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Is there a model or formula that can describe the output value of a DAC?

		
	
				

			

									
					    Miaowazhongzi
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jun 18, 2025 
				
			
			
		

		
		                    	    

        	    
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                The user observed nonlinearity in the output of the MAX538ACSA+ DAC, particularly at low data codes, which is attributed to a zero-code deadband. The datasheet specifies linearity from code 11 upward, and the user can improve accuracy by ignoring lower codes or applying open-loop calibration techniques. The user also noted periodic errors with Tminor = 64 and Tmajor = 256, suggesting a consistent internal pattern that may be modeled for further correction.
                        	    

                
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Category: Hardware

    		        		            		    
Product Number:  max538acsa, max538 

    		        		    		    

		    		    
		    			

			    
Hi, I used a multimeter (with 10 μV accuracy) to record the output of a DAC (PN: MAX538ACSA+), and compared the actual values with the theoretical ones. I found that when the data code is relatively small, the ratio (actual/theoretical) is much lower. Around a data code of 500, the ratio approaches 0.999. Is this normal? Is there a model or formula that can describe this variation so that I can accurately determine the DAC's output value? Thanks.


 



			

			
									
		                             
                        

    

                                            
                 hardware
                
                                                    
                 Voltage Output D/A Converters
                
                                                    
                 max538acsa
                
                                                    
                 Single-Supply Voltage Output D/A Converters
                
                                                    
                 max538
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			








	
	
	
	



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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Jun 19, 2025 11:30 PM
            
            
						
			            		
    
		
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    Hi,
    

    Per a quick look at the MAX538 datasheet and considering standard DAC behavior, I think the output you're seeing is likely expected. This effect is often called a zero-code deadband, where the output stays flat for the first several digital codes. It’s mainly due to two factors in single-supply designs: (1) the amplifier's internal offset, which can attempt to drive the output below ground, and (2) the output stage’s footroom requirement, especially under load. The MAX538 datasheet highlights this by specifying linearity only from code 11 upward. Once the input code is high enough to overcome the deadband, the remaining deviation is mostly gain error, which explains why the actual/theoretical ratio gradually settles around 0.999 
    

      , kindly provide more insight for this product. Thanks
    

    Best Regards,
    

    Den
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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                on Jul 20, 2025 9:21 PM
            
            
												
						in reply to dendalisay
					
										
			            		
    
		
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    Hi Den,
    

    

    Could you please give me some suggestions regarding the question raised on July 10, 2025? The specific content is in the loop above, thanks.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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