文獻(xiàn)標(biāo)識(shí)碼： A
文章編號(hào)： 0258-7998(2013)09-0061-02
隨著印制電路板(PCB)集成度的提高，寄生參數(shù)會(huì)破壞PCB電源分配網(wǎng)絡(luò)(PDN)的穩(wěn)定性[1],，PDN的阻抗ZPDN會(huì)產(chǎn)生尖峰（反諧振點(diǎn)）,，參考文獻(xiàn)[2]通過(guò)去耦電容削弱ZPDN的尖峰并將其推移至PCB的非工作頻段，指出了并聯(lián)去耦電容的等效特性阻抗會(huì)產(chǎn)生反諧振點(diǎn),，且該點(diǎn)不可以大于目標(biāo)阻抗,。參考文獻(xiàn)[3]總結(jié)了各種電容器隨著頻率升高，其特性阻抗,、有效容值受寄生電阻的影響,；參考文獻(xiàn)[4]是從場(chǎng)角度研究電容特性阻抗與寄生參數(shù)的關(guān)系，參考文獻(xiàn)[5]采用運(yùn)算放大器來(lái)增加電容的有效容值,。以上文獻(xiàn)都均未給出寄生參數(shù)和去耦電容特性阻抗反諧振點(diǎn)關(guān)系的完整模型,。
參考文獻(xiàn)[6]詳細(xì)描述了單個(gè)電容寄生參數(shù)與特性阻抗之間的關(guān)系；參考文獻(xiàn)[7-8]從等效電路角度計(jì)算出了ZPDN尖峰的頻率位置,；參考文獻(xiàn)[9]將PDN等效為微波網(wǎng)絡(luò)計(jì)算出了ZPDN尖峰的頻率位置,；上述文獻(xiàn)中，僅給出了寄生參數(shù)變化對(duì)反諧振點(diǎn)的影響的仿真圖形,，并沒(méi)有給出相應(yīng)數(shù)學(xué)模型,。
本文主要在參考文獻(xiàn)[6，8]的基礎(chǔ)上,，推導(dǎo)并驗(yàn)證了并聯(lián)電容特性阻抗反諧振點(diǎn)與電容寄生參數(shù)的數(shù)學(xué)模型,，即合理選取最佳去耦電容來(lái)盡可能壓低反諧振點(diǎn)的阻抗，然后在Cadence開(kāi)發(fā)環(huán)境中實(shí)施了該方法,，從而在選取去耦電容器這一環(huán)節(jié)上給出了重要的理論參考,。
1 電容特性阻抗分析
圖1為并聯(lián)電容的等效電路模型[7]，阻抗為：
本文從并聯(lián)電容的等效電路模型出發(fā),，推導(dǎo)出電容參數(shù)與反諧振點(diǎn)頻率,、反諧振點(diǎn)幅度的數(shù)學(xué)模型，然后將此模型應(yīng)用到基于目標(biāo)阻抗的設(shè)計(jì)中,。通過(guò)簡(jiǎn)單計(jì)算,，驗(yàn)證了電容組選取的合理性。此方法簡(jiǎn)單直觀,，為高速電路設(shè)計(jì)人員在選擇去耦電容時(shí)提供了有價(jià)值的參考,。
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