What is the difference between passive crystal and active crystal?

1, passive crystal No source crystal needs to use the oscillator in the DSP chip, under the datasheet. There are recommended connection methods. The passive crystal has no voltage problem, the signal level is variable, that is, according to the excitation circuit to decide, the same crystal can be applied to a variety of voltages, can be used for a variety of different clock signal voltage requirements of the DSP, and the price is usually lower, Therefore, it is recommended to use crystals for general applications if conditions permit, which is especially suitable for producers with rich product lines and large batches. The defect of passive crystal relative to crystal oscillator is that the signal quality is poor, and it is usually necessary to match the peripheral circuit (capacitor, inductor, resistor, etc.) for signal matching, and the peripheral configuration circuit needs to be adjusted accordingly when replacing crystals with different frequencies. It is recommended to use quartz crystals with higher accuracy, and do not use ceramics with low accuracy as much as possible.

2, active crystal oscillator an active crystal oscillator does not need the internal oscillator of the DSP, the signal quality is good, relatively stable, and the connection mode is relatively simple (mainly to do a good power filter, usually using a capacitor and inductor composed of PI filter network, the output end with a small resistance value of the resistance to filter the signal can be), do not need complex configuration circuit. The usual usage of active crystal oscillator :- feet suspended, two grounded, three pin output, four pin voltage. Compared with passive crystals, the defect of active crystal is that the signal level is fixed, and the appropriate output level needs to be selected, which is poor in flexibility and high in price. For applications with sensitive timing requirements, I personally believe that active crystal vibration is better, because more precise crystal vibration can be selected, and even [sensitive word] temperature compensation crystal vibration. Some DSPS have no internal vibration circuit and can only use active crystal vibration, such as TI's 6000 series. Active crystal oscillators are usually larger than passive crystals, but many active crystal oscillators are now surface attached, the volume is comparable to the crystal, and some are even smaller than many crystals.