Analog Angle Article

Silicon MEMS clocks for Stratum 3 attack quartz-based timing approaches

Sunnyvale, Calif.—The venerable crystal-based clock/oscillator as the ubiquitous beating heart of so many designs is feeling the heat, figuratively speaking, as MEMS-based clocks offer better performance, smaller size, and other virtues.

The SiT5301 and SiT5302 silicon MEMS timing solutions from SiTime Corp. offer small size, low power, and extreme frequency stability compared to existing quartz oven-controlled oscillators (OCXO) and temperature-controlled oscillators (TCXO) approaches. They target Stratum 3-class applications (Telcordia GR-1244 standard), such as SONET and synchronous Ethernet-based core and edge routers, IP timing, and smart grids.


Frequency stability (ppm) of Si530x from 0 to +70°C.

The SiT5301 (1 to 60 MHz) and SiT5302 (60 to 220 MHz) feature these key specifications:

•±0.1 ppm frequency stability over commercial temperature (0 to +70°C)

•±0.37 ppm 24hour holdover stability

•±4.6 ppm frequency stability over 20 years

•Available in a 0.75 mm-high, industry-standard 2520-size package (as well as others), for what the vendor claims is the industry’s smallest ±100 PPB solution—a 60% reduction in size compared to other Stratum 3 TCXOs and 10× smaller than the OCXO

•Wide frequency range with 6 digits of accuracy, which allows designers to easily program-in custom frequencies

•No “activity dips” (unlike quartz) which enables a more-stable reference clock over temperature

•Operating voltage of 2.5V to 3.3V, eliminates level translation

•Integrated RMS phase jitter (12 kHz to 20 MHz) of 500 femtoseconds (typical)

•Configurable rise/fall time control improves trace impedance matching and reduces EMI

•Available voltage control with pull range of up to ±12.5 PPM, for in-system calibration and fine-tuning over time

•Silicon reliability of 500 Million hours MTBF (10× better than quartz)

•50,000 g shock and 70 g vibration resistance (10× better than quartz)

•Power consumption <75 mW, compared to >1W for a quartz OCXO and <15mW for a quartz TCXO

Availability : Samples are available now.

For more information : go to; for the SiT5301 datasheet, click here, and for the SiT5302 datasheet, click here.

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