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HMC821 frequency synthesizer



		

			

									
						Mete
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 12, 2015 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    
 
    We designed a PCB for @HMC821 frequency synthesizer as much as similar to the one depicted in the datasheet of HMC821. and we load registers as below to obtain 1900MHz RF at the output
    
 
    reg02  : 00000001
    
 
    reg06:  0003074a
    
 
    reg09: 00003264
    
 
    reg05: 0000e80d
    
 
    reg05:   0000ab95
    
 
    reg05: 0000d11d
    
 
    reg05: 00000005
    
 
    reg03: 000000be
    
 
    reg04: 00000000
    
 
    but we obtain in spectrum three different frequencies at approxiametly 900MHz, 1821 MHz ,and 2700MHz, although it says LOCKED.
    
 
    We couldn't find what can cause this. 
    
 
    is it possible to find source code ?
    
 
    We also have the eval board of the HMC821 but we are not able to set frequency via its interface when we use an external reference frequency of 10 MHz. I think it works only with 50 MHz reference, which is on the board. 
    
 
    We would appreciate if you suggest.
    
 
    thank you.
    
 
    Mete 
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

					
    
			
    


    

	
    
		
	
    















    
	
    
	
    
					



			


				
	









	
      
	

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                on Nov 13, 2015 1:36 AM
            
            
					
      
	
      

		
		
      
					
      Attached is a list of register values that will lock the HMC821 to a 10MHz reference and output a 1900MHz tone, Integer Mode.
      
 
      The eval board can operate with 10MHz reference input, however, if in Fractional Mode the CP Offset current (Reg09h[20:14]) should be reduced for the lower comparison frequency.  In Integer Mode, the CP Offset current should be disabled (Reg09h[22:21]=00b).
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Nov 24, 2015 12:56 AM
            
            
					
      
	
      

		
		
      
					
      We don't give out the evaluation software source code.
      
 
      Can you provide more information about the problem you are observing?
      
 
      Are you able to write to and read from the device registers?  For example can you read from Reg00h and get the correct Chip ID (which is 95187h).  Customers frequently have issues with SPI communication because the HMC821 has two SPI modes which can cause problems.  This is discussed here -->   https://ez.analog.com/docs/DOC-11784
      
 
      and here -->  https://ez.analog.com/docs/DOC-12778
      
 
      If you are not able to communicate with the device then you will see tones at 900MHz (high amplitude), 1800 & 2700MHz (lower amplitude) because the device powers up in 'divider' mode (VCO output 'divide-by-2' enabled).
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Aug 2, 2018 3:16 PM
            
            
					
      
	
      

		
		
      
					
      This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

      Thank you,
      EZ Admin
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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