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LTC6362 Recommended for New Designs
The LTC6362 is a low power, low noise differential op amp with rail-to-rail input and output swing that has been optimized to drive low power SAR ADCs...
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LTC6362 on Analog.com

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ltspice simulation model LTC6362



		

			

									
					    master89
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 23, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    		            		        
    Category: Software
    
    		        		            		    
    Product Number:  LTC6362 
    
    		        		        		        
    Software Version: LTspice 17.0.34.0
    
    		    		    	
			
    HI,
    

    

    I have been trying to simulate the noise of the LTC6362 and I would like to compare the results with the datasheet of the component.
    

    from the datasheet I can see that the common mode noise is 14.3nV/rtHz.
    

     
    

    

    HOwever, if I measure the noise from one of the output of the FDA in buffer configuration I do not get this value at 100kHz. HEre below my simulation :
    

     
    

    Simulation results show that the common mode noise at 100kHz is 55nV/rtHz, am I right? or am i interpreting the results in a wrong way?
    

    Unfortunately the LTC6362 spice model is built in in LTSPICE and the sub file is encripted, so i cannot check the implementation. 
    

    Any tips?
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

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                on Nov 28, 2022 3:35 AM
            
            
					
        
	
        

		
		
        
					
        Hi,
        

        It seems that you have not connected anything to the Vocm input, which is causing the additional noise. If you look closely at the datasheet, you can see a voltage divider on the block diagram.
        

         
        

        The resultant resistance is 170 kOhm, which causes thermal noise:
        

         
        

        The noise of 55nV/rtHz measured in the simulation corresponds to the sum of the common mode noise (given in the datasheet) and the thermal noise from the voltage divider. You can solve this problem by connecting a 100 nF capacitor. This, together with the resistors, creates a low-pass filter so that the noise is significantly reduced at 100 kHz.
        

         
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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