Which One Fits your Need: TCXO or OCXO?

If you want to learn more, please visit our website.

A crystal oscillator is an electronic oscillator circuit that uses a quartz crystal to create an electrical signal with precise frequency. It is often used in precision timing applications (clocks) to provide a stable clock signal for digital integrated circuits and stabilize frequencies for radio transmitters and receivers.

Crystal oscillators are subject to influence from environmental factors, like humidity, temperature, pressureand vibration. Temperature Compensated Crystal (Xtal)Oscillators (TCXO) and Oven Controlled Crystal (Xtal) Oscillator (OCXO) are quartz crystal-based modified oscillatorsthat limit the level of these influences.Both provide exceptional short-term stability with main differences in the complexity of the electronic components in the circuit and the effects of crystal aging.Withadvancements in crystal oscillator technology, the gap between TCXOs and OCXOsis shrinking, making it potentially difficult to determine which one is best suited for your needs. 

TCXOs

Temperature in the external environment can affect the crystal oscillator's ability to maintain its frequency output stability. TCXOs were developed to easily adapt to changes in temperature in various external environments.A majority of TCXOs contain a voltage control mechanism called a voltage-controlled crystal oscillator (VCXO).It includes a temperature sensor that monitors temperature changes andapplies a correctional voltage to the voltage control pin. The counter-balance circuitry of the VCXOallows the TCXO to provide stable frequency. 

The temperature coefficient of the capacitors used to adjust frequency affects the temperature coefficient of the crystal, which can lead to problems with adjustments for crystal aging and long-term stability. The change in the temperature coefficient can be ignored inlower precision TCXOs butrequires adjustment for higher precision TCXOs.TCXOs counteract crystal aging by allowing the frequency to be reset periodically through external adjustments. The level of accuracy required determines the time needed between calibration resets, but general recommendations are every six months to a year. However, shorter periods are needed for higher levels of accuracy. Issues with the crystal cannot be corrected, which makes the crystal design and manufacturing a crucial and difficult element.

OCXOs

The quartz crystal inside an OCXO is heated by an oven-like device. The oven has precise temperature control and heats the crystal to its turn over temperature, maintaining it throughout the duration of its use. This helps keep the crystal temperature constant and prevents fluctuations from external temperature changes that lead to compromises in its desired frequency stability. 

The cut of the quartz crystal affects OCXO performance. There are two types used: AT cut and SC cut. AT cut crystals are more widely used in OCXOs and are preferred for a wide temperature range. SC cutcrystals provide a higher level of frequency stability and precision compared to AT cut and are more suitable for elevated operating temperatures. It should be noted that OCXO crystals are subject to about a quarter of the crystal aging sensitivity that TCXOs undergo. 

Comparison and Applications

Size and Complexity

OCXOs are typically larger than TCXOs due to the mechanical components they consist of: IC, heater and controller, and the crystal. TCXOs are smaller and simpler since they only consist of IC and the crystal. This makes OCXOs more suitable for operations that require a high degree of stability and TCXOs better for smaller devices that need to be portable. 

Cost and Power Consumption

OCXO requires higher power consumption because they need a longer warm up period to reach the precise temperature before they function. They also need a constant heat supply to maintain the &#;oven&#; temperature. This makes them costlier than TCXOs, which require a significantly shorter warmup period and less power to maintain its temperature. 

Applications

OCXOs are best for operations that require better frequency stability and precision clocking, like the 5 GNSS Constellations (GPS, QZSS, BEI Dou, GALILEO, and GLONASS). Applications include any operation requiring GPS, like military data links and test equipment, but OCXOs are too bulky to be used in battery-powered devices. Due to TCXO&#;s high level of performance and smaller size, you are likely to find them in many of today'ssmart phones, GPS devices, and other base station applications.

For a more comprehensive list of applications, please check our OXCO devices by clicking hereor our TCXO devices by clicking here

Summary

OCXOs are better for communication/network applications that require high precision frequency and provide better long-term stability. TCXOs are preferred when size and power are critical to the application. They are more economical and provide reasonable stability. These tend to be better for portable or battery operated devices.

TCXO

OCXO

Size

smaller

larger

Complexity

lower

higher

Link to Huixun

Cost 

lower

higher

Power consumption

lower

higher

Frequency/Temp Stability

high

highest

Understanding the Differences Between TCXO and OCXO

When designing circuit boards, two types of crystal oscillators are commonly used - constant temperature (OCXO) and temperature-compensated (TCXO) oscillators. 

Knowing when to use each type can help you optimize your circuits for better performance. In this article, we will explore the differences between 

TCXO and OCXO from three perspectives.

Definition

OCXO stands for Oven Controlled Crystal Oscillator. As the name suggests, OCXOs use a constant temperature bath to maintain a stable environment for the quartz crystal resonator, minimizing frequency changes caused by temperature fluctuations. Typically, a differential series amplifier that uses a thermistor "bridge" is used to achieve temperature control.

TCXO stands for Temperature Compensated X'tal (crystal) Oscillator. It is a crystal oscillator that uses electronic means to compensate for frequency-temperature offsets in the crystal component, resulting in a more stable device. The TCXO compensates for the frequency-temperature stability of the crystal element by using the change of the crystal load reactance with temperature.

Working Principles

OCXOs keep the temperature of the oscillator constant to minimize the output frequency change caused by temperature changes. The crystal oscillator's oscillation frequency changes with temperature, so keeping it at a constant temperature improves its phase-frequency characteristics.

TCXOs reduce the variation of oscillation frequency caused by ambient temperature changes through their additional temperature compensation circuit. The oscillator compensates the frequency drift of the resonator due to changes in ambient temperature by changing the load capacitance in the oscillating circuit, which changes with temperature.

Measurement Accuracy

OCXOs typically have a frequency stability more than two orders of magnitude higher than that of TCXOs. For example, the frequency stability of a TCXO is generally around -7, while an OCXO can reach -9. This makes OCXOs ideal for high-end measuring instruments, such as frequency counters, signal generators, network analyzers.

TCXOs have better start-up characteristics. Even with the best heating element, OCXOs still require a heating process that can take up to five minutes to reach -7 and even up to a day to reach -9. Therefore, they are not suitable for devices that need to work as soon as they are turned on.

Conclusion

In summary, both TCXO and OCXO are active crystal oscillators that require power to work. OCXOs use a constant temperature bath to keep the temperature of the oscillator constant, while TCXOs use electronic means to compensate for frequency-temperature offsets in the crystal component. While OCXOs have better frequency stability, TCXOs have better start-up characteristics. Knowing when to use each type of oscillator will help you design circuits that perform optimally.

Contact us to discuss your requirements of ocxo . Our experienced sales team can help you identify the options that best suit your needs.