The clock source of the microcontroller can be divided into two categories: a clock source based on a mechanical resonator, such as a crystal, a ceramic resonant tank; an RC (resistance, capacitance) vibrator. One is a Pierce vibrator configuration, suitable for crystal and ceramic resonant tank. The other is a simple discrete RC vibrator.
Oscillators based on crystal and ceramic resonant tank routines can often provide very high initial accuracy and low temperature coefficient.
RC vibrators can be quickly launched, the cost is relatively low, but usually in the full temperature and operating voltage range of precision is poor, the nominal output frequency of 5% to 50% scale change.
But its function is affected by environmental conditions and selection of circuit components. The component selection and circuit board planning of the vibrator circuit should be taken seriously. In use, the ceramic resonant tank and the corresponding load capacitance need to be optimized according to the specific logic series. Crystals with high Q values are not sensitive to the selection of amplifiers, but are prone to frequency drift (and possibly even damage) during overdrive. Environmental factors that affect vibrator operations are electromagnetic interference (EMI), mechanical sensation and shock, humidity and temperature. These elements increase the output frequency
Of the change, adding insecurity, and in some cases, will also form a vibrator to stop the vibration. Normal day
In the most popular, the naked eye can see that all the time with the show, such as: TV, electronic watches, quartz clock, electrical appliances, etc., the time control circuit has used crystal components.
Most of the above problems can be prevented by using a vibrator module. These modules come with vibrators, supply low resistance square wave output, and can ensure that the operation under certain conditions. The two most commonly used types are crystal oscillator modules and integrated RC vibrators (silicon vibrators). The crystal oscillator module provides the same accuracy as a discrete crystal. The accuracy of the silicon vibrator is higher than that of the discrete RC vibrator, and in most cases it is possible to supply the ceramic resonator

When the precision.