On Oct 12, 2009, at 11:01 AM, alan smith wrote:

>
> http://ftp.cse.sc.edu/jdavis/csce613/Xilinx/Vertex-AppNotes&Sample%20Code/xapp158.pdf

Yes, but this is from 2001 and they divide caps into three categories:

>> Proper placement is very important for high-frequency capacitors  
>> (0.1uF to 0.001uF low-inductance ceramic chip). It is less  
>> important for middle-frequency capacitors (47uF to 100uF tantalum),  
>> and even less important for low-frequency capacitors (470uF to  
>> 3300uF).

What I'm most curious about is the ceramic chip caps 0.1uF < C < 47uF  
that they don't talk about.   They're still small; are they still high- 
frequency? (in general; I suppose I could look at individual data  
sheets for specifics.)  If I sprinkle 10uF ceramics where there used  
to be 0.1uF ceramics, do I relax the needs for the middle-freq caps?   
Or have the capacitance of "small" ceramics just barely kept pace with  
the increased power demands of most chips?

BillW

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