浅析旁路电容的特性及其在PCB中的应用

Brief Analysis Shunt Capacitor's Characteristic and Application in PCB

文章主要介绍了电容的一些基本应用,旁路电容可以降低电源的波动,降低SSN和串扰,抑制EMI等。电容的频率特性决定了寄生电感和电阻的存在,这是我们要考虑到的问题。电容特性还会受到封装结构和所用介质材料的影响,封装尺寸也会对其产生一定的作用,不同种类的电容应用的场合也不尽相同。我们只要知道去耦电路的谐振频率,就可以计算出所需的电容值。采用多个电容并联的方式来降低ESR和ESL,使电容值增大,而谐振频率则保持不变。另外,在PCB中还要降低引线的长度,以减小引线电感。

This article mainly introduced electric capacity＇s some basic applications,the shunt capacitor may reduce power source＇s fluctuation,reduces SSN and the crosstalk,suppresses EMI and so on.Electric capacity＇s frequency characteristic had decided parasitic inductance and resistance existence,this is the question which we must consider.The electric capacity characteristic will also receive the seal structure and uses the medium material the influence,the seal size also to have certain function to it,the different type＇s electric capacity application＇s situation will also be different.So long as we knew the lotus root electric circuit＇s resonance frequency,may calculate the capacitance value which needs.Selects the many electric capacity parallel methods,reduces ESR and ESL,causes the capacitance value to increase,but the resonance frequency maintains invariable.Moreover,must reduce the lead wire in PCB the length,reduces the lead inductance.