he first thing to be clear is that crystal oscillators are divided into two categories: passive crystal oscillators and active crystal oscillators.
There are two points to address the situation of passive crystal oscillators being burned out:
2. Incorrect selection of input voltage parameters
Analysis shows that the active crystal oscillator was subjected to voltage and current exceeding its own load after being powered on, resulting in the gold wire melting and circuit breaking, causing the crystal oscillator to stop vibrating. Subsequent verification has proven that this is indeed the case.
Why did my crystal oscillator burn out again?
Release date：2023/8/23 20:47:00 Number of clicks：644 次 news source：
Based on the differences in the internal structure and working principles of these two types of crystal oscillators, the situation of crystal oscillators being burned out should also be divided into two categories.
1. Improper manual welding operation
If high temperature or prolonged heating is used on the guide foot, it can cause damage to the silver plating layer inside the crystal oscillator, excessive resistance, and other issues, causing the crystal oscillator to not vibrate.
2. Excessive excitation power
According to the different application fields, choose a crystal oscillator with appropriate excitation power, and do not arbitrarily change the magnitude of the excitation power input to the crystal oscillator just to change its output frequency. Due to the excessive excitation power provided by the circuit, the amplitude of the quartz chip may increase, resulting in an increase in temperature in the vibration area of the quartz chip due to excessive heat generation. The quartz chip itself generates gradient temperature rise, directly damaging frequency stability. Due to the mechanical deformation of the chip, it may exceed the elastic limit, causing irreparable displacement of the lattice and permanent frequency deviation of the crystal oscillator output frequency. In more severe cases, the quartz chip shatters, causing the crystal oscillator to completely fail to vibrate (stop vibrating), which is what we call "burning out". Causing an increase in equivalent resistance (note: generally, the resistance value of the crystal oscillator is 10-100 Ω), affecting the oscillation start, and in severe cases, causing the crystal oscillator to stop. Excessive excitation power may also lead to damage to the conductive adhesive that adheres to the chip and base, such as breakage, resulting in an open circuit in the internal circuit of the crystal oscillator and a shutdown of the crystal oscillator.
In the circuit application of passive crystal oscillators, the voltage applied at both ends of the crystal oscillator is very low, so there are very few cases of passive crystal oscillators being burned out. However, such accidents often occur in the improper application of active crystal oscillators, which requires special attention.
The situation of active crystal oscillators being burned out can also be divided into the following two points:
1. Wrong direction of voltage input connection
The usual usage of quartz crystal oscillators is: one foot suspended, two feet grounded, three feet output, and four feet voltage connected.
Correct voltage connection method: 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 oscillator will be "burned out" by the current.
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 is a high risk of crystal oscillator burnout.
As shown in the following figure:
Active crystal oscillator 2.048MHz burnt out case
The active crystal oscillator 2.048MHz has normal electrical parameters before welding. After welding, vibration stops.
In response to the opening inspection of the crystal oscillator, it was found that there were no abnormalities in the electrode surface and IC of the chip, and the gold wire showed obvious melting and balling phenomenon, resulting in a circuit break.
Special reminder for active crystal oscillators: Active crystal oscillators will only be broken down when they are fed into an overloaded high-voltage power supply. Do not connect the input voltage incorrectly or inversely.
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