How to avoid crystal oscillator failure? Third party testing agency for electronic products

Date：2022-10-12 15:56:11Views：663

The quality of crystal oscillator is directly related to the stability of the whole system. The specific selection not only requires detailed control of crystal oscillator parameters, but also refers to the requirements of different systems. Improper selection may cause the crystal oscillator to fail to vibrate. This paper will analyze the specific factors leading to crystal oscillator failure? How to avoid or solve this problem.

1、 During material selection, the crystal oscillator fails to vibrate due to parameter mismatch

1. The 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 shift from the nominal frequency, which causes the crystal oscillator to fail to vibrate;

Solution: Select the product with appropriate PPM value.

3. Too large or too small negative impedance will cause the crystal oscillator to fail to vibrate

Solution: Adjust the external capacitance of the crystal oscillator, as shown in Figure 3, C1 C2. Generally speaking, the negative impedance should be no less than 3-5 times the nominal maximum impedance of the crystal oscillator. If the negative impedance is too large, the external capacitors Cd and Cd of the crystal oscillator can be increased to reduce the negative impedance;

4. Too large or too small excitation level causes the crystal oscillator to fail to vibrate;

Solution: Adjust the excitation level of oscillation circuit to crystal oscillator output by adjusting the size of Rd in the circuit. In general, the smaller the excitation level, the better. In addition to low processing power consumption, it is also related to the stability of the oscillation circuit and the service life of the crystal oscillator.

2、 The crystal oscillator does not vibrate due to nonstandard use of welding and storage

1. When welding, the temperature is too high or the time is too long, resulting in abnormal electrical performance indicators inside the crystal oscillator, which causes the crystal oscillator to fail to vibrate

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

2. Improper storage environment leads to the deterioration of the electrical performance of the crystal oscillator, which leads to failure to start vibration

Solution: Use and store under normal temperature and humidity as much as possible to prevent crystal oscillator or circuit board from getting damp.

3. The crystal oscillator fails to vibrate due to EMC problems

Solution: Generally speaking, metal encapsulated products are superior to ceramic encapsulated products in terms of electromagnetic interference resistance. If the EMC of the circuit is large, metal encapsulated products shall be selected as far as possible. In addition, do not use signal lines under the crystal oscillator to avoid interference.

3、 The crystal oscillator fails to vibrate due to manufacturing and quality problems

1. The internal crystal chip is broken or damaged during the production or transportation of the crystal oscillator, causing the crystal oscillator to fail to vibrate

Solution: replace the crystal oscillator. At ordinary times, it should be noted that the foam should be thicker during transportation to avoid midway damage; During the manufacturing process, avoid falling, heavy pressure, impact, etc. Once the above situations occur, it is prohibited to use again.

2. Impurities or dust on the crystal chip inside the crystal oscillator cause the crystal oscillator to fail to vibrate

Solution: Replace the crystal oscillator with a new one. When selecting crystal oscillator suppliers, it is necessary to consider the manufacturer's equipment, workshop environment, process and process capabilities, which is related to the quality of products.

When it is found that the crystal oscillator does not vibrate during use, the above three points can generally be used to find the reason. If the vibration stops, it is necessary to check whether it is hot, which may be the reason for the high excitation level; Or the crystal oscillator gradually stops during operation and starts to work again after touching or heating the crystal oscillator pin with an electric soldering iron. 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 Cd of the crystal oscillator need to be adjusted to meet the return gain of the oscillation circuit.

The above is the "crystal oscillator failure analysis" related content brought about by this core creation test. I hope it can help you, and we will bring more wonderful content later. The company's testing services cover: testing and verification of electronic components, IC authenticity identification, product design material selection, failure analysis, functional testing, factory incoming material inspection, tape weaving and other test items. Welcome to call Chuangxin Testing, we will serve you wholeheartedly.