Author Topic: SMT Crystal Oscillator Teardown  (Read 314 times)

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Offline WizardTim

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SMT Crystal Oscillator Teardown
« on: July 26, 2020, 02:25:01 am »


"Taking a look at the construction and inner workings of a common SMT ceramic LCC package quartz crystal oscillator from Daishinku Corporation (KDS) manufactured in the late 1990s."

I’ve tried making videos in the past to give back to the YouTube community that’s always giving although they didn’t really turn out any good mostly because they’re not something I would actually watch. This video however was driven by my actual interest about something I wanted to find out so I think it might also interest to some of you.

Full disclosure I’m shilling myself here in an attempt to get the video out of the YouTube algorithm’s pit of obscurity as I doubt it’s going to serve my video if I just sit back and twiddle my thumbs. If you enjoyed it I would appreciate your likes as offerings to the algorithm and if you think something might become of my “fantastic” production quality consider subscribing to my video RSS feed, or the bell thing to play YouTube’s notification lottery.

Also, I’m interested in your opinion of the actual device, I’m not a silicon design engineer nor a quartz mechanical engineer so I’m sure I’ve missed or got something wrong.


 
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Offline thm_w

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Re: SMT Crystal Oscillator Teardown
« Reply #1 on: July 30, 2020, 02:47:16 am »
Way more in depth than I was expecting, great.

So you are saying they use a high frequency crystal and then divide it down, Eg 40MHz -> 10MHz. Is that due to small size of the crystal used?

Here is a PLL style unit but its not cheap ($10): https://www.silabs.com/documents/public/data-sheets/si540-datasheet.pdf
 
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Offline WizardTim

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Re: SMT Crystal Oscillator Teardown
« Reply #2 on: July 31, 2020, 12:54:08 am »
I suspect they use an 80 MHz crystal with a divide by 2 (current similar models from KDS list f0 as 80 MHz). However, if this were true, I would expect the quartz strip to be less than 0.05 mm thick but it’s 0.10 mm thick alluding to it being a lower frequency (around 16 to 25 MHz) however I’m not sure if the quartz frequency constant works the same way as conventional round disks as with strip resonators.

PLLs are much more complex and thus a lot more expensive to implement than a simple divider and they tend to have limitations especially in phase jitter and start up performance so I would assume KDS would avoid using one as much as possible, I’m wishing I powered and probed it without the lid, would have made it a lot easier.

For AU$10.45 that Si540 could be an interesting teardown there might be some RF wizardry going on to get the 1.5 GHz performance.
 
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