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The LT3751 is a high input voltage capable flyback controller designed to rapidly charge a large capacitor to a user-adjustable high target voltage set...
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LT3751 on Analog.com

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Which Voltage is applied to the gate of external NMOS from LT3751 IC?

		
	
				

			

									
					    contr2889
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 13, 2022 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  LT3751 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi everyone,
    

        I was trying to use the LT3751 IC but even when I replicate the schematic directly from the datasheet it didn't work. Then I read more in detail the datasheet and I got confused in the Voltage applied to the gate of the external NMOS because the gate driver operation says the gate driver has an internal, selectable 10.5V or 5.6V clamp but also the pin HVgate says the internal gate driver will drive the voltage to within VCC – 2V during each switch cycle and LVgate pin says depending of the connection the internal gate driver will drive the voltage to the VCC rail. 
    

    Then, Which voltage is applied to the gate of external NMOS? 
    

    Thanks for your help.
    
			
    
			
									
		                             
                        

    
    
                                            
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                 Datasheet/Specs
                
                                                    
                 LT3751
                
                                                    
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 20, 2022 10:18 PM
            
            
						
			            		
      
		
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      Hi contr2889,
      

      I checked with the product expert and here is the response:
      

      

      The LT3751 has 2 internal pull-up drivers. The main driver is an emitter follower and can only pull-up the HVGATE pin to within 2V of VCC or the clamp voltage, whichever is the lower voltage.    
      

      The LVGATE pin has a low voltage PMOS pull-up that can operate up to 8V VCC. Strapping the LVGATE to HVGATE allows the GATE to be driven all the way to VCC. This helps drive the FET harder in low voltage applications.  
      

      The CLAMP pin selects an internal clamp circuit to limit the gate voltage to either 10.5V or 5.6V and can help lower switching losses when operating at higher VCC voltages. Operating LVGATE above 5.6V requires the CLAMP to be set to 10.5V.  
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

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