Quartz crystal units of assessed quality - Part 4: Crystal units with thermistors (IEC 60122-4:2019); German version EN IEC 60122-4:2019
1Key Takeaways
This part of IEC 60122 applies to crystal oscillators with thermistors, which are predominantly used in mobile communications applications requiring high frequency stability, for example, as local reference signal generators for mobile phone base stations or GPS. This document provides technical guidance for crystal os…
2Expert Interpretation
This in-depth analysis of the DIN EN IEC 60122-4:2019 international standard for thermistor crystal units covers technical specifications, performance requirements, test methods, and application cases, providing professional guidance for mobile communications and high-precision frequency control equipment.
Standard Overview and Technical Background
DIN EN IEC 60122-4:2019 is the quality assessment standard for thermistor crystal units, published by the International Electrotechnical Commission. It officially came into effect in Germany on October 1, 2019. Developed by IEC/TC 49, "Piezoelectric, Dielectric, and Electrostatic Devices and Related Materials," this standard specifically addresses the stringent high-frequency stability requirements of the mobile communications sector.
Core Technology and Innovation
The core innovation of this standard lies in integrating a thermistor and a crystal oscillator into the same package, significantly improving the temperature sensing accuracy of traditional temperature-compensated crystal oscillators (TCXOs). By reducing the temperature difference between the crystal element and the thermistor, higher-precision frequency stability is achieved.
Technical Architecture Comparison
| Technical Parameters | Traditional TCXO | Thermistor Crystal Unit | Improvement Range |
|---|---|---|---|
| Temperature Detection Accuracy | ±0.5°C | ±0.1°C | Increase by 5 times |
| Frequency Stability | ±0.5ppm | ±0.1ppm | Increase by 5 times |
| Response Time | ＞10 seconds | ＜2 seconds | Increase by 5 times |
| Temperature Gradient | Significant | Extremely Small | Significantly Improved |
Key Technical Requirements and Parameter Specifications
Agreed Characteristics Specified in Section 4.4
The standard requires that suppliers and users must reach an agreement on the following key parameters:
- FT Characteristic Coefficients: First-order, second-order and third-order frequency-temperature characteristic coefficients
- Residual Frequency Stability Gradient: The temperature difference between the actual FT data and the calculated FT value
- Normal Zero Load Resistance: The resistance value at the standard reference temperature of 25°C
- B Value: Thermal Index, which characterizes the thermal sensitivity of the thermistor
Structural Design Requirements
The standard specifies two typical structural configurations in detail:
- Internal integration structure: The thermistor is placed inside the crystal package.
- Avoids the risk of short circuit between the thermistor and the crystal connection terminal.
- Large back connection area, with shock absorption by solder.
- Resin encapsulation provides thermal release protection.
- External attachment structure: The thermistor is placed outside the package.
- Lower cost, the thermistor can be installed after crystal verification.
- Smaller temperature difference between crystal and thermistor.
- Fewer restrictions on thermistor connection.
Test and Verification Methods
Conformance Verification Test Conditions
Annex A of the standard specifies the detailed test methods:
| Test Number | Test Object | Temperature Rise Rate | Temperature Range | Test Purpose |
|---|---|---|---|---|
| Test 1 | Thermistor Crystal Unit | 0.2°C/min | -30°C to 90°C | Establish a benchmark for actual temperature characteristics |
| Test 2 | Standalone Thermistor on a PCB | 5°C/min | -30°C to 90°C | Compare to the performance of a traditional solution |
| Test 3 | Thermistor Crystal Unit | 5°C/min | -30°C to 90°C | Verifying Performance Under Rapid Temperature Changes |
Test results show that even at a 25x temperature increase (Test 3), the temperature characteristics of the integrated thermistor crystal unit are still closer to the baseline characteristics (Test 1) than the traditional separation solution (Test 2).
Application Areas and Implementation Recommendations
Main Application Scenarios
This standard is mainly aimed at the following high-requirement application areas:
- Mobile communication base stations: As local reference signal generators, they require extremely high frequency stability
- Satellite positioning systems: Local reference signal generation for navigation systems such as GPS
- High-precision timing equipment: Time reference equipment requiring microsecond-level accuracy
- Test and measurement instruments: Test equipment requiring extremely high frequency stability
Implementation Recommendations
- Design phase: Select the appropriate structural configuration based on the application ambient temperature range
- Purchase specifications: Clarify the specific numerical ranges of the four key parameters required in Section 4.4
- Test verification: Conduct consistency verification according to the test methods in Appendix A
- Quality Control: References the quality and reliability requirements of Chapter 4 of IEC 60122-1.
Standard Evolution and Future Outlook
IEC 60122-4:2019 represents a significant advancement in crystal frequency control technology, achieving a quantum leap in temperature sensing accuracy through the integration of thermistors. With the development of new technologies such as 5G communications, the Internet of Things, and autonomous driving, the demand for frequency stability will further increase, and this standard provides an important technical foundation for such applications.
Possible future development directions include:
- Higher-precision digital temperature compensation technology
- Distributed temperature sensing using multi-thermistor arrays
- Miniaturization solutions combined with MEMS technology
- Enhanced designs for extreme environmental conditions
The implementation of this standard will bring significant technological advancements and product quality improvements to related industries, particularly in the field of high-precision frequency control.