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LT3045 Recommended for New Designs
The LT3045 is a high performance low dropout linear regulator featuring LTC’s ultralow noise and ultrahigh PSRR architecture for powering noise sensitive...
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LT3045 current limit overshoot at startup (10 mA setting)

		
	
				

			

									
					    Atsushi123
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on May 18, 2026 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user observed an output current transient exceeding 10 mA during startup of the LT3045 with a 10.1 μF output capacitor. The final answer confirmed that the current limit function may not take immediate effect, leading to a charging current that can temporarily exceed the set limit. The user's actual measurement showed an inrush current of about 50 mA for 10 μs, which is considered normal for the capacitor charging. The engineer recommended reviewing the attached data for further insights.
                        	    

                
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Category: Hardware

    		        		            		    
Product Number:  LT3045  

    		        		    		    

		    		    
		    			

			    


Hello,


 


I am using the LT3045 with the current limit set to 10 mA.


 


During startup, I observed that the output current may temporarily exceed 10 mA immediately after power is applied. The output has a 10.1 µF capacitor connected.


 


I would like to ask the following:


 


1. Is it possible that the current limit function does not take effect immediately after power-up, allowing a transient current higher than the set limit?


 


2. If this is generally not expected, could it still happen due to part-to-part variation?


 


3. What startup control or external circuit/design method is recommended to reliably avoid this behavior?


 


4. Is this temporary current increase considered normal charging current for the output capacitor, or does it indicate that the current limit loop has not fully taken control yet?


 


Any guidance would be greatly appreciated.


Best regards,

			

			
									
		                             
                        

    

                                            
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                on May 26, 2026 1:05 AM
            
            
						
			            		
    
		
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    Hi Satoru,
    

    Thanks a lot for checking this on actual hardware.
    

    We understand your explanation that IOUT is controlled by ILIM and is around 10 mA, based on both the measurement and the C·dv/dt calculation. The behavior with PGFB shorted and CSET minimized also makes sense to us.
    

    We’ll take a closer look at the attached data and follow up if needed.
    

    Thanks again for your support.
    

    Best regards,
     Atsushi
    

    

    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
				
				
				
		
		
    
			
		
    
	
    

    

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                on May 26, 2026 1:05 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    

    Hi Satoru,
    

    Thanks a lot for checking this on actual hardware.
    

    We understand your explanation that IOUT is controlled by ILIM and is around 10 mA, based on both the measurement and the C·dv/dt calculation. The behavior with PGFB shorted and CSET minimized also makes sense to us.
    

    We’ll take a closer look at the attached data and follow up if needed.
    

    Thanks again for your support.
    

    Best regards,
     Atsushi
    

    

    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
				
				
				
		
		
    
			
		
    
	
    

    

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