Crystal oscillator:
A, crystal oscillator is a time / frequency device consisting of crystal resonator and oscillating circuit. Classification of B and crystal oscillators:
According to its functional types, it can be divided into four types:
SPXO simple crystal oscillator
VCXO voltage controlled crystal oscillator
TCXO temperature controlled crystal oscillator temperature compensated crystal oscillator
OCXO constant temperature crystal oscillator temperature controlled crystal oscillator C and conventional batch production can achieve stability:
spxo vcxo tcxo ocxo
0 to 70℃ 10 ppm 10 ppm 0.1 ppm 0.005 ppm
-20 to 70℃ 25 ppm 25 ppm 0.3 ppm 0.01 ppm
-40 to 85℃ 30 ppm 30 ppm 0.5 ppm 0.03 ppm
Ppm 50 - 55 to 125℃ 50 ppm 1.0 ppm N / a Stability requirements in the operating temperature range require typical application oscillator types.
The clock reference OCXO of + 0.2ppm telecommunication transmission equipment
Stratum 3 clock benchmark OCXO for telecommunication transmission equipment with (+0.2 -+0.5 ppm) and TCXO with analog integrated circuits
+ 0.5 ~ + 1.0ppm military radio equipment, E-911 cellular phone locator, TCXO with analog IC.
+ 1 ~ + 2.5ppm mobile radio equipment (such as emergency communication equipment) with analog integrated circuit TCXO
+ 2.5 ~ + 10ppm mobile phone TCXO with electrothermal adjustment
+ 10 to + 20ppm fax machine TCXO, VCXO, SPXO
> + 20ppm computer clock signal source SPXO/XO D, crystal oscillator main technical indicators:
1) nominal frequency
2) center frequency deviation
3) frequency adjustment range (mechanical or voltage control)
4) working temperature range
5) voltage control characteristics (voltage range, polarity, linearity, voltage controlled input impedance)
6) output waveform (sine wave; square wave: rising / falling edge time, duty cycle, high / low level)
7) working current and power consumption
8) frequency stability of voltage variation
9) load variation frequency stability
10) temperature frequency stability
11) load capacity
12) frequency aging (long term frequency stability)
13) short term frequency stability
14) phase noise
15) boot characteristics E, crystal oscillator -SPXO:
Simple package crystal oscillator, no voltage control and temperature compensation, frequency and temperature characteristics depend on the crystal unit.
称为SPXO（Simple Packaged Crystal Oscillator ）或时钟（Clock）。 F, temperature compensated crystal oscillator -TCXO:
1. direct temperature compensated crystal oscillator
2. indirect temperature compensated crystal oscillator G, constant temperature crystal oscillator - OCXO
In recent years, due to the development of technology, OCXO mostly uses the direct heating method of power devices, and only some OCXO with high specifications require constant temperature tank. IEC standard for H and OCXO main technical indicators
1）标称频率（Nominal frequency）
The operating frequency indicated by the oscillator.
2）中心频率偏差 (Frequency accuracy)
The deviation between the measured frequencies and the nominal frequencies in the reference temperature environment (25 65507
3）频率调谐范围（Frequency adjustment range）
The frequency range that the oscillator frequency can be changed with some variable element.
Note: purpose of adjustment:
1) transfer the frequency to any specific value within the specified adjustment range.
2) The oscillator frequency can be corrected to a specified value after frequency offset due to aging and other conditions.
The way of adjustment is:
3) there are two ways of adjustment: mechanical adjustment and voltage regulation.
4) variable elements usually refer to varactor diodes, multi ring potentiometers, etc.
4）工作温度范围 (Operating temp. range)
The oscillator can work normally, and its frequency and other output signal performance do not exceed the temperature range of allowable deviation.
Note: 1) The lower the lower the operating temperature range, the greater the power consumption of the oscillator, and the more difficult to achieve the frequency and temperature stability.
2) The higher the upper limit of operating temperature range, the higher the inflection point, the more the crystal cost rises.
5) voltage control characteristics (voltage range, polarity, linearity, voltage controlled input impedance)
When the control voltage changes, the output of the oscillator frequency, waveform characteristics and other electrical characteristics changes.
Note: 1) voltage range: adjustable range of voltage used to regulate frequency. There are 0 ~ 3.3V, 0.3 ~ 3.0V, 0 ~ 5V, 0.5 ~ 4.5V and so on.
2) Voltage Control Range: The range in which the oscillator frequency can vary when the voltage control voltage changes within the voltage range.
3) Polarity: When the frequency of the oscillator increases with the voltage control voltage, the voltage control polarity is positive, and vice versa.
4) Linearity: The ideal relationship between voltage and frequency variations is linear, but there is always a deviation, which is
The degree of linearity that represents the degree of ideal is usually expressed as a percentage.
5) If the system can not give a stable voltage signal, or has strict control requirements for the output frequency, the oscillator can usually give itself
The precise voltage after voltage stabilization is used for voltage control, and the precise voltage is the reference voltage.
6) output waveform (Output waveform) sinusoidal: load capacity
Square wave: rising time, falling edge time, duty cycle, high / low level.
The output waveform and the specific characteristics of the waveform when the oscillator works.
Note: common output waveforms and output characteristics:
1) sine wave (Sine): harmonic suppression (Harmonic attenuation).
Clutter suppression (Noise attenuation), load (Load) and output amplitude (Output level).
2) peak clipping sine wave (Clipping Sine): load (Load) and output amplitude (Output level).
3) Fang Bo (Square): it is divided into two types: MOS and TTL.
Load (Load), duty cycle (Duty cycle), rise / fall time (Rise/fall time),
High and low level ("1" and "0" level).
7）工作电流、功耗 (Input current, power consumption)
8）频率温度稳定度 (Frequency stability over temp.)
When other conditions remain unchanged, the frequency offset relative to the reference temperature is caused by the oscillator operating in a specified temperature range.
9）负载变化频率稳定度 (Frequency stability Vs voltage+/-5% )
When other conditions remain unchanged, the frequency offset relative to the specified load conditions is caused by the change of load impedance within a specified range.
10）电源变化频率稳定度 (Frequency stability Vs Load+/-10% )
When other conditions remain unchanged, the frequency offset relative to the specified supply voltage is caused by the variation of the supply voltage within a specified range.
11）老化率（长期频率稳定度）(Aging , long term stability)
The relationship between oscillator frequency and time.
Note: This frequency shift is caused by long-term changes in quartz crystals or/or other components of the circuit and can be represented by relative changes in the average frequency over a specified time interval.
Frequency aging is inevitable. At the same time, the direction may be positive or negative.
Also known as the aging rate, long stability, etc.
12）短期频率稳定度(Short term stability)
The frequency of random fluctuations of the oscillator in a short time.
Note: in seconds, it is also known as the second base stability, second stability and short stability.
13) 相位噪声 (phase noise)
The frequency-domain measure of short-term frequency stability of an oscillator is usually expressed by the corresponding fluctuating power spectral density S_(f), where the phase fluctuation function is_(f) = 2piFt-2piF0t.
Note: Jitter is a time-domain measure of oscillator short-term frequency stability. In fact, both phase noise and jitter are measurements of frequency short-term stability.
14) Other indicators: power consumption, startup characteristics, reproducibility, operating temperature range, mechanical impact resistance, electrical pulse impact resistance, storage temperature range,
Frequency stability of gravity acceleration, constant temperature alarm, three state control TCXO Temperature Compensated Crystal OscillatorstcxoTCVCXO TemperatureCompensatedVoltageControlled Oscillators Temperature compensated voltage controlled crystal oscillator
