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???
12/03/05 13:28
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 		 #104625 - Noise could come from comparator itself
Responding to: ???'s previous message
Kai said:
Another cause of mistriggering could come from noisy supply voltage. So, you should filter the point where the parts of comparator are connected to supply voltage.

The noise can come from the micro itself, when the comparator skips. This can cause a spike or dip on Vcc, can cause a momentary shift of comparator threshold and can result in a series of mistriggerings.
Also, don't include R21 to this filtering, only Rp, Rq and D8.

Kai

List of 35 messages in thread
TopicAuthorDate
LPC922 Comparator Interrupt Problems.            01/01/70 00:00      
   Vcc?            01/01/70 00:00      
      Vcc=3.0 to 3.3 Volts.            01/01/70 00:00      
         Possible causes            01/01/70 00:00      
            Noise could come from comparator itself            01/01/70 00:00      
               Re: Noise from Ground.            01/01/70 00:00      
                  Filter            01/01/70 00:00      
                     Exactly!            01/01/70 00:00      
                  R21 is contaminated            01/01/70 00:00      
                     Hystresis is 1.7 mV            01/01/70 00:00      
                        It's 20mV!            01/01/70 00:00      
                           oops calculation error            01/01/70 00:00      
                              waaaay too small a hysteresis..            01/01/70 00:00      
                                 Not at all !            01/01/70 00:00      
                                    there are (at least) 2 ways to skin this            01/01/70 00:00      
                                       Extreme care??            01/01/70 00:00      
                                          correct, but there has been umpteen post            01/01/70 00:00      
                     Please Suggest some filtering.            01/01/70 00:00      
                        100R plus 47µF            01/01/70 00:00      
                           Re: 100E + 47uF            01/01/70 00:00      
                              Like that...            01/01/70 00:00      
                                 Red LED.            01/01/70 00:00      
                                    Every red LED should work            01/01/70 00:00      
                                       also be aware            01/01/70 00:00      
                                          At 500µA...            01/01/70 00:00      
            Noisy ground?            01/01/70 00:00      
            Re: Possible Causes.            01/01/70 00:00      
               Mains Signalling?            01/01/70 00:00      
                  Mains filtering            01/01/70 00:00      
                     mains filtering            01/01/70 00:00      
                        Very informative!            01/01/70 00:00      
   Problem Frequency.            01/01/70 00:00      
      Filtering will help!            01/01/70 00:00      
         Problem Solved.            01/01/70 00:00      
            Nice to hear!            01/01/70 00:00      

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