• State Suggested Answer
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 40 subscribers
  • Views 431 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		












	
	
			
	
			
		
	
	
		

		
Ltc3260 noise reduction



		

			

									
					    gZoppi550
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 6, 2020 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hello, 
    

    I am involved in  the design  of the amplifying and clipping section of a guitar audio processor embedding your Ad528x digipots. For that a dual supply +-5V is necessary and we are currently exploiting (in the first working prototype)  the LTC3260
    

    The involved circuit has a very high gain, so, having the cleanest supply is mandatory.
    

    What appears upping the gain is that  the switching noise is somehow downconverted thus generating an audible tone which is unwelcome especially when the instrument is not playing.
    

    The switching noise is present at both positive and negative rails.
    

    Do you have any suggestion ? Maybe exploiting an lc filter with snubber?
    

    Is there any additional solution with different PN that might fit our needs?
    

     
    

    

     
    

    

    Thanks in advance for your support.
    

    BR
    

    GZ
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Sep 8, 2020 1:43 PM
            
            
					
        
	
        

		
		
        
					
        Hello, it seems that the input voltage is too low for the configuration with the external diode divider. I will try upping a bit the input voltage andbthen I will change configuration removing the divider.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	

      • 
	
        



	
		
	
	



        
	
        
		
        
							
					
        
		
        
			
													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Sep 8, 2020 5:41 PM
            
            
												
						in reply to gZoppi550
					
									
          
	
          

		
		
          
					
          Update: after restoring the configuration  without diode divider nothing changes: at high gain the switching noise is clearly present. 
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

          • 

	

        • 
	
          



	
			
		
	



          
	
          
		
          
							
					
          
		
          
			
													0
							
			
				
									
							        
			
			
			
          •  Analog Employees  
          
            
			                            
                        
                on Sep 23, 2020 2:48 PM
            
            
												
						in reply to gZoppi550
					
									
          
	
          

		
		
          
					
          Hello, A couple things that might need to be done to reduce the noise. First look at the layout. Make sure there is an adequate GND plane, the input, flying, and output caps are close to the IC with a good path to GND. Make sure there are no sensitive nodes or components near any of the switching components and all sensitive returns are not in the path of the switching return paths or input cap return to the IC paddle. 
          

          If the 12V input is shared with other sensitive components a conductive EMC π filter using ceramic caps and a ferrite bead with help reduce any noise feeding back from the input. 
          

          Using ceramic caps with low ESL and low ESR will help reduce the spikes. Smaller packages have lower ESL and using as small of a package that will allow the proper capacitance can help. 
          

          If needed another π filter on the outputs might also be needed.
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
						
						
				
				
		
		
          
			
		
          
	
          

          

          •