Voltage-Controlled Crystal Oscillator - VCXO's

Suntsu VCXO’s are available in through-hole or surface-mount packaging. We offer a wide frequency range and many different voltages and logic options. Pick out a standard part number from the data sheets listed below or contact our sales team to request any custom parameters that you desire and we will design to your specific needs.

Voltage-Controlled Crystal Oscillators are used when the frequency of operation needs to be adjusted. The frequency of a voltage-controlled crystal oscillator can be varied typically by a hundred parts per million (ppm), because the high Q factor of the crystals allows “pulling” over a range of frequencies.

Reasons for using a VCXO are to adjust the output frequency to match (or perhaps be some exact multiple of) an accurate external reference or where the oscillator drives equipment that may generate radio-frequency interference (adding a varying voltage to its control input can disperse the interference spectrum to make it less objectionable).

SeriesLogicPackageStability ToVoltage(s)FrequencyReelKey FeatureDatasheet
SVC32CCMOS3.2X2.5 CERAMIC SMD (6 PAD) VCXO±20ppm1.8V, 2.5V, 3.3V1.000MHz - 55.000MHz3KFund., Miniature Package
SVC53CCMOS5.0X3.2 CERAMIC SMD (6 PAD) VCXO±20ppm1.8V, 2.5V, 3.3V1.000MHz - 200.000MHz1KFund., PLL
SQV53CCMOS5.0X3.2 CERAMIC SMD (6 PAD) VCXO±20ppm1.8V, 2.5V, 3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SQV53PLVPECL5.0X3.2 CERAMIC SMD (6 PAD) VCXO±20ppm2.5V, 3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SQV53LLVDS5.0X3.2 CERAMIC SMD (6 PAD) VCXO±20ppm2.5V, 3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SVC75CCMOS7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm2.5V, 3.3V1.000MHz - 300.000MHz1KFund., PLL
SVC75PLVPECL7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm1.8V, 2.5V, 3.3V9.500MHz - 800.000MHz1KFund., PLL
SVC75LLVDS7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm3.3V9.500MHz - 800.000MHz1KFund., PLL
SQV75CCMOS7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SQV75PLVPECL7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm2.5V, 3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SQV75LLVDS7.0*5.0 CERAMIC SMD (6 PAD) VCXO±20ppm2.5V, 3.3V8.000MHz - 1500.000MHz1KLow Jitter, Programmed VCXO
SVCHSCCMOS8 PIN DIP VCXO±20ppm2.5V, 3.3V1.000MHz - 160.000MHzN/AHalf Size Dip VCXO
SVCFSCCMOS14 PIN DIP VCXO±20ppm1.8V, 2.5V, 3.3V1.000MHz - 160.000MHzN/AFull Size Dip VCXO
SVCF4CCMOS14.3X8.7 PCB SMD (4 PAD) BASE (FR4)±20ppm2.5V, 3.3V10.000MHz - 130.000MHz500pcsUltra-Low Phase Noise and Jitter
SVCF6CCMOS14.3X8.7 PCB SMD (6 PAD) BASE (FR4)±20ppm2.5V, 3.3V10.000MHz - 800.000MHz500pcsLow Jitter
SVCF6PLVPECL14.3X8.7 PCB SMD (6 PAD) BASE (FR4)±25ppm2.5V, 3.3V10.000MHz - 800.000MHz500pcsLow Jitter
SVCF6LLVDS14.3X8.7 PCB SMD (6 PAD) BASE (FR4)±20ppm3.3V10.000MHz - 800.000MHz500pcsLow Jitter
SQV32CCMOS3.2X2.5 CERAMIC SMD (6PAD) VCXO±20ppm2.5V, 3.3V8.000MHz - 1500.000MHz3kMiniature Package

Quick Summary

Features Benefit Manufacturing Location(s) Monthly Capacity
• Pullable frequency
• High frequency with mesa blank available
• High Q factor crystals
• Pullable by up to 150ppm
• Custom configurations available
• Taiwan
• South Korea
• >1M units

What Is a Voltage-Controlled Crystal Oscillator (VCXO)?

A voltage-controlled crystal oscillator (VCXO) is a type of crystal oscillator that relies on a voltage control input to adjust the oscillation frequency that is generated by the oscillator’s crystal. It allows for the adjustment of the frequency of the electronic device across small ranges. The principle of VCXO frequency offset is also described as pulling.

How Does a VCXO Work?

The VCXO circuit design is very similar to that of a traditional crystal oscillator except that a VCXO includes a varactor diode to which the voltage current is applied at a specified voltage. The purpose of this is to alter the frequency of the oscillator’s crystal. The oscillator’s diodes are typically arranged back to back and function as a variable capacitor. The tuning range of the voltage applied to the oscillator’s diode can go from -150ppm up to +150ppm depends on the oscillator crystal’s high Q factor that enables pulling over a frequency range. The oscillator’s capacitance level dictates the maximum amount of pulling that can be applied to the crystal to alter the oscillation frequency level. When an electronic device requires that the VCXO be pulled over a wide range, an inductor is typically utilized within the oscillator’s circuit.

Applications for VCXO

A VCXO is commonly found in devices used in the telecommunications and broadcast industries. They are frequently used in temperature-controlled crystal oscillators (TCXOs) to minimize drift by applying the temperature-stabilizing voltage to the VCXO’s control terminal. In addition, a VCXO can be used in narrow-band phase-locked loops (PLLs) that need a small amount of frequency alteration and maintain appropriate phase noise levels in their closed loops.

VCXO Performance: Pros and Cons

Although a VCXO can efficiently achieve a frequency alteration of more than  a hundred ppm, this may result in a decline in the performance of the oscillator’s circuit. Also, temperature controls may be required to reduce the amount of temperature drift resulting from the pulling of voltage across the circuit. A major advantage of including VCXOs as part of the circuitry of an electronic device is that they are much more affordable than other oven-controlled crystal oscillators.

When Specifying a VCXO, the Following Parameters Are Normally Needed:

Often, a VCXO is procured from a specialty supplier of these modules. Without the proper specifications for the VCXO, it may not work as intended for the desired purpose. Be sure to refer to the specific information sheets for the VCXOs that you are ordering.

A. Frequency

The frequency of the specific VCXO will be identified in terms of MHz when it is at 1.0 MHz or above. When the frequency is below that level, it will be designated in kHz. Be sure that you are also matching up the correct decimal places when examining the frequency specifications for a VCXO.

B. Output

The VCXO’s output requirements must be defined and matched to ensure the proper functioning of the VCXO for its individual application. The application of VCXOs can vary from analog to driving various forms of logics like CMOS, Clipped sinewave, Sinewave, LVPECL, and LVDS

C. Frequency Stability

The VCXO’s frequency stability is designated in ppm in standard intervals of 25 ppm, including 25 ppm, 50 ppm and 100 ppm. This range is generally specified at both room temperature and when the oscillator is at its operational level.

D. Supply Voltage

The supply voltage is crucial to maintain so that the proper amount of pulling can be achieved across the crystal. A high-quality VCXO will function slightly outside of this range to ensure efficiency.

E. Operating Temperature Range

There are generally three main operating temperature ranges for VCXOs. First, the commercial temperature operating range for oscillators in laboratory conditions is from -20 degrees Celsius to 70 degrees Celsius. The industrial temperature range for a VCXO is from -40 degrees Celsius to 85 degrees Celsius. Lastly, the VCXO operating temperature range for use in military equipment is from -40 degrees Celsius to 125 degrees Celsius.

F. Pullability & Absolute Pull Range

For a VCXO, the pullability refers to the oscillation frequency range that the oscillator can be pulled across to alter the control voltage. With a higher pullability range, the VCXO will have a larger tuning range for using voltage to control the oscillator’s frequency. The trade-off for a lower pullability range in a VCXO is an improvement in its frequency stability and a reduction in the oscillator’s phase noise.

F. Pullability & Absolute Pull Range

For a VCXO, the pullability refers to the oscillation frequency range that the oscillator can be pulled across to alter the control voltage. With a higher pullability range, the VCXO will have a larger tuning range for using voltage to control the oscillator’s frequency. The trade-off for a lower pullability range in a VCXO is an improvement in its frequency stability and a reduction in the oscillator’s phase noise.

G. Package

The package for the VCXO should be specified according to its application. There are options for either dip type or surface mount VCXOs. In addition, when manufacturing VCXOs in mass quantities, it is also possible to specify tape and reel package requirements for surface mounted type.

H. Linearity

Linearity for a VCXO is identified as a percentage in terms of a deviation from the tuning curve along a straight line fit. Given that the slope over the curve can vary considerably at either end, the linearity for a VCXO may be expressed as a range of percentages.

What Is the Difference Between a Current-Controlled Device and a Voltage-Controlled Device (VCO)?

While the DC voltage input controls the oscillation frequency of a VCO, a current-controlled device depends on the amount of the current to determine the oscillation frequency. The difference in these types of oscillators is the types of inputs that are used to alter or maintain the devices’ frequencies.

What Is the Function of a VCO?

Primarily, a VCO is used for the modulation of frequency or phase and is also the main component of a PLL. The application of a DC voltage to the control input of the VCO allows for this modulation.

What Is the Main Difference Between VCO and a Fixed Frequency Oscillator?

Unlike a VCO, a fixed frequency oscillator does not rely on input controls in the form of voltage or current to alter the oscillator’s frequency. Its frequency output signals are not subject to alteration or modulation. In comparison to a VCO, a fixed frequency oscillator typically has a higher Q factor and less phase noise and jitter.

Why Do We Use PLL?

Given that a PLL relies on an input signal to alter and adjust its oscillation frequency, it is useful in stabilizing or recovering a signal from a communications channel that has suffered from an interruption in data. PLLs enable wireless communications and digital data transmission.

Frequently Asked Questions

To specify a VCXO, you can either stipulate the performance of the oscillator in all operating conditions or the device performance in only a specific range of operating conditions. Many more parameters are required for defining the performance in a specific range rather than its overall performance in all conditions, such as the VCXO’s desired frequency, frequency stability, pullability, output load, package, supply voltage and operating temperature range.

The absolute pulling range (APR) refers to the one variable specification for a VCXO that will guarantee that the PPL stays constantly locked. The desired APR is determined by the input signal’s overall accuracy in terms of frequency. The APR for a specific VCXO is found on that product’s information sheet from the manufacturer. Many purchasers of VCXOs prefer to rely on the APR of a device to specify the VCXO needed because it is far less complicated than keeping track of the many other variables that affect the VCXO’s performance in a specific operating environment. Absolute Pull Range value can be achieved the frequency stability includes aging and tolerance deducted from the pullability. For example, if the pullability is ±100ppm, but VCXO requires ±25ppn stability includes aging and tolerance, the APR(Absolute Pull Range) is ±75ppm.

The pullability, also called the frequency deviation for a VCXO, refers to the frequency range that can be achieved from a specific input voltage to a VCXO. It is expressed as ppm as it relates to a change in the input voltage signal.

In electronic components, linearity describes the principle of scaling, which involves two variables that have a linear relationship to each other. This is expressed mathematically as homogeneity.

In terms of VCXOs, linearity in electronic components refers to the relationship between the VCXO’s output frequency and the voltage input. The linearity requirements for a PPL are less strict than what would be required for use in frequency modulation.

Capacitors and inductors in VCXOs operate according to mathematical scaling properties, which means that they are linear. This is crucial for the VCXO schematic because it means that the circuit design and inputs can be measured and solved exactly, which makes adjustments to signal inputs and frequency output very precise.

The input impedance of a VCXO refers to the load of the control voltage input pad and is measured in ohms. It is specified for the VCXO’s product range by the manufacturer. On the other hand, the output impedance refers to the relationship between a reduction in the device’s voltage and the load network drawing in current. The measurement of the output impedance, also in ohms, of the electronic device is important for accurately modeling the oscillator’s response to current flow.

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