关于晶体负载电容参数选取问题，请高手指教，谢谢！

login

遇到一个芯片要求外接晶体负载电容＞＝８Ｐ，在８到１２Ｐ都可以工作，请问这个负载电容是选得越大越好还是越小越好（晶体频率选择相同前提下）？非常感谢！

f86h

仿真一下看你外部时钟线上的分布电容吧！

willyamyue

You can use it have a try  .

(CL)=C1*C2 /(C1+C2)  + CS   ,and  C1 =C2 .  (CL) value come from component  spac
The capacitors C1 and C2 form the load capacitance for the crystal. The optimum load capacitance (CL) for a given crystal
is specified by the crystal manufacturer. The equation to calculate the values of C1 and C2 is

Where CS is the stray capacitance on the printed circuit board, typically a value of 5pf can be used for calculation
purposes. Now C1 and C2 can be selected to satisfy the above equation. Usually C1 and C2 are selected such that they
are approximately equal. Large values of C1 and/or C2 increases frequency stability but decreases loop gain and may
cause start-up problems.[em01]

login

非常感谢两位的指点![em08]

ventoa14

3楼的公式是正确的。
另外还是需要楼主根据实际测量下再确定最后的值。

willyamyue

[em02]