Products Mentioned

LT8390 Recommended for New Designs
The LT8390 is a synchronous 4-switch buck-boost DC/DC controller that regulates output voltage, input or output current from an input voltage above, below...
Datasheet
LT8390 on Analog.com

LT8390A Recommended for New Designs
The LT8390A is a synchronous 4-switch buck-boost DC/DC controller that regulates output voltage, input or output current from an input voltage above, below...
Datasheet
LT8390A on Analog.com

Thread Details

  • State Verified Answer
  • Replies 4 replies
  • Subscribers 40 subscribers
  • Views 1196 views
  • Users 0 members are here 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
LT8390, LT8390A

		
	
				

			

									
					    kurt555
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 27, 2022 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user is designing a Buck-Boost Voltage Regulator using the LT8390 or LT8390A and asks about the use of diodes between BST1/BST2 and INTVCC in the LT8390A. The final answer explains that the diode prevents current from flowing back into the INTVCC, which could damage the bias supply, and allows the high-side voltage to exceed the bias voltage to drive the top FET. The accompanying answers note that the LT8390A has internal diodes, but external diodes are used to ensure fast switching and minimize losses.
                        	    
    
                
                     AI Generated Content
                
    	    
    
             
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  LT8390 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello!
    

    I am making a Buck-Boost Voltage Regulator using LT8390 or LT8390A.
    

    Comparing the typical applications listed in the datasheet of the LT8390 and LT8390A, in the case of the LT8390A, BST1 and BST2 are connected to INTVCC through a diode.
    

    I'd like to know why I should use a diode and what the problems would be if I didn't.
    

    

    Kind regards
    
			
    
			
									
		                             
                        

    
    
                                            
                 Datasheet/Specs
                
                                                    
                 lt8390
                
                                                    
                 External Power Switch Buck-Boost Controllers
                
                                                    
                 Buck-Boost Regulators
                
                                                    
                 LT8390A
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



Parents
	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							FormerMember
					
      
		
      
		    
		    		    
			
				
									FormerMember
							        
			
			
			
    
            
						
                            
            
            				
            
                on Nov 28, 2022 1:02 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    Hello,
    

    The diode is used to block current coming back into the INTVCC. You should use diodes that are fast, typically schottky diodes are used as they have very good reverse recovery time, this should minimize the losses.
    

    

    Regards,
    

    Jhun
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
				
				
				
		
		
    
			
		
    
	
    

    


	

  • 
	
    



	
		
	
	



    
	
    
		
    
							
					
    
		
    
		    
		    		    
			
				
									
							        
			
			
			
      
            
						
                            
            
            				
            
                on Nov 28, 2022 2:03 AM
            
            
												
						in reply to FormerMember
					
										
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hello,
      

      Thank you for your reply.
      

      Please can you tell me what happens if I don't add a diode?
      

      Regards,
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
				
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
			
		
	



      
	
      
		
      
							FormerMember
					
      
		
      
		    
		    		    
			
				
									FormerMember
							        
			
			
			
            
						
                            
            
            				
            
                on Nov 28, 2022 2:18 AM
            
            
												
						in reply to kurt555
					
										
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      The current that returns to the Bias Supply might damage the bias, destroying your system.
      

      Read about how bootstrap circuit works. The diode also lets the Voltage on the High Side to be greater than the Bias in order to drive the top FET.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

      • 

	



Reply

        


      • 
	
        



	
			
		
	



        
	
        
		
        
							FormerMember
					
        
		
        
		    
		    		    
			
				
									FormerMember
							        
			
			
			
      
            
						
                            
            
            				
            
                on Nov 28, 2022 2:18 AM
            
            
												
						in reply to kurt555
					
										
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      The current that returns to the Bias Supply might damage the bias, destroying your system.
      

      Read about how bootstrap circuit works. The diode also lets the Voltage on the High Side to be greater than the Bias in order to drive the top FET.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      





Children