[SI-LIST] Re: Bypass Capacitor Selection
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 31 Dec 2003 08:47:25 +0800
Dear martin:
In our experience, we do simulation on power integrity. It is of no use that
saying this or that kind of cap are enough before simulation or measurement.
In our simulation, all the model is measured. The model given by vendor may be
not correct. According to my experience, there is no obvious difference in cera
cap and there is great difference in tan cap and al cap.
Best Regards
Zhangkun
2003.12.31
----- Original Message -----
From: "SI List" <si-list@xxxxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, December 30, 2003 9:21 PM
Subject: [SI-LIST] Bypass Capacitor Selection
> Dear All,
>
> After studying many books, the bottom line for high frequency bypass
> capacitor selection seems to be the following:
>
> Use the smallest possible package and then take the largest valued
> capacitor available in that package.
>
> Although 0201 capacitors are available, they are kind of hard to
> assemble. So in our design, we are thinking of using 0402 X5R parts.
>
> In a 0402 package, the largest value available seems to be 1 uF.
>
> My frequency range of interest is DC to 500 MHz. In addition to the
> bypass capacitors, I know that there must be a pair of closely spaced
> VCC/GND reference planes.
>
> My questions:
> 1. Does it make sense to only use 1 uF 0402 capacitors for bypassing?
> Other people often use a combination of 1 nF/10nF/100nF. 2. I have been
> looking at the frequency characteristic of 100 nF 0402 X5R capacitors
> given in the data sheets of different manufacturers. The impedance vs.
> frequency plot often looks quite different from manufacturer to
> manufacturer. Should I choose the manufacturer with the best frequency
> characteristic or are all such parts almost equivalent? 3. Does it make
> sense to use surface mount capacitor arrays for bypassing?
>
> Thanks for all your expert feedback.
>
> Best regards,
> Martin Heimlicher, heimlicher__at__enclustra//dot//com
>
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