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More drive for RS485 Application



		

			

									
					    pavalentine
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on May 6, 2019 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    I'm currently using the ADM2587E Signal and Power Isolated RS-485 Transceiver for both RS-422 and RS485 applications.  For my internal  networks where I communicate with my own devices everything works well.  Sometimes when I communicate to numerous 3rd party equipment (e.g. 20-50 VFDs) I find that I need to use a 3rd party, powered isolator to blow-through the noise/load.
    

    Is there an iso-power solution where I can supply my own power supply on the network-side of the device and maybe get some more push?
    

    Paul
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on May 7, 2019 10:39 AM
            
            
					
      
	
      

		
		
      
					
      Hi Paul,
      

      Any idea on what the combined load of the 20 - 50 VFDs is? The ADM2587E can drive a network with a total of 32 unit loads (12kohm) present. If you require to add additional power in order to drive this network, I would expect the network to have a combined load higher than what the ADM2587E is rated to drive.
      

      Having said what we can check you configuration to see how you can get the most out of the ADM2587E. What supply voltage do you have on the VCC pin of your ADM2587E? The integrated DC-DC converter present in the ADM2587E will be able to provide the most output current with a 5V VCC supply voltage.
      

      If you wish to provide extra power onto the network side of the device, you could do this by connecting an external power source  to the VISOIN pin of the ADM2587E. In this case, I would recommend leaving the VISOOUT pin of the ADM2587E disconnected from the VISOIN pin. The ADuM5020-5BRIZ would be a good fit here. It can supply 100mA at 3.3V when powered with 5V on its VDDP supply, and 70mA at 3.3V when powered with 3.3V on its VDDP supply. It has the added benefit of being optimized to minimize any radiated emissions.
      

      https://www.analog.com/media/en/technical-documentation/data-sheets/adum5020-5028.pdf
      

      Regards,
      

      Neil
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on May 7, 2019 10:39 AM
            
            
					
      
	
      

		
		
      
					
      Hi Paul,
      

      Any idea on what the combined load of the 20 - 50 VFDs is? The ADM2587E can drive a network with a total of 32 unit loads (12kohm) present. If you require to add additional power in order to drive this network, I would expect the network to have a combined load higher than what the ADM2587E is rated to drive.
      

      Having said what we can check you configuration to see how you can get the most out of the ADM2587E. What supply voltage do you have on the VCC pin of your ADM2587E? The integrated DC-DC converter present in the ADM2587E will be able to provide the most output current with a 5V VCC supply voltage.
      

      If you wish to provide extra power onto the network side of the device, you could do this by connecting an external power source  to the VISOIN pin of the ADM2587E. In this case, I would recommend leaving the VISOOUT pin of the ADM2587E disconnected from the VISOIN pin. The ADuM5020-5BRIZ would be a good fit here. It can supply 100mA at 3.3V when powered with 5V on its VDDP supply, and 70mA at 3.3V when powered with 3.3V on its VDDP supply. It has the added benefit of being optimized to minimize any radiated emissions.
      

      https://www.analog.com/media/en/technical-documentation/data-sheets/adum5020-5028.pdf
      

      Regards,
      

      Neil
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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