Crystal Vs MEMS Oscillators  - Page 1
Forum section: electronics / beginners

author: 2X
author_rank: Frequent Contributor
timestamp: July 13, 2025, 12:13:43 pm
content: Hi, I would like your opinions about Crystal oscillators Vs MEMS oscillators; please confirm or no what I have write and tell me your opinion where I have question marks what is true?Crystal oscillators Vs MEMS oscillator:Crystal oscillators are more susceptible to vibration than MEMS.Because the crystals have high “Q” have lower phase noise a lower jitter instead of MEMS.Because the crystals have high “Q” have high frequency stability over temperature variations instead of MEMS.Oscillator Start-Up?Crystal oscillators consume less power due to their simple circuit structure instead of MEMS due to complex circuitry.Electromagnetic Interference (EMI)?Crystals have bigger package than MEMS in generally.Crystal oscillators need external capacitors –at the below link (1) from the mouser at filters have CL capacitance; why have this column if they don’t need external capacitors?Applications?Also, there crystals and MEMS with TCXO (Temperature Compensated Crystal Oscillator) I am not sure what is true:Crystal TCXO Oscillators Vs MEMS TCXO Oscillator:Crystal TCXO oscillators are more susceptible to vibration than MEMS TCXO.Phase noise & jitter?Frequency stability over temperature variations?Oscillator Start-Up?Power consumption?Electromagnetic Interference (EMI)?Crystals TCXO oscillators have bigger package than MEMS TCXO in generally.Crystal TCXO oscillators need external capacitors?Applications?(1) Crystals Oscillators & MEMS:https://eu.mouser.com/c/passive-components/frequency-control-timing-devices/oscillators/standard-clock-oscillators/Links for more information about Crystal Oscillators & MEMS Oscillators:MEMS vs. Crystal Oscillators: It’s All in the Applicationhttps://www.electronicdesign.com/technologies/embedded/article/21263965/q-tech-corp-mems-vs-crystal-oscillators-its-all-in-the-applicationMEMS vs Quartz Crystal Oscillators: Benefits, Reliability & Applicationshttps://www.sitime.com/company/newsroom/blog/mems-vs-quartz-crystal-oscillators-benefits-reliability-applicationsCrystal Oscillator vs MEMS Oscillatorshttps://components101.com/articles/crystal-vs-mems-oscillatorQuartz Crystal Design and Oscillator Basics: Lightboard InstructionThe working principle of a crystal oscillatorhttps://www.youtube.com/shorts/MblqHkni8AsEEVblog 1614 - Circuit Design TIP: Crystal OscillatorsUnderstanding Piezoelectric effect!8 Reasons to Replace Crystals with MEMS Oscillators

author: jwet
author_rank: Frequent Contributor
timestamp: July 13, 2025, 01:49:17 pm
content: Here is my take, I worked on MEMS development on the biz side at Maxim in the early 2000's.Most of these statements are kind of myths and can be addressed with engineering if a need exists. Companies like SiTime have been working on MEMS for a long time and have produced what they have deduced their customers want and worked hard to overcome any shortcomings. The list of intrinsic pros and cons is pretty short and both can meet most needs- there are corners where one of the other isn't suitable. You can do a market survey and see where the state of development stands now but don't assume these are fixed or represent the technology.XO's vs MEMSToday: MEMs are more rugged. MEMs are integratable given the right process. MEMS operate at lower frequencies with lower Q. MEMS have higher drift with temp.QUARTZ TCXO's vs. MEMS TCXO'sToday: MEMS are not easily "pullable"; temp comp is usually done in digital domain.(eg DS3221 vs DS3231M), the ultimate drift achievable isn't as good at the same cost/area

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 13, 2025, 02:11:51 pm
content: My experience -(Microchip) MEMS osc driving a W5500 Ethernet chip caused a 1% packet loss, presumably due to jitter. 100% confirmed by substitution.Most but not all higher-level protocls will usually hide this so didn't notice any issues until I used a protocol that didn't ( Artnet poll replies over UDP)

author: 2X
author_rank: Frequent Contributor
timestamp: July 13, 2025, 04:34:07 pm
content: Quote from: jwet on July 13, 2025, 01:49:17 pmSo between XO's vs MEMS if the temprature drift of the enviroment is big is better to use crystal oscillator instead of MEM?Also, Crystal oscillators and MEMs need external capacitors? -> at the below link (1) from the mouser at filters have CL capacitance; why have this column if they don’t need external capacitors?(1) Crystals Oscillators & MEMS:https://eu.mouser.com/c/passive-components/frequency-control-timing-devices/oscillators/standard-clock-oscillators/

author: edavid
author_rank: Super Contributor
timestamp: July 13, 2025, 06:05:39 pm
content: Quote from: 2X on July 13, 2025, 04:34:07 pmA packaged oscillator does not need external capacitors. The output capacitance spec is the maximum where the oscillator is guaranteed to meet its other specs (probably just rise/fall time).A bare crystal is different and needs to see the specified capacitance to oscillate on frequency.Mouser is being stupid and misleading by including that column for oscillators, but it's far from the worst website crime committed by them or other distributors.

author: TimFox
author_rank: Super Contributor
timestamp: July 13, 2025, 06:19:11 pm
content: Different crystal-oscillator circuits (fundamental or overtone mode) operate at either the series-resonant or parallel-resonant frequency, depending on the oscillator circuit configuration.The series resonance is insensitive to the shunt (load) capacitance, but the parallel resonance has a relatively-low dependence on the load.For the parallel-resonant circuits, this allows tweaking the frequency with a trimmer capacitor included in the load capacitance.General reference: R J MatthysCrystal Oscillator Circuits, original J Wiley & Sons (1983), revised Krieger Publishing (1992). See Chapters 3 and 5, with practical circuits of both kinds in Chapters 10 and 11.

author: 2X
author_rank: Frequent Contributor
timestamp: July 13, 2025, 07:16:13 pm
content: Quote from: edavid on July 13, 2025, 06:05:39 pmYou mean that the maximum capacitance is the maximum capacitance of the output pin from the packaged oscillator? For instance if the output pin of a packaged oscillator is drive many inputs or a single input with a capacitace bigger thah the maximun load capacitance will not oscillate or the signal will be deformed?

author: edavid
author_rank: Super Contributor
timestamp: July 13, 2025, 07:32:18 pm
content: Quote from: 2X on July 13, 2025, 07:16:13 pmIt's the test condition for the other AC values on the datasheet.If you exceed it, usually the only consequence is that the rise and fall time will increase.

author: jwet
author_rank: Frequent Contributor
timestamp: July 14, 2025, 12:57:20 am
content: QuoteSo between XO's vs MEMS if the temperature drift of the environment is big is better to use crystal oscillator instead of MEM?Its all engineering of course. If the drift is adequate and the ruggedness is more important then you'd go with MEMS. If drift is the main problem and the shock/vib is benign, then xtal.Also, Crystal oscillators and MEMs need external capacitors? -> at the below link (1) from the mouser at filters have CL capacitance; why have this column if they don’t need external capacitors?This is BS. Bare parallel resonant crystals need load caps but oscillator modules don't. MEMS are only available as packaged oscillators. Packaged oscillators should have a local bypass cap both types.Can I ask what the purpose of this is- just curious.

author: 2X
author_rank: Frequent Contributor
timestamp: July 14, 2025, 05:54:54 am
content: Quote from: jwet on July 14, 2025, 12:57:20 amI was searching for an oscillator so to place it on a FPGA and I saw that there many options and for curiosity then I decided to search it.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 14, 2025, 09:44:23 am
content: Quote from: 2X on July 13, 2025, 12:13:43 pmJust want to point out: 'Q' has nothing to do with temperature stability. A very high Q oscillator can have poor temperature stability.Q can be defined mathematically in a number of ways, but basically it refers to the inherent damping factor in the resonant element. A high Q means less losses, so less drive energy is required, so the resonant element is harder to "pull" away from its resonant frequency.

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2025, 02:10:31 pm
content: Quote from: SteveThackery on July 14, 2025, 09:44:23 amAs you said, nothing to do with temperature stability.However, the very highQof the crystal resonance gives good stability against changes in phase shift of the active circuit in the oscillator.

author: radiolistener
author_rank: Super Contributor
timestamp: July 14, 2025, 11:44:46 pm
content: I haveDSC6011ME2A- 12 MHz MEMS from Microchip. And its just a crap and needs to be replaced with usual crystal based oscillator. I tried using it as a clock source for an FPGA (Cyclone 10), with subsequent frequency multiplication via PLL, but its instability proved so severe that the PLL wouldn’t lock at high frequencies. Additionally, using it to clock a UART resulted in a high error rate.The main issue is that its frequency is very unstable and as we commonly say "wobbles like crap in an ice hole".These MEMS oscillators are excessively sensitive, for example, even bringing a hand within 10 cm causes a noticeable effect. They are also highly sensitive to temperature variations. Even under stable conditions, their frequency randomly drifts as if acting like a random number generator.I do not rule out the possibility that using a standard RC oscillator could achieve greater stability and much lower phase noise.To be honest, I don’t quite understand their purpose, they are likely used simply to reduce costs by replace classic crystal based oscillators. However, considering the relatively low cost of standard crystal oscillators, such a substitution appears unjustified.Overall, the downsides include frequency instability, high noise levels, strong sensitivity to temperature, and a proximity effect (likely capacitive in nature). I haven’t found any advantages whatsoever. They might potentially serve as a source of randomness, given their highly unstable frequency.

author: KE5FX
author_rank: Super Contributor
timestamp: July 15, 2025, 01:00:14 am
content: You're testing some really awful MEMS parts. Try SiTime.

author: SteveThackery
author_rank: Super Contributor
timestamp: July 15, 2025, 10:02:10 am
content: Quote from: TimFox on July 14, 2025, 02:10:31 pmExactly! That's what I meant by "pulling" the frequency, but yours is a better way to put it. 😄

author: Kleinstein
author_rank: Super Contributor
timestamp: July 15, 2025, 11:47:10 am
content: Using the PLL to do temperature effect corrections can be a problem. It can work well for quite some time, but if at he edge there would be steps in the frequency. So OK jitter most of the time, but with some possible glitches when the temperature changes. So the RMS period jitter may no show the weak points.If the PLL in the FPGA fails with the MEMS oscillator it could also be a PLL that is a bit picky about the clock. So to a part it can also be a poor PLL in the FPGA.Failure for the UART would be more consequence of glitches from the external PLL that amplifies phase noise from the oscillator. An UART is normally OK even with a relatively crude RC based oscillator if the temperature is stable.

author: radiolistener
author_rank: Super Contributor
timestamp: July 15, 2025, 02:00:09 pm
content: I don’t think the Cyclone 10 has a poor PLL implementation. For testing, I checked the spectrum of MEMS oscillator with radio receiver - the result was quite disappointing. Unlike crystal oscillators, where the carrier is stable and shifts smoothly with temperature, here the frequency was randomly jumping up and down. I believe this is the issue - probably the PLL simply doesn't like such unstable clock signal.It’s quite possible that I just encountered an unlucky batch, but my experience with MEMS oscillators has been negative, and I have no interest in using them again. I was expecting some improvement compared to standard crystal oscillators, but instead, the result turned out significantly worse. You can get a TCXO in the same size, so I don’t see any practical reason to use MEMS instead.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 15, 2025, 03:40:34 pm
content: Modern XOs also got quite smaller and with this often also more robust to shock. I would also prefer a real quarz crstall over mems, especially if a really stable clock is needed. When pusing the MEMs oscillators they tended to compare to the older XOs from the time when MEMS were new.An issue between the PLL inside a FPGA and the MEMS clock is a point to note and keep in mind.Compared to a FPGA the extra size, power and costs of a real crstal oscillator would not be that significant. It would be more small µCs where the oscillator could make a difference. Here the mems oscillator may have to also compete with an old style ceramic resonator.

author: fourfathom
author_rank: Super Contributor
timestamp: July 15, 2025, 04:02:05 pm
content: There are various types of TCXOs, and those with digital correction can have significant frequency jumps in their compensation response. Here's the frequency of a cheap "Fox" 10 MHz Quartz crystal TCXO as I increased the temperature from 37 to 39 deg C, then reduced it to 35C over a ten minute period. The small 0.08Hz "stairsteps" show the resolution of the homebrew counter I was using (a time-interval counter using a 100 MHz clock), but the large (approx 1 Hz) steps are where the Fox TCXO applied some correction. At the 200-second mark the temperature is essentially stable and the TCXO is apparently sitting at a correction threshold. I don't know if this TCXO is changing the internal PLL dividers, or switching capacitance, or using a D-to-A to drive a voltage-variable capacitor, but it's definitely not using a purely analog compensation method.I've gone through a few TCXOs and MEMs oscillators (SiTime), and while the Fox xtal osc is the only one I've seen with this frequency jump, rather than a smooth freq vs temperature curve, no doubt there are others. FWIW, the Fox unit met all it's specs, but this behavior made it completely unusable for the narrow-band RF modulation I was designing for.Since I made these measurements I've improved the measurement resolution of my counter by a factor of about 100, so I ought to try this test again. This wouldn't change the outcome, just make the graph prettier.

author: radiolistener
author_rank: Super Contributor
timestamp: July 15, 2025, 05:12:15 pm
content: Here’s how the MEMS oscillator’s carrier appears on the receiver. I didn’t bother soldering wires or adding an attenuator for a direct connection - instead, I simply captured the signal using an EMI probe placed near the oscillator. The scale is in Hertz. The MEMS carrier is at 700 Hz mark.Note the random nature of the frequency jumps, occurring despite stable environmental conditions.

author: fourfathom
author_rank: Super Contributor
timestamp: July 15, 2025, 07:00:18 pm
content: Quote from: radiolistener on July 15, 2025, 05:12:15 pmI first noticed the frequency jumps during "stable environmental conditions", but as you can see in my plot above these jumps can occur if the stable temperature happens to be at a TCXO adjustment transition point.My point is that this may not be a MEMs issue, but a temperature compensation implementation. The SiTime MEMS oscillator (and other quartz TCXOs) I tested showed a smoothly compensated frequency over a wide temperature range.

author: radiolistener
author_rank: Super Contributor
timestamp: July 15, 2025, 10:08:16 pm
content: You may well be right, but unfortunately I don’t have other models of MEMS oscillator for comparison to verify this.

author: 2X
author_rank: Frequent Contributor
timestamp: July 16, 2025, 09:17:45 pm
content: A fourm friend "bson" suggest me on the below thread to use the "LTC6905IS5-80#TRPBF". If anyone has try this please share his experience.https://www.eevblog.com/forum/fpga/lcmxo640c-3tn144c-clock-pins-configuration/new/?topicseen#newLTC6905IS5-80#TRPBFhttps://eu.mouser.com/ProductDetail/584-C6905IS5-80TRPBFA good/reliable brand for MEMS is "SiTime"?About crystal oscillators what brand/s is/are releiable (@radiolistener: could you tell us what brand do you use for the standard crystals?https://eu.mouser.com/c/passive-components/frequency-control-timing-devices/oscillators/standard-clock-oscillators/?product%20type=Standard%20Oscillators

author: 2X
author_rank: Frequent Contributor
timestamp: July 20, 2025, 08:33:40 pm
content: Quote from: fourfathom on July 15, 2025, 04:02:05 pmJust for curiosity, I am going to give a try with the below MEM oscillator from SiTime:SiT9121AI-2BF-33E50.000000Xhttps://gr.mouser.com/ProductDetail/SiTime/SiT9121AI-2BF-33E50.000000X?qs=Jslch3jnSjm1KzUuTMjmQA%3D%3DAbout a crystal oscillator and TCXO what brand would you suggest me from the side of temperature stability?

author: radiolistener
author_rank: Super Contributor
timestamp: July 20, 2025, 09:01:22 pm
content: I personally like ultra low phase noise oscillators from Abracon.I haven’t tried their TCXOs, but I’d expect them to offer good performance as well.