All About Oscillating Crystals - The Basics

Oscillating crystals made high-precision wristwatches affordable for everyone. Now, they have become increasingly important as a reliable time base, including use in GPS positioning. 

To learn about oscillating crystals, it's important to understand their parameters.

Frequency

The frequency of oscillating crystals, just like in physics, is given in Hertz [Hz]; i.e. the number of vibrations per second. A 10 MHz quartz, for example, vibrates 10,000,000 times per second. Thinner quartz plates vibrate at higher frequencies.

Different applications and circuits require different frequencies of crystals. GPS applications, for example, typically operate at a clock frequency of 26 MHz.

Maintaining a stable frequency is particularly important for systems that exchange data with each other. Should the wrong clock frequency be selected, data loss or connection interruptions can occur.

New Packaging

In the past, oscillating crystals were only offered in familiar metal packages, mounted and soldered via two connecting wires to the circuit board. With the advent of surface mount technology (SMT), the components have become smaller and are now mostly ceramic.

Industry standard packages range from 7.0 x 5.0 mm2 to 1.2 x 1.0 mm2. Mini packages are also now available at 1.0 x 0.8 mm2.

Frequency tolerance

Frequency tolerance indicates the extent to which the oscillating crystal deviates from the nominal frequency at room temperature.

Less is not always more; choosing components with a lower frequency tolerance than is required will increase costs with no real benefit.

Frequency stability

Frequency stability is the amount the frequency changes over the temperature range. It directly correlates to the cutting angle of the quartz blank.