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Very low noise DAC



		

			

									
						DMW
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 2, 2020 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    


    I need a low noise DAC for a precision low-frequency (<500Hz) application, resolution >= 16 bits, 3.3V, SPI
    

    I am thinking of using the LTC6655BHMS8-2.5 as a reference, but trying to find a DAC that doesn't swamp its 400nVpp low frequency (0.1-10Hz) noise is difficult.
    

    In your product selector guide the LTC2641 is shown as a low noise DAC but its datasheet doesn't provide much information on noise, what is its 0.1-10Hz peak-peak noise?
    

    Is there a lower noise output part that you can suggest?
    

    (The AD5780 has 1.1uVpp typical)
    

    

    Many thanks,
    

    Dominic
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

					
    
			
    


    

	















    
	
    
	
    
					



			








	
	
	
	



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													+1
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Jun 28, 2022 10:51 AM
            
            
												
						in reply to DMW
					
									
        
	
        

		
		
        
					
        Hello DMW,
        

        AD5791 has better Output Noise Spectral Density in comparison with AD5542a  (7.5 < 11.8). 
        Don't forget that portion of indicated noise for AD5791 is contributed by AD8676 opamp.
        

        regarding the DC noise they have same value. but the noise value has been scaled by reference voltage.

        

        as a result, AD5791 is a better choise for output voltage higher than 5v. however, design is going to be more difficult because of the need for at least 5 volts negative rail supply.
        . If you don't need really 20bits resolution and the output voltage swing is below 5v and want to avoid negative voltage, I would say AD5542a is a better choice.
        

        Regards
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
				
						
						
				
				
		
		
        
			
		
        
	
        

        

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