VCXO Oscillators

VCXO Oscillators (Voltage controlled crystal oscillators) are used in designs that need to control the output frequency via an external digital PLL. The VCXO frequency is &147pulled&148 by the control voltage (Vc) applied. The function of this can be to maintain a fixed desired output frequency over time to counteract the ageing of the crystal that would otherwise cause a drift. The designer/engineer will need to know what the &147Pull Range&148 is for the selected VCXO.

Total Pull Range is equal frequency shift from minimum to maximum control voltage; typically 50ppm to 200ppm max.


Absolute Pull Range (APR)


Another common parameter used when specifying VCXO is &147Absolute Pull Range&148 or (APR) with VCXO’s offering ±35ppm to 50pp min.

APR is defined as the minimum pull range after taking into account other aspects that affect the frequency, such as temperature, ageing, power supply variations, and load variations.

APR = Total Pull Range minus expected changes from temperature, ageing, power supply variations, and load variations.

A designer picks an APR that is expected to cover all drifts for the life of the product.

VCXO’s designs fall into three types, those with a fundamental crystal, or a 3rd OT crystal, and those using an internal PLL to multiply the frequency and extend the output frequency.

Fundamental crystal types are limited to ∼80MHz, 3rd OT designs offer higher frequencies to ∼200MHz and the best phase noise/jitter performance. PLL types offer the broadest range of frequencies up to 2100MHz and can be utilized using programmable oscillators.


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Description Price Oscillator Type Output Frequency Frequency Stability Load Capacitance Package Type Output Level Minimum Operating Temperature Maximum Operating Temperature Height Dimensions
RS Stock No. 478-9230
Mfr. Part No.LFVCXO011125
BrandIQD
kr 182,97
Each
Units
- 10 MHz ±50ppm 15pF PDIP HCMOS, TTL 0 °C +70 °C 5.1mm 21 x 13.08 x 5.1mm
RS Stock No. 905-5850
Mfr. Part No.CVHD-950-100
BrandCrystek
kr 177,67
Each
Units
VCXO 100 MHz ±20ppm - SMD CMOS 0 °C +70 °C 5.3mm 14.2 x 9.14 x 5.3mm
RS Stock No. 178-2040
Mfr. Part No.315LB3I1228T
BrandCTS
kr 68,693
Each (On a Reel of 1000)
Units
Clock Oscillator 122.88 MHz ±50ppm - SMD HCMOS -40 °C +85 °C 1.3mm 5 x 3.2 x 1.3mm
RS Stock No. 179-0821
Mfr. Part No.347LB3I1536T
BrandCTS
kr 180,46
Each
Units
VCXO 153.6 MHz ±50ppm - SMD LVPECL -40 °C +85 °C 1.7mm 7 x 5 x 1.7mm
RS Stock No. 179-0024
Mfr. Part No.347LB3I1536T
BrandCTS
kr 97,208
Each (On a Reel of 1000)
Units
VCXO 153.6 MHz ±50ppm - SMD LVPECL -40 °C +85 °C 1.7mm 7 x 5 x 1.7mm
RS Stock No. 671-5789
Mfr. Part No.LFVCXO026156
BrandIQD
kr 38,28
Each
Units
- 20 MHz ±100ppm 15pF SMD HCMOS 0 °C +70 °C 1.7mm 7 x 5 x 1.7mm
RS Stock No. 178-2696
Mfr. Part No.315LB3I1228T
BrandCTS
kr 94,72
Each
Units
VCXO 122.88 MHz ±50ppm - SMD HCMOS -40 °C +85 °C 1.3mm 5 x 3.2 x 1.3mm