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ADRF5720 Recommended for New Designs
The ADRF5720 is a silicon, 6-bit digital attenuator with 31.5 dB attenuation control range in 0.5 dB steps. This device operates from 9 kHz to 40 GHz with...
Datasheet
ADRF5720 on Analog.com

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ADRF5720 unstable attenuation when using parallel mode

		
	
				

			

									
					    ZhangZhongli
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 7, 2023 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user experienced unstable attenuation and incorrect operation when using the ATTEN3/SEROUT pin, despite keeping PS low and toggling LE high. The final answer suggests checking if the part is damaged by verifying correct currents from the supply and control pins, testing in other modes, and trying different attenuation states. The power-up sequence is not considered the cause of the issue.
                        	    
    
                
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    Category: Hardware
    
    		        		            		    
    Product Number:  ADRF5720 
    
    		        		    		    
    
		    		    
		    			
    
			    
    I just kept PS low, however the ATTEN3/SEROUT pin kept high, and when I toggled high LE,attenuation couldn't be changed correctly, however it was quite unstable. I wonder if it is because I didn't use a series 1 kΩ resistor to limit the current flowing in to the control pin, or I powered up VSS and VDD at the same time.
    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 Digital Step Attenuators
                
                                                    
                 ADRF5720
                
                                                    
                 attenuators
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Apr 10, 2023 7:27 AM
            
            
						
			            		
      
		
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      Hi ZhangZhongli
      

      

      Thanks a lot for the question. At first glance, your application issue is unrelated with the power-up sequence. However, it is always good practice to follow the recommended sequence and use case.
      

      I've got points you could check if the part is operating correctly.
      

      1) Could you read correct currents from the supply and control pins as described in the datasheet? If currents are incorrect, it is highly probable that the part is damaged.
      

      2) Were you be able to operate the part in any other mode (parallel/ serial)? If not so, could you try the simplest option?
      

      3) Is any other attenuation state work in your application? If you haven't tried, could you try couple?
      

      Gokhan
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
				
				
				
		
		
      
			
		
      
	
      

      

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