What are the faults after the crystal oscillator is damaged? What are the causes of failure?

Date：2022-07-20 15:02:42 Views：2122

There are patch crystal oscillator and plug-in crystal oscillator, passive crystal oscillator and active crystal oscillator with voltage. Crystal oscillator is very easy to damage. When choosing crystal oscillator, we should not only consider the cost performance, but also the matching of crystal oscillator parameters. What are the faults after the crystal oscillator is damaged? What are the causes of failure? This article has collected and sorted out some materials, which are expected to be of great reference value to readers.

Fault phenomenon after crystal oscillator is damaged

1. 12 MHz crystal oscillator. Now, 12 MHz crystal oscillator appears on some motherboards. This crystal oscillator is mainly used for USB interface. If it is damaged, it may cause problems such as USB interface failure.

2. 14.318 MHz clock crystal oscillator, used for clock chip. 14.318 MHz crystal oscillator does not vibrate, which will affect the motherboard_ There is no reset of the whole board after power on. Abnormal starting waveform may also lead to unstable startup of the host.

3. The 24.576 MHz audio crystal oscillator is connected to the sound card chip. If the crystal oscillator fails to vibrate, there may be problems such as no audio signal and unable to grasp the sound card.

4. The 32.768 kHz cylindrical crystal oscillator, real-time crystal oscillator, is connected to the South Bridge. The 32.768 kHz crystal oscillator can directly affect the accuracy of the clock of the motherboard system. If it is damaged, the clock will go inaccurate, which is the same reason with the inaccurate time of watches and mobile phones. Different motherboards have different problems caused by crystal oscillator damage. If the 32.768 kHz crystal oscillator on the motherboards of Intel, AMD and ATI chips does not vibrate, the motherboard will not power on or the whole board will not reset after power on. If the 32.768 kHz crystal oscillator in NVIDIA chip motherboard fails to vibrate, it will run CF or 45 (the corresponding digital card), and the digital card will run FF.

5. The 25 MHz crystal oscillator is connected to the network card chip. The failure of the crystal oscillator to vibrate will affect the failure to power on, or the phenomenon of power failure or non startup after power on. The phenomenon of power failure after power on also occurs when the crystal oscillator is vibrated unilaterally. When used for network card chip, if it does not vibrate, it will not grasp the network card, and if the frequency is abnormal, the network will not be connected or the network light will not be on.

6. The 27 MHz crystal oscillator provides the relevant working clock for the VGA part inside BGA. If the 27 MHz crystal oscillator fails to vibrate, it will affect the VGA display.

Reasons for failure of crystal oscillator

When selecting materials, the parameters do not match

1. Equivalent load requires 6pF and 15pF is selected.

Solution: replace the specification and model that meet the requirements. If necessary, please confirm with the original MCU manufacturer or crystal oscillator manufacturer.

2. The frequency error (PPM) is too large, causing the actual frequency to deviate from the nominal frequency, resulting in the failure of the crystal oscillator.

Solution: choose products with appropriate ppm value.

3. Too large or too small negative impedance will cause the crystal oscillator not to vibrate.

Solution: adjust the external capacitance of the crystal oscillator, such as C1 and C2 in Figure 3. Generally speaking, the negative impedance value should be no less than 3-5 times the nominal maximum impedance of the crystal oscillator. If the negative impedance is too large, the negative impedance can be reduced by increasing the values of the crystal oscillator external capacitors CD and CG;

4. The excitation level is too large or too small, resulting in the failure of the crystal oscillator.

Solution: adjust the excitation level of the oscillation circuit to the crystal oscillator output by adjusting the size of RD in the circuit. Generally speaking, the smaller the excitation level, the better. Besides the low processing power consumption, it is also related to the stability of the oscillation circuit and the service life of the crystal oscillator.

Nonstandard use of welding, storage, etc

1. When welding, the temperature is too high or the time is too long, which leads to the abnormality of the internal electrical performance index of the crystal oscillator and the failure of the crystal oscillator.

Solution: solution: during the welding process, the operation must be standardized, and the setting of welding time and temperature should meet the requirements of crystal oscillator. If you have any questions, please contact us for confirmation.

2. Improper storage environment leads to deterioration of the electrical performance of the crystal oscillator and failure to vibrate.

Solution: use and store it under normal temperature and humidity as far as possible to avoid crystal oscillator or circuit board being affected by moisture.

3. EMC problem leads to crystal vibration failure

Solution: Generally speaking, metal packaged products are superior to ceramic packaged products in terms of anti electromagnetic interference. If the EMC of the circuit is large, try to choose metal packaged products. In addition, do not use the signal line under the crystal oscillator to avoid interference.

Crystal oscillator manufacturing and quality problems

1. During the production or transportation of crystal oscillator, the internal crystal sheet is broken or damaged, resulting in the failure of crystal oscillator to vibrate.

Solution: at ordinary times, we need to pay attention to the thicker foam package during transportation to avoid damage in the middle; Avoid falling, heavy pressure, impact, etc. during the manufacturing process. Once the above conditions occur, it is forbidden to reuse and replace the crystal oscillator.

2. Impurities or dust are attached to the crystal chip inside the crystal oscillator, which makes the crystal oscillator unable to vibrate.

Solution: replace the crystal oscillator with a new one. When choosing crystal oscillator suppliers, we need to consider the manufacturer's equipment, workshop environment, process and process capability, which is related to the quality of products.

When it is found that the crystal oscillator does not start to vibrate during use, it is generally necessary to find the reason from the above three points. If the vibration stops, you need to see whether it is hot, which may be the reason for the high excitation level; Or the crystal oscillator gradually stops vibrating during operation, and the crystal oscillator pin is touched by hand or heated with an electric soldering iron to start working again. The general reason is that the negative impedance value in the oscillation circuit is too small, and the values of the external capacitors CD and CG of the crystal oscillator need to be adjusted to meet the loop gain of the oscillation circuit.

The above is related to the damage and failure phenomenon of the crystal oscillator and the cause analysis of the core detection and small editing. I hope it will be helpful to you. Shenzhen Chuangxin Online Testing Technology Co., Ltd. is a well-known professional testing institution for electronic components in China, with 3 standardized laboratories covering an area of more than 1000 square meters. The scope of testing services covers: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, component X-ray testing, taping and other test items.