MEMS vs Quartz Oscillators: SiTime SiT3372 and the Jitter Question

The Old Debate, Updated for 2026

Ten years ago the MEMS oscillator argument was about reliability and startup, not jitter. That changed. SiTime's Elite platform claims integrated RMS phase jitter of 0.23 ps in the 12 kHz–20 MHz band — a thousand-fold class improvement over the company's early parts (SiTime itself cites a trajectory from roughly 175 ps to 0.23 ps over about a decade). At those numbers, MEMS oscillators now appear in 400G Ethernet SerDes, PCIe reference clocks, and 5G radio timing — applications that a decade ago demanded quartz and nothing else.

So where does the jitter argument actually stand in 2026? The honest answer: it depends on which jitter number you read, and in which environment the board runs. We get asked this constantly in clock RFQs — the first question back is always which jitter number the spec writer meant.

What the Jitter Number Actually Means

The spec that matters for high-speed links is integrated RMS phase jitter over a defined integration band — usually 12 kHz to 20 MHz for general-purpose clocking, or the Ethernet mask (1.875 MHz–20 MHz) for network gear. The band choice changes the headline number substantially: the same oscillator that shows ~0.2 ps over the wide band can show ~0.1 ps under the 10GbE mask, because the low-offset noise near the carrier is excluded.

Do not confuse this with period jitter, which measures each individual edge's deviation and is always larger. A part can show 0.2 ps RMS phase jitter while its period jitter sits around 1 ps — both are true, and both belong in different design conversations. When a vendor quotes "jitter," always ask: integrated over which band, including spurs or not? We usually design against the wide-band number; it's the conservative one.

SiT3372: What the Datasheet Says

The SiT3372 is SiTime's programmable differential MEMS VCXO, part of the Elite platform, available in LVPECL, LVDS and HCSL outputs. Here are the headline numbers:

Frequency: 1 to 220 MHz, programmable to six decimal places — above that, SiTime points you to the SiT3373 (up to 720 MHz). One part number family spans your whole clock plan.
Phase jitter: 0.225 ps typ / 0.270 ps max (0.275 ps max in smaller packages), random RMS at 156.25 MHz over 12 kHz–20 MHz, spurs included, across all supply voltages and a 100 ppm pull range.
Stability: ±15, ±25, ±30 or ±50 ppm total (initial tolerance, temperature, supply, load and first-year aging included).
Pull range (APR): options from ±25 ppm to ±3200 ppm, 1.0% max pull linearity — real VCXO territory, not a fixed-frequency oscillator with a pin.
Environment: 2.5/2.8/3.0/3.3 V supplies, packages down to 3.2 × 2.5 mm, temperature ranges to −40 to +105°C, 3.0 ms max startup.

For a datacom designer, the practical magic is the programmability: any frequency in range is available from stock, so you stop carrying a dozen custom-cut crystal SKUs.

Where MEMS Beats Quartz — and Where It Doesn't

The strongest MEMS argument is not the static jitter number; it is jitter under stress. Under a 7.5 Grms random vibration profile (15 Hz–2 kHz), quartz oscillators show roughly a 20 dB phase noise degradation while MEMS shows no discernible increase — because the MEMS resonator mass is 1/1000 to 1/3000 that of quartz. Elite parts claim ~0.1 ppb/g vibration immunity, 20–30× better than quartz. For anything that rides on a vehicle, a robot, or a datacenter fan tray, that is the difference between a link that stays up and a field return. In those builds we'll take the vibration immunity over the headline jitter number any day.

Thermally, the DualMEMS architecture places the temperature-sensing resonator within 200 µm of the timing resonator (30 µK resolution), eliminating the thermal lag that quartz TCXOs suffer when ambient temperature swings quickly. Elite Super-TCXOs hold ±0.1 ppm over −40 to +105°C with 3×10⁻¹¹ Allan deviation at 10 s averaging — better than typical quartz TCXOs.

So when does quartz still win? The niche is close-in phase noise: applications demanding femtosecond-class ultra-low noise at low offset frequencies — high-end RF test instruments, radar and some measurement systems — still favor premium quartz OCXOs, where MEMS has not yet matched the best crystal oscillators. Quartz also remains cheaper at extreme high volume for fixed, unqualified frequencies, and existing qualified designs are rarely worth requalifying.

Selection and Sourcing

Picking between a MEMS VCXO and quartz comes down to environment first, jitter band second: vibration-exposed, thermally dynamic, multi-frequency designs favor the SiT3372; static, single-frequency, ultra-low-noise benches stay with quartz OCXOs. If you go MEMS, one programmable family covers every frequency in the product line — and because parts program to order, lead times beat custom-cut crystals by weeks.

Need a comparison of your actual frequencies? Search SiT3372 and quartz oscillator parts or upload your clock BOM — partscubeglobal.com will match both MEMS and quartz options against stock and deliver a side-by-side quote.