Do you know how to distinguishing between crystal and oscillator?

In the PCB design, the crystal (crystal oscillator) is a very important electronic component, which believes that most PCB engineers will not be unfamiliar with. Do you know how to tell them very clearly and what’s the difference between them?

一、Crystal

Crystal is a non-polarity component with two pins that require oscillating signals by means of clock circuitry, it is unable to oscillate.

The crystal reference circuit has a poor source of crystal signal, which typically needs to accurately match the peripheral circuit (for signal matching capacitance, inductor, etc.), and the peripheral configuration circuit needs to be adjusted when replacing crystals of different frequencies. It is generally recommended to adopt a high precision of quartz crystals, and do not use ceramic crystals with low precision.

二、Oscillator

The oscillator is 4 pins, a complete oscillator, except for quartz crystals, as well as transistors and sealing elements, and therefore the volume is large. The package of active crystals has 4 pins, which are VCC (voltages), GND (ground), OUT (clock signal output), NC (empty foot).

Oscillator reference circuit oscillator does not require the internal oscillator of the CPU, stable signal, good quality, and the connection mode is relatively simple (mainly for power filter, usually use a capacitor and inductor constitute a filter network, The output is filtered with a small resistance value.) and does not require a complex configuration circuit.

The difference between crystal and oscillator

1. Oscillator is relatively expensive, but the oscillator vibrates on its own. And whether there is a crystal or oscillator, it has its own advantages and disadvantages. If you consider product costs, it is recommended to select a crystal circuit; if you consider product performance, it is recommended to choose an oscillator circuit that saves time and can guarantee product performance.

2. The highest precision of the crystal is 5 ppm, and the precision of the oscillator can reach 0.1 ppm. The higher the accuracy, the frequency stability is better. The oscillator is better than the source of crystal, but there is also a small defect, the signal level of the oscillator is fixed, so it is necessary to select a suitable output level, poor flexibility.

3. Oscillator is generally 4 feet, a power supply, a ground, a signal output, an NC (empty foot). There is a point marker to 1 pin, press the counterclockwise (downward), respectively, 2, 3, 4.

4. Crystal has 2 pins, to generate an oscillating signal by means of an external clock circuit (the oscillating circuit inside the primary IC) that can generate an oscillation signal.