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???
08/14/07 17:51
Modified:
  08/14/07 17:54
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 		 #143268 - Pull-downs at inputs of battery powered CMOS-RAM
Responding to: ???'s previous message
I would suggest to add pull-downs at inputs of battery powered CMOS-RAM. Why? Extremely low supply current consumption of these CMOS-RAMS is only valid, if input levels are either exactly 0V of Vcc, otherwise the current consumption can heavily increase!

If you power down your digital circuit, then the unavoidable leakage currents (out or into the CMOS-RAM) can cause relevant voltage drops across the substrate pn-junction of micro or eventual protections diodes at its inputs, causing the input voltage of CMOS-RAM floating to unsanely high levels, causing an excessive supply current.

100kOhm pull-downs is enough normally.

Kai

List of 39 messages in thread
TopicAuthorDate
the mysterious data loss in BBRAM            01/01/70 00:00      
   I just used the Dallas parts!            01/01/70 00:00      
      I've heard only praises to the Dallas chips, too..            01/01/70 00:00      
         I agree re Dallas            01/01/70 00:00      
            another method            01/01/70 00:00      
               I don't understand            01/01/70 00:00      
                  nah            01/01/70 00:00      
                     ... I just would expect that..            01/01/70 00:00      
                        You are absolutely right, of course!            01/01/70 00:00      
                     You should dig deep when posting here!            01/01/70 00:00      
                        nope, but ...            01/01/70 00:00      
                           But, what if your post is just wrong??            01/01/70 00:00      
                              well, it was not            01/01/70 00:00      
                                 What has this to do with Jan's application??            01/01/70 00:00      
                                    everything            01/01/70 00:00      
                                       When you use a second supervisor chip, ...            01/01/70 00:00      
                                          it does - IF            01/01/70 00:00      
                                             For occasional writes you have the FLASH            01/01/70 00:00      
                                                this depends on application, too            01/01/70 00:00      
                                                   But why??            01/01/70 00:00      
                                                      early power fail interrupt .....            01/01/70 00:00      
                                                         this is the purpose of reset            01/01/70 00:00      
                                                            Sadly, there's no guarantee it does that!            01/01/70 00:00      
                                                               ensure the same voltage on mcu and RAM/supervis            01/01/70 00:00      
                                                               yeah, sure            01/01/70 00:00      
                                                            OK, once more            01/01/70 00:00      
                                                               given a proper ground and power plane ...            01/01/70 00:00      
                                                         I have to agree ...            01/01/70 00:00      
                                             this depends on application            01/01/70 00:00      
                                             There's room for doubt ...            01/01/70 00:00      
                                       thanks            01/01/70 00:00      
                                 sounds reasonably            01/01/70 00:00      
   Pull-downs at inputs of battery powered CMOS-RAM            01/01/70 00:00      
      Observation technique affects the outcome            01/01/70 00:00      
         Some comments and two questions            01/01/70 00:00      
   Designing a pre-test environment ...            01/01/70 00:00      
      Eager to hear the results!            01/01/70 00:00      
         You'll have to be patient ...            01/01/70 00:00      
   Has anyone tried THIS?            01/01/70 00:00      

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