Products Mentioned

LTspice Production
LTspice® is a powerful, fast, and free SPICE simulator software, schematic capture and waveform viewer with enhancements and models for improving the simulation...
LTspice on Analog.com

LT3580 Production
The LT3580 is a PWM DC/DC converter containing an internal 2A, 42V switch. The LT3580 can be configured as either a boost, SEPIC or inverting converter...
Datasheet
LT3580 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 2 replies
  • Subscribers 39 subscribers
  • Views 792 views
  • Users 0 members are here
Related Content

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
LT3580IDD#PBF Minimum output voltage?

		
	
				

			

									
					    Drenkoz
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Aug 21, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  LT3580  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi,
    

    The LT3580IDD#PBF part seems to be missing its minimum output voltage.
    

    I'm trying to boost a 3.3V to a 3.6V. Would this work with the part?
    

    Some other sites like Digikey mention it has a minimum output of 5.0V, but I can get 3.3V on my LTSpice model?
    

    Thanks for your help.
    
			
    
			
									
		                             
                        

    
    
                                            
                 Datasheet/Specs
                
                                                    
                 SEPIC Regulators
                
                                                    
                 lt3580
                
                                                    
                 switching regulators
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



Parents
	



Reply



Children
	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Aug 21, 2025 2:26 PM
            
            
												
						in reply to MStokowski
					
										
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        Sounds like I should be fine then. As my duty cycle will only be 18% according to my calculations.
        

        Duty Cycle
        

        DC = VOUT - VIN + VD / VOUT + VD - VCESAT
        

        VD = 0.380V
        

        (3.6-3.3+0.38)/(3.6+0.38-0.3)=0.1848 = 18% Duty Cycle
        

        And the equation on page 8 seems to imply I can go up to 93%. It almost so wide a margin I kinda question if its right?
        

        Fsw = 1.2Mhz
        

        Tp = 0.83us
        

        Min off time = 60ns
        

        DCMax = (Tp-min off time)/Tp x 100%
        

        DCMax = (0.83-0.060)/0.83 x 100%=0.9277 = 93% DCMAX
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

        •