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LTM8071 Recommended for New Designs
The LTM8071 is a 60VIN, 5A (continuous) step-down Silent Switcher µModule® (power module) regulator. The Silent Switcher architecture minimizes EMI while...
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LTM8071 on Analog.com

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VIN Short Failure

		
	
				

			

									
					    Bubbles27
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 27, 2026 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  LTM8071  
    
    		        		    		    
    
		    		    
		    			
    
			    
    We have four LTM8071 in parallel, and they are all synced with an LTC6909. 
    

    

     
    

     
    

    

    Across the input, we have a TVS diode that has a stand-off voltage of 32V.
    

    We have had a number of failures where all four DCDCs fail on the input side. Hard short to GND. 
    

    We very much doubt that it is an input over-voltage as the TVS is still working correctly.
    
			
    
			
									
		                             
                        

    
    
                                            
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                on Mar 5, 2026 4:15 AM
            
            
						
			            		
        
		
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        Here is a screenshot of the LTM8071 short circuit failure:
        

         
        

          

        • We have to following situation:

            

          • System is powered up

              

            • No load on the 13V Rail
              • 

            

            • 

          • Motor cranking switch is enabled
            • 

          • A short circuit occurs on the Stater

              

            • System voltage collapses from 28V to 12V 
              • 

            

            • 

          • Motor cranking switch reaches short circuit current limit and switches off

              

            • System voltage rises rapidly and overshoots to 36V - TVS diodes engage to prevent overvoltage
              • 

            • LTM8071 output voltage also rises and overshoots the 13V setpoint - maximum 15V 
              • 

            

            • 

          • System voltage collapses again due to oscillations

              

            • LTM8071 output voltage starts to drop
              • 

            

            • 

          • System voltage rises again due to oscillations

              

            • LTM8071 undershoots 13V setpoint and starts to regulate up. 
              • 

            • Spike seen on AUX-BIAS 
              • 

            

            • 

          • System voltage collapses rapidly due to LTM8071 internal short circuit
            • 

          • System current reaches 200A short circuit limit 

              

            • System input protection switches input off.
              • 

            

            • 

          

          • 

        

         
        

          

        • Is the LTM8071 robust to rapid dv/dt changes on VIN? 

            

          • DCDC Input voltage was measured at the input of the LTM8071
            • 

          • No overvoltage or negative voltage observed
            • 

          

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Reply

        


      • 
	
        



	
		
	
	



        
	
        
		
        
							
					
        
		
        
		    
		    		    
			
				
									
							        
			
			
			
          
            
						
                            
            
            				
            
                on Mar 5, 2026 4:15 AM
            
            
						
			            		
          
		
										0
					
	
          

		
		
          
		
          
                                
                                                            
          
					
          Here is a screenshot of the LTM8071 short circuit failure:
          

           
          

            

          • We have to following situation:

              

            • System is powered up

                

              • No load on the 13V Rail
                • 

              

              • 

            • Motor cranking switch is enabled
              • 

            • A short circuit occurs on the Stater

                

              • System voltage collapses from 28V to 12V 
                • 

              

              • 

            • Motor cranking switch reaches short circuit current limit and switches off

                

              • System voltage rises rapidly and overshoots to 36V - TVS diodes engage to prevent overvoltage
                • 

              • LTM8071 output voltage also rises and overshoots the 13V setpoint - maximum 15V 
                • 

              

              • 

            • System voltage collapses again due to oscillations

                

              • LTM8071 output voltage starts to drop
                • 

              

              • 

            • System voltage rises again due to oscillations

                

              • LTM8071 undershoots 13V setpoint and starts to regulate up. 
                • 

              • Spike seen on AUX-BIAS 
                • 

              

              • 

            • System voltage collapses rapidly due to LTM8071 internal short circuit
              • 

            • System current reaches 200A short circuit limit 

                

              • System input protection switches input off.
                • 

              

              • 

            

            • 

          

           
          

            

          • Is the LTM8071 robust to rapid dv/dt changes on VIN? 

              

            • DCDC Input voltage was measured at the input of the LTM8071
              • 

            • No overvoltage or negative voltage observed
              • 

            

            • 

          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
				
				
				
		
		
          
			
		
          
	
          

          

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