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HMC980LP4E Active Bias Controller VNEG Pin



		

			

									
					    thyung
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 14, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  HMC980LP4E 
    
    		        		    		    	
			
    I am designing a circuit using HMC980LP4E active bias controller and HMC863ALC4 power amplifier. On the HMC980LP4E, I am using the depletion mode of the amplifier (VNEG = Internal) following figure 34 in the datasheet. I expected VNEG input should be -2.46V as described in table 7 (Mode Selection). But, VNEG is measured as +2.8V. This doesn't make sense. I read both Application note AN-1363 and HMC980LP4E datasheet very carefully, but could not find any clue as to why this is. Could you please give any advice as to what is causing this issue.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Jul 21, 2022 8:27 PM
            
            
					
      
	
      

		
		
      
					
      Hi thyung,
      

      This is certainly unusual.. If possible, can you give me more detail of your start up and shut down sequencing? As well as the timing between bringing each voltage up? It may also be helpful if you could provide a schematic of your circuit/design..
      

      Thanks,
      

      DanO
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Jul 22, 2022 2:36 AM
            
            
												
						in reply to DanO2
					
									
        
	
        

		
		
        
					
        Thank you for your reply.
        

        I applied externally -2.5V to VNEG. And then I found that VGATE and VDRAIN works correctly when I applied the EN signal. But, still I don't know why the internal negative voltage generator doesn't work.
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
				
				
						
				
				
		
		
        
			
		
        
	
        

        

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