R-Type Voltage Controlled Crystal Oscillators (VCXO)

1 - A 0.1 µF low-frequency tantalum bypass capacitor in parallel with a 0.01 µF high-frequency ceramic capacitor is recommended.
2 - Figure 2 defines these parameters. Figure 3 illustrates the equivalent five-gate MTTL load and operating conditions under which these parameters are specified and tested.
3 - Symmetry is the ON TIME/PERIOD with V_S = 2.5 V for CMOS, per Figure 2.

Absolute pull range (APR) is specified by the fourth character of the product code. The APR is the minimum guaranteed frequency shift from f_O over variations in temperature, aging, power supply, and load. Both frequency and environment limit the specified APR.

With V_C between 0.5 V and 4.5 V, total pull range for the R-Type VCXO is typically between 200 ppm and 400 ppm.

A 50 ppm APR VCXO fully tracks a 50 ppm source oscillator or any other 50 ppm reference over the specified operating temperature range, life of the product, power supply and measurement variations.

Quartz-based oscillators exhibit a change in output frequency with time. Two dominant mechanisms for this phenomena are change in the stresses on the quartz resonator and mass-loading of the quartz resonator.

Changes in output frequency due to stress are a result of relaxation in the mounting stresses of the quartz resonator or transmittal of environmental stresses through the mounting arrangement. The R-Type oscillator contains a state-of-the-art miniature rectangular AT-Cut resonator, rather than the arrangement that has very little stress relaxation and isolates the quartz resonator from external stresses.

Mass-loading of the quartz resonator, which generally drives the frequency lower, is a result of outgassing of materials within a package or a lack of package hermeticity. Higher frequency resonators are more susceptible to this aging mechanism. The R-Type oscillator contains a minimum number of parts internal to the package, a monolithic IC and a quartz resonator, resulting in an internal environment that is well controlled and characterized.

Isothermal aging studies on the R-Type oscillator performed at elevated temperatures have shown a small frequency change due to mass-loading. With an application of 40° and under normal conditions, the oscillator aging is typically 2 ppm the first year, 1 ppm for the second year, and continues to logarithmically decline every ear thereafter.