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ADA4932-Dynamic Performance at low frequencies



		

			

									
						Sai Kiran S
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Feb 7, 2021 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hello,


I want to use ADA4932-2 as ADC driver for the ADC AD7768, but my frequency of interest is DC to 100 KHz and input power level in the range of -90 dBm to -10 dBm.


In the datasheet the dynamic performance for frequency less than 100 KHz is not mentioned.


When comparing the dynamic performance of  ADA4932-2 with the ADC (AD7768) suggested device ADA4896-2, at lower frequencies less than 100 KHz which is having the dynamic performance?


ADA4896-2 meets my requirement but I want to go with ADA4932-2 because I have already used in my previous applications and hence reducing the design and implementation time.


Is ADA4932-2 is on par with ADA4896-2 in terms of dynamic performance at frequencies less than 100 KHz ?




Regards


Sai Kiran S.

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	















	

	

					



			








	
	
	
	



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                on Mar 11, 2021 11:18 PM
            
            
					
    
	
    

		
		
    
					
    Hi sai-kiran-s,
    

    I'm not really an expert on the 24-bit AD7768 ADC that you're targeting, but I'll give you my opinion anyway (hopefully other experts could chime-in if they know better?).
    

    For such a large dynamic range ADC (24-bits), you'd want to pick the driver with the lowest THD (distortion or sometimes called HD) and the one with the lowest noise and the lowest 1/f noise corner frequency. If you have any choice for selecting the ADC Full Scale voltage and Vref, I'd think you'd want to choose the smallest value possible to minimize the swing on the driver in order to minimize the distortion terms.
    

    I think the distortion performance of ADA4932-2 and ADA4896-2 at or below 100kHz are going to be very similar to each other. But, the noise of ADA4896-2 (Figure 22) is better (1nV/RtHz) vs. that of ADA4932-2 (Figure 38) at around 3.5nV/RTHz. Also, the 1/f noise corner is lower for ADA4896-2 than that of ADA492-2. So, unless I'm overlooking something, without a rigorous analysis and side-by-side comparison, I'd say ADA4896-2 is a better choice in your case driving a 24-bit ADC because of its lower voltage noise.
    

    I hope other people on the forum double-check my reasoning and correct me if I'm wrong?
    

    

    Regards,
    

    Hooman
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                                                                   
      
                            
    • 
                                 Super User 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Mar 11, 2021 11:18 PM
            
            
					
    
	
    

		
		
    
					
    Hi sai-kiran-s,
    

    I'm not really an expert on the 24-bit AD7768 ADC that you're targeting, but I'll give you my opinion anyway (hopefully other experts could chime-in if they know better?).
    

    For such a large dynamic range ADC (24-bits), you'd want to pick the driver with the lowest THD (distortion or sometimes called HD) and the one with the lowest noise and the lowest 1/f noise corner frequency. If you have any choice for selecting the ADC Full Scale voltage and Vref, I'd think you'd want to choose the smallest value possible to minimize the swing on the driver in order to minimize the distortion terms.
    

    I think the distortion performance of ADA4932-2 and ADA4896-2 at or below 100kHz are going to be very similar to each other. But, the noise of ADA4896-2 (Figure 22) is better (1nV/RtHz) vs. that of ADA4932-2 (Figure 38) at around 3.5nV/RTHz. Also, the 1/f noise corner is lower for ADA4896-2 than that of ADA492-2. So, unless I'm overlooking something, without a rigorous analysis and side-by-side comparison, I'd say ADA4896-2 is a better choice in your case driving a 24-bit ADC because of its lower voltage noise.
    

    I hope other people on the forum double-check my reasoning and correct me if I'm wrong?
    

    

    Regards,
    

    Hooman
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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