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AD5660 supply & Ref_out

		
	
				

			

									
					    RaffC
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 7, 2022 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  AD5660CRMZ-2 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hallo everyone.
    

    My problem is the following: i'm using (on an existing board), an AD5660CRMZ-2 (2.5V ref out) with the supply at 3.3V (instead of 5V typical mentioned in the d.s.).
    

    Basically, i'm supposing to have it as it is and I want to understand the risks
    

    It's not clear to me IF :
    

    - it's a possible choice or there are risks of malfunctions and in case what kind of malfunctions (for example oscillations?)
    

    - Remark:the DAC is used to generate output voltages below 1V; does this fact reduce the criticality?
    

    - the 2.5V internal reference works properly (what is the minimum supply voltage required?)
    

    - does the Ref pin output capacitor size change something?
    

    Best Regards
    

    RC
    
			
    
			
									
		                             
                        

    
    
                                            
                 Single-Channel Voltage Output D/A Converters
                
                                                    
                 Datasheet/Specs
                
                                                    
                 AD5660CRMZ-2
                
                                                    
                 Voltage Output D/A Converters
                
                                                    
                 ad5660
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Sep 7, 2022 5:37 AM
            
            
						
			            		
      
		
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      Hi RC, 
      

      The risk when operating outside of the specified voltage (but within max rating) is that we couldn't guarantee the parts' performance. The data provided on Table 2 of the ds for variants *-2 and *-3 are tested with VDD = 4.5 - 5.5V. For example, the 2.5V reference's initial accuracy may not be within +/-5mV, this would affect the accuracy in the best case. The worst case is the part might even exhibit unusual behavior. I can't give clear examples of what would happen.
      

      My suggestion would be, to replace the DAC with the *-1 models which are pin compatible. or if possible, use other DACs that are characterized at 3.3V operation. I did a quick check for us but we don't have other direct pin compatible options for the AD5660.
      

      Regarding capacitor size, I assume you're referring to the physical size of the capacitor. In my experience, size doesn't really affect the reference performance. What's important is the effective capacitance value with DC voltage.
      

      Regards,
      

      ~ian
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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