Mems Technology Brings New Advantages To Vcxo Applications

By Author: Martin Lobo
Total Articles: 355
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For several decades, quartz crystals have been used as the basis for a number of timing solutions. These timing devices are available in the form of quartz crystal oscillators and resonators. They provide a timing signal in both non-electronic devices such as watches as well as a multitude of electronic applications from radio transmitters/receivers to high-end communications systems.

As electronic systems add more features and increase performance, stability of frequency becomes increasingly important. The increased use of fine tune frequency control methods, such as those employed in voltage-controlled oscillators (VCXOs), highlights the need for precision in timing solutions.

Today’s oscillators are based on two main technologies: Quartz and MEMS
Quartz oscillators consist of piezoelectric crystals in addition to analog circuits. They are packaged together in ceramic or metal packages and provide clocks that meet the needs of many electronic applications. However, there are some important limitations as listed below.
• Quality ...
... and performance variation over multiple lots and across manufacturers
• Long lead times and lack of availability
• Lack of flexible features and customization
• Lack of integration

Today, with advances in micro electro-mechanical systems (MEMS) technology, electronic manufacturers are opting for silicon MEMS timing solutions for various clocking needs. MEMS oscillators provide a highly accurate and stable clock, plus they have overcome the limitations of quartz oscillators. Some of the benefits of MEMS timing solutions are listed below.
• Superior quality and reliability
• Short lead times and easy availability
• Wide range of programmable features with complete customization
• Integration capabilities

Today’s VCXO leverage the advantages of MEMS technology
VCXOs can fine tune their output clock frequency, and that makes them ideal for high performance telecom, networking, audio/video and instrumentation applications. MEMS-based VCXOs provide higher performance and greater flexibility for these types of applications than their quartz counterparts. MEMS-based VCXOs can easily be programmed to operate at any custom frequency between 1 to 800 MHz with up to six decimal places of precision. This allows a designer to specify any output frequency they require to optimize their system. And they can receive customized samples within a week. In addition, MEMS VCXOs are available in a broad range of frequency stabilities (as low at 0.5 PPM), operating voltages, package styles, as well as pull ranges that are much wider than the pull range available from quartz VCXOs.
Other key features of MEMS VCXOs are listed below.

• Up to 1600 PPM pull range, which is more than eight times better than most quartz VCXOs
• Tuning slope (Kv) consistency and linearity of 0.1 to 1%, which is 10 to 100 times better than most quartz VCXOs
• 0.5ps typical RMS integrated phase jitter, which provides excellent timing margin
• 50,000 g shock and 70 g vibration resistance, which is ten times better than quartz VCXOs respectively

MEMS-based timing solutions provide more flexibility, higher reliability and better stability as they eliminate the performance trade-offs (noise vs. tuning/pull range) found in quartz-based devices. This is especially important in today’s high performance applications that benefit from fine-tuning frequency control methods such as those used in VCXOs. Many of the benefits of silicon MEMS timing extend beyond VCXOs and can be found in other classes of oscillators such as temperature-compensated oscillators (TCXOs) and differential oscillators.

Learn more about :- Clock Generator & Differential Oscillator