Crystal oscillators are divided into two categories: passive crystal oscillators and active crystal oscillators. Based on the differences in the internal structure and working principle of these two types of crystal oscillators, the crystal oscillator is burned out of the case should also be divided into two categories.
For the passive crystal is burned out in the following two cases
1. improper hand soldering operation
If the use of high temperature or a long time to guide the foot part of the heating, will lead to the destruction of the internal chip silver plating layer, the resistance of ultra poor and other problems, triggering the crystal does not oscillate.
2. the excitation power is too large
According to the different applications, choose the appropriate excitation power crystal oscillator, do not only to change the output frequency of the crystal oscillator, arbitrarily change the size of the excitation power input to the crystal oscillator circuit. Because the excitation power provided by the circuit is too large may lead to the amplitude of the quartz chip becomes large, so too much heat generated by the quartz chip vibration area temperature rise. The quartz wafer itself generates a gradient temperature climb, which directly destabilizes the frequency. The mechanical deformation of the wafer may exceed the elastic limit, causing irreversible displacement of the lattice, resulting in permanent frequency deviation of the crystal output frequency. In more serious cases, the quartz wafer shatters, causing the crystal to completely stop vibrating (stopping), or what we call "burnout". Causes the equivalent resistance to become large (Note: the general crystal resistance value of 10 ~ 100Ω), affecting the crystal oscillation, in serious cases caused by crystal vibration stop. Excessive excitation power may also result in causing damage to the conductive glue that holds the wafer to the base, such as fracture, with the consequence of causing the internal circuit of the crystal to break and the crystal to stop.
In the circuit application of passive crystal, the voltage added to the two ends of the crystal is very low, so the passive crystal is burned out is very rare. The accident occurs more often in the improper application of the active crystal, so it needs special attention.
For the active crystal is burned out of the case is also divided into the following two points
1. voltage input connected to the wrong direction
The usual usage of quartz crystal oscillator: one foot hanging, two feet grounded, three feet connected to the output, four feet connected to the voltage.
Voltage correct connection: the voltage input must be connected to the voltage input pin (VCC) of the crystal oscillator. If wrongly connected to the grounding pin, the crystal will be current "burned".
2. the input voltage parameters are selected wrong
General input voltage: 1.8V, 2.8V, 3.3V, 5V. If the 5V is supplied to the active crystal with a rated voltage of 1.8V, it will bring a high risk of the crystal being burned out.
Special reminder for the active crystal: the active crystal will be broken only if it is fed with overload high voltage power. Do not connect the wrong input voltage or reverse.
