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Supply voltage for ADV7125 and decoupling of VREF pin



		

			

									
						y_suzuki
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Apr 23, 2015 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hello,

 
I have two questions about ADV7125.

 
1. The VAA pin is described "Analog Power Supply(5V +/-5%)." in table-6 ,datasheet.

 
   But VAA is allowed 3.3V in Table-2. I think the "Analog Power Supply" contains not only 5V but also 3.3V.

 
   Is it true ?

 
2. About decoupling for VREF pin.

 
   In the ADV7123 datasheet(Rev.D), I can see following description in P.18 reference input section.

 
     "The VREF pin is normally terminated to VAA through a 0.1uF capacitor"

 
   ADV7125 should be same connection ?

 
   ADV7125 should not be connected to GND through 0.1uF capacitor ?

 
   I saw "https://ez.analog.com/message/165693#165693" and there is following comment.

 
     "The compensation loop is referenced to Vaa so the comp cap needs to be tied to Vaa."

 
   I assume that this comment describes about VREF pin.

 
   It is true ?

 
Regards,

 
ysuzuki

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	










	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
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                on Dec 17, 2015 5:22 AM
            
            
					
    
	
    

		
		
    
					
    Hi
    
 
    This might be repeated question.
    
 
    What is ADI recommended chircuit about ADV7123/7125 VREF pin when internal reference used?
    
 
    0.1uF decoulping to VAA was mentioned in the schematic of old datasheet and P18/24 of the latest datasheet
    
 
    but 1uF decoulping to GND when external ref(AD1580) used.
    
 
    Latest datasheet saying
    
 
    REFERENCE INPUT
    
 
    The ADV7123 contains an on-board voltage reference. The VREF pin is normally terminated to VAA through a 0.1 μF capacitor. Alternatively, the part can, if required, be overdriven by an external 1.23 V reference (AD1580).
    
 
    Regards,
    
 
    Tomoto 
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Dec 17, 2015 5:22 AM
            
            
					
    
	
    

		
		
    
					
    Hi
    
 
    This might be repeated question.
    
 
    What is ADI recommended chircuit about ADV7123/7125 VREF pin when internal reference used?
    
 
    0.1uF decoulping to VAA was mentioned in the schematic of old datasheet and P18/24 of the latest datasheet
    
 
    but 1uF decoulping to GND when external ref(AD1580) used.
    
 
    Latest datasheet saying
    
 
    REFERENCE INPUT
    
 
    The ADV7123 contains an on-board voltage reference. The VREF pin is normally terminated to VAA through a 0.1 μF capacitor. Alternatively, the part can, if required, be overdriven by an external 1.23 V reference (AD1580).
    
 
    Regards,
    
 
    Tomoto 
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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