What does a Temperature-compensated Crystal Oscillator do? You Need to Know These Things
What is a temperature-compensated crystal oscillator? A temperature-compensated crystal oscillator is defined as a quartz crystal oscillator, which is produced using a compensation method. The original physical characteristics of the piezoelectric time-sensitive crystal (frequency changes in a cubic curve with temperature under the piezoelectric effect under the piezoelectric effect) are reversed through the peripheral circuit so that the original physical characteristics of the time-sensitive crystal are reversed. There is as little frequency variation as possible with temperature.
Fig.1
In the application of a temperature-compensated crystal oscillator in wireless transmission, the wireless transparent transmission module has a small size and low power consumption as important development indicators. Under normal operating conditions, the frequency accuracy of common crystal oscillators can reach 50 parts per million, while the accuracy of temperature-compensated crystal oscillators is even higher. The temperature-compensated crystal oscillator is composed of a constant temperature bath control circuit and an oscillation circuit. Temperature control is usually achieved using a differential series amplifier composed of a thermistor "bridge".
High precision, low power consumption, and miniaturization are the main advantages of temperature-compensated crystal oscillators. There are many difficulties in miniaturization and chip production, among which there are two main points: First, miniaturization will make the frequency variable range of the time-sensitive crystal oscillator smaller, making temperature compensation more difficult; second, after dual-chip packaging, the key During the welding operation, since the welding temperature is much higher than the maximum allowable temperature of the temperature-compensated crystal oscillator, the frequency of the crystal oscillator will change. If local heat dissipation and cooling measures are not taken, it is difficult to control the frequency change of the temperature-compensated crystal oscillator below 0.5ppm.
The crystal oscillator is the simplest. It only integrates the crystal resonator with the oscillator circuit without temperature compensation and temperature control. The addition of a temperature-compensated crystal oscillator allows the module to adapt to working environments ranging from -40 to 85 degrees Celsius and does not affect wireless transmission even in harsh environments.
The characteristics of temperature-compensated crystal oscillators still need to understand your own needs. In particular, the temperature-compensated crystal oscillator is a quartz crystal oscillator that uses an additional temperature-compensation circuit to reduce changes in oscillation frequency caused by changes in ambient temperature. Direct compensation TCXO is a temperature compensation circuit composed of a thermistor and a resistor-capacitor component, which is connected in series with a time-sensitive crystal back oscillator. These are all things that need to be understood.
The resistance of the thermistor and the capacitance of the crystal's equivalent series capacitance also change accordingly, thereby offsetting or reducing the temperature drift of the oscillation frequency. This compensation method has a simple circuit, low cost, saves the size and space of the printed circuit board, and is suitable for small sizes, low voltage, and small current situations. When the accuracy of the crystal oscillator is required to be less than 1ppm, the direct compensation method is not suitable. These are the characteristics of temperature-compensated crystal oscillators, and the improvement of the temperature-compensated crystal oscillator technology has not reached its limit. The content and potential of innovation are still large. Understand these After selecting the characteristics of the temperature-compensated crystal oscillator, you will know how to use and select it.
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