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ADF4356 Synthesiser - AVDD and DVDD rails



		

			

									
						Mike.perdikakis@aceaxis.co.uk
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Mar 2, 2022 
				
			
			
		


				
		

		    		    
		    
		    	
			
Dear Analog Devices,


We are about to use the ADF4356 in one of of our new designs and I have got a question:


In the datasheet, it says that we should use to separate regulators (low noise LDOs) for the 3V3 Analog and 3V3 Digital respectively. Do we have to use TWO regulators for this purpose? Is ONE not going to do in terms of ensuring decent phase noie? If the 3V3 can be supplied by a single low noise linear regulator (that can handle the overall output current for both AVDD and DVDD) can we not power them up from the same regulator?


Cheers,


Michael 

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	














	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
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                on Mar 7, 2022 7:18 AM
            
            
					
    
	
    

		
		
    
					
    Hi Michael,
    

    The part is characterized with separate supplies and I don't have data taken with shared supplies. We are using HMC1060 ( single chip having 4 LDOs) on the evaluation board and isolation is poorer comparing separate LDO case. We did not see any performance degradation on the EVB. However, this part is not recommended for new designs now.  From this perspective, if you can provide enough isolation between AVDD and DVDD supplies, you can use single LDO. You can consider to use ferrite beads to separate supply lines and this can provide the isolation between AVDD and DVDD. 
    

    Regards,
    

    Kudret 
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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													+1
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Mar 7, 2022 7:18 AM
            
            
					
    
	
    

		
		
    
					
    Hi Michael,
    

    The part is characterized with separate supplies and I don't have data taken with shared supplies. We are using HMC1060 ( single chip having 4 LDOs) on the evaluation board and isolation is poorer comparing separate LDO case. We did not see any performance degradation on the EVB. However, this part is not recommended for new designs now.  From this perspective, if you can provide enough isolation between AVDD and DVDD supplies, you can use single LDO. You can consider to use ferrite beads to separate supply lines and this can provide the isolation between AVDD and DVDD. 
    

    Regards,
    

    Kudret 
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

    • 





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