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MAX11216 Production
The MAX11216 is a 24-bit delta-sigma ADC that achieves excellent 140dB SNR while dissipating low 10mW. Sample rates up to 64ksps allow both precision DC...
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MAX11216 on Analog.com

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PGA gain

		
	
				

			

									
					    psupine
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Dec 22, 2025 
				
			
			
		
    
		
		                    	    
    
        	    
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                The user encountered issues with the PGA on the MAX11216, where PGA settings 2-7 produced incorrect sample values. The problem was due to a DC offset introduced by a test card modification, which was not visible on the oscilloscope due to AC coupling. After fixing the DC offset, the higher PGA gains worked as expected.
                        	    
    
                
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    Category: Hardware
    
    		        		            		    
    Product Number:  MAX11216  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Has anyone else tried using this part?
    

    I can use PGA = 0 (x1) or PGA = 1 (x2) with sensible results. PGA = 0 gives sample values that are roughly the same as the direct buffered values, and PGA = 1 gives sample values that are twice that. Good so far. PGA = 2 gives sample values somewhat less than PGA = 0 and PGA = 3,4,5,6,7 are the same as PGA = 2.
    

    I'm using the same code for all of these cases. The PGAEN bit is set. It makes no difference if I use LPMODE or not. BUFEN is clear when I'm using the PGA and I'm leaving the undefined DGAIN bits ate their default values of zero. I also read back from the control register I've written and the read back matches.
    

    Has anyone managed to to use the PGA on this part?
    

    (I expect what will happen is that I'll be advised to contact Tech Support, who will not answer and then silently drop the support request. Maybe this time will be different?)
    
			
    
			
									
		                             
                        

    
    
                                            
                 Single Channel A/D Converters
                
                                                    
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                 MAX11216
                
                                                    
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Dec 23, 2025 4:08 AM
            
            
						
			            		
      
		
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      Hi  ,
      

      Apologies for the inconvenience. Unfortunately. we don't have an expert on this forum for the MAX11216 part, and the best advice is to contact Tech Support. As a side note, upon reading the datasheet, you might also consider monitoring the CAPP and CAPN pins having the 10nF capacitors. Hope you understand.
      

      Thanks.
      

      Regards,
      Francis
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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                on Dec 23, 2025 4:47 AM
            
            
												
						in reply to FMarasigan
					
										
			            		
        
		
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        Hi Francis,
        

        Looking at the CAPP and CAPN pins is a good idea. I suspect that they will be driven all over the place by the modulator, but I might still be able to see a shift in magnitude.
        

        For the benefit of the forum, I'll report what I find.
        

        -- Psupine
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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                on Dec 23, 2025 3:49 PM
            
            
												
						in reply to FMarasigan
					
										
			            		
          
		
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          I'm delighted to be able to report that it was entirely my fault.
          

          I had modified a test card to reduce the noise level, but that change had introduced a dc offset between the differential inputs. The digital HPF removed this offset and so at low gain I didn't see it in the sampled data. I also didn't see in using the oscilloscope because I had the probe ac coupled so that I could crank the vertical scale up to the maximum to be able to see the tiny sinusoid test signal.
          

          At higher gains the dc offset drove the input signals outside the valid useable input range (Fig 2 of datasheet). I remember reading somewhere that the two inputs clip differently and I guess that was what why I was seeing a remnant of the signal in the sample stream even though the inputs were clipping.
          

          I fixed the dc offset problem and now the higher gains work as advertised.
          

          I prefer when it is my fault because it means I can fix it!
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
				
						
						
				
				
		
		
          
			
		
          
	
          

          

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