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LTC4221 Recommended for New Designs
The LTC4221 is a 2-channel Hot Swapâ„¢ controller that allows a board to be safely inserted and removed from a live backplane. Using two independent high...
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LTC4221 on Analog.com

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LTC4221 Not working correctly on custom board

		
	
				

			

									
					    jitu56
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 1, 2025 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user implemented the LTC4221 on a custom board, which works correctly in LTspice but fails on the board when the 12V input on channel 2 exceeds 5.9V, causing a fault and auto retry mode. The final answer suggests checking the PCB design and soldering for issues. No specific URL or additional details were provided.
                        	    
    
                
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    Category: Hardware
    
    		        		            		    
    Product Number:  LTC4221  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi there..
    

    

    I have implemented LTC4221 of my custom board as in LTspice simulation. It is working correctly in LTspice but not on my board.
    

    The problem is 12V input on channel 2 causing fault as i can probe on oscilloscope. it is working only till 5.9V input and above that triggering fault and LTC4221 goes into auto retry mode. 
    

    Below is schematic (also same on my board)
    

     
    

    I appreciate for any help!
    

    

    With regards
    

    Jitu
    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 LTC4221
                
                                                    
                 Low Voltage Hot Swap Controllers
                
                                                    
                 Hot Swap Controllers
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Oct 2, 2025 8:11 AM
            
            
						
			            		
      
		
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      Jitu,
      

      

      I don't see anything wrong with the LTspice circuit that you have posted. I can only suggest that you carefully check the design of your custom PCB and the soldering.
      

      Regards,
      

      JayBee
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 26, 2025 7:17 AM
            
            
						
			            		
      
		
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      The LTC4221 IC is tripping its overcurrent or fault threshold when the input on Channel 2 exceeds 5.9 V. This suggests a configuration or a PCB layout issue and not the the IC itself. In your testing ensure that the VCC2 of the channel 2 is not greater than the VCC1 of the channel 1, as that might trigger the fault and LTC4221 would go to auto retry mode. Another thing is the layout. Try and follow the layout guide in the datasheet. Also ensure the sense resistors are kelvin connected in the PCB, so the IC does not see overcurrent at higher voltage. 
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

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