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AD9959 Recommended for New Designs
The AD9959 consists of four direct digital synthesizer (DDS) cores that provide independent frequency, phase, and amplitude control on each channel. This...
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AD9959 on Analog.com

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AD9959 stops random

		
	
				

			

									
					    Giordano21
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 9, 2025 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user experienced an issue with the AD9959 3-phase generator where the output signals would become stuck at negative maximum after some time. The problem was resolved by adding pull-up resistors to the chip select and pull-down resistors to the IO update and DDS reset lines, which allowed the system to run indefinitely after setup. The issue was not related to the DDS chip itself but to the control signals, particularly a transient on the reset signal when the microcontroller was sent to sleep.
                        	    
    
                
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    Category: Hardware
    
    		        		            		    
    Product Number:  AD9959  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Dear All,
    

    I'm playing with an AD9959, need 3 phase generator with accurate freq and phase shift between the outputs. Using single tone. My problem is, after I initialize, it works for a wile, than, sometime after a few minutes, other time after half hour it stops and the output signals are stuck at lowest on all channel (not zero, negative max after amplification).
    

    I'm trying to find the cause for several hours now, but no success. The power seems to be clean and stable, no foreign signals on control lines or reset pin.
    

    What could cause the chip stuck at negative maximum? 
    

    If I put it in reset, it is at zero level at the output, not negative max.
    

    Thanks!
    

    JG
    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 clock and timing
                
                                                    
                 Clocks & Timers
                
                                                    
                 ad9959
                
                                                    
                 Direct Digital Synthesis (DDS)
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Mar 13, 2025 1:57 AM
            
            
						
			            		
      
		
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      Hi  ,
      

      Just curious when you mentioned after some time, it is like just idle. Are you using a custom board? Did you program the registers manually or you used the evaluation software? Thanks. 
      

      All the best,
      

      Jules
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Mar 16, 2025 2:07 PM
            
            
												
						in reply to Jules.Nikko
					
										
			            		
        
		
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        Hi Jules!
        

        Thank You for looking into these. 
        

        I've designed and built my own board and use an stm32 controller to control it.
        

        BUT, now I've inserted pullup resistors to chip select, pull down on IO update and DDS_reset and able to separate the control board from the DDS board after setup. After I separate, it runs forever. This means it is not DDS related. 
        

        I was also playing with the input signals manually and realized if I insert a DDS reset than I get this output. This means I insert a DDS reset and (this is not relevant here, but) at sending the uC to sleep I have a transient on the reset signal. If I do not send to sleep, it does not happen.
        

        On the other hand, unfortunately it has no connection to my other issue with the phase reset during frequency update.
        

        Thanks,
        

        JG
        

        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
				
						
						
				
				
		
		
        
			
		
        
	
        

        

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