SiTime, Silicon MEMS Oscillators and Clock Generators

MEMS Oscillator and TCXO Frequency Stability

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The frequency of all oscillators (quartz and MEMS-based) varies over temperature. This variation is a crucial performance specification that is expressed as frequency stability in parts per million (PPM).

Reference timing products are categorized based on stability. XOs (oscillators) offer 10 to 100 PPM stability, while TCXOs (temperature compensated oscillators) offer 0.1 to 10 PPM stability.

SiTime offers both MEMS TCXOs with 0.1 to 5 PPM frequency stability and MEMS XOs with 10 to 50 PPM frequency stability. This stability rating is inclusive of variation over temperature, voltage, process and soldering. Typical quartz XOs offer 25 to 100 PPM stability.

 

 

SiTime TCXO 0.5 PPM Frequency Stability

Certain applications such as wireless, GPS and wireline infrastructure, require very tight frequency stability of 0.1 to 5  PPM over temperature. These applications have been traditionally serviced by quartz TCXOs (temperature compensated oscillators) hat are specially calibrated to meet these tight specifications. SiTime offers MEMS TCXOs that replace quartz TCXOs without any board layout changes. The graph below shows the measured frequency stability of a 0.5 PPM SiTime TCXO that operates over the industrial temperature range.

FS-plot3-TXCO

 

SiTime XO 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.

FS-plot1-10PPM

 

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

FS-plot2-25PPM