Products Mentioned

AD7706 Not Recommended for New Designs
The AD7705 / AD7706 are complete analog front ends for low frequency measurement applications. These 2-/3-channel devices can accept low level input signals...
Datasheet
AD7706 on Analog.com

AD7710 Production
The AD7710 is a complete analog front end for low frequency measurement applications. The device accepts low level signals directly from a strain gage...
Datasheet
AD7710 on Analog.com

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Daisy chain AD7706

		
	
				

			

									
					    drew.h
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Sep 19, 2011 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Is it possible to daisy chain the AD7706?  If not, can anyone recommend a 16bit ADC that can be, preferably in a DIL package?
    
 
    I have an application that requires over 50 ADCs, with 50 or 60 readings per second, so daisy chaining them would make it easy for me.  I also use the AD7710 a lot, knowing if that to can be daisy chained to would be useful.
    
			
    
			
									
		                             
                        

    
    
                                            
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                on Sep 19, 2011 10:21 AM
            
            
						
			            		
        
		
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        Thanks Rob.
        
 
        The AD977 looks like it will do the job.  With the number of ADCs on the board I'd prefer to have them in DIL sockets, so if one goes it can be replaced.  As its a one off project the age of the component is not important.  The AD7980 also looks good, but I'd have to mount them on daughter boards.  No need for an evaluation board, I'll just buy a couple from Farnell.
        
 
        The project needs to measure 64, or possibly 128, potentials at 50 or 60 readings per second, so we can filter mains noise.  The potential will be bi-polar, but conditioning for a uni-polar ADC would be possible.  Great accuracy is not needed, but I chose 16 bit because its two bytes exactly so no wasted bits.  I'll be using a dsPIC to read the ADCs and send the data to the PC.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
						
                            
            
            				
            
                on Sep 19, 2011 2:58 PM
            
            
						
			            		
        
		
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        Hi Drew,
        
 
        Neither the AD7706 or the AD7710 parts can be daisychained. Using the product selection table for ADC's located at http://www.analog.com/en/analog-to-digital-converters/ad-converters/products/index.html and the three requirements of 16-bit, daisy chaining and DIP package the only device which has all three is the AD977(A). The datasheet is located at http://www.analog.com/static/imported-files/data_sheets/AD977_977A.pdf and contains information on how to daisy chain these parts. Please review the datasheet to deteremine if this part is suitable for your application. This part is quite old however, as are the AD7706 and AD7710, and I'm not sure if there is still an evaluation board still available for the AD977(A). Let me know if you wish to choose this part and I can check the status of the evaluation board.
        
 
        The requirement of a DIP package is the most limiting factor for your choice here. There are other parts which have daisy chain capablility but not in a DIP package. For example please have a look at the AD7980 (http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7980/products/product.html). This part is relatively new and does have an evaluation board available.
        
 
        Can you give me some more information on your application and perhaps we can refine your requirements and find a suitable part for you ?
        
 
        Regards,
        
 
        Rob
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
						
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
						
                            
            
            				
            
                on Sep 21, 2011 1:50 PM
            
            
						
			            		
        
		
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        Thanks for the feedback Drew.
        
 
        Let me know if you have any further questions.
        
 
        Regards,
        
 
        Rob
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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