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The difference between passive and active Crystal and Crystal

Edit: Global Link Electronic (Shenzhen) Co.,Ltd    Date: Aug 13, 2015

1, source-free Crystal--source-free crystal oscillator using DSP chip can also be, in the Datasheet on the recommended connection method. Passive crystals do not have a voltage problem, the signal level is variable, that is, according to the starting circuit to decide, the same Crystal can be applied to a variety of voltages, can be used for a variety of different voltage requirements of DSP clock signal, and prices are generally lower, so for general application if conditions permit, it is recommended to use the Crystal, which is especially suitable for rich product line quantity producers. Passive vibration Crystal whisker in terms of its shortcomings are poor signal quality, usually require an exact match the external circuit (for signal matching capacitors, inductors, resistors, etc), switch to a different frequency of the Crystal Configuration around the circuit needs to be adjusted accordingly. Recommends using a high precision quartz crystal using low precision ceramic alert as possible.

2, Active Crystals – active Crystal does not need DSP's internal oscillators, signal quality, more stable, and the connections are relatively simple (mostly good power supply filtering, usually using a PI-filter network consisting of capacitors and inductors, the output signal with a small resistance of the resistor), does not require complex configuration of the circuit. Active usage of crystals usually: one foot dangling two feet grounded, three-pin output, four-leg voltage. Compared to passive Crystal Active crystal defects in its signal level is fixed, you need to select the appropriate output levels, less flexible, and the price is high. For time sensitive applications, view active Crystal is also good, because it can use more sophisticated Crystal, even high-end temperature compensated crystal oscillator. Some within the DSP does not start oscillating circuit, only active Crystal can be used, such as TI 6000 series. Active Crystals compared to passive crystals are usually larger, but now many active Crystal SMD, and Crystal size, some even smaller than a lot of Crystal.

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