WHAT IS A TCXO?
In some applications, lighter frequency tolerance is required than can be provided by a clock oscillator and the cost would be prohibitive to use an OCXO. In cases such as this. a TCXO is often used.
TCXO is an acronym for "Temperature Compensated Crystal Oscillator". This oscillator compensates the natural temperature sensitivity of the crystal. In general, a network of compensating components is used to either directly (thermistor / capacitor) or indirectly (thermistor / varactor) change the oscillator frequency so it maintains the desired level of performance.
BENEFITS OF A TCXO
The benefits of the TCXO include: (1) better temperature performance than a clock oscillator: (2) smaller size, less costly, no warm-up lime required and less input power required than an OCXO.
As noted in the crystal section of this catalog, all quartz crystals exhibit the effects of slow changes in frequency over time. known as aging. The aging rate in a TCXO is affected by a number of factors. The primary factor in aging is the size of the crystal blank. The main cause of this aging is the mass loss caused by the vibrations that occur as a function of the crystals operation. With the crystal frequency determined by its mass. the larger the overall mass vs. the amount of mass loss over time determines the aging rate. This means that the higher frequency crystals may not have as good an aging characteristic as a larger, lower frequency part.