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LT1242 Production
The LT1241 series devices are 8-pin, fixed frequency, current mode, pulse width modulators. They are improved plug compatible versions of the industry...
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LT1242 on Analog.com

LT1246 Production
The LT1246/LT1247 are 8-pin, fixed frequency, current mode, pulse width modulators. These devices are designed to be improved plug compatible versions...
Datasheet
LT1246 on Analog.com

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Boost Converter Simulation With LT1242 or LT246 PWM Controller



		

			

									
					    NIsık445
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 29, 2021 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    1246_Boost.asc
    

    Hi, my name is Nebi. I am a hardware design engineer. I am working on a boost converter. My converter parameter is as follows.
    

    Vin_min=20 VDC, Vin_max=31 VDC, Vout=75 VDC, Pout=2500 W and frequency=150kHz
    

    I made simulations with LT1242 and LT1246 PWM Controllers in LtSpice. But I have some questions.
    

    The simulation circuit and waveform graph are as follows. In the LT1246 simulation, the Mosfet PWM signal is intermittent. Something is resetting. I changed sense resistor but did not solve this problem. What could be causing this situation?
    

          
    

    I set up the same circuit for LT1242. A similar reset situation happened here. If sense resistor value is not correct, how can I calculate this resistor value?
    

         
    

    In addition, I did not find LTpowerCAD model for LT1242 and LT1246. Therefore I could not loop compensation. How can you help with this? Could it be that the output voltage is incorrect because my compensation values are wrong?
    

    Thanks for be interest.
    

    Have a nice day!
    

    

    

    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
			                            
                        
                on Jul 30, 2021 8:34 AM
            
            
					
      
	
      

		
		
      
					
      Hi Nebi,
      

      

      I check your circuit, LTspice wise, i did not find an issue with the simulation, parameters, etc. however we need to make sure if all conditions are with specs to verify if the problem is related to an issue of this specific model itself. I forward your concern to our Application Engineering team to help you in checking those stuffs. In case an issue is indeed confirm, there will be steps needed to be done and it will take some time to resolve the problem.
      

      Thank you.
      

      

      Regards,
      

      PaulDaria
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
			                            
                        
                on Jul 30, 2021 3:32 PM
            
            
					
      
	
      

		
		
      
					
      HI Nebi,
      

      

      I received a response from the apps engineering team. Base on their assessment, this is not a spice issue either, which was what I thought at first but rather, the 2500W load is just too much for this model. A typical application in datasheet on a offline supply application is only at 30W and LT1242 is not designed to drive large FET or parallel FET to support large current.
      

      

      You may what to try looking for the suitable part for your design. Please also note to always check the datasheet for its operating region as each models are only designed to operate with the boundary of its specification.
      

      

      Regards,
      

      

      PaulDaria
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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                on Aug 2, 2021 2:11 PM
            
            
												
						in reply to PaulDaria
					
									
        
	
        

		
		
        
					
        Hi PaulDaria,
        

        Firstly, thanks for response. And then, do you have any suggestion as suitable controller for our given design parameters previously.
        

        Vin_min=20 VDC, Vin_max=31 VDC, Vout=75 VDC, Pout=2500 W and frequency=150kHz
        

        Secondly, I consider how much power we can transmit on boost topology as maximum with a single circuit. 
        

        Thanks,
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
			                            
                        
                on Aug 3, 2021 8:01 AM
            
            
												
						in reply to NIsık445
					
									
        
	
        

		
		
        
					
        Hi NIsik445,
        

        Please check our part LT8551. You should have more freedom to do higher power boost converter. www.analog.com/.../lt8551.html
        

        There is a demo board if you want to have a reference design. 
        

        Please use LTpowerCAD. It should help you about how much power you can get on a single-channel boost. You can find articles and references in datasheets too about computations.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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