Products Mentioned

AD632 Not Recommended for New Designs
The AD632 is an internally trimmed monolithic four-quadrant multiplier/divider. The AD632B has a maximum multiplying error of ±0.5% without external trims...
Datasheet
AD632 on Analog.com

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AD632 used as analog divider.  Effect of using +-Vs = +-12V ?

		            
		

			

									
					    ttt
					
							


			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 1, 2017 
				
			
			
		
    
		
     
				
		
    
		    		    
		    
		    	
			
    Hello,
    
 
    This chip seems to fulfil all of my needs, but providing +-15V is turning out to require a lot of redesign on the rest of my system which I would rather not do.  From the datasheet, I can see min +-Vs=+-8V.  I can also see that the output swing at +-Vs=+-15V is only +-11V, so perhaps one might lose some output swing (to +-8V?).
    
 
    If this is the only thing that happens, then I am fine with it, but I want to check to make sure that
    
 
    1.  the "reference" in the block diagram still functions at +-Vs=+-12V.  i.e. that the accuracy will be roughly similar.
    
 
    2.  the thermal accuracy coefficient remains roughly the same.  I do not really care about the absolute accuracy.  I only care about the thermal stability.  I would like the divider to give a consistent result over time, given the same inputs.
    
 
    Thanks!
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 ad632
                
                                                    
                 Analog Functions
                
                                                    
                 Analog Multipliers & Dividers
                
                                
            
    
    
    

		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jun 1, 2017 11:19 AM
            
                                    
					
      
	
      

		
		
      
					
      Hello and thanks for the question.
      
 
      he AD632 precedes my tenure at ADI but I've done a bit of bench work with the AD633 over the years. The architecture of the various multipliers are some what similar, at least in concept so the headroom assumption you make is valid. If you can tolerate the loss in accuracy with a lower supply you should be happy with the performance.
      
 
      I don't know if the part was tested over time, when I worked with AD633s I didn't notice any short-term drift with respect to time but parts can change over longer periods.
      
 
      The +/-15V supply would be the trim and test voltage. The 11V swing w/+/-15V supplies will mean that if you use the part at +/-8V your output would be about +/-4V. My observation is the headroom is essentially constant, as this is due to stacked/regulated current sources; these types of multipliers use the junction equations as their basic mode of operation so the operating headroom doesn't change a lot.
      
 
      Best thing to do (if you have the luxury of time) is make yourself an eval-board with a sample part and see if it meets your needs. Wish I could help more.
      
 
      js
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Jun 1, 2017 11:25 AM
            
                                    
					
        
	
        

		
		
        
					
        Hi js,
        
 
        Thanks for your answers.  Did you mean headroom in this part?  Or did you really see a loss in accuracy.
        
 
        "If you can tolerate the loss in accuracy with a lower supply you should be happy with the performance."
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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