Products Mentioned

LT3090 Recommended for New Designs
The LT3090 is a 600mA, low dropout negative linear regulator that is easily parallelable to increase output current or spread heat on surface mounted boards...
Datasheet
LT3090 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 1 reply
  • Subscribers 39 subscribers
  • Views 1103 views
  • Users 0 members are here 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
I would like to ask about the input voltage of the LT3090.

		
	
				

			

									
					    seunguk
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Aug 7, 2018 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hello. I am a graduate student studying at Chungbuk National University in South Korea.

    Nowaday, I used the LT3090 and I made it according to the configuration of the Basic Adjustable Regulator described in Datasheet.

    But I did not see the input voltage on the data sheet up to -10V. So I entered -15V with my fault. IC seems to be broken.

    The Floating 3-Terminal Adjustable Regulator on the datasheet shows only input voltages from -17V to -22V.

    Does the LT3090 have input voltages below -10V? I wonder.

    If I can input a voltage below -10V, how should I configure it?
    
			
    
			
									
		                             
                        

    
    
                                            
                 LT3090
                
                                                    
                 LDO Linear Regulators
                
                                                    
                 Negative Linear Regulators (LDO)
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Aug 7, 2018 3:14 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      This is what I normally tell people so they will be ready to work with LDOs: 
      
 
      NOTE WHEN WORKING WITH LDOS (written for positive LDOs but in general applies to negative LDOs as well):  An input voltage that is too close to the programmed output voltage (too low) may cause dropout operation and a loss of output voltage regulation.  An input voltage that is too high above the output may increase power dissipation to an unacceptable level.  Finally, a protection feature within the LT3090 reduces output current capability at higher input voltages.
      
 
       
      
 
       
      
 
      The image below shows the circuit that you mentioned - The Basic Adjustable Regulator:
      
 
      
 
      VIN of the Basic Adjustable Regulator shown above is limited to 10V because
      
 
        
  
      1. my general comments about LDO power dissipation above and
        2. 
  
      2. the LT3090 has reduced output current capability (also mentioned above) for larger VIN to VOUT differentials according to the Internal Current Limit curve shown below from the datasheet.
        3. 
 
      
 
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

      •