Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

  • State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 328 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM3406HV: LM3406HV: Temperature problem.

mst er
Prodigy 110 points
Part Number: LM3406HV
Other Parts Discussed in Thread: LM3406,

I'm using lm3406 in my led driver project. I'm having a temperature problem. Parameters of the circuit:

Fswitching: 500kHz

Output Current:0.7A

Input Voltage:48V DC

Output Voltage 40V DC

My circuit is LM3406 datasheet typical application. Circuit components calculated by application note. Why LM3406 IC rised temperature?

  • 0
    TI__Mastermind 28655 points

    Hello,

    What do you mean by temperature problem?  At 0.7A and over 80% duty cycle there is some conduction loss.  There will be switching loss as well at 500 KHz.  The part is intended to do this and will rise in temperature.  The LM3406 has an exposed pad for heatsinking, what have you provided for heatsinking the LM3406?  How large is your PCB pad for removing heat from the LM3406.  Does the pad have vias to pull heat to another plane?

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Prodigy 110 points

    Thanks for answer. My PCB properties

    1-LM3406 has not via

    2- My PCB temperature normal

    3- I am gonna try big LM3406 thermal pad and %50 duty,200kHz

    I hope this problem fix

  • 0 in reply to mst er
    TI__Mastermind 28655 points

    Hello,

    If your output is 40V and input is 48V the duty cycle is determined, approximately 40V/48V (not including losses), or 83%.

    It will work with your specifications if it has a decent thermal connection to the bottom pad.

    You can look at the LM3406HV EVM.  It runs at 500 KHz, up to 1.5A.  It has thermal vias to the bottom side of the board.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Prodigy 110 points 
    My project circuit LED Driver LM3406HV still have temperature problem. Maybe the task cycle is 50% and fsw = 200kHz to troubleshoot this problem. Thanks.
    

    

    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
    • 

		
	
  • 
		
    
			 


	
			
		
	









    
	
    
		
    
							
					
    
		
    
			
													0
							
			
				
									
							
						
				
			
			
			
												
						in reply to mst er
					
									
    
	
    
	                                    
                      
    
                        
                          TI__Mastermind
                        28655 points
                      
    
                          
                   		
		
    
					
    Hello,
    

    I haven’t heard back from you, I’m assuming you were able to resolve your issue. 
    If not, just post a reply below (or create a new thread if the thread has locked due to time-out)
    

    Also, make sure you are using a schottky diode for the freewheel diode, or a diode capable of high frequency operation.  Using the wrong diode can cause excess heat in the LM3406, D1 in the typical application diagram 3.1 of the datasheet on page one.
    

    Best Regards,
    

    

    

    

    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
    • 

		
	
  • 
		
    
			 


	
			
		
	









    
	
    
		
    
							
					
    
		
    
			
													0
							
			
				
									
							
						
				
			
			
			
												
						in reply to Irwin Nederbragt
					
									
    
	
    
	                                    
                      
    
                        
                          Prodigy
                        110 points
                      
    
                          
                   		
		
    
					
    Thanks for answer. I solved the problem by designing new cards
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
    •