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LT1573 Not Recommended for New Designs
The LT1573 is a regulator driver IC designed to provide a low cost solution for applications requiring high current, low dropout and fast transient response...
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LT1573 on Analog.com

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LT1573 How to configure the COMP pin?

		
	
				

			

									
					    Analog Challenged
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 8, 2021 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Given I am more of a digital engineer, I find myself challenged with an observation using the LT1573 to convert +5V to +3.3V.  While trouble-shooting a design that nearly matches the first example application depicted in the part's data sheet, an inadvertent swipe of my finger across the circuitry caused the +3.3V processor to reset.  I quickly ruled out a static discharge event.  Upon closer inspection, I discovered how easily I can cause the regulator output to shoot up past +4.5V by simply placing my finger on the COMP input pin trace.  Is this normal?  My application does not need a super fast response time given there no major swings in supply load.  All cases wherein the COMP input is unused shows it as a No-Connect, but trying this has the same effect.  Could my issue be a component value error?  Seeking advice on how to eliminate this unwelcomed sensitivity.  Thank you in advance for any recommendation.
    
			
    
			
									
		                             
                        

    
    
                                            
                 LT1573
                
                                                    
                 LDO Linear Regulators
                
                                                    
                 Discrete Pass Element Linear Regulators (LDO)
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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                on Mar 9, 2021 12:26 PM
            
            
						
			            		
        
		
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        Do electronic component companies no longer have Application Engineers that you can speak with?
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
						
                            
            
            				
            
                on Mar 10, 2021 1:43 AM
            
            
						
			            		
        
		
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        Hi Mark,
        Good day!

        Oscillation you see on the output when touching the board especially the COMP pin is normal.
        This COMP pin is sensitive to noise since it is part of your IC's control.
        This pin is made sensitive so that it could respond to the output of the regulator.
        Touching the COMP pin is like adding capacitance across it which will definitely affect with the compensation.
        Also, it is not advisable to touch by bare hands any part of a circuit when it is operational.

        You may want to refer to the "Compensation" section of the datasheet, page11 and the typical application circuit on page 13 (3.3V/5A Microprocessor Supply).

        Thanks! :)
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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                on Mar 11, 2021 6:17 PM
            
            
												
						in reply to ACaldejon
					
										
			            		
          
		
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          Thank you for the response.  Yes...I understand the advice about not touching circuitry while it's operating, however, I would have thought that a consequence of touching the COMP pin would be a slower, or faster, transient response time... and NOT one that would cause the regulated output to rail near the input voltage.  Such results could be disastrous given the +3.3V feeds much of the system.  I was hoping to hear that the pin can be tied to a rail to eliminate such response.  If not, I will likely be looking for an alternative solution altogether as I do not find this behavior to yield an acceptable risk.
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
				
				
				
		
		
          
			
		
          
	
          

          

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          •  Analog Employees  
          
            
						
                            
            
            				
            
                on Mar 14, 2021 8:38 PM
            
            
												
						in reply to Analog Challenged
					
										
			            		
          
		
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          Hi, 
          

          COMP pin is not the only pin that is affected when you touch the circuitry while it is operating. You are probably introducing noise as well on the FB pin which may greatly affect the regulation of the output. Take note that this is not a common practice and you should not touch sensitive parts while your circuit is operating.
          

          If you really want to avoid having an overvoltage on the output at all times even when you touch the IC, I would suggest to (1) put a voltage clamper on the output of LT1573 or (2) put a voltage supervisor on the output which will shutdown the LT1573 when there is an excessive voltage on its output. 
          

          Regards, 
          

          Fritz
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
						
				
				
				
		
		
          
			
		
          
	
          

          

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