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???
11/19/07 18:28
Modified:
  11/19/07 18:34
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 		 #147206 - Thank you!
Responding to: ???'s previous message
Richard said:
Just be careful with the decoupling capacitors, as Kai says use 100nF /X7R's and DON'T use any other values in parallel, this is often seen on application notes (say 100nF + 10nf), even three is not uncommon. This will actually cause more problems than it appears to solve.

You are the first person here I know who also recommends to avoid this paralleling of decoupling caps! I thank you very much, indeed.

I have analyzed this issue many years ago and was the only one who stated that this kind of paralleling can show adverse effects.

I have discussed this issue here:

http://www.8052.com/forum/read.phtml?id=142878
http://www.8052.com/forum/read.phtml?id=142882
http://www.8052.com/forum/read.phtml?id=142936

Nowadays, you can find it being mentioned even in datasheets:

http://www.analog.com/UploadedF.../AD797.pdf

Calculation examples can be found here:

http://www.8052.com/forum/read.phtml?id=143008

Kai


List of 88 messages in thread
TopicAuthorDate
Atmel 89 Series and EMI            01/01/70 00:00      
   FAQ            01/01/70 00:00      
      Thanks, but...            01/01/70 00:00      
         yes it is            01/01/70 00:00      
            EMI design consideration...            01/01/70 00:00      
               reset pulses?            01/01/70 00:00      
                  Finally a note to the OP            01/01/70 00:00      
                     well, sometimes...            01/01/70 00:00      
                     Fire Extinguisher            01/01/70 00:00      
                        extinguisher            01/01/70 00:00      
                  Latched-up CMOS!            01/01/70 00:00      
                     logic, and beyond            01/01/70 00:00      
                     not a cure            01/01/70 00:00      
   EMI Design            01/01/70 00:00      
      restated in one sentence            01/01/70 00:00      
         Don't jump to the conclusion...            01/01/70 00:00      
            then just say "outside the specs, no can do"            01/01/70 00:00      
      Thanks...            01/01/70 00:00      
   What PCB do you use?            01/01/70 00:00      
      Two Layer            01/01/70 00:00      
         No surprise, then!            01/01/70 00:00      
            Ground...            01/01/70 00:00      
               About naked firefighters...            01/01/70 00:00      
               Absolutely it is fair            01/01/70 00:00      
   Some advice            01/01/70 00:00      
      Yes, it's a bunch of measures...            01/01/70 00:00      
      Good points.            01/01/70 00:00      
         No, no, no,....            01/01/70 00:00      
            Remember            01/01/70 00:00      
         CMOS Latch up            01/01/70 00:00      
         NOPE            01/01/70 00:00      
            You think so...            01/01/70 00:00      
               No, it is not            01/01/70 00:00      
               A proper design would stand it!            01/01/70 00:00      
                  Proper design            01/01/70 00:00      
                     some of my definitions            01/01/70 00:00      
                     Me thinks...            01/01/70 00:00      
                        the real point            01/01/70 00:00      
            More advice            01/01/70 00:00      
               Does that mean, that...            01/01/70 00:00      
                  It's the designers responsibility            01/01/70 00:00      
                     No joke, but...            01/01/70 00:00      
                  EMI and 2 layers            01/01/70 00:00      
                     Yes, for tiny projects...            01/01/70 00:00      
               that something is possible/done succesfully            01/01/70 00:00      
   Show us your design...            01/01/70 00:00      
      Why? You want to make fun of it? :)            01/01/70 00:00      
         Or            01/01/70 00:00      
            You mean...            01/01/70 00:00      
               I do not know what Steve ment            01/01/70 00:00      
               Yes !            01/01/70 00:00      
         how about a schematic            01/01/70 00:00      
            Relays            01/01/70 00:00      
               Even then...            01/01/70 00:00      
         From what I can see            01/01/70 00:00      
            Mostly agree.            01/01/70 00:00      
               Layers, layouts...            01/01/70 00:00      
                  are you serious, or did you forget            01/01/70 00:00      
                     Sorry, I forgot...            01/01/70 00:00      
                     Is it good?            01/01/70 00:00      
                        Just a few points.            01/01/70 00:00      
                           I believe you!            01/01/70 00:00      
                        No harm, usually            01/01/70 00:00      
                  Separate Ground Planes            01/01/70 00:00      
                     Inter-plane coupling            01/01/70 00:00      
                     Cable entry point            01/01/70 00:00      
                        Thanks            01/01/70 00:00      
            what I do ..            01/01/70 00:00      
            half measures            01/01/70 00:00      
            Taking notes...            01/01/70 00:00      
               the downfall of many            01/01/70 00:00      
               Do some tests            01/01/70 00:00      
                  This can be deadly!            01/01/70 00:00      
                     Deadly?            01/01/70 00:00      
                        I'm sorry...            01/01/70 00:00      
         Farshad, I would never make fun of it!            01/01/70 00:00      
            Very Informative            01/01/70 00:00      
               Decoupling            01/01/70 00:00      
                  Thank you!            01/01/70 00:00      
               and not a word about 4 layers            01/01/70 00:00      
   paralelling            01/01/70 00:00      
      Why not using 10µF/10V/X5S ceramics?            01/01/70 00:00      
   more information?            01/01/70 00:00      
      Schematics would not be very "helpfil"            01/01/70 00:00      
      More information            01/01/70 00:00      
      The best stuff I have ever seen is...            01/01/70 00:00      
         Sorry, I forgot, that you must suscribe first...            01/01/70 00:00      
      John, I have seen....            01/01/70 00:00      

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