Products Mentioned

AD7175-2 Recommended for New Designs
The AD7175-2 is a low noise, fast settling, multiplexed, 2-/4- channel (fully/pseudo differential) S-? analog-to-digital converter (ADC) for low bandwidth...
Datasheet
AD7175-2 on Analog.com

Associated Drivers

AD7172-2 Recommended for New Designs
TThe AD7172-2 is an intelligent, low noise, low power, multiplexed, S-? analog-to-digital converter (ADC) with 2- or 4-channel (fully differential/single...
Datasheet
AD7172-2 on Analog.com

Associated Drivers

AD7177-2 Recommended for New Designs
The AD7177-2 is a 32-bit low noise, fast settling, multiplexed, 2-/4-channel (fully/pseudo differential) S-? analog-to-digital converter (ADC) for low...
Datasheet
AD7177-2 on Analog.com

Associated Drivers

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Questions about AD7172/5/7-2



		

			

									
					    HAW
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 14, 2016 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    I have questions about AD7175-2, but I beleive they would also valid for AD7172-2 and AD7177-2, so the answers would be relevant for their users too.
    
 
      
  
    1. May the inputs be shared between the channels? E. g if Ain0 and Ain1 set up for differntial measurement on channel 0, may the Ain1 be used for single ended measurement on channel 1?
      2. 
  
    2. I am a bit confused about dat rate and channels. if the data rate is 100 SPS, would it mean 50 SPS effective rate with 2 channels?
      3. 
  
    3. For the reason of simplicity the ADC is to be used to measure following signals with full scale voltages:
      4. 
 
    
 
      
  
    1.  +/- 1 V bipolar differential signal. (eg channel 0) 
      2. 
  
    2. 5 V unipolar pseudodifferintal (channel 1)
      3. 
 
    
 
    The b) forces to use 5 V external refernce, which is disadvantageous for measurement on channel 1. Luckily, the ADC has inetrnal 2.5 V reference, which could be used on channel 1 to bring it closer to optimum range. Would it make sense to do so?
    
 
    I may have further questions as I move on with the programming.
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Multiplexed A/D Converters
                
                                                    
                 ad7177-2
                
                                                    
                 ad7175-2
                
                                                    
                 Precision A/D Converters
                
                                                    
                 ad7172-2
                
                                
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Nov 22, 2016 1:18 PM
            
            
					
      
	
      

		
		
      
					
      Hi,
      
 
      In relation to the input bias current when the inputs are connected to the mux during sampling the typical input current is of the order of 30nA typical. When the inputs are not being sampled, the input pin is connected to a switch internally in the ADC Mux, which is in the off position, and the other side of the switch connects to the Mux output. The current in an unselected input will be much less than 30nA typ, typically in the order of 5nA, as I mentioned previously we don’t have a lot of data gathered on this, so unfortunately we don’t have a plot to show. Also another thing to note is that the leakage will be temperature dependent.
      
 
      Thanks,
      
 
      Jellenie
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Nov 22, 2016 1:18 PM
            
            
					
      
	
      

		
		
      
					
      Hi,
      
 
      In relation to the input bias current when the inputs are connected to the mux during sampling the typical input current is of the order of 30nA typical. When the inputs are not being sampled, the input pin is connected to a switch internally in the ADC Mux, which is in the off position, and the other side of the switch connects to the Mux output. The current in an unselected input will be much less than 30nA typ, typically in the order of 5nA, as I mentioned previously we don’t have a lot of data gathered on this, so unfortunately we don’t have a plot to show. Also another thing to note is that the leakage will be temperature dependent.
      
 
      Thanks,
      
 
      Jellenie
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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