In today's electronic technology era, we can't do without the smart products in life, especially mobile phones. In this fast-paced city of mobile payment, maybe you can try a life without a mobile phone for a day, I am afraid there will be many inconveniences. The mobile phone relies on it, a crystal oscillator smaller than the rice grain determines the "life and death" of the entire circuit board. If it doesn't work, the whole system will be paralyzed, and people in the industry can be compared to the heart of the board.
Crystal vibration stop
The crystal oscillator is the "heartbeat" generator of each board, and the crystal oscillator is selected to ensure the durability of the board. However, it is inevitable that the crystal will stop vibrating. The role of the crystal oscillator is to provide the reference frequency to the various parts of the graphics card, network card, motherboard, etc. It is the most important component in the clock circuit. The crystal oscillator is like a ruler. The unstable working frequency will cause the operating frequency of the related equipment to be unstable, which is naturally prone to problems. In practical applications, when the crystal oscillator is stopped, it must be combined with the actual situation and product specifications.
There are a lot of crystal oscillators that can't be used to cause the whole machine to have no electricity problem.
● The reason of the crystal itself: chip fragmentation, parasitic, poor DLD, excessive impedance, poor frequency, insufficient or excessive crystal pulling force.
● Circuit reason: The dispersion of stray capacitance caused by other components, load capacitance or circuit design or processing is large, the voltage at both ends of the crystal is insufficient, and the static working point of the circuit is problematic.
What are the characteristics of the crystal oscillator in the working circuit?
Crystal damage is divided into two categories
● Completely stop the vibration: If the crystal oscillator stops, it may not be able to start normally for the mobile phone. Just like the heart suddenly stops beating, the circuit with the crystal oscillator as the clock signal will stop and strike.
●Instability: There are many reasons for instability, which may be crystal quality problems. More reasons are that the crystal parameters do not match the circuit parameters. For example, the system requires 20ppm accuracy, and the crystal parameters are only 50ppm. The capacitor requires 12 PF, and the actual capacitance is only 9 PF for many reasons.
When it is completely damaged, it can be removed, and the positive and negative resistance of each pin to ground can be measured compared with the normal integrated circuit of the same type. It is always found that one or several of the pins have abnormal resistance.
2. With instability
Consult the crystal oscillator supplier to calculate the correct capacitor matching value to replace the crystal oscillator, or replace the external capacitor. Replace the crystal with the correct accuracy. If it is unstable due to other problems, cool the suspected integrated circuit with absolute alcohol. If the fault occurs or the fault no longer occurs, it can be judged. Usually only new integrated circuits can be replaced to eliminate them.
Crystal vibration stop attention points
●Since the crystal oscillator is prone to mechanical stress and thermal stress during the shearing and soldering, the solder temperature is too high and the action time is too long, which will affect the crystal, which will easily lead to the crystal in a critical state, and even when the vibration occurs, the vibration will not stop or even stop. Vibration.
●When soldering, when the tin wire penetrates through the small hole in the circuit board, the pin is connected to the outer casing, or the crystal is in the manufacturing process, and the tin point of the pin on the base is connected with the outer casing to cause single leakage. , will cause a short circuit, causing the vibration to stop.
● When the crystal frequency shifts in frequency and exceeds the crystal frequency deviation range too much, the center frequency of the crystal cannot be captured, resulting in the chip not vibrating.
●Because the thickness of the chip itself is very thin, when the excitation power is too large, the internal quartz chip will be damaged, resulting in vibration loss.
●In the leak detection process, the crystal is prone to shelling under the pressure of alcohol, that is, the chip and the outer casing are easily collided when vibrating, so that the crystal is prone to vibration or vibration when it occurs.
Contact: Lillian Zhu
Add: Hongtian industry,baoan area,shenzhen city,guangdong ,china