• State Verified Answer
  • Replies 5 replies
  • Subscribers 33 subscribers
  • Views 2186 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		












	
	
			
	
			
		
	
	
		

		
REF input of AD5449



		

			

									
					    Jacky
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 7, 2015 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi:
    
 
    I want to use AD5449 in my design. The REF pin must be provided the external reference input, while the input resistance of REF pin is  11K ohm. The datasheet suggest to use ADR*** to generate the reference input, like ADR06(output current is 10mA) or ADR433 (output current is 30mA).
    
 
     I am doing a multi-channel DAC design. I want to know how to determine that how many channels of AD5449 can share a reference input voltage?
    
 
    When the DAC output level change, will it generate a spike at the reference?
    
 
    Thanks
    
 
    Regards
    
 
    Jacky
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Series Voltage References
                
                                                    
                 Precision D/A Converters
                
                                                    
                 ad5449
                
                                                    
                 ADR433
                
                                                    
                 Multiplying Current Output D/A Converters
                
                                        
                                            
                
                
                                
                    Show More
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 7, 2015 8:46 PM
            
            
					
      
	
      

		
		
      
					
      Hi Jacky,
      
 
      I don't have this data available but you may do a quick computation on this one.
      
 
      You may first measure the current consumption of the reference pin of the part when the DAC is in full scale. Dividing the reference's current supply with the current consumption will give you the rough estimate number of DACs that can be connected to the reference.
      
 
      Regards,
      
 
      Mark
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 9, 2015 1:49 PM
            
            
					
      
	
      

		
		
      
					
      Hi Jacky,
      
 
      When a digital line is in open-drain configuration, it will still function as an output pin although it will require pull-up resistors for it to be used properly. When disabling the SDO pin, there is no data that will come out of the pin. I'm not sure right now if it will be high-Z of if it is grounded. Most likely it is in the high-Z mode. I will get back to you on this.
      
 
      Regards,
      
 
      Mark
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Jul 9, 2015 10:03 PM
            
            
					
        
	
        

		
		
        
					
        Mark:
        
 
        Thanks for your reply. I appreciated your work.
        
 
        In the page 20 of the datasheet, it's said that SDO pin can be configured as different output mode, like Full SDO driver, Weak SDO driver, open drain or Disable SDO output.
        
 
        I just confused about Open drain and Disable SDO output. Which is in High-Z output?
        
 
        Thanks
        
 
        Jacky
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	

      • 
	
        



	
		
	
	



        
	
        
		
        
							
					
        
		
        
			
													0
							
			
				
									
							        
			
			
			
        •  Analog Employees  
        
            
						
                            
            
            				
            
                on Jul 20, 2015 6:10 PM
            
            
					
        
	
        

		
		
        
					
        Hi Jacky,
        
 
        The SDO pin is in high-impedance when the SDO is disabled. Take note that if you are using the part in daisy-chain operation, the connection will be open and there will be no data coming out of the part.
        
 
        Regards,
        
 
        Mark
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	

      • 
	
        



	
			
		
	



        
	
        
		
        
							
					
        
		
        
			
													0
							
			
				
									
							        
			
			
			
          
            
						
                            
            
            				
            
                on Aug 2, 2018 11:06 AM
            
            
					
          
	
          

		
		
          
					
          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
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
				
						
						
				
				
		
		
          
			
		
          
	
          

          

          •