Products In This Thread

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

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

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

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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.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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													0
							
			
				
									
							        
			
			
			
        
            
			                            
                        
                on Jul 31, 2017 6:53 PM
            
            
					
        
	
        

		
		
        
					
        Hi, I have an issue here.
        
 
        I built my measurement system on PCB that uses AD7175-2. As part of the verification I tested the ADC for noise performance. In particular , for testing differential measurement the following circuit was used (minimal presentation). The MAX5318 DAC was set to 1.23 V and 10000 Samples were taken
        
 
        
 
        I wanted to compare single conversion mode vs continious conversion mode and external vs internal reference. I got following results,The results are actually very good. But the single conversion conversion mode is spoiled by the fact that it took ~100 conversions to stabilize. I don't think it has something to do with the mode, but rather with the fact it was the first test to run.
        
 
        The question: is a such long settling time (?) normal?
        
 
        The settings of the ADC:
        
 
        3 channels running
        
 
        On all channels:
        
 
        input buffers enabled, reference buffer disabled, SINC5 filter, ODR100
        
 
        One more issue regarding the data sheet. The use of term "single-ended"  in the data sheet is misleading. Those are in fact pseudo-differential and should be called as such.
        
 
        Thank you
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Jul 31, 2017 6:53 PM
            
            
					
          
	
          

		
		
          
					
          Hi, I have an issue here.
          
 
          I built my measurement system on PCB that uses AD7175-2. As part of the verification I tested the ADC for noise performance. In particular , for testing differential measurement the following circuit was used (minimal presentation). The MAX5318 DAC was set to 1.23 V and 10000 Samples were taken
          
 
          
 
          I wanted to compare single conversion mode vs continious conversion mode and external vs internal reference. I got following results,The results are actually very good. But the single conversion conversion mode is spoiled by the fact that it took ~100 conversions to stabilize. I don't think it has something to do with the mode, but rather with the fact it was the first test to run.
          
 
          The question: is a such long settling time (?) normal?
          
 
          The settings of the ADC:
          
 
          3 channels running
          
 
          On all channels:
          
 
          input buffers enabled, reference buffer disabled, SINC5 filter, ODR100
          
 
          One more issue regarding the data sheet. The use of term "single-ended"  in the data sheet is misleading. Those are in fact pseudo-differential and should be called as such.
          
 
          Thank you
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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