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The AD7785 is a low power, low noise, complete analog front ends for high precision measurement applications. It contains a low noise 20-bit Σ-Δ ADC...
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AD7785 on Analog.com

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In the datasheet, why is the maximum value of Vt(+) 2V and the minimum value of Vt(-) 0.8V?

		
	
				

			

									
					    miky
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 29, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  AD7785  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello.
    

    Please let me ask new questions about AD7785 here.
    

    For example, with a hysteresis of 017V, Vt(-)=1.83V when Vt(+)=2V, which violates the maximum value of Vt(-), which is 1.7V.
    

    Does this mean that Vt(+)=2V is impossible?
    

    Similarly, with hysteresis 017V, when Vt(-) = 0.8V, Vt(+) = 0.97V, which violates the 1.4V minimum for Vt(+).
     Does this mean that Vt(-)=0.8V is also impossible?
    

    In the datasheet, why is the maximum value of Vt(+) 2V and the minimum value of Vt(-) 0.8V?
    

    Best regards
    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jan 31, 2025 5:51 AM
            
            
						
			            		
      
		
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      Hi  ,
      

      I am currently in contact with the product owner regarding this datasheet query. I will get back to you soon.
      

      Thanks and regards,
      

      Rod
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Feb 12, 2025 9:18 PM
            
            
												
						in reply to RAdante
					
										
			            		
      
		
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      Hi  
      

      Apologies for the delay in responding to this.
      

      The input signals are Schmitt-trigged. it is recommended to use a Vt(+) of 2V min and a Vt(-) of 0.8 V max.
      

      There is some hysteresis on the inputs. So, there is not a single threshold point where the input transitions from Vt(+) to Vt(-). When ramping up, it may be 2V that is needed before the input transitions to a Vt(+). Ramping down, it is 1.4V before the input will transition to being a Vt(-). This prevents glitches on the logic inputs from causing Vt(-) to Vt(+) transitions or vice versa.
      

      Thanks and regards,
      

      Rod
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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