The crystal load capacitance is one of the critical electrical parameters of the crystal oscillator, and this value is specified by the chip and cannot be arbitrarily changed. For the crystal itself, the smaller the load capacitance CL, the smaller the power consumption. On the other hand, the choice of crystal load capacitor CL directly affects the change of its output frequency. For example, if the TS value of the crystal oscillator is 12, this means that for every 1PF change in the load capacitance CL, the output frequency of the crystal oscillator will change by 12ppm.
晶振负载电容为晶振的重要电气参数之一,该值由芯片方案指定,不可任意更改。对于晶振单体而言,其负载电容CL越小,说明功耗越小。另一方面,晶振负载电容CL的选择直接影响着晶振输出频率的变化。比如,若该晶振的TS值为12,这就说明负载电容CL每变化1PF,晶振的输出频率就会有12ppm的变化量。
It can be seen from the above that even if a crystal oscillator with a frequency accuracy of ±10ppm is selected and utilized, once the load capacitor CL is selected incorrectly, the actual output frequency accuracy of the crystal oscillator may deviate by ± 10ppm. The law is that when the load capacitor CL deviates too much from the actual demand value and the crystal oscillator TS value is large meanwhile, the frequency deviation will be out of range. When the crystal frequency is deviated to a certain extence , the chip will fail to capture the clock signal output from the crystal oscillator, and eventually causing failures to the related functions.
由以上可见,即使在晶振选型时选择了频率精度为±10ppm的晶振,一旦晶振负载电容CL选错,晶振的实际输出频率精度可能偏离±10ppm。其规律是,当负载电容CL偏离实际需求值越大时,另外加上晶振TS值越大时,晶振的频率偏差就会越大。当晶振频偏到一定程度,就会造成芯片无法捕捉到晶振输出的时钟信号,最终导致设备相应功能失效。
在实际应用中,会根据不同的应用场景选择合适的负载电容晶振。
As a crystal oscillator manufacturer, Genuway Technology hopes every crystal provided can be used correctly and perform at its best.
作为晶振制造厂家,希望所提供的每一颗晶振都被正确应用且处于最佳状态运行。