Crystal oscillators are available in a variety of packages characterized by a variety of electrical functional specifications. There are several different types: voltage-controlled crystal oscillator (VCXO), temperature-compensated crystal oscillator (TCXO), oven-controlled crystal oscillator (OCXO), and digitally compensated crystal oscillator (MCXO or DTCXO), each type All have their own unique properties. If you need to make the equipment ready to use, you must choose a VCXO or temperature-compensated crystal oscillator. If the stability is required to be above 0.5ppm, you need to choose a digital temperature-compensated crystal oscillator (MCXO). The imitation temperature compensated crystal oscillator is suitable for requirements with stability requirements between 5ppm and 0.5ppm. VCXO is only suitable for products with stability requirements below 5ppm. In situations where out-of-the-box use is not required, if signal stability is required to exceed 0.1ppm, OCXO can be selected.
Frequency Stability Considerations
One of the primary characteristics of a crystal oscillator is stability within the operating temperature, which is an important factor in determining the price of the oscillator. The higher the stability or the wider the temperature range, the higher the price of the equipment.
Other factors related to stability include supply voltage, load variation, phase noise, and jitter, and these goals should be specified. For industrial products, vibration and impact targets are sometimes required. Products and aerospace equipment often have more requirements, such as tolerances when pressure changes, tolerances when exposed to radiation, etc.
output
Other parameters that must be considered are output type, phase noise, jitter, voltage characteristics, load characteristics, power consumption, packaging style and, for industrial products, sometimes shock and vibration, and electromagnetic interference (EMI). The crystal oscillator is HCMOS/TTL compatible, ACMOS compatible, ECL and sine wave output. Each output type has its common waveform characteristics and uses. Attention should be paid to the requirements for tri-state or complementary outputs. Symmetry, rise and fall times, and logic levels may also be specified for some applications.
encapsulation
Similar to other electronic components, clock oscillators are also coming in increasingly smaller packages. We manufacture crystal oscillators of various types and sizes according to customer needs (please refer to the product manual for specific materials). Typically, smaller devices are more expensive than larger surface mount or through-hole package devices. Therefore, small packages often require compromises between performance, output selection and frequency selection.
working environment
The actual environment in which the crystal oscillator is used requires careful consideration. For example, high-intensity oscillations or shocks can cause problems for oscillators. In addition to the possibility of physical damage, oscillations or shocks can cause erroneous operation at certain frequencies. These externally induced perturbations can cause frequency jumps, increased noise content, and intermittent oscillator failure. Regarding uses that require special EMI compliance, EMI is another priority. In addition to selecting appropriate PC motherboard layout techniques, it is important to select a clock oscillator that provides the smallest amount of radiation. Generally speaking, oscillators with slower rise/fall times exhibit better EMI characteristics.
Summarize:
Generally, some margin should be left when selecting a crystal oscillator to ensure the reliability of the product. Choosing higher quality equipment can further reduce the probability of failure and bring potential benefits. This should also be considered when comparing product prices. To make the "overall performance" of the oscillator balanced and reasonable, it is necessary to weigh many factors such as stability, operating temperature range, crystal aging effects, phase noise, cost, etc. The cost here not only includes the price of the equipment, but And it includes the cost of using the product throughout its life.
