Contents:

1. What is a crystal oscillator
2. What is the working principle of crystal vibration
3. What are the types of crystal vibration
4. Main parameters and specifications of crystal vibration
5. Crystal vibration selection and application
5.1 How to choose the right crystal oscillator
5.2 Crystal vibration selection criteria in different application scenarios
5.3 How to select a specific frequency crystal oscillator
6. Crystal vibration fault troubleshooting
6.1 Reasons and solutions for crystal vibration failure
6.2 The output frequency of crystal oscillator is unstable or deviates from the nominal value
6.3 Other common problems in the use of crystal vibration and their solutions
7. Conclusion

Have you ever encountered a selection or usage problem related to crystal oscillators? This is actually very common in the design and assembly of electronic devices. Do not understand the working principle and technical parameters of the crystal oscillator, may lead to instability of the system, or even completely unable to work normally. But don't worry, today's article will help you solve these problems. Below, INFINITECH introduces the basics of crystal oscillators, including how they work, what types are available, and how to choose the right crystal oscillator for your specific needs.

I believe that through this sharing, you can have a comprehensive understanding of crystal vibration, and can better deal with various problems that may be encountered in practical applications. Both beginners and experienced professionals can benefit greatly from it. So let's get started.

1. What is a crystal oscillator

A crystal oscillator, or crystal oscillator, is an electronic component that uses the piezoelectric effect of a quartz crystal to produce a stable frequency signal. Quartz crystals have very stable physical properties, generating electrical charges (i.e. piezoelectric effects) when subjected to mechanical stress, and deforming when a voltage is applied. Based on this property, when the appropriate circuit is added to the quartz crystal, it can vibrate at a specific natural resonance frequency, and this frequency is very precise and stable. Therefore, crystal oscillators are widely used in a variety of applications requiring high-precision timing or clock signals.

2. What is the working principle of crystal vibration

The working principle of crystal oscillators is based on the piezoelectric effect of quartz crystals, a phenomenon in which a material generates an electric charge when subjected to mechanical stress or deforms when a voltage is applied. In a crystal oscillator, when an electrical signal is applied to a quartz crystal, the crystal begins to vibrate at its specific natural resonant frequency due to its piezoelectric nature. To maintain and enhance this vibration, the crystal oscillator usually forms an oscillating circuit together with the amplifier and feedback network. In this process, the crystal functions as a highly selective filter, allowing only signals that match its resonant frequency to pass through, thus significantly enhancing that frequency component.

For different types of crystal oscillator, its implementation will be different. The active crystal oscillator is integrated with a drive circuit, which can directly provide stable frequency output. Passive crystal oscillator, on the other hand, needs to rely on the appropriate circuit provided by the outside to work. In addition, in order to improve frequency stability, some special designs such as temperature compensated crystal oscillator (TCXO) use temperature compensation technology to reduce the impact of ambient temperature changes, and constant temperature controlled crystal oscillator (OCXO) puts the crystal in a small constant temperature box to maintain a constant temperature, in order to achieve higher frequency stability and accuracy. These technologies make the crystal oscillator an indispensable component in modern electronic devices, especially in applications where timing accuracy is highly required.

3. What are the types of crystal vibration

Knowing the common types of crystal oscillator can help you choose the right type of crystal oscillator for your application. Here are several widely used crystal oscillator types:

Passive crystal oscillator:

Passive crystal oscillator refers to a quartz crystal without a built-in oscillator circuit, which requires an external circuit to generate oscillation. It usually has two pins and is non-polar. These types of crystal oscillators are low cost, small in size, and consume relatively little power, but they require external components such as amplifiers and feedback networks to form a complete oscillator.

Active crystal oscillator:

The active crystal oscillator is integrated with the necessary driving circuit, which can directly output a stable frequency signal. They have higher stability and accuracy, but correspondingly higher cost, volume and power consumption will be larger. Active crystal oscillator is suitable for applications that require high frequency stability.

Temperature compensated Crystal oscillator (TCXO) :

TCXO reduces frequency drift due to ambient temperature changes through an integrated temperature compensation circuit. This type of crystal oscillator provides better frequency stability over a wide temperature range and is often used in wireless communication equipment.

Thermostatic Controlled Crystal Oscillator (OCXO) :

The OCXO places the crystal in a small incubator to keep the operating temperature of the crystal almost constant, which greatly improves frequency stability. While OCXOs offer very high performance, they are costly and consume a lot of power.

Voltage Controlled Crystal Oscillator (VCXO) :

The VCXO allows you to fine-tune the output frequency by adjusting the applied voltage. This type of crystal oscillator is mainly used in applications where frequency fine-tuning is required, such as phase-locked loop (PLL) systems.

Differential crystal oscillator:

Differential crystal oscillator provides differential output signal. Compared with single-ended output, differential output has better anti-interference ability, which is suitable for high-speed digital communication system.

Low frequency crystal and high frequency crystal:

Depending on the operating frequency, the crystal oscillator can also be distinguished into low frequency (usually refers to the kHz level) and high frequency (MHz and above level). Crystal oscillators of different frequency ranges are used in different electronic devices.

Each type of crystal oscillator has its own specific application scenario, and choosing the right crystal oscillator depends on the specific needs, including frequency stability, temperature characteristics, size constraints, and cost considerations.

4. Main parameters and specifications of crystal vibration

The main parameters and specifications of crystal oscillator are the key indicators used to describe its performance characteristics. Understanding the relevant parameters can help engineers choose the most suitable crystal oscillator according to the requirements of specific application scenarios.

Here are some of the main crystal oscillator parameters:

Nominal frequency: The standard frequency that a crystal oscillator is designed to produce. This is the most basic and important parameter.

Frequency stability: indicates the degree to which the output frequency of the crystal oscillator changes with time, temperature and other environmental factors. It is usually expressed in ppm (parts per million), for example ±20ppm means that the frequency deviation is within plus or minus 1/200,000th of the nominal value.

Temperature stability: Describes the change of crystal frequency with temperature. This parameter is particularly important for types such as TCXO or OCXO. It usually gives the maximum allowable frequency offset over a temperature range.

Aging rate: Over time, the crystal frequency will change slowly, this phenomenon is called aging. The aging rate is measured as a yearly frequency drift, usually in ppm/year.

Load capacitance: When a passive crystal oscillator needs to be used in conjunction with an external circuit, this parameter specifies the capacitance value under the external load conditions for optimal operation.

Drive level: The minimum input power required to maintain the normal operation of the crystal oscillator. Too high a drive level may cause crystal damage.

Startup time: The time required from power-on to reach a stable frequency. This is important for some instant-response applications.

Package size: refers to the physical size of the crystal, which affects the PCB layout and space requirements.

Operating voltage: For active crystal oscillator, refers to the operating voltage range provided to the internal circuit.

Phase noise: refers to the impact of random fluctuations in the signal on the frequency, it is an important indicator to measure the purity of the signal, especially in the communication system.

Jitter: Time deviation of the output signal relative to the ideal period, often used to evaluate the quality of digital communication systems.

5. Crystal vibration selection and application

5.1 How to choose the right crystal oscillator

Choosing the right crystal oscillator first needs to be clear about the specific needs of the application. The first step is to determine the desired clock frequency, which is the most basic parameter in the design. Next, you need to evaluate the frequency stability requirements and determine the standard of the desired frequency stability based on the equipment's need for time accuracy. For example, precision measuring instruments may require a frequency deviation of ±5ppm or even smaller, while consumer electronics can accept a relatively loose ±50ppm standard. The temperature range of the working environment and its effect on the frequency should also be considered; If the application environment has a large temperature difference and high frequency stability requirements, it may be necessary to use temperature compensated crystal oscillator (TCXO) or thermostatically controlled crystal oscillator (OCXO) to ensure good frequency stability over a wide temperature range.

For long-term operating systems, the aging rate of the crystal oscillator is also an important consideration, because it directly affects the performance of the device over time. At the same time, it is also necessary to pay attention to power consumption and drive level when selecting crystal oscillator, especially for portable or low-power device application scenarios. The choice of package size and form is also critical, depending on the space limitations of the PCB and whether a miniaturized design is required. The cost factor can also not be ignored, in the premise of meeting the technical specifications, should look for the most cost-effective solution, and take into account additional features such as impact resistance, shock resistance and other special needs.

Finally, the selection of crystal oscillator should also confirm that the product meets the relevant industry standards and regulatory requirements, especially for medical, automotive and other specific fields of application. The supplier's technical support capabilities, lead times and product quality consistency are also important considerations. By considering all of the above requirements and consulting an experienced engineer or directly contacting the crystal manufacturer for professional advice, you can help you make the most appropriate choice to ensure the reliability and performance of the final product.

5.2 Crystal vibration selection criteria in different application scenarios

When selecting crystal oscillator in different application scenarios, it is necessary to determine the most suitable parameters and specifications according to specific needs. The following are some typical application scenarios and their corresponding crystal selection criteria:

Consumer electronics (e.g. mobile phones, tablets)

• Frequency stability: Standards of ±20 to ±50ppm are generally acceptable.

• Temperature range: Generally -20°C to +70°C.

• Package size: Tend to use miniaturized packages to save space.

• Power consumption: Due to battery power, low power consumption is one of the key considerations.

• Cost: The cost-benefit ratio is high, as this type of product is usually pursued for mass production.

Communication equipment (e.g. base station, router)

• Frequency stability: High requirements, may reach ±5ppm or less.

• Temperature compensation: TCXO or OCXO is often used to ensure stable performance in different environments.

• Phase noise and jitter: Very important for high-speed data transmission, low phase noise and jitter levels are required.

• Operating voltage: According to the specific requirements of the equipment design.

Industrial automation and control systems

• Reliability: Long-term stability and reliability are critical.

• Anti-interference ability: In the environment where electromagnetic interference may exist, select a crystal oscillator with good anti-interference characteristics.

• Temperature range: You may need to accommodate a wide temperature range, such as -40°C to +85°C.

• Aging rate: Considering the scenario of long-term use, products with low aging rate should be selected.

Medical equipment

• Accuracy and stability: Medical equipment has strict requirements for time accuracy, so it requires very high frequency stability and very low aging rate.

• Certification and compliance: Must meet the safety standards and regulatory requirements of the medical industry.

• Packaging: Special packaging may be required to meet biocompatibility or other specific conditions.

aerospace

• Extreme environmental adaptability: able to withstand harsh conditions such as extreme temperature changes, vibration and shock.

• High accuracy: Aerospace applications often require extremely high frequency stability and low phase noise.

• Reliability and longevity: Long-term reliability and long life are key considerations.

• Weight and volume: Considering the space and weight limitations of an aircraft, lightweight and compact design are also important.

Automotive electronics

• Temperature range: The internal temperature of the car fluctuates greatly, so a crystal oscillator capable of operating in the range of -40°C to +125°C is required.

• Anti-vibration: the car will encounter various vibrations during the driving process, and the crystal vibration needs to have good seismic performance.

• Aec-q Certification: complies with the quality standards set by the Automotive Electronics Council (AEC) to ensure that products are suitable for the in-vehicle environment.

5.3 How to select a specific frequency crystal oscillator

When selecting a crystal oscillator with a specific frequency, it is necessary to clarify the precise operating frequency required by the system or equipment, which is the most basic and most important parameter. Then, the crystal oscillator with appropriate frequency stability is selected according to the time accuracy requirement of the application. For example, a precision instrument may require a deviation of ±5ppm or even less. At the same time, it is necessary to analyze the temperature change of the working environment, and select the crystal vibration that can maintain good performance in the temperature range; For environments with large temperature changes, temperature compensated crystal oscillators (TCXOs) or thermostatically controlled crystal oscillators (OCXOs) can be considered to improve temperature stability. If the application needs to run for a long time and has high requirements for frequency stability, a crystal oscillator with a low aging rate (such as <±1ppm/year) should be selected. In addition, for portable or battery-powered devices, low power consumption is an important consideration; It is also critical to ensure that the circuit design provides the right drive power to avoid damaging the crystal oscillator. It is also necessary to select the crystal vibration of the appropriate package size according to the spatial layout of the PCB, and consider the mechanical characteristics such as shock resistance and earthquake resistance.

Under the premise of meeting the technical specifications, comprehensively compare the product prices of different suppliers, find the most cost-effective solution, and ensure that the crystal vibration meets the relevant industry standards and regulatory requirements, especially in the medical, automotive and other industries is particularly important. Select a supplier with a good track record of technical support and service, and consider product availability and supplier delivery times to fit the production schedule. Finally, before purchasing in bulk, it is best to obtain a small number of samples for actual testing to verify that its performance meets all the expected technical requirements. Through these steps, you can be more targeted to select a crystal oscillator that meets the requirements of a specific frequency and other key parameters.

6. Crystal vibration fault troubleshooting

6.1 Reasons and solutions for crystal vibration failure

Crystal vibration failure is usually caused by a variety of factors, including circuit design problems, insufficient supply voltage, poor welding and unsuitable environmental conditions. First of all, the passive crystal oscillator needs a suitable external oscillation circuit to support its work, if the feedback network design is not reasonable or the load capacitor is not matched, the crystal oscillator may not be able to vibrate normally. In addition, for active crystal oscillators, the supply voltage must be within the specified range and stable, otherwise it may not be able to provide enough energy to make it work. Welding problems are also common causes, such as welding, short circuit or poor contact can cause the crystal to fail to vibrate. Environmental factors, such as temperature and humidity outside the operating range of the crystal oscillator, or mechanical stress and vibration, can also affect the performance of the crystal oscillator. Finally, the crystal oscillator itself may have a manufacturing defect or physical damage that prevents it from working properly.

In order to solve the problem of crystal vibration failure, the following measures can be taken: check and optimize the design of the oscillation circuit to ensure that the feedback network and load capacitance are set correctly; Verify that the power supply voltage is within the specified range, and use a voltage regulator or filter to ensure power supply stability; Carefully check the welding quality of the crystal oscillator and its surrounding components to ensure that there is no virtual welding or short circuit phenomenon; Ensure that the temperature and humidity of the working environment meet the requirements of the crystal vibration, and avoid mechanical shock and vibration; If you suspect that there is a problem with the crystal oscillator itself, try to replace a new crystal oscillator of the same model for testing. Through these steps, it is usually possible to find and solve the causes of crystal vibration failure and restore the normal operation of the system.

6.2 The output frequency of crystal oscillator is unstable or deviates from the nominal value

Problems with unstable or deviated crystal output frequencies can be caused by a variety of factors, including temperature changes, aging, power supply voltage fluctuations, load capacitance mismatches, mechanical stress or vibration, electromagnetic interference (EMI), crystal quality issues, and inappropriate drive levels. Temperature is an important factor affecting the frequency of quartz crystals, especially in the absence of temperature compensation. Over time, the crystal may age, causing the frequency to gradually deviate from the initial value. In addition, the instability of the supply voltage can affect the performance of the active crystal oscillator, while the passive crystal oscillator is very sensitive to the load capacitance in the external circuit, and any mismatch will cause the frequency to shift. External mechanical stress, vibration, and strong electromagnetic fields or radio frequency interference may also affect the frequency stability of the crystal oscillator. If the crystal itself has manufacturing defects or damage, it can also lead to frequency problems. Too high drive level or too low drive level can also affect the performance of the crystal oscillator.

In order to solve these problems, a series of measures can be taken: using temperature compensated crystal oscillator (TCXO) or constant temperature controlled crystal oscillator (OCXO) to reduce the influence of temperature on frequency; For applications requiring long-term stability, periodically calibrate the system to compensate for frequency changes caused by aging; Ensure that the supply voltage supplied to the crystal oscillator is stable, which can be achieved by voltage regulators or filters; Adjust the load capacitance in the external circuit according to the crystal oscillator data book to match the recommended value; Avoid introducing additional mechanical stress through proper installation and reduce physical impact; Use shielding measures or relayout PCBS to reduce electromagnetic interference; If the crystal oscillator itself is suspected to have problems, try to replace a new crystal oscillator of the same model; Adjust the drive level to the recommended range according to the specifications provided by the manufacturer; Finally, the design of the oscillating circuit is optimized to ensure that all components are selected and connected correctly.

6.3 Other common problems in the use of crystal vibration and their solutions

Crystal vibration in the process of use may encounter a variety of problems, in addition to the crystal vibration and frequency instability or deviation from the nominal value, there are other common problems.

Understanding these issues and their solutions can help ensure the stable operation of your system. Here are some common crystal oscillator problems and their solutions:

Output waveform anomaly

• Reasons: improper circuit design, load capacitance mismatch, electromagnetic interference, drive level inappropriate.

• Solution:

  • Optimize circuit design: Re-check and adjust the design of the oscillating circuit to ensure that all components are selected and connected correctly.

  • Adjust the load capacitance: Adjust the load capacitance in the external circuit according to the crystal vibration data book to match the recommended value.

  • Shielding electromagnetic interference: Reduce the impact of electromagnetic interference through appropriate shielding measures or relayout of the PCB.

  • Adjust the drive level: Adjust the drive level to the recommended range according to the specifications provided by the manufacturer.

Frequency drift

• Causes: temperature changes, aging, power supply voltage fluctuations, load capacitance changes, mechanical stress, etc.

• Solution:

  • Temperature compensation: TCXO or OCXO is used to reduce the effect of temperature changes on frequency.

  • Periodic calibration: For applications requiring high long-term stability, periodic system calibration is performed to compensate for frequency changes caused by aging.

  • Stable power supply: Use a voltage regulator or filter to ensure that the supply voltage supplied to the crystal oscillator is stable.

  • Adjust the load capacitance: Adjust the load capacitance in the external circuit according to the crystal vibration data book to match the recommended value.

  • Reduce mechanical stress: Ensure that the crystal installation does not introduce additional mechanical stress and avoids physical shock.

Excessive phase noise and jitter

• Reasons: poor circuit design, power supply noise, electromagnetic interference, crystal quality problems.

• Solution:

  • Optimize circuit design: Redesign the oscillating circuit, especially the feedback network and power filter parts.

  • Reduce power supply noise: Use a low-noise linear regulator or add a power filter to reduce power supply noise.

  • Shielding electromagnetic interference: Take shielding measures or rearrange the PCB to reduce electromagnetic interference.

  • Select high quality crystal oscillator: Select high quality crystal oscillator with low phase noise and jitter characteristics.

The amplitude of oscillation is unstable

• Reasons: drive level is not appropriate, power supply voltage fluctuations, load capacitance changes, etc.

• Solution:

  • Adjust the drive level: Adjust the drive level to the recommended range according to the crystal data manual.

  • Stable power supply: Use a voltage regulator or filter to ensure that the supply voltage supplied to the crystal oscillator is stable.

  • Adjust the load capacitance: Adjust the load capacitance in the external circuit according to the crystal vibration data book to match the recommended value.

Long-term frequency shift due to aging

• Reason: Crystal aging is a natural phenomenon, over time, the crystal will gradually lose its initial frequency characteristics.

• Solution:

  • Periodic calibration: For applications that require long-term stability, the system is calibrated periodically to compensate for changes due to aging.

  • Select a low aging rate crystal oscillator: Select a crystal oscillator product with a low aging rate, especially in high-precision applications.

Poor environmental adaptability

• Reason: The crystal oscillator may not be able to adapt to extreme temperature, humidity or other harsh environmental conditions.

• Solution:

  • Select the appropriate crystal oscillator type: Select the crystal oscillator that can adapt to the corresponding conditions according to the actual working environment, such as a wide temperature range crystal oscillator or a sealed package crystal oscillator.

  • Enhanced protection: When necessary, additional protective measures can be used, such as adding protective housings or coatings.

Through the above method, various problems encountered in the use of crystal vibration can be effectively solved. If the problem persists, it is recommended to contact a professional technical support team or crystal supplier for further help.

7. Conclusion

Well, through today's content, I believe that everyone has a certain understanding of all aspects of crystal vibration. From the basic concepts and working principles of crystal oscillators, to the characteristics and applications of different types of crystal oscillators, to the key parameters that need to be considered when selecting crystal oscillators, I hope that these contents will help you to be more comfortable in the face of crystal oscillators related problems.

We also discuss some common faults and their solutions, such as crystal vibration failure, frequency instability or deviation from nominal values, and provide practical troubleshooting and repair suggestions. With this knowledge, you will be able to diagnose and solve problems more effectively to ensure the stable operation of the system.

In short, crystal excitation is an indispensable component in electronic equipment, and the correct selection and use of it is crucial to ensure system performance. I hope that through this sharing by INFINITECH, you will not only have a more comprehensive understanding of crystal vibration, but also be able to use this knowledge more confidently in actual projects. If you encounter any questions about crystal oscillators in the future, remember to go back to these basics to find answers.

Thank you for listening and hope to share more interesting content with you next time! If you have any questions, feel free to ask. I wish you all greater success in your respective fields!