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ADP7182 Recommended for New Designs
The ADP7182 is a CMOS, low dropout (LDO) linear regulator that operates from −2.7 V to −28 V and provides up to −200 mA of output current. This high...
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ADP7182 on Analog.com

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ADP7182 Adjustable Not Allowing -1.2V output

		
	
				

			

									
					    sca
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jun 17, 2019 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
I've wired the Adj pin directly to Vout to produce a -1.22V output with the Adjustable version. -5.5Vin and -1.2Vout. Unfortunately I'm getting -5V out. I've checked the part case lettering and it appears to be correct for the adjustable version so why isn't this working?

			

			
									
		                             
                        

    

                                            
                 adp7182
                
                                                    
                 LDO Linear Regulators
                
                                                    
                 Negative Linear Regulators (LDO)
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

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                on Jun 18, 2019 4:00 PM
            
            
						
			            		
    
		
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    I think I've resolved it. The -1.2V is connected to the high supply side of a bipolar OPAMP used to bias the gate of an RF amp. The OPAMP's supply input needs to sync current but the ADP7182 is also sinking current.  Adding a resistor to ground from Vout should solve the problem by supplying a current source from ground.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
				
				
				
		
		
    
			
		
    
	
    

    

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