• State Verified Answer
  • Replies 3 replies
  • Subscribers 43 subscribers
  • Views 600 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		












	
	
			
	
			
		
	
	
		

		
AD9235 setup



		

			

									
					    anapoly
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Dec 3, 2014 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Let me confirm how to set up　AD9235 (12bit AD Conveter) with AD8132(Differential Amp.).
    
 
    My question is the relation between SENSE, VREF in AD9235 and VCOM in AD8132.
    
 
    In my understanding, VREF can be connected with external voltage as an input. 
    
 
    So if I set the SENSE as AVDD, I can get 2 x VCOM accordingto the data sheet.
    
 
    If I set the VCOM as +1.5V by volume, I can get 3Vp-p output from AD9235, am I correct?
    
 
    Or I may be able to set SENSE using external resistor(R1:1K, R2:2kohm) to get VREF as 1.5V
    
 
    like Figure40. Then I can get the same 3Vp-p, am I corrct? 
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Dec 6, 2014 3:01 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      
 
      You are correct that you can provide an external VREF when SENSE is tied to AVDD.  The AD9235 is characterized for operation between 1 to 2Vpp differential.  Greater voltages like 3Vpp differential can be accommodated, but distortion performance will degrade.
      
 
      The internal reference generator has not been characterized to output 1.5 V, so I would not depend on that to generate the VREF in that case. 
      
 
      You may gain some headroom with higher analog supply voltage, which in-turn will increase the Vcm that the AD9250 outputs and give the input sampling circuitry a little more margin.  
      
 
      Anthony  
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Dec 16, 2014 3:40 PM
            
            
					
        
	
        

		
		
        
					
        Thank you for your comment. (Sorry to be late)
        
 
        1. I was a little bit surprised to know that I cannot get 1.5V at VREF. So I should forget the R1,R2 setup solution.
        
 
        2. I will use AD8132 to set VCOM as 1.0~1.2V and set SENSE in AD9235 as AVDD as well. Also I would increase analog input as you mention to get 2.5V typ. as AD9235 output.  I definitely need 2.0V min as output. Because I have to connect AD9235 with FPGA(CMOS) via D-FF which requires 2V as VOH.
        
 
        If you have any comments on this, please let me know otherwise I will proceed to PCB design.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	

      • 
	
        



	
			
		
	



        
	
        
		
        
							
					
        
		
        
			
													0
							
			
				
									
							        
			
			
			
        •  Analog Employees  
        
            
			                            
                        
                on Aug 2, 2018 2:51 PM
            
            
					
        
	
        

		
		
        
					
        This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

        Thank you,
        EZ Admin
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
				
						
						
				
				
		
		
        
			
		
        
	
        

        

        •