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AD9635 SNR with 1Vpp input span



		

			

									
						sberla
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Jul 31, 2018 
				
			
			
		


				
		

		    		    
		    
		    	
			
I noticed that if I change the value of register 0x18 from 0x04 to 0x00, the input span of the AD9635 become 1Vpp.

 
Do I have to expect a change in SNR in this configuration?

 
Thanks

 
Regards

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	















	

	

					



			


				
	









	
    
	

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                                 Analog Employees 
                                
                            
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                on Jul 31, 2018 10:28 PM
            
            
					
    
	
    

		
		
    
					
    Hi Sberla,
    
 
    Thank you for your interest in AD9635.
    
 
    AD9635 Register 0x18 Bits[2:0] does a digital scaling so that a smaller input swing results in a full-scale output.
    
 
    The AD9635 datasheet SNR numbers are based on a full-scale input swing of 2Vpp_differential. The definition of SNR is directly tied to the amplitude of the signal; lower signal means lower SNR (assuming noise is unchanged). For this reason, if you set Register 0x18 = 0x00 SNR will be reduced compared to datasheet numbers.
    
 
    Thank you.
    
 
    Doug
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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