1. Passive crystal A passive crystal needs to use the on-chip oscillator of the DSP, and there is a suggested connection method on the datasheet. Passive crystals do not have voltage problems. The signal level is variable, that is to say, it is determined according to the oscillator circuit. The same crystal can be applied to a variety of voltages, and can be used for a variety of DSPs with different clock signal voltage requirements. And the price is usually low, so for general applications, if conditions permit, it is recommended to use crystals, which is especially suitable for producers with abundant product lines and large quantities. Compared with crystal oscillator, the defect of passive crystal is poor signal quality, and it usually needs to accurately match the peripheral circuit (capacitance, inductance, resistance, etc. for signal matching). When replacing crystals with different frequencies, the peripheral configuration circuit needs to be adjusted accordingly. . It is recommended to use high-precision quartz crystals, and avoid using low-precision ceramics as much as possible.

2. Active crystal oscillator An active crystal oscillator does not require the internal oscillator of DSP, the signal quality is good, relatively stable, and the connection method is relatively simple (mainly to do a good job of power filtering, usually a PI filter network composed of capacitors and inductors, The output end can be filtered with a small resistance resistor), no complicated configuration circuit is required. The usual usage of active crystal oscillator:-Pins are suspended, two pins are grounded, three pins are connected to output, and four pins are connected to voltage. Compared with passive crystals, the disadvantage of active crystal oscillators is that their signal level is fixed, and a suitable output level needs to be selected. The flexibility is poor and the price is high. For applications with sensitive timing requirements, I personally think that an active crystal is better because you can choose a more precise crystal or even a high-end temperature compensation crystal. Some DSPs have no internal oscillator circuit and can only use active crystal oscillators, such as TI's 6000 series. Compared with passive crystals, active crystals are usually larger in size, but now many active crystals are surface-mounted, the size is equivalent to crystals, and some are even smaller than many crystals.