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???
03/31/07 03:39
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 		 #136250 - Power Up / Down
Responding to: ???'s previous message
It may be a good idea to evaluate how clean the normal VCC to the RTC rises and falls. In paricular at power down time if the +5V is non-monotonic and/or has a very fast fall time there could be problems resulting from this. A fast step in the power could cause an operating point transient in the oscillator circuit causimg it to stop running.

To test if this is the case you can try putting a sizeable capacitor on the Vcc supply right at the RTC (try 22 uF for grins) and then isolate the RTC Vcc from the normal DC power rail through a 100 to 270 ohm resistor.

If this improves the situation then you have a clue that the problem is power delivery related.

- mkaras


List of 34 messages in thread
TopicAuthorDate
DS1307 back up problem            01/01/70 00:00      
   backup problem            01/01/70 00:00      
   To Pradheep            01/01/70 00:00      
      back up problem            01/01/70 00:00      
         Are you sure?            01/01/70 00:00      
   Are you sure...            01/01/70 00:00      
   Something else            01/01/70 00:00      
      To Jon            01/01/70 00:00      
         Have a look at this            01/01/70 00:00      
            seems?            01/01/70 00:00      
               Help me            01/01/70 00:00      
                  Extract fron the datasheet            01/01/70 00:00      
         Open Drain Output            01/01/70 00:00      
   Crystal            01/01/70 00:00      
      To a different kind?            01/01/70 00:00      
         crystal            01/01/70 00:00      
            In the link            01/01/70 00:00      
               pull up            01/01/70 00:00      
                  Yes, but...            01/01/70 00:00      
      Yes, looks like a poor crystal...            01/01/70 00:00      
         Power Up / Down            01/01/70 00:00      
            Problem Solved            01/01/70 00:00      
               Not so fast...            01/01/70 00:00      
                  'testing' revisited            01/01/70 00:00      
                     The same thought I !            01/01/70 00:00      
               request            01/01/70 00:00      
                  Learn to debug            01/01/70 00:00      
                     Very useful post, Andy!            01/01/70 00:00      
                        Other part of rule #1            01/01/70 00:00      
                        a great goal, do you achieve it every time ?            01/01/70 00:00      
                           Revision Letters            01/01/70 00:00      
                           Here's how            01/01/70 00:00      
                              and pay $25,000,000 to the descendants            01/01/70 00:00      
                        Hopefully, it leads that way            01/01/70 00:00      

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