Smallest Xtal

Dec 16, 2005 14 Replies

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.

See this page:

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for a typical selection.

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

Cheers

PeteS

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 (remove caps, dashes and .invalid from e-mail address to reply by mail) Often statistics are used as a drunken man uses lampposts -- for support rather than illumination.

Another thought: Some small micro's have built-in oscs, but these are usually not very fast and not too accurate.

Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) You may have heard that a dean is to faculty as a hydrant is to a dog. -- Alfred Kahn

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

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The smallest SMT crystals typically have rather low maximum power dissipations, often

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

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

Bob wrote On 12/16/05 03:05,:

Surface mount. It does not get any smaller.

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.

"Bob" wrote

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 Muijnck

Depending on the shape of the available space, maybe you could use aw atch crystal type package sitting on top of other parts.

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

If you get hold of a old/bad computer motherboard, there is likely a very small 14.something MHz crsytal on there.

Mat Nieuwenhoven

Likewise, old NTSC video gear.

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