Something About Crystals

Oscillators have a number of types, and the pin’s definition for each is different, so is the method of connecting, Now let songji to introduce pin’s identification on oscillators.

The one where there is a dot is 1st pin, going counterclockwise (pin down), next respectively the 2nd , 3rd, 4th.

Oscillator’s usual usage: the 1st pin floats, the 2nd one grounded, the 3rd one connected to the output, the 4th one connected to the voltage.

It is not necessary to be equipped with DSP internal resonator for oscillators ,its signal is very stable, and the ways to connecting is relatively simple( What shall be attached importance is good power filter.It is commonly achieved by using PI-shape filter network consisting of a capacitor and inductor, and as well as a out put terminal with a tiny capacitor for filtering signal.)There is no need to equip a complex circuit. Compared to crystals, oscillator’s disadvantage is that the signal power level is permanent, so it is necessary to choose output power level. It is not very flexible, and also expensive.

Oscillators are formed by quartz crystals, quartz crystal chips can be used as resonators based on the piezoelectric effect: an electric field applied on the two poles of the chip makes the crystal produce mechanical deformation; and alternating electric field applied on the two poles of the chip makes the crystal mechanically oscillate. At the same time , mechanical deformation and resonation in turn produce alternating electric field, Although the alternating electric field is not very obvious, its frequency is quite stable. Once that the frequency of the alternating voltage added at its two poles is same as the natural frequency of the crystal chip(which is determined by its size and shape), the range of resonating will rapidly increasing, which is called “piezoelectric resonance”. The establishment and maintenance of the piezoelectric resonant state must be achieved by means of an oscillator circuit.