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SMD Crystal for Prop — Parallax Forums

SMD Crystal for Prop

nicolad76nicolad76 Posts: 164
edited 2010-05-09 13:28 in Propeller 1
I have been looking a little around in order to find (if existing) some crystal for the Prop with a minimal footprint. SMD would be great.
Any advice? Parallax does not sell any...that's a shame [noparse]:([/noparse]
Thanks
Nicola

Comments

  • Nick McClickNick McClick Posts: 1,003
    edited 2010-05-04 18:46
    How about something like this? Haven't tried it myself, but there are a lot of SMD 5Mhz xtals on mouser

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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-04 18:47
    A surface mount "tin box" Xtal used a larger surface area than a through hole type. There are loads of extremely small oscilator modules that are smaller than the Xtal/resonator shown in the photo (they were always too small for me to be serious about). This was removed from an old PCB and is 13.5MHz and runs quite happily on pll8x. This ploy might help as the higher the frequency the smaller the Xtal is inside.

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  • David CarrierDavid Carrier Posts: 294
    edited 2010-05-04 19:48
    Toby,
    We will generally sell anything that we stock, whether or not it is on the web page. You may be interested in the 10 MHz crystal used on the Spin Stamp. If it would work, you can call our sales department at 1-888-512-1024 and ask for part number 253-10000.

    — David Carrier
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-04 21:49
    David

    I was only trying to point out that there were other types than the "tin box" types. I an afraid that I recycle almost everything, that is most of it is dragged off of scrap. If only I could find some scrapped boards with Props on them.

    If I were to order anything it would have to go through the Finance Controller, and SHE wouldn't like it. Every Prop is a quarter of a pair of shoes (at English Prop prices) and that just would not do!

    Hey-Ho.

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  • David CarrierDavid Carrier Posts: 294
    edited 2010-05-04 23:25
    Toby,
    Sorry, I meant to address Nicola with that last response.

    — David Carrier
  • RaymanRayman Posts: 14,887
    edited 2010-05-05 00:56
    This is the SMD 5MHz crystal that I normally use:

    Digikey XC670CT-ND

    But, it's not exactly small...

    mpark has·a recent thread where he got a watch crystal working. That's probably the smallest option...

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-05 02:18
    The small cylindrical watch crystals and cheap and have the same specs as the bulky HC49 units. Even though these are "through hole" they take up the least amount of copper plus the two pads are very close together and at one end of the crystal so you can have a very tight pcb layout.

    http://forums.parallax.com/showthread.php?p=897202

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-05 02:26
    The only problem with these "watch" crystals is that they have to be immobilized, since their skinny leads on one end will allow them to flop around otherwise. Either hot melt glue or soldering the can to a neutral pad will be required.

    -Phil
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-05 02:41
    Phil, I know that the actual watch crystals themselves are even smaller and this style here is the traditional size. However you have me checking my boards now and I haven't found a problem with them flipping around before. Maybe if I designed a board for a missile I might have to think about securing the crystal (and everything else).

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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-05 06:46
    I also think it would take something more than hot glue to imobilize the xtal on a missile, especially at the end of it's journey.

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-05 06:57
    Don't worry, the missile will never explode unless it has the obligatory 7-segment LED clock counting down. I'm not stupid, I've seen enough movies.....

    I can say though that I really like the small footprint of these crystals as I have always resented having to use the "sasquatch" footprint of the HC49 smd version which is such a nuisance to route around and also keep noise free.

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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-05 09:17
    I remember HC6U cans !

    Clusso would get a CP/M system into one of those.

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  • nicolad76nicolad76 Posts: 164
    edited 2010-05-05 12:14
    Hi David
    thanks...I got that was for me [noparse]:)[/noparse]
    It is nice for me, when I buy for Parallax, to be able also to buy all those little thing I need to get my prop "spin".
    I usually buy my prop from you and then I go looking around for all other pieces from other sites....which add costs and loss of time...that's why my comment smile.gif
    Thanks for you tip!
    Nicola
  • KenBashKenBash Posts: 68
    edited 2010-05-05 15:52
    Nicolad,

    Attached is a photo of a board I designed a couple of years ago. It has 3 props on it. I made the pads for the crystal large enough that I could use regular "Cans" but also has a surface mount trace as well.

    It's been long enough ago that I don't remember who makes/made them but if you look at props "B" and "C" they have a small surface mount 5 mhz oscillator/crystal mounted next to them. It took a bit of searching on Digikey, but SOMEBODY makes them ( or at least did a couple of years ago )

    I don't even know whether they ARE crystals or ceramic oscillators but I do know that they work great for all the boards I've built. No problems with TV, Vga, or anything that I have done related to timing.

    I know I have some laying around somewhere but try to find them on Digikey first. If you don't find 'em I'll dig up an old Digikey purchase order and see what the numbers were.

    Ken B.

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-05 16:36
    Given that center ground pin, they look more like ceramic resonators. Such resonators work fine, unless you're trying to generate video or something else that requires accurate frequency control.

    -Phil
  • David CarrierDavid Carrier Posts: 294
    edited 2010-05-05 21:08
    For anyone looking at using 32 kHz crystals for their small size, the RTCC on the Spinneret Web Server will be using Digi-Key part number 535-9544-1-ND. It comes in a 3.2 x 1.5 mm surface-mount package.

    — David Carrier
  • Tracy AllenTracy Allen Posts: 6,666
    edited 2010-05-06 09:24
    The smallest one I have found at 5 MHz is from Jauch, the JXG75P4 series, 5mm x 7 mm x 1.8 mm.. The photo shows it at the far left in comparison to the QFN and QFP Propellers and a couple of other crystal packages.

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-06 11:53
    I have used very small smd crystals like the one from Jauch but usually they are expensive and hard to obtain. Also my beef about all types of smd crystals is that the pcb pads footprint covers a large area, as large as the crystal or more whereas the watch crystal style has two very small pads just at one end, in fact you can use vias. The watch crystal is also very cheap at around 36 cents a piece in 100 lots.

    Another thing, I thought the cut of the crystal would be different from the HC49 varieties but a careful examination of the datasheets reveals that these crystals have the same specs as the HC49 units, although the maximum operating temperature appears to be 10'C lower.

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  • Tracy AllenTracy Allen Posts: 6,666
    edited 2010-05-06 17:00
    Peter, I appreciate what you have emphasized about the layout advantage of the watch style crystal. I see that Digikey also stocks a 5.12 MHz version, so 5 MHz must also be possible, and the data sheet from Citizen says as much. I'm surprised it's not a stock part. 10MHz is outside the Parallax official PLL range (4-8 MHz), but obviously it works fine for many purposes. I just feel uncomfortable designing outside the design range when the end product is going to see environmental extremes.

    My issue with that cylindrical crystal is that I have to certify operation to -40 and +85 Celsius, and it is only rated -20 to +70. The Jauch crystals are almost all custom order, but they drop to around 65 cents each on full reels. That is for a -40 to +105 °C part.

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    www.emesystems.com
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-05-06 17:09
    Toby said...
    I remember HC6U cans !

    Clusso would get a CP/M system into one of those.
    I recall some pretty large crystal blocks in some old valve transmitters. I don't know what size they were.·I could get CPM into a crystal oven I used in the 70's with room to spare. The biggest size is the powerpack - and we all ignore that fact! LOL

    BTW I am thinking of making RamBlade II (slightly smaller pcb than RamBlade for sbc only) to fit into a Hammond Translucent Blue 1551FLTB box which is 50x35x15mm.

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-07 00:20
    Tracy Allen said...
    Peter, I appreciate what you have emphasized about the layout advantage of the watch style crystal. I see that Digikey also stocks a 5.12 MHz version, so 5 MHz must also be possible, and the data sheet from Citizen says as much. I'm surprised it's not a stock part. 10MHz is outside the Parallax official PLL range (4-8 MHz), but obviously it works fine for many purposes. I just feel uncomfortable designing outside the design range when the end product is going to see environmental extremes.

    My issue with that cylindrical crystal is that I have to certify operation to -40 and +85 Celsius, and it is only rated -20 to +70. The Jauch crystals are almost all custom order, but they drop to around 65 cents each on full reels. That is for a -40 to +105 °C part.

    Mouser have 5MHz cylindrical crystals in stock au.mouser.com/ProductDetail/ABRACON/AB308-5000MHZ/?qs=sGAEpiMZZMsBj6bBr9Q9aUe%252bp9Tek3UMjFhI3QXVlxo%3d at 40 cents each in 100 lots. The operating temperature is quoted as being 0 to 70 'C which is normal commercial temperature range for any device.

    I like the price of the Jauch crystals at 65 cents each "on full reels''!!! smile.gif Meanwhile, thousands of dollars later.... But it is good crystal to use for extended temperature ranges.

    EDIT: I have attached a screenshot of some of the different crystal footprints I have built in my Protel library. Notice the crystal that takes up the least amount of copper and has the terminals closest together is....

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    *Peter*

    Post Edited (Peter Jakacki) : 5/7/2010 12:49:55 AM GMT
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  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-07 06:46
    Along the way I have scrounged a couple of 10MHz and one 12MHz cylinder types. The only way to recover their board area would be to mount them over the Prop.

    That would be a second use for the X in the part number, thats where the glue goes. smile.gif

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  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2010-05-07 18:34
    Why are all the 20pF crystals on digikey (and everywhere else I've seen) only go up to 70C. My latest projects have required higher temperatures (in the 80C range). So I switched over to 18pF crystals which can go all the way up to 125C (for some).

    What is the reasoning for this? I haven't had any problems with the 18pF. Any foreseeable problems with this? Or is there a SMD crystal with 20pF and 85C spec someone can point me to?

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  • LeonLeon Posts: 7,620
    edited 2010-05-07 19:41
    Most crystal manufacturers can supply crystals for elevated temperatures, here is an example:

    www.golledge.co.uk/docs/products/xtlspec.htm

    You probably won't find them at suppliers like Digi-Key, though.

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  • Cluso99Cluso99 Posts: 18,069
    edited 2010-05-07 20:45
    Peter: Have you seen the Digikey TXC smt crystals 5x3.2mm? They require pcb space 5.4x3.3mm which is smaller than HC49US and 2 pads. About the size of 10uF tantalum smt 1206.
    They are available in 10MHz, 12MHz, 13MHz and 14.31818MHz for PLLx8. Pricing <60c ea per 100.

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2010-05-09 13:28
    Sorry I'm only just backing to Ray, those crystals look good and the price does too. They only seem to have the 10MHz in stock but that's ok. I will look into some more.

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