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選擇合適的系列電壓基準源的絕對精度電壓輸出

作者： 時間：2012-01-30 來源：網(wǎng)絡(luò) 收藏
GHT: 0px; PADDING-LEFT: 0px; PADDING-BOTTOM: 0px; MARGIN: 0px; PADDING-TOP: 0px">
0°C to 70°C (commercial)
-40°C to 85°C (extended)
15°C to 45°C ( commercial)
Signal BW
10Hz to 10kHz
DC to 1kHz
DC to 10Hz
DC to 10Hz
DAC Calibration
None
Annual (gain and offset)
One-time factory (gain and offset)
None
Max Error Target
15625ppm (16LSB @ 10 bits)
122ppm (2LSB @ 14 bits)
977ppm (4LSB @ 12 bits)
3906ppm (16LSB @ 12 bits)

Each example is analyzed, focusing on the specifications that apply to that particular design. The results of this analysis, along with the results of the previous section, are summarized in an error budget in Table 5.

It is most convenient to do the error-budget accounting in ppm, although this could be done equivalently in other units such as %, mV, or LSBs. It's important to apply the proper scaling and to use the proper normalization factor to get the correct error values. Reference error terms can be equivalently calculated relative to the reference voltage or the DAC output voltage. For example, if we assume a reference error of 2.5mV (noise, drift, etc.) and a reference voltage of 2.5V, we get the following:
Reference Output Error = 106 × 2.5mV / 2.5V = 1000ppm
If we assume that the DAC output amplifier has a gain of 2.0, both the error and the reference voltage are scaled, so we get the same result at the DAC output (5V full-scale range):
DAC Output Error = 106 × (2.5mV × 2) / (2.5V × 2) = 1000ppm
Table 5. Error-Budget Analysis

      Parameter
      Design A
      Design B
      Design C
      Design D
      Main Design Objectives
      Low cost, loose accuracy
      High absolute accuracy and precision
      One-time calibrated, low drift
      Low voltage, battery powered, moderate accuracy
      Example Application
      Consumer audio device
      Lab instrument
      Digital offset and gain adjustment
      Portable instrument
      Reference Initial Error
      4000ppm
      -
      -
      1600ppm
      Reference/DAC Post- Calibration Error
      -
      0ppm
      244ppm
      -
      Reference Tempco Error
      		
				
      
					
					
		  			
		  			
					
				
      
			
                
			
							
      
                
			            
                            
              
            
		
		
      
		
      
		
      
		
      
			
        
				
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