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???
05/19/07 13:53
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 		 #139513 - I see two possibilities
Responding to: ???'s previous message
To achieve a good resolution and accuracy we thought it would be better to separate the digital ground of microcontroller with that of the DAC since the fast switching characteristics of the digital section can induce noise in the DAC. Now for this purpose we plan to isolate the control signals of the DAC namely , cs/ld, sck, sdi ,sro,ldac from the digital gnd of microcontroller and hence we are using 6n137 optoisolator.

To achieve a good resolution there will be no change in 'resolution' whatever you do. do not confuse resolution with precision.

There is NO NEED for optoisolation if you do it right

read http://www.8052.com/faqs.phtml?FAQ=128848.

I see two possibilities a) you are shooting for the moon i.e. more precision that you will ever achieve or b) you are trying to get a decent result without following 'the rules'. In either case you will lose. Please state which - or possibly - another.

Do state a) that you WILL (not) use a 4 or 6 layer board with separate analog and digital ground and b0 which precision (NOT resolution) you aim for. with that info it will be possible to help you.

Erik

List of 37 messages in thread
TopicAuthorDate
need for isolating signals            01/01/70 00:00      
   avoiding the inverter            01/01/70 00:00      
      sinking the current            01/01/70 00:00      
         Sinking and sourcing            01/01/70 00:00      
            the bulb blinked !!!            01/01/70 00:00      
               Don't guess!            01/01/70 00:00      
                  trnasfer char.            01/01/70 00:00      
                     Transfer characteristic            01/01/70 00:00      
   More so            01/01/70 00:00      
   I see two possibilities            01/01/70 00:00      
      accuracy            01/01/70 00:00      
         0.01% approx 14 bits            01/01/70 00:00      
         Hardly...            01/01/70 00:00      
   No need...            01/01/70 00:00      
      need to place inverter            01/01/70 00:00      
      my design            01/01/70 00:00      
         FRC?            01/01/70 00:00      
            FRC?            01/01/70 00:00      
               or may be this......            01/01/70 00:00      
                  Not really            01/01/70 00:00      
                  Flat Ribbon Cable connector            01/01/70 00:00      
               FRC Connector!            01/01/70 00:00      
            You don't know the Flat Ribbon Cable?            01/01/70 00:00      
               Not by that name!            01/01/70 00:00      
         FAQ: How to post pictures?            01/01/70 00:00      
         you are grasping for straws            01/01/70 00:00      
         sure, but to what use            01/01/70 00:00      
         grounds etc            01/01/70 00:00      
            not entirely correct            01/01/70 00:00      
               single plane            01/01/70 00:00      
                  A very well qualified layout person can do 'magic'            01/01/70 00:00      
                     but he can hardly outsmart the laws of physics            01/01/70 00:00      
                  Nevertheless, there IS a difference            01/01/70 00:00      
                     the difference            01/01/70 00:00      
                        Yes, yes, yes, but...            01/01/70 00:00      
   Aside: Other Isolation Technologies            01/01/70 00:00      
   no response            01/01/70 00:00      

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