Products Mentioned

AD7674 Production
The AD7674 is an 18-bit, 800 kSPS, charge redistribution, successive approximation register (SAR) fully differential analog-to-digital converter (ADC)...
Datasheet
AD7674 on Analog.com

AD4003 Production
The AD4003 / AD4007 / AD4011 are high accuracy, high speed, low power, 18-bit, Easy Drive, precision successive approximation register (SAR) analog...
Datasheet
AD4003 on Analog.com

AD8672 Production
The AD8671/AD8672/AD8674 are very high precision amplifiers featuring very low noise, very low offset voltage and drift, low input bias current, 10 MHz...
Datasheet
AD8672 on Analog.com

ADA4945-1 Recommended for New Designs
The ADA4945-1 is a low-noise, low-distortion, fully differential amplifier with two selectable power modes. The device operates over a broad power supply...
Datasheet
ADA4945-1 on Analog.com

ADAQ4003 Recommended for New Designs
The ADAQ4003 is a μModule® precision data acquisition (DAQ), signal chain solution that reduces the development cycle of a precision measurement system...
ADAQ4003 on Analog.com

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The common mode voltage range requirement of AD7674 and AD4003

		
	
				

			

									
					    liubenyuan
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on May 24, 2023 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  AD7674 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi, we are evaluating 18 bit, >500KSPS <2 INL ADCs. The signal we are sampling is current difference signals, with 100~120 uA common mode range and +- 50uA difference. We use two I to V amplifier AD8672 to convert Ia, Ib to Va, Vb.
    

    1, We would like to know, is there any common mode voltage restrictions on Va and Vb for AD7674? can we directly connect Va, Vb to RC filters and AD7674?
    

    2, If we are using AD4003 instead of AD7674, is ADC differential driver mandatory for sensing Va - Vb?
    

    Thanks
    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on May 30, 2023 11:46 AM
            
            
						
			            		
      
		
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      Hi  ,
      

      I can answer about the AD4003.
      

      The AD4003 does require a common mode voltage of VREF/2 at its inputs at all times to operate properly. If VREF = 5V for example, then the common mode voltage has to be 2.5V.
      

      A fully differential amplifier is a relatively simple way to guarantee that requirement is met, since most have a VOCM pin that sets the DC offset of both +OUT and -OUT outputs. See ADA4945-1 for example.
      

      We also offer the ADAQ4003 which integrates a fully differential amplifier and 18-bit ADC. Data sheet specifications (including INL) apply to both the amplifier and the ADC.
      

      Thanks,
      

      Tyler
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on May 30, 2023 11:46 AM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi  ,
      

      I can answer about the AD4003.
      

      The AD4003 does require a common mode voltage of VREF/2 at its inputs at all times to operate properly. If VREF = 5V for example, then the common mode voltage has to be 2.5V.
      

      A fully differential amplifier is a relatively simple way to guarantee that requirement is met, since most have a VOCM pin that sets the DC offset of both +OUT and -OUT outputs. See ADA4945-1 for example.
      

      We also offer the ADAQ4003 which integrates a fully differential amplifier and 18-bit ADC. Data sheet specifications (including INL) apply to both the amplifier and the ADC.
      

      Thanks,
      

      Tyler
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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