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AD9257 Recommended for New Designs
The AD9257 is an octal, 14-bit, 40 MSPS and 65 MSPS analog-to-digital converter (ADC) with an on-chip sample-and-hold circuit designed for low cost, low...
Datasheet
AD9257 on Analog.com

AD8138 Production
The AD8138 is a major advancement over op amps for differential signal processing. The AD8138 can be used as a single-ended-to-differential amplifier or...
Datasheet
AD8138 on Analog.com

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AD9257 waveform jump



		

			

									
					    ZhaoC
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 11, 2018 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hello,
    

    I‘ve had a problem using AD9257. I used it to acquire a sine wave, but the waveform will jump if the input exceed a value, as shown below.
    

     
    

    The problem does not occur in all of the 8 channels. 
    

    I made a few test boards, and each board has different error channels.
    

    I use AD8138 as the differential Driver. I watched the differential input of AD9257 with an oscilloscope, and it is a standard sine wave.
    

    I used the test pattern function of AD9257 to test my driver program, and I can receive the test pattern correctly.
    

    What is the possible reason for this problem?
    

    

    Appreciate all your efforts and help.
    

     
    

    Thanks
    

    Zhao
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Oct 12, 2018 12:39 AM
            
            
					
      
	
      

		
		
      
					
      Hi Zhao,
      

      Thank you for using the AD9257. You mentioned that the problem does not occur on all channels, and different boards show the problem on different channels. On a given board, are the problem channels the same from power-up to power-up? For example, if only Channel A is not working on one board, will it always be only Channel A that does not work?
      

      If you are able to post your schematic, I would be glad to look at them.
      

      Also, as a sanity check, please try a Digital Reset as described in the CLOCK STABILITY CONSIDERATIONS section of the AD9257 datasheet.
      

      SPI_Write (0x08, 0x03); # Start Digital Reset
      

      SPI_Write (0x08, 0x00); # Finalize Digital Reset and Return to Normal Operation
      

      Thank you.
      

      Doug
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Oct 12, 2018 12:39 AM
            
            
					
      
	
      

		
		
      
					
      Hi Zhao,
      

      Thank you for using the AD9257. You mentioned that the problem does not occur on all channels, and different boards show the problem on different channels. On a given board, are the problem channels the same from power-up to power-up? For example, if only Channel A is not working on one board, will it always be only Channel A that does not work?
      

      If you are able to post your schematic, I would be glad to look at them.
      

      Also, as a sanity check, please try a Digital Reset as described in the CLOCK STABILITY CONSIDERATIONS section of the AD9257 datasheet.
      

      SPI_Write (0x08, 0x03); # Start Digital Reset
      

      SPI_Write (0x08, 0x00); # Finalize Digital Reset and Return to Normal Operation
      

      Thank you.
      

      Doug
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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