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AD723 Production
The AD723 is a low cost RGB-to-NTSC/PAL encoder that converts analog red, green, and blue color component signals into their corresponding luminance and...
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AD723 on Analog.com

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The color burst from AD723 seems to move on AD723 Eval Board.

		
	
				

			

									
					    Tamu
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on May 28, 2013 
				
			
			
		
    
		
		                    	    
    
        	    
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                The user inquired about the variability of the color burst start point on the AD723 Eval Board (AD723EB rev.B). The engineer confirmed that the maximum phase error due to asynchronous operation is one cycle of 4FSC (90 degrees at 3.579545 MHz), and variations due to temperature, process, and voltage are negligible. The user should focus on the accuracy of the external 4FSC oscillator (14.318180 MHz) for assessing the burst start point variation.
                        	    
    
                
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    Hello,
    
 
    I have questions about AD723.
    The start point of color burst from AD723 seems to move on AD723 Eval Board (AD723EB rev.B).
    Could you see attached file "Color_burst_AD723_rev01.xlsx" for more detail?
    
 
    Thank you!
    
 
    Best regards.
    Tamu
    
			
    
			
									
		                             
                        

    
    
                                            
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							Color_burst_AD723_rev01.xlsx
					        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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                on May 29, 2013 11:34 AM
            
            
						
			            		
        
		
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        Hello,
        
 
        Thank you for your reply.
        
 
        There are monitors that generate chroma not by referring input color burst but by referring color burst generated by itself from HSYNC.
        When output from AD723 (has the moving burst) connects to the monitor, it seems that we can see abnormal chroma on the monitor.
        
 
        According to your comment,
        I think asynchronous 4FSC causes moving the start point of color burst.
        Is it right?
        
 
        How much phase does the start point of color burst move at the maximum?
        Is it one subcarrier (3.579545MHz for NTSC)?
        
 
        Thank you!
        
 
        Best regards.
        Tamu
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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                on May 29, 2013 11:34 AM
            
            
						
			            		
          
		
										0
					
	
          

		
		
          
		
          
                                
                                                            
          
					
          Hello,
          
 
          Thank you for your reply.
          
 
          There are monitors that generate chroma not by referring input color burst but by referring color burst generated by itself from HSYNC.
          When output from AD723 (has the moving burst) connects to the monitor, it seems that we can see abnormal chroma on the monitor.
          
 
          According to your comment,
          I think asynchronous 4FSC causes moving the start point of color burst.
          Is it right?
          
 
          How much phase does the start point of color burst move at the maximum?
          Is it one subcarrier (3.579545MHz for NTSC)?
          
 
          Thank you!
          
 
          Best regards.
          Tamu
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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