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???
11/02/07 15:37
Modified:
  11/02/07 15:38
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 		 #146507 - Of course, they are, but...
Responding to: ???'s previous message
...you can make them to appear totally noisefree! Take the right layout, proper parts and a shield eventually and you will no longer "see" the noisy switcher.

A good example is LM2674, which I widely use as a pre-switcher. See the datasheet, everything is there, a recommended layout, recommended parts (even with phone numbers of manufacturers!), dimensioning forumulas and even selection tables:

http://cache.national.com/ds/LM/LM2674.pdf

In a certain product I use three of them. During the CE testing the guy told me to turn-on the product. It was already, but he couldn't see any radiated noise...

Kai

List of 32 messages in thread
TopicAuthorDate
AC Wall adapters - Power rating?            01/01/70 00:00      
   unreliable            01/01/70 00:00      
      PI Chips?            01/01/70 00:00      
         ti.com            01/01/70 00:00      
            Re:            01/01/70 00:00      
               what?            01/01/70 00:00      
   why not buy a wall-wart?            01/01/70 00:00      
      No Wall-wart because..            01/01/70 00:00      
         tell "the customer" ...            01/01/70 00:00      
            Certification..            01/01/70 00:00      
               rather            01/01/70 00:00      
                  agreed.            01/01/70 00:00      
                  Switchers are ALWAYS noisy!            01/01/70 00:00      
                     agreed agreed!            01/01/70 00:00      
                        You have to live with it            01/01/70 00:00      
                           But what is the method?            01/01/70 00:00      
                     Switchers are ALWAYS noisy!            01/01/70 00:00      
                        I only use them when I have to ...            01/01/70 00:00      
                           We don't have much of a choice, from time to time            01/01/70 00:00      
                              Of that there can be no doubt            01/01/70 00:00      
                     Of course, they are, but...            01/01/70 00:00      
   Do Not forget the Power Factor            01/01/70 00:00      
      PF for switchers?            01/01/70 00:00      
   Transformers also draw spiky currents!            01/01/70 00:00      
      Spiky currents!            01/01/70 00:00      
         There is a theory, but the way to go is...            01/01/70 00:00      
         EN61000-3-2            01/01/70 00:00      
            Power Factor            01/01/70 00:00      
               If making is a pain why noy buy it ?            01/01/70 00:00      
                  Vacation over!            01/01/70 00:00      
                     quantities            01/01/70 00:00      
                        Phihong            01/01/70 00:00      

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