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AD7671 Production
The AD7671 is a 16-bit, 1 MSPS, charge redistribution SAR, analog-to-digital converter that operates from a single 5 V power supply. It contains a high...
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AD7671 on Analog.com

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AD7671 Output has step



		

			

									
					    daydayzhq26
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Dec 13, 2017 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    
 
     When I use AD7671 to convert signal (1Hz to 1kHz), I found steps in the output.
    
 
    Attachment figure 1 is the waveform, where green line is input of AD7671;yellow line is the output of AD7671 (a DCA output, the DAC operated well).
    
								
    

							
    
				
				
			
    
					
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Dec 20, 2017 7:17 AM
            
            
					
      
	
      

		
		
      
					
      Hi Henry Zhang,
      
 
         You mentioned that you did a voltage divider on the ADR01 to have an output of 2.5V as reference to the AD7671. Where was the resistor connected? The total impedance on the reference output can interact with the ADC required reference voltage. With the impedance and the 200uA reference current of the AD7671 would affect the stability of the reference voltage during conversion. The AD7671 technology is a  switch cap dac. During transition from acquisition phase there is a large current requirement from the reference.
      
 
         On one of the snapshot, the time between each level is 62khz which is almost equal to the sampling rate. Would you be able to check the result when lowering the sampling rate.
      
 
      Regards,
      
 
      Jonathan
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
			                            
                        
                on Dec 20, 2017 7:17 AM
            
            
					
      
	
      

		
		
      
					
      Hi Henry Zhang,
      
 
         You mentioned that you did a voltage divider on the ADR01 to have an output of 2.5V as reference to the AD7671. Where was the resistor connected? The total impedance on the reference output can interact with the ADC required reference voltage. With the impedance and the 200uA reference current of the AD7671 would affect the stability of the reference voltage during conversion. The AD7671 technology is a  switch cap dac. During transition from acquisition phase there is a large current requirement from the reference.
      
 
         On one of the snapshot, the time between each level is 62khz which is almost equal to the sampling rate. Would you be able to check the result when lowering the sampling rate.
      
 
      Regards,
      
 
      Jonathan
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 


    


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