SiTime, Silicon MEMS Oscillators and Clock Generators

MEMS Oscillator Frequency Stability

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The frequency output of all oscillators, whether quartz- and MEMS-based, varies over temperature. This variation is a crucial performance specification that is expressed as frequency stability and measured in parts per million (PPM). This stability rating is inclusive of variation over temperature, voltage, process and soldering.



SiTime 32 kHz Frequency Stability

In terms of frequency stability, SiTime’s revolutionary TempFlat™ MEMS 32 kHz oscillators are two times more accurate than quartz XTALs. The measured frequency variation of SiTime’s MEMS-based 32 kHz oscillators is plotted in blue lines as shown below. The red lines represent the frequency variation range of 32 kHz crystal resonators (XTALs). At room temperature (25°C), SiTime’s 32 kHz devices are trimmed to < 10 PPM, while quartz XTALs demonstrate 20 PPM variation. Over the entire industrial temperature range, SiTime’s devices exhibit < 75 to 100 PPM stability compared to typical quartz XTALs with -160 to -200 PPM.


With temperature compensation added, SiTime’s 32 kHz TCXOs exhibit frequency stability well within their ±5 PPM specification over temperature as shown below. SiTime has achieved TCXO-level stability in a timing solution that consumes up to 50% less power and is up to 80% smaller than quartz-based solutions.


SiTime MHz Oscillator Frequency Stability

The frequency variation of standard AT cut quartz crystal oscillators is shown below, along with the stability of typical MEMS oscillators from SiTime. Since SiTime's revolutionary MEMS oscillators have built-in temperature compensation, these devices exhibit very flat frequency stability over the entire industrial temperature range, with adequate margin at the low and high temperatures to meet the specifications of high performance applications.

SiTime offers a 10 PPM XO, as shown in the plot below, which quartz companies cannot offer. In fact, SiTime's 10-25 PPM XOs outperform quartz, SAW, and overtone oscillators at frequencies above 70 MHz. This is another fundamental change that SiTime is bringing to the timing market.


SiTime also offers 25 PPM XOs, as shown in the plot below, that have better frequency stability characteristics compared to quartz 25 PPM XOs.