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Smallest Xtal

Discussion in 'Embedded' started by Bob, Dec 16, 2005.

  1. Bob

    Bob Guest

    I am working on a design that needs to be as small as possible. I
    am using 0201 caps and resistors, and the smallest microcontroller
    I can find. So now the biggest component is the crystal. What is
    the smallest crystal package available?

    I am not too picky about the freq, something in the range of 10 to
    20 MHz.
     
    Bob, Dec 16, 2005
    #1
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  2. Bob

    PeteS Guest

    See this page:
    http://www.golledge.co.uk/docs/products/xtl_sm/xtl_sm.htm

    for a typical selection.

    The smallest I see is 2.6 x 2.1 x 0.6 (all mm)

    Cheers

    PeteS
     
    PeteS, Dec 16, 2005
    #2
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  3. Bob

    Stef Guest

    In comp.arch.embedded,
    Does it have to be a crystal? You may have better luck finding smaller
    resonators and those also come with built-in caps. One example is the
    Murata CSTCG_V series (20.00-33.86MHz), 2.0x1.3mm, built-in caps.
     
    Stef, Dec 16, 2005
    #3
  4. Bob

    Stef Guest

    In comp.arch.embedded,
    Another thought: Some small micro's have built-in oscs, but these
    are usually not very fast and not too accurate.
     
    Stef, Dec 16, 2005
    #4
  5. Bob

    MK Guest

    There are some very small crystals available but do your sums and test them
    carefully - I've found that AVRs can be very reluctant to start with small
    crystals. It's much smaller (and cheaper) to use the built in RC oscillator
    if you can. Silabs 8051 core parts and some AVRs these are pretty good.

    MK

    www.mkesc.co.uk
     
    MK, Dec 16, 2005
    #5
  6. The smallest SMT crystals typically have rather low maximum power
    dissipations, often <= 100uW, compared to the several mW that you can
    safely pump into a HC49 can without damaging it. That means the
    oscillator design is more fussy to get a circuit that will reliably
    start over the temperature range without damaging it. Yeah, it's
    usually just one extra resistor on the typical Pierce on-chip
    oscillator, but...


    Best regards,
    Spehro Pefhany
     
    Spehro Pefhany, Dec 16, 2005
    #6
  7. Do you need the Xtal ? No crystal is the smallest :)
    Quite a number of uC now have on chip OSC, that are calibrated,
    and in the 10-30MHz region.
    Actel's fusion specs 100MHz with 1% precision on chip osc.
    (No curves published yet, but if true, and indication of the leading
    edge....)
    -jg
     
    Jim Granville, Dec 16, 2005
    #7
  8. If your micro will accept a clock input, you might try a LTC1799
    resistor-set oscillator. It would require only the space of
    an SOT23-5 and an 0603 resistor.

    Mark Borgerson
     
    Mark Borgerson, Dec 16, 2005
    #8
  9. Bob

    Scott Moore Guest

    Bob wrote On 12/16/05 03:05,:
    Surface mount. It does not get any smaller.
     
    Scott Moore, Dec 16, 2005
    #9
  10. Could you use a MCU with an on-chip RC oscillator. e.g. the newer PICs can be as good as 1% - if you
    need better could you calibrate agains some external signal ?
    I think Dallas/Maxim do some programmable oscillator chips that may be worth a look if cost is not
    too critical.

    Another possibility is to use an LC oscillator - I think many MCU on-chip oscillators can be used
    with an LC combination instead of a crystal.
     
    Mike Harrison, Dec 17, 2005
    #10
  11. If exact frequency is not needed, either use a MCU with internal
    RC-oscillator (as suggested) or use an SMD inductor instead of the XTAL,
    most chips work fine with that.
    Frequency is 1 / (2 * pi * squareroot(L * C)) with C being the series
    replacement of the external caps (half the C's value if both are equal).
     
    Arie de Muynck, Dec 18, 2005
    #11
  12. Depending on the shape of the available space, maybe you could use aw atch crystal type package
    sitting on top of other parts.
     
    Mike Harrison, Dec 18, 2005
    #12
  13. Use one of the new generation silicon clock generators. They are
    available in very small packages. Some can be programmed over a
    1 wire bus to the frequency you need. Others use one external resistor
    to set the frequency. Maxim, Linear Technology and others manufacture
    these devices.

    Regards
    Anton Erasmus
     
    Anton Erasmus, Dec 19, 2005
    #13
  14. If you get hold of a old/bad computer motherboard, there is likely a very
    small 14.something MHz crsytal on there.

    Mat Nieuwenhoven
     
    Mat Nieuwenhoven, Dec 20, 2005
    #14
  15. Bob

    Jim Stewart Guest

    Likewise, old NTSC video gear.
     
    Jim Stewart, Dec 20, 2005
    #15
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