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negative ground with ADuM7440



		

			

									
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					 Analog Employees 
					
				
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				                on Dec 9, 2011 
				
			
			
		


				
		

		    		    
		    
		    	
			
I would like to hook up an ADuM7440 to convert 4 signals from NEGCMOS [Logic ‘1’ = 0V, Logic ‘0’ = -5V] to normal +3.3V LVCMOS [Logic ‘1’ = +3.3V, Logic ‘0’ = 0V] on the other side.

   NEGCMOS side:
   VDD1 -  GND
   GND1 -   -5V

 LVCMOS side: 
   VDD2 - +3.3V
   GND2 - GND

 Is  this is acceptable?  The datasheet seems to imply that only positive rails are acceptable, even though the 1kV of digital isolation should be sufficient.