Products Mentioned

LTC3114-1 Recommended for New Designs
The LTC3114-1 is a versatile, wide operating voltage range synchronous monolithic buck-boost DC/DC converter with programmable average output current....
Datasheet
LTC3114-1 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 2 replies
  • Subscribers 39 subscribers
  • Views 918 views
  • Users 0 members are here 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
LTC3114-1 Secondary Foldback Current Limit

		
	
				

			

									
					    Yuki.
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on May 11, 2021 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hi, Guys.
    

    Thank you for your support.
    

    

    I have some question about the secondary foldback current limit (Datasheet page12).
    

    Q1: Is it the characteristic of the foldback function that a graph of "Avarage Output Current vs Vout" on datasheets page6 ?
    

    Q2: If Q1 is Yes, is the characteristic the same even if the value of Rprog is changed?
    

    Q3: Is the characteristics also the same at a startup cycle?
    

    

    I tried to check using LTspice, but I can't understand it.
    

    

     
    

    

    LT3114-1_CCCV-2.ascLT3114-1_CCCV-2.asc
    

    

    Best regards,
    

    Yuki.
    
			
    
			
									
		                             
                        

    
    
                                            
                 LTC3114-1
                
                                                    
                 Buck-Boost Regulators
                
                                                    
                 Internal Power Switch Buck-Boost Regulators
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on May 13, 2021 10:39 AM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi,
      

      The waveform on page 6 of the datasheet is an example of programable output current limit across Vout range for a given Rprog .The output current limit changes and so does the characteristic curve will vary with Rprog. However for Vout below 2V the current limit will not be proportional to Rprog.  In the simulation, I think the load is set higher than the current limit so the Vout starts to drop after startup. 
      

      Thanks
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on May 20, 2021 3:46 AM
            
            
												
						in reply to ADIApproved
					
										
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        Hi, Anisha
        

        

        Thank you for your reply.
        

        May I ask a question again.
        

        Dose a function of secondary foldback current limit also work at startup ?
        

        I tried to check it in LTspice, but the LT3114-1 model did not implement the function.
        

        

         
        

        PDF
        

        

        Best regards,
        

        Yuki.
        

        

        

        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

        •