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Tailoring the AD7173-8 ADC input range



		

			

									
						jfitzger131
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Aug 11, 2015 
				
			
			
		


				
		

		    		    
		    
		    	
			
I would like to take full advantage of the ADC's input range while using the internal buffers.

 
I have configured the ADC to run from a single +3.3V supply.

 
If the internal buffers are turned on, the absolute analog input range become 0 to 2.2V.

 
If I use a 1.1V external reference, the ADC range will match the absolute analog input range.

 
I don't think I want to use a resistor divider off of the ADR441 to create a 1.1V reference.

 
Should I buffer this signal with an amplifier for the reference?

 
- James

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	















	

	

					



			








	
	
	
	



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                on Aug 14, 2015 5:44 PM
            
            
					
    
	
    

		
		
    
					
    Hi Jonathan,
    
 
    I don't think the ADR512 is a suitable replacement.
    
 
    It has 4x the output noise; 20x the temperature coefficient.
    
 
    I noticed that the ADR441 is used on the evaluation board and that there appears to be a resistor divider between the output of the part and the input of reference inputs.  
    
 
    I'm thinking about inserting an amplifier in a non-inverting configuration with a gain of 0.44 to create the 1.1V reference from the 2.5V reference output of the ADR441.  Is this a suitable approach to the problem and if so what amp would you reccommend?
    
 
    I'm thinking a low input bias current amp like the AD8615 would do the job.
    
 
    What are your thoughts?
    
 
    - James
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                    			
			                            
                        
                on Aug 14, 2015 5:44 PM
            
            
					
    
	
    

		
		
    
					
    Hi Jonathan,
    
 
    I don't think the ADR512 is a suitable replacement.
    
 
    It has 4x the output noise; 20x the temperature coefficient.
    
 
    I noticed that the ADR441 is used on the evaluation board and that there appears to be a resistor divider between the output of the part and the input of reference inputs.  
    
 
    I'm thinking about inserting an amplifier in a non-inverting configuration with a gain of 0.44 to create the 1.1V reference from the 2.5V reference output of the ADR441.  Is this a suitable approach to the problem and if so what amp would you reccommend?
    
 
    I'm thinking a low input bias current amp like the AD8615 would do the job.
    
 
    What are your thoughts?
    
 
    - James
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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