Products Mentioned

AD7626 Production
The AD7626 is a 16-bit, 10 MSPS, charge redistribution successive approximation register (SAR) based architecture analog-to-digital converter (ADC). SAR...
Datasheet
AD7626 on Analog.com

ADA4899-1 Production
The ADA4899-1 is an ultralow noise (1 nV/√Hz) and distortion (<−117 dBc @1 MHz) unity-gain stable voltage feedback op amp, the combination of which...
Datasheet
ADA4899-1 on Analog.com

ADA4932-1 Recommended for New Designs
The ADA4932-1 / ADA4932-2 are the next generation AD8132 with higher performance and lower noise and power consumption. They are an ideal choice for driving...
Datasheet
ADA4932-1 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 2 replies
  • Subscribers 20 subscribers
  • Views 746 views
  • Users 0 members are here
Options 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
Queries on CN-0105: drive ckt for AD7626

		
	
				

			

									
					    atrajesh
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 25, 2024 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hi,
    
 
    I am new to using ADCs. I have 3 different kinds of signals which I need to sample and process. The frequencies are 1KHz, 10KHz & 100 Khz, and all are single-ended. I want around 100 samples per cycle, with about 12-14 bit accuracy. So I have chosen AD7626 (16-bit) with 10MHz sampling rate. When I sample the highest frequency signal (100KHz), I will run the ADC with 10MHz clock, and when I receive the other signals, I will bring down the sampling rate by a factor of 10 & 100 accordingly. How is the idea?
    
 
    In addition, I want to use the ADA4932 for driving the AD7626 rather than ADA4899. In CN-0105, it is mentioned that ADA4899 is the recommended driver at lower frequencies. I want to know what are the issues with ADA4932 at lower frequencies (1KHz - 100KHz). I like ADA4932 since it is a single chip solution. If it is input referred noise, I am okay with it, since some amount of noise is not much of an issue with me. 
    
 
    I have a third query. It will be difficult for me to generate +7.25V required for the +Vs power of ADA4932. So I am planning to use +5V instead. I want to know what is the effect of this. Will it just bring down the dynamic range of the output. I can take care of that by reducing the input swing. 
    
 
    thanks and regards,
    
 
    rajesh
    
			
    
			
									
		                                 
    Thread Notes  
    
                
    
        
                                        
                        

    
    
                                            
                 Operational Amplifiers (Op Amps)
                
                                                    
                 Single Channel A/D Converters
                
                                                    
                 amplifiers
                
                                                    
                 ada4899-1
                
                                                    
                 Differential Amplifiers and ADC Drivers
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                
                    Show More
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jan 9, 2013 1:27 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi rajesh,
      
 
      ADA4932 is recommended for higher frequencies because of its excellent distortion performance at these higher frequencies. You are correct that at lower frequencies, ADA4899 has better noise performance compared to ADA4932. However, it doesn't mean that ADA4932 can't be used for lower frequencies. You can use the ADI Diff-Amp Calculator to simulate the ADA4932 and see if its overall noise performance is acceptable in your design. You are also correct that by reducing the +Vs from +7.25 to +5V reduces the dynamic range of the output. You can verify that using the ADI Diff-Amp Calculator.
      
 
      Regarding your concern on the ADC, you may contact the Precision ADC Community. They will be more than willing to help you on your ADC needs.
      
 
      Thank you for considering ADI products in your design.
      
 
      Hope this helps.
      
 
      Neil
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jan 10, 2013 2:55 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi Rajesh,
      
 
      I co-wrote the CN-0105, I'd like to make a few additional comments here. As for the ADA4899 vs.ADA4932, as Neil mentioned the ADA4932 provides better high frequency performance. The ADA4899 does offer better distortion performance at lower freq (~<1MHz). As for supply voltages, yes you can use lower supplies for the ADA4932 as long as you stay within the operating range (input and output) of the device and if you have smaller signals that should not be an issue. 
      
 
      As for the sampling questions, I spoke with our PulSar apps engineer and she had the following to say.
      
 
      "On the sampling question, I don’t see an issue with his proposal. He could continue to sample at 10MHz for all of the input frequencies if he wishes. Maybe there is a particular reason he wants to slow the sampling for the lower input tones? 
      
 
      One thing I would say, if he only needs 12/14 bits and the max bandwidth of his signal is 100kHz, the AD7626 is probably overkill – the AD7980 would probably do the job also or even the AD7944 at 14 bits. Possibly the LVDS interface on the AD7626 is a requirement?"
      
 
      I hope this helps answer your questions, let me know if there is anything else I can do to help.
      
 
      Regards
      
 
      JohnA
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

      •