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ADAS3022 code to voltage conversion



		

			

									
						tech1
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on May 10, 2021 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hi,


I'm working with the ADAS3022 and would like to convert the 16 bit codes it produces into voltages. I am currently using the following formula:


V = (CODE / GAIN) * (2*VREF)/32768


This produces reasonable values, but it appears that the LSB value is double what it should be for a given PGIA gain. E.g. with a gain of 0.8, LSB = 312.5 uV.


Am I misunderstanding the way the ADC is converting values differentially? I attempted to follow the formula given in an earlier answer, but I can't quite grasp it:


((CODE-32768)/(2^15-1) = V * GAIN/VREF


Thanks for your help

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	














	

	

					



			








	
	
	
	



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                on May 11, 2021 4:27 PM
            
            
												
						in reply to tech1
					
									
    
	
    

		
		
    
					
    Tech1,
    

    You are close but the real reason is the output encoding as it is fixed to account for the bipolar range which gives 2x the voltage span but as a consequence the LSB weight is also 2x larger than if you could select unipolar operation.  Later products like the LTC2358 family address this limitation of the ADAS3022 by adding unipolar input ranges in addition to the bipolar input range.   The measurement is still differential but allowable input range is now fixed to positive voltages only.
    

    Sean
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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