Crystal oscillators are divided into two categories: passive crystal oscillators and active crystal oscillators.

Based on the differences in the internal structure and working principles of these two types of crystal oscillators, the situation when the crystal oscillator is burned out can also be divided into two major categories:

There are two points for the situation where the passive crystal oscillator is burned out:

1. Improper hand welding operation

If the pins are heated at high temperatures or for a long time, the silver-plated layer of the internal chip of the crystal oscillator will be damaged, the resistance will be out of tolerance, etc., causing the crystal oscillator to not vibrate.

2. Excessive excitation power

Depending on the application field, when choosing a crystal oscillator with appropriate excitation power, you must not arbitrarily change the excitation power input to the crystal oscillator from the circuit just to change the output frequency of the crystal oscillator. Because too much excitation power provided by the circuit may cause the quartz wafer to become larger in amplitude, excessive heat generation results in an increase in temperature in the vibration area of the quartz wafer. The quartz chip itself produces a gradient temperature rise, which directly destroys frequency stability. Because the degree of mechanical deformation of the chip may exceed the elastic limit, causing irrecoverable displacement of the crystal lattice, resulting in a permanent frequency deviation of the crystal oscillator output frequency. In more serious cases, the quartz crystal chip is shattered, causing the crystal oscillator to completely stop vibrating (stopping vibration), which is what we call "burning out". This causes the equivalent resistance to increase (note: the general crystal oscillator resistance value is 10~100Ω), which affects the start-up of the crystal oscillator, and in severe cases causes the crystal oscillator to stop oscillating. Excessive excitation power may also cause damage to the conductive adhesive that fixes the chip and the base, such as breakage. The consequence is that the internal circuit of the crystal oscillator will be broken and the crystal oscillator will stop vibrating.

In the circuit application of passive crystal oscillator, the voltage applied to both ends of the crystal oscillator is very low, so the passive crystal oscillator is rarely burned out. However, such accidents mostly occur in the improper application of active crystal oscillators, so special attention needs to be paid.

The situation when the active crystal oscillator is burned out is also divided into the following two points:

1. The voltage input is connected in the wrong direction.

The usual usage of a quartz crystal oscillator is as follows: one pin is floating, two pins are connected to ground, three pins are connected to the output, and four pins are connected to the voltage.

Correct voltage connection: The voltage input must be connected to the voltage input pin (VCC) of the crystal oscillator. If it is connected to the ground pin incorrectly, the crystal oscillator will be "burned out" by the current.

2. Wrong selection of input voltage parameters

General input voltage: 1.8V, 2.8V, 3.3V, 5V. If 5V is supplied to an active crystal oscillator with a rated voltage of 1.8V, there will be a high risk of the crystal being burned out.

As shown below:

Case of active crystal oscillator 2.048MHz being burned out

Before welding, the electrical parameters of the active crystal oscillator 2.048MHz were normal. After welding, vibration stop occurs.

After opening the cover of the crystal oscillator and inspecting it, it was found that there were no abnormalities on the chip electrode surface and IC, and the gold wire showed obvious fuse balling, which caused the circuit to open.

Picture of wafer electrode surface

It is analyzed that after the active crystal oscillator was powered on, it was subjected to voltage and current exceeding its own load, causing the gold wire to melt and the circuit to be open, causing the crystal oscillator to stop vibrating. Subsequent verification proved this to be the case.

Special reminder for active crystal oscillators: Active crystal oscillators will only be broken down when overloaded high-voltage power is input. Never connect the input voltage incorrectly or reversely.

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