![]() ![]() Temperature stability of quartz and MEMS. MEMS oscillators also have higher phase noise for high offsets (12 kHz to 20 MHz) because they use a low-Q LC oscillator for the PLL circuit.įigure 6: Quartz Oscillator and MEMS Oscillator Stability Plotĥ) Frequency Over Temperature Characteristics Phase noise at low offsets is critical for wireless communications and can cause some errors in optical communications. At 10 Hz, the quartz oscillator has 36 dB better phase noise than the MEMS oscillator. MEMS oscillators have higher phase noise for low offsets because the silicon resonator has poor “Q” or Quality factor as compared to quartz. Laboratory measurements also demonstrate that the quartz oscillators have much better phase noise than the MEMS oscillators. The ECS part was selected for the comparison because it is a “standard oscillator” used in many applications and manufactured in large volume. This is nearly eight times better than the MEMS oscillator. When testing the quartz-based crystal oscillator across the SONET bandwidth of 12 kHz to 20 MHz we achieve a 0.18 pS rms jitter. When measuring the jitter of the MEMS oscillator from 12 kHz to 20 MHz, we get 1.5 pS rms jitter measured. One with a MEMS-based resonator and one with a quartz based resonator. We choose off the shelf comparably priced oscillators. As a result, the MEMS oscillator draws 6.09 mA and the standard quartz oscillator draws about 3.16 mA, that’s two times more current needed by the MEMS to only achieve comparable jitter and phase noise levels to the quartz oscillator.įigure 3: Oscillator Start-Up Characteristics 40 MHz The PLL and LCVCO raise the total power consumption. Quartz-based oscillators have much lower power consumption because they have the advantage of a fundamental or harmonic oscillation and a simple circuit structure.īy contrast, MEMS-based oscillators consume more power because they have more circuitry. ![]() 7) Reliability: Mean time between failures.6) Vibration Sensitivity: Performance under adverse conditions.5) Frequency Stability: How stabile is the frequency when measured at 25☌?.Temperature Characteristics: How stable is the frequency with respect to changes in temperature? 3) Jitter and Phase Noise: What is the noise performance (a critical factor in communications equipment)?.2) Oscillator Start Up: How quickly does the oscillator start after power is applied?.1) Power Consumption: How much current is consumed?.ECS Inc also offers a summary of compiled data: The basic structure of these oscillators is shown in Figure 1.ĮCS Inc International tested and measured quartz-based oscillators and MEMS-based oscillators and compared them for six parameters which are critical for the design of communications, networking, industrial, and consumer electronic devices. They also require manufacturing calibration to operate correctly. In contrast, MEMS oscillators have a complex structure consisting of a MEMS resonator, a fractional-n PLL and temperature compensation network. In this side-by-side comparison, we will look at and directly compare a quartz-based oscillator with a MEMS oscillator.Ī crystal oscillator uses a quartz crystal reference and a simple oscillator circuit.Ī MEMS oscillator uses a silicon resonator as the oscillating source and requires a PLL circuit to correct the frequency for manufacturing tolerances and temperature coefficient.Īs these basic structures indicate, crystal oscillators are high quality clocks that are simply built. So, a comparison of an oscillator to a crystal is not a true test of the oscillator’s performance. It is proven that any oscillator be it quartz, SAW, ceramic, or MEMS will always outperform any standalone resonator. You may have seen another video from a MEMS manufacturer comparing MEMS oscillators to stand alone quartz crystals. These are the critical parameters that will decide the performance level of your product. When selecting the oscillator for your electronic devices or communications equipment, some of the timing considerations you need to think about are system performance, system clocking, signal quality and reference signal sources. Many frequency control manufacturers private label from both companies, with the exception of ECS, who does not see any value in the practice. Today, only a few remain and the leading MEMS-based oscillator manufacturer accounts for around 1% of the total timing market. In the last 15+ years, a handful of companies have developed MEMS-based oscillators. ![]() What is the choice for performance in critical applications, MEMS (Micro-Electro-Mechanical Systems) or quartz-based oscillators? MEMS-based oscillators have been available on the market since 2005. When the discussion of oscillators comes up, the same question will arise. ![]()
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