关于晶体负载电容参数选取问题，请高手指教，谢谢！

login · 发表于 2008-3-25 16:22:58

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 · 发表于 2008-3-26 09:02:20

仿真一下看你外部时钟线上的分布电容吧！

willyamyue · 发表于 2008-3-27 23:05:40

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 · 发表于 2008-3-31 11:09:40

非常感谢两位的指点![em08]

ventoa14 · 发表于 2008-4-2 11:07:00

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 · 发表于 2008-4-4 14:39:54

[em02]

		自动登录	找回密码
密码			注册

[讨论] 关于晶体负载电容参数选取问题，请高手指教，谢谢！