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AD9102 Production
The AD9102 TxDAC and waveform generator is a high performance digital-to-analog converter (DAC) integrating on-chip pattern memory for complex waveform...
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AD9102 on Analog.com

AD9106 Production
The AD9106 TxDAC® and waveform generator is a high performance, quad digital-to-analog converter (DAC) integrating on-chip pattern memory for complex waveform...
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AD9106 on Analog.com

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AD9106/AD9102 clock issue



		

			

									
					    yorkpa
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 29, 2015 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    I have a really strange issue with SPI communication on the AD9106.
    
 
    When I disable my DAC clock (TI CDC421 156 MHz LVPECL), SPI communication (330 kHz) works great, but when I turn the DAC clock on, I lose SPI communication-- I can no longer read from the registers.
    
 
    How could the DAC clock affect SPI communication?
    
 
    Perhaps I'm not terminating my DAC clock or AC-coupling it properly, but I think it's fine:
    
 
    
 
    I see the common mode voltage properly sitting at 0.9 V and I see a 500 mV peak-to-peak swing from CLKP to CLKN
    
 
    One thought is that there might be a setup time issue that arises with using the faster clock.
    
 
    Or, if I'm not terminating it correctly, there's some sort of over-current issue?
    
 
    I'd really appreciate some insight into what might be going on.
    
 

    Pete
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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                on Jul 2, 2015 1:14 AM
            
            
					
        
	
        

		
		
        
					
        Thanks, Larry. I think there's still something strange going on with the DAC clock.
        
 
        SPI works great if the DAC clock is disabled or if TRIGGER_BAR is disasserted.
        
 
        I lose SPI if I enable the DAC clock and assert TRIGGER_BAR. Then, if I disassert TRIGGER_BAR, SPI is not restored, but if I turn off the DAC clock, SPI comes back. So strange!
        
 
        Do you have any insight as to why this would happen? I seriously think it's a clock issue. I'm trying to use the clock circuit in the picture above. I'll probably end up trying to use a different clock, but I'd really like to know why/if this one is fouling things up.
        
 

        Pete
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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													0
							
			
				
									
							        
			
			
			
          
            
			                            
                        
                on Jul 2, 2015 1:14 AM
            
            
					
          
	
          

		
		
          
					
          Thanks, Larry. I think there's still something strange going on with the DAC clock.
          
 
          SPI works great if the DAC clock is disabled or if TRIGGER_BAR is disasserted.
          
 
          I lose SPI if I enable the DAC clock and assert TRIGGER_BAR. Then, if I disassert TRIGGER_BAR, SPI is not restored, but if I turn off the DAC clock, SPI comes back. So strange!
          
 
          Do you have any insight as to why this would happen? I seriously think it's a clock issue. I'm trying to use the clock circuit in the picture above. I'll probably end up trying to use a different clock, but I'd really like to know why/if this one is fouling things up.
          
 

          Pete
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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