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Question about AD9549 output clk frequency



		

			

									
						Se-woong
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Nov 24, 2021 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hello,




My customer use AD9549 and ask some question about AD9549 output clk frequency in their below test result.




They set AD9549 PLL output with S/R Devider x4, and then test below conditions.


1) If source is 25MHz, output of AD9549 is exact 100MHz. (25x4 = 100)


2) But if source is 49.952Mhz, output of AD9549 is 199.840MHz, not 199.808MHz. (49.953 x 4 = 199.808)




Q1) Is above result correct? ( Source input is a 10 bit digitized signal.)


  


Q2) Would you let me know whty this difference is occurred?


       Is this a PLL characteristic? conversion error? error from PPM? 


      or need to review schematic & configuration? device fault?




Please advise me.




Regards,


Se-woong






 

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	














	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Nov 24, 2021 4:31 PM
            
            
					
    
	
    

		
		
    
					
    HI,
    

    in order to determine the AD9549 configuration, they must have used the AD9549 evaluation software. Please send me the stp file they created.
    

    Then I'll respond to your questions
    

    Petre
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                    			
			                            
                        
                on Dec 1, 2021 12:06 PM
            
            
												
						in reply to pminc48
					
									
    
	
    

		
		
    
					
    Dear Petre,
    

    

    Thank you for your kind concern.
    

    

    Please refer attached their STP file.
    

    ABLEE AD9549.zip
    

    Regards,
    

    Se-woong
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Dec 3, 2021 1:40 PM
            
            
												
						in reply to Se-woong
					
									
    
	
    

		
		
    
					
    Hi,
    

    I took an AD9549 evaluation board, I provided REFA=10.24MHz (from an AD9545 evaluation board, HSTL, 15 mA driver) and SYSCLK=25MHz (from a Rohde & Schwartz SMA 100A, 2dBm), I launched the evaluation software and I loaded the stp program you sent me. I then measured the OUT frequency with a Agilent E5052B as 24.479998 MHz.
    

    So the output was exactly the desired frequency.

    

    You say: "If source is 25MHz, output of AD9549 is exact 100MHz. (25x4 = 100)"
    

    When you say source, I suppose you refer to REFA, so if I set the feedback divider to 4, I would get a 100MHz. I changed accordingly the setup and save it. I then powered down the board and closed the evaluation software. I then powered back the board (this time I provided 25MHz at REFA from the AD9545 evaluation board, HSTL, 15 mA driver), launched the evaluation software and loaded the setup. I measured 99.999988 MHz, which I believe is very good.
    

    I then repeated the procedure for REFA=49.952MHz. I obtained 199.807976MHz, which I consider very close to the targeted 199.8080000000010 MHz indicated by the evaluation software.
    

    I suppose the error you get if from the clock source which you say is digital on 10 bits. I recommend measuring the 49.952MHz clock to see if the frequency is the one desired.
    

    I attach the stp files I used for REFA=25MHz and REFA=49.952MHz.
    

    AD9549_setup_REFA_25M_49p952M.zip
    

    Petre
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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													+1
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Dec 3, 2021 1:40 PM
            
            
												
						in reply to Se-woong
					
									
    
	
    

		
		
    
					
    Hi,
    

    I took an AD9549 evaluation board, I provided REFA=10.24MHz (from an AD9545 evaluation board, HSTL, 15 mA driver) and SYSCLK=25MHz (from a Rohde & Schwartz SMA 100A, 2dBm), I launched the evaluation software and I loaded the stp program you sent me. I then measured the OUT frequency with a Agilent E5052B as 24.479998 MHz.
    

    So the output was exactly the desired frequency.

    

    You say: "If source is 25MHz, output of AD9549 is exact 100MHz. (25x4 = 100)"
    

    When you say source, I suppose you refer to REFA, so if I set the feedback divider to 4, I would get a 100MHz. I changed accordingly the setup and save it. I then powered down the board and closed the evaluation software. I then powered back the board (this time I provided 25MHz at REFA from the AD9545 evaluation board, HSTL, 15 mA driver), launched the evaluation software and loaded the setup. I measured 99.999988 MHz, which I believe is very good.
    

    I then repeated the procedure for REFA=49.952MHz. I obtained 199.807976MHz, which I consider very close to the targeted 199.8080000000010 MHz indicated by the evaluation software.
    

    I suppose the error you get if from the clock source which you say is digital on 10 bits. I recommend measuring the 49.952MHz clock to see if the frequency is the one desired.
    

    I attach the stp files I used for REFA=25MHz and REFA=49.952MHz.
    

    AD9549_setup_REFA_25M_49p952M.zip
    

    Petre
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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