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ADM1491E Production
The ADM1490E / ADM1491E are RS-485 transceivers with ±8 kV ESD protection and is suitable for high speed, full-duplex communication on multipoint transmission...
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ADM1491E on Analog.com

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Can we assure the status of Z and Y when VCC decrease below 4.5V?

		
	
				

			

									
					    howardaaa
					
							

            
            			
				
									
											
			
			
				
  •  Analog Employees  

			
			
			    	
			                    
                
				                on Mar 25, 2025 
				
			
			
		

		
		                     
				
        		

		    
		    		    

		      		            		        
Category: Hardware

    		        		            		    
Product Number:  ADM1491E  

    		        		    		    

		    		    
		    			

			    
Hi,




If DE, DI input status are kept constant(high or low) when the device is powered down, can we assure the status of Z and Y during the power down period?


For example, if DE is kept low, Z and Y are in high-Z mode when VCC is between 4.75V and 5.25V, then we power down the device, can we assure Z and Y are still in high-Z mode when VCC is between 0-4.75V?

			

			
									
		                             
                        

    

                                            
                 hardware
                
                                                    
                 RS-232 / RS-422 / RS-485 / RS-562
                
                                                    
                 ADM1491E
                
                                                    
                 RS-485 and RS-422
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Mar 28, 2025 2:33 PM
            
            
						
			            		
    
		
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    Hello,
    

    I would be happy to help you with this question.
    

    Unfortunately, functionality for the ADM1491 cannot be guaranteed when the supply is less than 4.75V (as outlined in the electrical characteristics table), unless specifically specified in the EC table.
    

    In my personal experience, I would expect, with high confidence, that the driver outputs will be high impedance when VCC is below the operating range, however we have not tested the device under those conditions and cannot guarantee that is the case.
    

    Thank you,
    

    Shasta
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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