive concept, the resonator overcomes the classical issue of weak electro-mechanical coupling at high resonance frequency, which is encountered in conventional silicon MEMS resonators.
•         Lower temperature drift. The NXP resonator exhibits 10 times less temperature drift compared to conventional silicon resonators, and is comparable to quartz-crystal tuning forks. The reduction in temperature drift is realised passively, and therefore does not require any additional power that is often needed in conventional temperature drift correction schemes. As a result, the oscillator is able to realise very high frequency stability of only a few parts-per-million (ppm).

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