Comparing TCXO, VCXO, and OCXO Oscillators

Learn All About These Specialized Quartz Crystal Oscillator Products

While quartz oscillators are a common electronic component used to generate frequency, there are specific situations where engineers in the design community need a product that ensures a stable, clean frequency, so that any particular use-case for the oscillator is effective. 

Quartz oscillators in and of themselves are very durable as a solution where conditions might otherwise affect frequency, and yet there are still some circumstances where that durability can be augmented with specialized components. 

Three of these specialized quartz crystal oscillators - TCXOs, VCXOs, and OCXOs - provide a versatile series of benefits in particular conditions where frequency stability is essential. In this article, each of these products’ benefits and key differences from each other are explored, so that engineers can get an understanding of which component to use in a given context. While this exploration is by no means comprehensive, it will give you a general understanding, so that when you work with a manufacturer to find the product you need, you’ll have a leg up on your competition.

VCXOs (Voltage Controlled Crystal Oscillators)

A voltage-controlled crystal oscillator (VCXO) is a crystal oscillator that can vary its frequency based on voltage that is applied to the oscillator. These oscillators are often applied in addition to another crystal oscillator to ensure that the primary oscillator’s frequency drift is as minimal as possible. Therefore, the VCXO is used in the pulling (or adjusting) of a frequency and is considered a support mechanism on your circuit board for another crystal oscillator like the TCXO.

TCXOs (Temperature Compensated Crystal Oscillators)

A temperature-compensated crystal oscillator (TCXO) is effective in circumstances where the circuit board is going to be located in a high temperature environment. While quartz crystal in general is an effective resonating surface for an oscillator at a variety of temperatures, if an engineer is looking for a completely stable, clean signal at a particularly high temperature - and requires the smallest amount of drift or any variation - the TCXO is the most ideal option.

For example, if an application that uses a crystal oscillator is on a roof, in a particular climate zone, or even within machinery that generates a great deal of heat, the TCXO can compensate for the hotter temperature. Even for products that are not necessarily going to experience high temperatures all the time, but could potentially be exposed to heat (such as a product that is left in the sun) a TCXO can be integrated into a circuit board to effectively engineer for  the particular contexts in which the application finds itself. 

OCXOs (Oven Controlled Crystal Oscillators) 

An oven-controlled crystal oscillator (OCXO) contains a device that essentially operates like a tiny oven in order to compensate for temperature changes. The crystal oscillator is heated to make sure that the frequency operates with maximum stability and limited frequency drift. Crystal oscillators can end up in applications where temperature shifts occur or in particularly cold temperatures. The OCXO is a highly desirable product as it can enhance stability under nearly any condition, but with one caveat: the OCXO uses a great deal more power than other crystal oscillators, and this is consideration for applications that do not have an additional power source and are being deployed remotely. 

Comparisons Between TCXOs, OCXOs, and VCXOs

It becomes apparent when looking at these specialized crystal oscillators that engineering requires a great deal of give and take, as well as strategic decision making. You may want an electronic component in a circuit board to operate under certain conditions, but those conditions can’t be met without an additional component working for the benefit of the original. Or, on the other hand, an awareness of the capabilities or limitations of certain products might change the way you go about your design. 

Additionally, engineers will ocassionally “over-engineer” a product, simply to ensure that they have the best frequency stability possible. Engineering for a circuit board is not merely a science, but a creative pursuit and an artform - and yet to engage with engineering at this level, you first have to understand the tools at your disposal. 

If you have to choose between these three crystal oscillators, here are some details about each of these products placed in comparison with each other, so that you can potentially decide between them for any particular use-case. 

Power consumption:

• As mentioned, OCXOs consume more power than TCXOs and VCXOs

Temperature: 

• TCXOs are more likely to be used in high-temperature situations
• OCXOs are more likely to be used in low-temperature situations
• VCXOs do not compensate for temperature like TXCOs and OCXOs

Frequency stability:

• OCXOs provide more stability than TCXOs, and are larger than TCXOs

Usage:

• VCXOs are supporting oscillators for TCXO capability 

How to Find Superior Manufacturers of TCXOs, OCXOs, and VCXOs 

If your application requires voltage control or temperature compensation, and you’re considering crystal oscillators that provide these benefits, you then have to decide which manufacturer will meet your needs, so that you can move forward with your project efficiently.

The following recommendations will help you make your decision about which manufacturer to choose. If the manufacturer you are working with appears to meet all of the following criteria, they’re likely the superior choice for your TCXOs, OCXOs, and VCXOs, among other crystal oscillator products from real time clocks to AEC-Q200 certified components for use in the automotive industry.

Consider these questions when deciding on a manufacturer of quartz crystal components:

• Are TCXOs, OCXOs, VCXOs, and other specialized oscillators a part of their inventory?
• Does the manufacturer focus specifically on quartz crystal electronic components?
• Does the manufacturer have a directory of global distributors and sales teams for ease of access?
• Does the manufacturer provide engineering resources - including person-to-person support to help guide you through any questions or concerns during the design process?
• Does the manufacturer have a wide variety of resources online, including white papers, articles, technical guides, and other user-friendly support materials?
• If you don’t find the product you are looking for, is there evidence or language on their website that suggests that customizability is an option for engineers?

Answering “yes” to these questions will lead any engineer to a manufacturer who can not only supply the right components, but will deliver excellent customer service, support, efficiency, and affordability, so that your project moves forward as planned.