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???
06/24/09 00:58
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 		 #166407 - I partially disagree
Responding to: ???'s previous message
As Kai stated, some microcontrollers (like AT89S8253 and may be other flash derivatives) need fast Vcc rise time, in spite of any reset (special power supervisory chips, push button, RC, etc). I would pay atention to this issue: Vcc should rise in less than, say, 1ms to 67% of final value. It will reset all the internal logic.
Take a look at this thread:
http://www.8052.com/forum/read/132592
Good luck

Daniel

List of 58 messages in thread
TopicAuthorDate
soft-start powersupply and controllers            01/01/70 00:00      
   supervisor chip or processor with good brownout detection            01/01/70 00:00      
      Per gives a good solution if you can tolerate restarts            01/01/70 00:00      
   Long rise times of Vcc are critical!            01/01/70 00:00      
      replace the 7805            01/01/70 00:00      
         Lot of information            01/01/70 00:00      
            look at PowerTrends (TI)            01/01/70 00:00      
            Some answers...            01/01/70 00:00      
               Bigget reset capacitor and resistor            01/01/70 00:00      
                  it is NOT the capacitor value            01/01/70 00:00      
                     Thanks Erik            01/01/70 00:00      
                        I partially disagree            01/01/70 00:00      
                           disagree with what?            01/01/70 00:00      
                              With thinking only in a reset chip.            01/01/70 00:00      
                                 Use the reset chip to reset the powersupply            01/01/70 00:00      
                        How about $0.15            01/01/70 00:00      
                     A small clarification            01/01/70 00:00      
                        3 pin regulators with uvlo            01/01/70 00:00      
                        Eh ?            01/01/70 00:00      
                           Only a clarification            01/01/70 00:00      
                           Steve, I meant turning on MCU supply            01/01/70 00:00      
                        and power down            01/01/70 00:00      
                           Erik, brown-out is handled by Silabs MCU!!            01/01/70 00:00      
                              Did I miss that?            01/01/70 00:00      
                                 But Erik...            01/01/70 00:00      
                                    In application notes, direct pull-ups have been used...            01/01/70 00:00      
                                       some idiot, not there any more ...            01/01/70 00:00      
                                          You seem to be wrong about the capacitor, Erik            01/01/70 00:00      
                                             Not necessarily...            01/01/70 00:00      
                                             the risetime has nothing to do with reset ... unless            01/01/70 00:00      
                                             which SiLabs part?            01/01/70 00:00      
                                                Andy..            01/01/70 00:00      
                                                   SILabs urban legends            01/01/70 00:00      
                                                      Interesting...            01/01/70 00:00      
                                                         you may            01/01/70 00:00      
                                                            Thank you, I really appreciate it!            01/01/70 00:00      
                                                      Clarifying, Erik, Kai            01/01/70 00:00      
                                                         The reset from the supply monitor will be there            01/01/70 00:00      
                                                            Good advice...            01/01/70 00:00      
                                                               I am guilty of not recalling all differences            01/01/70 00:00      
                                                         Only open-drain but not push-pull!            01/01/70 00:00      
                                                            Good one, Kai            01/01/70 00:00      
                                                            why the 'love' of the MAX1232?            01/01/70 00:00      
                                                               True, Erik            01/01/70 00:00      
                                                                  Have you seen this post?            01/01/70 00:00      
                                                                     Have you seen this post?            01/01/70 00:00      
                                                                        Turn on your brain, Erik, and read what I wrote!            01/01/70 00:00      
                                                                           a picture is worth 1000 words            01/01/70 00:00      
                                                                              So you haven't read the words??            01/01/70 00:00      
                                                               I was suggesting him the MAX1232...            01/01/70 00:00      
      Well, even more demanding...            01/01/70 00:00      
   Bigger, not bigget            01/01/70 00:00      
   Only external electronics can help you            01/01/70 00:00      
   Scheme to provide fast turn-on after full discharge            01/01/70 00:00      
      Regulator with output enable            01/01/70 00:00      
         You never exactly know what you get...            01/01/70 00:00      
            Bypass caps            01/01/70 00:00      
               Please don't stress this scheme too much...            01/01/70 00:00      

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