[SI-LIST] Re: Bypass vs Decoupling capacitors

  • From: Zhangkun <zhang_kun@xxxxxxxxxx>
  • To: istvan.novak@xxxxxxxxxxxxxxxx, steve weir <weirsp@xxxxxxxxxx>
  • Date: Fri, 27 Aug 2004 18:25:51 +0800

istvan and steve

I want to add some comments on this topic.

1.The power delivery system, which uses traces not plane, will have some defect 
for the leading inductance. We have done a lot of simulation about the leading 
inductance of decoupling capacitor. When the trace is taken placed by plane, 
the ESL gets less of about 6db.

2.The resonance about power plane could be eliminated by means of some effort. 
The frequency could be extended to about 1GHz or higher. However, in some 
product PCB, there is no space for this kind of measures. The PCB is too 
crowded. AVX has provided some high-ESR capacitor, whose ESR could be as large 
as 100 ohm.

3.Using trace for power delivery could be used for some special circuit such as 
PLL. There are some paper in IEEE International Symposium on EMC 2003 on this 

Best Regards


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