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Change the VCXO in EVAL-HMC7044 board



		

			

									
					    JoseATorr
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Oct 26, 2017 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    A VCXO at 122.88MHz is mounted in EVAL-HMC7044 board, so the inputs to the PLL1 must be divisors of this frequency. My input has to be a signal at 10MHz so I would like to have another frequency in the VCXO, for example 100MHz.
    
 
    Is it possible to connect an external VCXO through the CPOUT1 output and the OSCIN input? Or can I change the VCXO to another at 100MHz?
    
 
    Thanks in advance.
    
 
    Best Regards,
    
 
    Jose A. Torre.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Oct 30, 2017 10:10 PM
            
            
					
      
	
      

		
		
      
					
      Both is possible.
      
 
        
  
      • The on-board VCXO can be changed with 100MHz version.
        • 
  
      • The on-board VCXO can be disabled (insert JP2 -not included in the kit) and an external VCXO can be connected to OSCIN_N. It is even better to remove R227.
        • 
 
      
 
      Alternatively 122.88MHz VCXO can be locked to 10MHz reference signal without any problem. Use the following parameters:
      
 
      R0 prescaler = 5 (fLOS= 2MHz)
      R1 divider = 25 (fPFD=80kHz)
      VCXO prescaler = 60 (fLOS= 2.048MHz – fair close)
      N1 divider = 1536 (fPFD=80kHz)
      CP current = 8 (lower values may cause not locking)
      
 
      Note that, the frequencies from both branches to LOS section should be close (equal is not required). 
      
 
      Kazim
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

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    • 
	
      






      
	
      
		
      
							
					
      
		
      
			
											
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Oct 30, 2017 10:10 PM
            
            
					
      
	
      

		
		
      
					
      Both is possible.
      
 
        
  
      • The on-board VCXO can be changed with 100MHz version.
        • 
  
      • The on-board VCXO can be disabled (insert JP2 -not included in the kit) and an external VCXO can be connected to OSCIN_N. It is even better to remove R227.
        • 
 
      
 
      Alternatively 122.88MHz VCXO can be locked to 10MHz reference signal without any problem. Use the following parameters:
      
 
      R0 prescaler = 5 (fLOS= 2MHz)
      R1 divider = 25 (fPFD=80kHz)
      VCXO prescaler = 60 (fLOS= 2.048MHz – fair close)
      N1 divider = 1536 (fPFD=80kHz)
      CP current = 8 (lower values may cause not locking)
      
 
      Note that, the frequencies from both branches to LOS section should be close (equal is not required). 
      
 
      Kazim
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
				
						
				
				
		
		
      
			
		
      
	
      

      

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