SPECIFYING SURFACE MOUNT QUARTZ CRYSTALS
A typical surface mount quartz crystal specification reads
24.0140MHz 12SMX-B 15 30 20 18 Fund TR T
Frequency Tolerance at 25°C
Lower end of Operating Temp Range
Additional Text Code (for non-standard product)
The following notes define each element of the
Frequency is normally specified in kilohertz (kHz) up to
999.999kHz and in megahertz (MHz) from 1.0MHz. All our
computer-generated transaction documents follow this
standard convention automatically.
The frequency should be described to seven significant
figures. If seven significant figures are not used, we assume
that any figure that might follow those given may be taken
as zero.Thus a frequency given as 16.6MHz will be taken as
16.60, not 16.66667.
Some specifiers extend the use of kHz to all crystals
operating in fundamental mode, reserving MHz for
overtones. To minimise the possibility of misunderstanding
it is best to use the standard method and specify
fundamental or overtone mode separately.
Please contact the sales office for details of developed
Before manufacture of the crystal can start, the holder style
must be defined. Each holder style covers a frequency
range which is defined in the relevant specification.
The cost of manufacture depends partly on the accuracy
required at reference temperature (which in the case of the
AT-cut crystal, is usually 25°C).
Where high initial accuracy is important the additional
manufacturing cost should be weighed against the cost of
including a frequency trimming facility within the oscillator.
Frequency stability is normally specified as a frequency
tolerance over a defined operating temperature range with
respect to the frequency at reference temperature. The
temperature ranges are defined for each crystal in the
relevant data sheet. However the majority of crystals will
continue to operate quite satisfactorily outside the
temperature range for which they are specified, but
with a possible degradation in the value of frequency
stability. Under normal conditions this will not damage the
A crystal designed for operation over a restricted operating
temperature range, (such as from 0 to 50°C) has a better
frequency stability over that range than one designed for
operation over a wide operating temperature range.
Therefore it is important not to over specify the
temperature range, as doing so will result in inferior
performance for the same or greater cost; or greater cost
for the same or inferior performance.
Operating Temperature Ranges
The standard operating temperature ranges for a crystal
■ 0 to 50°C –40 to 90°C
–10 to 60°C –55 to 105°C
–20 to 70°C –55 to 125°C
–30 to 80°C
When the required temperature range is symmetrical about
25°C, it is indicated in the specification by the lower figure,
ie: –20 to 70°C would read ‘20’ as shown in the example. If
the required temperature range is not symmetrical about
25°C, both figures are used, ie: –55 to 85°C and appear in
the additional text code section (T).
The characters ‘SR’ are used to denote calibration of the
crystal at series resonance. If it is to be calibrated at load
resonance the characters represent the circuit load
capacitance in pF.
Tray packaging is available as an option for CX-1 products
outlined in the SM Quartz Crystal chapter.
Unless individual data sheets state Bulk packaging, items
will be Tape & Reel packed. Please note: only complete
reels are sold.
■ BU = Bulk packed
■ TR = Tape & Reel packed
■ TY = Tray packed
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