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???
07/01/09 18:30
Modified:
  07/01/09 18:44
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 		 #166630 - Not necessarily...
Responding to: ???'s previous message
Raj said:
- Use an external capacitor tied between /RST and GND to delay /RST rising until VDD is stable.


Hard to believe that they recommend something that is such senseless! Assume a very slowly rising Vcc that is starting from 0V on. How shall the cap be able to maintain 0V, when the datasheet tells that a current of 25µA is flowing out of the /RST pin??

Don't use the MAX1232 here. It's not well suited for micros needing an active low going reset.

I would give the DS1705 a try, with a pull-down of 4k7 at /RST output.

Kai



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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