Products In This Thread

AD7872 Production
The AD7871 / AD7872 are fast, complete, 14-bit analog-to-digital converters (ADC). They consist of a track-and-hold amplifier, successive approximation...
Datasheet
AD7872 on Analog.com

  • State Verified Answer
  • Replies 2 replies
  • Subscribers 72 subscribers
  • Views 1346 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		












	
	
			
	
			
		
	
	
		

		
INL specification AD7872



		

			

									
					    Dexter
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 5, 2012 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hello,
    
 
    At the moment I am looking at the spec's of the AD7872 ADC.
    
 
    I need to verify and measure some spec for our customer.
    
 
    One of those spec is the INL.
    
 
    Can you tell me how it is measured.
    
 
    - Is the reference line between the endpoints( code 0x0000 - code 0x3FFF) 
    
 
      or between midscale (code 0x1FFF and endpoints(code 0x0000 and code 0x3FFF) to cerrect for for the offest error.
    
 
    - Is the INL the result of the Endpoint or Bestfit line.
    
 
    - Have you got a graph of the INL
    
 
    Thanks in advance for handeling this question
    
 
    Ronald Dekker
    
 
    Engineer at Applicos 
    
									
			        
		
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



Parents
	
      
	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Apr 23, 2012 2:02 PM
            
            
					
      
	
      

		
		
      
					
      Hi Dexter, 
      
 
      Linearity is measured using the end point method. For this device running a signal either as a DC ramp or a Sine Wave through the ADC. Typically the input is slightly overranged, ensuring that all codes in the transfer function are exercised. By running a ramp or sine wave a histogram of codes for the full transfer function is taken, the analog input at each step of the ramp is known and measured along with the ADC output code for that particular analog input.
      
 
      The DNL (no missing codes) specification is firstly derived - this is the maximum change in the output code when a 1LSB change in analog input voltage is applied to the ADC. By stepping the analog input through all points in the transfer function it can be determined if there are no missing codes.
      
 
      From this data the INL can be derived - with INL error being the error between the ideal straight line transfer function and the actual ADC transfer function (given that you have an associated analog input with each ADC code output the maximum INL error can calculated).
      
 
      I was not able to find a plot of the INL error for the AD7872 my apologies on this.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	
    



Reply

      


    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Apr 23, 2012 2:02 PM
            
            
					
      
	
      

		
		
      
					
      Hi Dexter, 
      
 
      Linearity is measured using the end point method. For this device running a signal either as a DC ramp or a Sine Wave through the ADC. Typically the input is slightly overranged, ensuring that all codes in the transfer function are exercised. By running a ramp or sine wave a histogram of codes for the full transfer function is taken, the analog input at each step of the ramp is known and measured along with the ADC output code for that particular analog input.
      
 
      The DNL (no missing codes) specification is firstly derived - this is the maximum change in the output code when a 1LSB change in analog input voltage is applied to the ADC. By stepping the analog input through all points in the transfer function it can be determined if there are no missing codes.
      
 
      From this data the INL can be derived - with INL error being the error between the ideal straight line transfer function and the actual ADC transfer function (given that you have an associated analog input with each ADC code output the maximum INL error can calculated).
      
 
      I was not able to find a plot of the INL error for the AD7872 my apologies on this.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

      • 


    


Children
	
    No Data