subject: Select High-quality Crystal Designer Should Consider Several Key Parameters - Crystal - The [print this page] 1, operating frequency of the crystal frequency range is generally between 1 and 70MHz. But there are 32.768kHz watch crystal, such as common as a special low-frequency crystal. The physical thickness of the crystal limits the frequency limit. Due to a similar reverse table (invertedMesa) and other manufacturing technology, the crystal frequency limit of 30MHz from previous years to upgrade to 200MHz. Frequency generally based on operating temperature 25 C, are given.
Overtone crystal can be used to achieve higher output frequencies above 200MHz frequency crystal. In addition, with built-in PLL frequency multiplier crystal offers a frequency above 1GHz. When it comes to UHF and microwave frequency, the SAW wave (SAW) Oscillator Is an option.
2, frequency accuracy: the frequency precision tolerance, also known as the frequency of the crystal indicators measure the actual frequency of the application requires proximity between the frequency value. The common table degree is in specific frequency offset compared to the percentage or parts per million (ppm). For example, a precision of 100ppm of the 10MHz crystal oscillator, its actual frequencies between 10MHz 1000Hz. (100 / 1,000,000) 10,000,000 = 1000Hz the same meaning with the following formula: 1000/10, 000,000 = 0.0001 = 10-4, or 0.01%. Typical frequency accuracy range from 1 to 1000ppm, with the initial 25 C are given. High precision crystal oscillator to a few parts per billion (ppb) are given.
3, the frequency stability of the measure of a specific temperature range (such as: 0 C to 70 C and -40 C to 85 C), the actual frequency and extent of deviation from the nominal frequency. Stability is given by ppm, according to the different crystal types, the indicator changes from 10 to 1000ppm great.
4, aging aging refers to the frequency with the passage of time, long-term changes resulting from general to week, month or year period. It is the temperature, voltage and other conditions unrelated. Power used in the crystal within the first few weeks, the frequency of major changes will occur. This value can be between 5 to 10ppm. After the initial period, the frequency change caused by the aging rate will slow down to a few ppm.
5, the output has to provide different types of crystal oscillator output signal. Most of the output pulses or logic level, but there are sine wave and sine wave output clamping. Some common digital outputs include: TTL, HCMOS, ECL, PECL, CML and LVDS.
Many digital output duty cycle is 40% / 60%, but some models can achieve 45% / 55% output duty cycle. Some models also provide three-state output. General also to fan out the number or capacitance value (pF) approach gives the maximum load.
6, Working voltage 5V DC many crystal work. But the new products can work in 1.8,2.5 and 3.3V.
7, start time, the standard measure of a system is stable after power to the output required time. In some devices, there a control crystal oscillator output on / off enable pins.
