Products Mentioned

ADP125 Recommended for New Designs
The ADP124 / ADP125 are low quiescent current, low dropout linear regulators. They are designed to operate from an input voltage between 2.3 V and 5...
Datasheet
ADP125 on Analog.com

ADP124 Recommended for New Designs
The ADP124 / ADP125 are low quiescent current, low dropout linear regulators. They are designed to operate from an input voltage between 2.3 V and 5.5...
Datasheet
ADP124 on Analog.com

Thread Details

  • State Verified Answer
  • Replies 2 replies
  • Subscribers 39 subscribers
  • Views 2662 views
  • Users 0 members are here 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
ADP125: Protection diode required?

		
	
				

			

									
					    phip
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 24, 2015 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user inquired about the need for an external Schottky diode from VOUT to VIN for ADP125 LDOs, given the absolute maximum ratings. The final answer clarified that the internal body diode and protection diode prevent VOUT from being forced higher than VIN, and thus an external diode is not required. The user confirmed that no external power will be supplied to VOUT, only capacitance discharge is a concern, and the internal diodes should suffice.
                        	    
    
                
                     AI Generated Content
                
    	    
    
             
				
        		
    
		    
		    		    
		    			
    
			    
    Hi everyone,
    
 
    I'm designing a circuit with some ADP125 LDOs for the analog supplies. In the abs. max. ratings, there is a requirement for VOUT:
    
 
    VOUT to GND | -0.3V to VIN
    
 
    This would clearly indicate that the regulator needs a reverse diode from VOUT to VIN, however, this is not present on the evaluation board. Since the pass transistor is a P-channel MOSFET, I'd expect there to be an internal diode anyway. So is there still an external Schottky required?
    
 
    Thanks. Best regards,
    
 
    Philipp
    
			
    
			
									
		                             
                        

    
    
                                            
                 adp124
                
                                                    
                 adp125
                
                                                    
                 ldo
                
                                                    
                 LDO Linear Regulators
                
                                                    
                 Positive Linear Regulators (LDO)
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Oct 26, 2015 5:58 AM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi Philipp,
      
 
      You shouldn't be able to force VOUT higher than VIN unless you connect an external supply to VOUT. The restriction is for both the the protection diode which is from VOUT to GND and the body diode which is connected in parallel to the pass transistor. Turning on either of these diodes will damage the part.
      
 
      Hope this helps.
      
 
      Regards,
      
 
      Doc
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
				
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on Oct 26, 2015 6:04 PM
            
            
						
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        Hi Doc,
        
 
        thanks for your response! I won't supply external power to the output, it's just about the capacitance which is there and must be discharged. Since you mention a body diode and a protection, I suppose that the part has both and hence, I don't need to worry.
        
 
        Regards,
        
 
        Philipp
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

        •