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LT4363 Recommended for New Designs
The LT4363 surge stopper protects loads from high voltage transients. It regulates the output during an overvoltage event, by controlling the gate of an...
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LT4363 on Analog.com

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Overcurrent timer capacitor limitation for longer period

		
	
				

			

									
					    tells
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jun 16, 2025 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user is seeking a solution to monitor and limit a 3A current for 20 seconds before shutting down the system, using the LTC4363. The final answer suggests that while the controller can monitor the current, a 20-second timer may require a large capacitor (~1000uF), which could introduce stability issues. The user is advised to consider a FET with sufficient SOA performance and possibly explore other PMICs or power controllers that can handle the required timing and current limits without a latch function.
                        	    

                
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Category: Datasheet/Specs

    		        		            		    
Product Number:  LT4363  

    		        		    		    

		    		    
		    			

			    
Hi, 


I know there is a timer capacitor that controls overcurrent limit time before it shuts off the system. 


My application will require to handle up to 3A and remain 3A for around 20 seconds before it trips.  


Based on my requirement, timer capacitor seems way to big, which I think it will have some kind of stability problems. (~mH) 


Is this the right IC that I am using for my application? Can it handle 20 seconds for 3A assuming every other part of LTC4363 are properly selected? Is there any other recommendation ICs similar to LT4363 but can handle my requirement? 


We cannot introduce digital circuits (current sense + MCU and etc) so trying to design this with modular approach. I wasn't sure if I have to go by discrete design instead of modular. 


Thanks


Mike 

			

			
									
		                             
                        

    

                                            
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    •  Analog Employees  
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                on Jun 16, 2025 10:02 PM
            
            
						
			            		
    
		
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    What's your input voltage? This is necessary to know the timer current. 
    


    If you are in current limit for that long, I would expect output to droop, and then once VOUT<2V, your current limit folds back from 3A to ~1.5A.


    

    tells said:
    Is this the right IC that I am using for my application? Can it handle 20 seconds for 3A assuming every other part of LTC4363 are properly selected?
    

    The controller is fine, it's more about choosing a FET with enough SOA performance. 20 seconds of current limiting is probably too much to ask; I have never seen more than 1 second.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
				
				
				
		
		
    
			
		
    
	
    

    

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                on Jun 16, 2025 10:07 PM
            
            
												
						in reply to Ashapiro
					
										
			            		
    
		
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    There are many FETs that can handle DC current long enough with some sort of Heatsink. I was more concerned about the controller. Can I use this controller to monitor 20 seconds and reset it manually? auto reset doesn't seem to be possible with another 20 seconds of latch off then repeat. I don't need to have a latch function. Just needed to monitor that 20 second long while limiting the current 5A and shutdown then reset it manually somehow 

    My simulation using LT4363-1 suggests that I can monitor current 5A while limiting for ~30s but it will require massive capacitor (~1000uF,) then I can reset manually after awhile capacitor discharges low enough (0.5V) by pulling shutdown pin high. If there Isn't any concern with instability of having 1000uF, can I still use it? 

    P.S I figured that this is not possible as discharge time is way too long compared to charge time of the timer capacitor... Is there any PMIC or some sort of power controller that needs my design? Something that can monitor in seconds then latch off and on again in seconds? 
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
				
				
				
		
		
    
			
		
    
	
    

    

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