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ADAU1361 Production
The ADAU1361 is a low power, stereo audio codec that supports stereo 48 kHz record and playback at 14 mW from a 1.8 V analog supply. The stereo audio ADCs...
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ADAU1361 on Analog.com

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Maximum output current on CM pin?

		
	
				

			

									
					    Etiounne
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 28, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  ADAU1361  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi everyone
    

    I am actually using the CM pin of ADAU1361 as the negative input on a AOP differential amplifier.
    

    The impedance seen from the CM pin is around 40 kohm. The CM pin is also connected to LIN_P input pin.
    

    As a result, the CM voltage is not stable, around 1 to 1,4 V between different products, instead of 1,65V (AVdd/2).
    

    

    Is the current consumption too much for that pin? Is the impedance of my AOP amplifier too low?
    

    I did not find the answer on the forum...Sorry 
    

    

    Thanks a lot!
    

    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Apr 28, 2025 10:54 AM
            
            
						
			            		
      
		
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      Hello Etiounne,
      

      Thanks for looking around on the forum. The answer is probably somewhere but it can be difficult to find if the question was not only this question. I probably could not find it either! Slight smile
      

      The CM pin will have around a 5k output impedance so yes, a 40k load is a little too much (too low). I would use an Opamp in a voltage follower configuration with the input to the positive pin and use an Opamp with a fet style of input circuitry. Not bypolar differential.
      

      This should show an improvement for you. 
      

      Dave T 
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Apr 28, 2025 10:54 AM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hello Etiounne,
      

      Thanks for looking around on the forum. The answer is probably somewhere but it can be difficult to find if the question was not only this question. I probably could not find it either! Slight smile
      

      The CM pin will have around a 5k output impedance so yes, a 40k load is a little too much (too low). I would use an Opamp in a voltage follower configuration with the input to the positive pin and use an Opamp with a fet style of input circuitry. Not bypolar differential.
      

      This should show an improvement for you. 
      

      Dave T 
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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