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LTC3543 Production
The LTC3543 is a high efficiency monolithic synchronous current mode buck regulator. The switching frequency is internally set at 2.25MHz, allowing the...
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LTC3543 on Analog.com

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LTC®︎3543 is damaged in field, used as FPGA & DDR  2.5V power supply



		

			

									
					    RTech
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 22, 2021 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Dear Community,
    

      
    

    I’m facing issue with LTC3543. It is failing in field, returning from customer.
    

     
    

    Issue: 2.5V rail is damaged, is giving 0.6V.
    

     
    

    Resolution: Replacing U5 LTC3543 on the controller board brought system back to full operation.
    

     
    

    The 2V5 rail powers only the FPGA and DDR memories; both have no external connections; so it is unlikely the 2V5 rail output has gone out of range and damaged U5.
    

     
    

     
    

    I’m not sure about what can be plausible causes of 2.5V to misbehave. So, I cant apply any design modifications.
    

     
    

    I tried to burn one working board by apply ESD through ESD gun, but no effect.
    

     
    

     
    

      
    

     
    

    

    My question, is what can be plausible causes of 2.5V failure and what modification I can done for future?
    

    

     Thanks in advance.
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Micropower Buck Regulators
                
                                                    
                 LTC3543
                
                                                    
                 Step-Down (Buck) Regulators
                
                                
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
			                            
                                                                                                                        
            
				
			
            
					
      
	
      

		
		
      
					
      Hello,
      

      what is your input supply and how does it behave under operation? Fast startup? Coming from upstream 5V regulator?
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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						in reply to MarkusHP
					
									
        
	
        

		
		
        
					
        Hi MarkusHP,
        

        

        - Input Supply is 5.4V, 2A 
        

        - how does it behave under operation: I think it should be stable as current requirement is in few 100mA amps under operation. This 5.4V is build from 28VDC coming from aircraft using LT8609AHMSE. All protection circuirty is their at input and pass DO160G tests. 
        

        

        - No Fast Startup for 5.4V, it is soft start, its TRSS pin has Css 100nF. 
        

        - Coming from upstream 5V regulator? there is no 5V, Vmax(5.4V) is been used to build various FPGA voltages, only 2.5V is mis behaving. 
        

         
        

        

        Thanks for your help. Kinldy let me know if any further questions. 
        

        

        

        

        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
			                            
                                                                                                                        
            
				
			
            
												
						in reply to RTech
					
									
        
	
        

		
		
        
					
        Hi RTech,
        

        The Abs. Max. of VIN pin is 6V. Please ensure that this not violated especially the 2.5V failing rail. You may check during the transient conditions too: start-up input supply, turn-off, change in output load, etc.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
						
						
				
				
		
		
        
			
		
        
	
        

        

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