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11/18/11 10:31
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#184795 - Very interesting how this always comes up
Responding to: Andy Neil's previous message
This is a simple communication issue. Really what you're asking is application information.

I had a similar issue when I was working with someone else and they were wondering why I needed a specific part to vary a pulse width. Come to find out, that the answer that they were expecting was not one that I could have thought of on my own. The application engineer needed to get involved just to say that it was meant to specifically effect a sensor and that the sensor worked off of different pulse widths and would be tuned to these pulse widths. Although, I knew this information, it did not occur to me that this was the information that they were after. I thought they wanted to know more about the schematic and how specific blocks of the circuit worked. This came down to a point that the guy asking the question was just wondering if they could simplify the overall scheme by using a finite pulse width.

This scenario is no different. Let's just say that the 12 bits is used to tell the motor it's rotational speed. In this case, that might mean that the rotational speed may not rotate at an acceptable tolerance if the DAC only provided 4 bits. This really is not a problem to be solved, but more like art that needs to be formed because something may functionally be gained (but losing something else) by using a lower bit DAC without even knowing until the final prototype is built.

I do not know the OPs true application information as that was not greatly detailed, but in effect that's what you're asking about. I guess another way to ask would be what functionality is achieved between a 12 bit DAC and an 8 bit DAC? I do not believe that there is ever a "need" to go with one or the other, but whether the desired effects of choosing the part give designer the desired artwork.

List of 20 messages in thread
TopicAuthorDate
Multiple Analog Outputs.      Zeeshan Ashraf      11/17/11 08:14      
   Don't dismiss single DACs      Oliver Sedlacek      11/17/11 08:47      
   Resolution/precision      Per Westermark      11/17/11 09:03      
      RE: #184777 - Resolution/precision      Zeeshan Ashraf      11/17/11 10:49      
         But is 4k steps needed when you have play?        Per Westermark      11/17/11 11:22      
   not for commercial use      Erik Malund      11/17/11 09:57      
      RE: #184778 - not for commercial u      Zeeshan Ashraf      11/17/11 10:44      
         how else would you ...      Erik Malund      11/17/11 11:14      
            RE: #184782 - how else would you ...      Zeeshan Ashraf      11/17/11 11:25      
         Same-same      Per Westermark      11/17/11 11:27      
            RE: #184785 - Same-same      Zeeshan Ashraf      11/17/11 11:32      
               why do you think I said "high input impedance"?      Erik Malund      11/17/11 11:46      
      Similar stuff !      Zeeshan Ashraf      11/17/11 11:59      
   State the actual requirement!      Andy Neil      11/17/11 12:26      
      RE:#184789 - State the actual requirement!      Zeeshan Ashraf      11/17/11 14:16      
         Still no answer to "need"      Per Westermark      11/17/11 14:22      
         No, that is not a requirement!      Andy Neil      11/17/11 15:28      
            Very interesting how this always comes up      Justin Fontes      11/18/11 10:31      
            RE: #184792 - No, that is not a requirement!      Zeeshan Ashraf      11/19/11 16:48      
               Yes, bits matter      Per Westermark      11/19/11 17:03      

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