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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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							FormerMember
					
      
		
      
		    
		    		    
			
				
									FormerMember
							        
			
			
			
    
            
						
                            
            
            				
            
                on May 28, 2013 4:47 PM
            
            
						
			            		
    
		
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    Hi Tamu,
    
 
    According to SMPTE-170M the color burst is suppose to start 19 subcarriers after the falling edge of Hsync.  One subcarrier is ~226ns.  Depending on the phase of the subcarrier the actual count down may begin at slightly different times.  What  is important that the subcarrier begins at approxiametly the right time and last long enough for the monitor to phase lock to the frequency so the correct color can be generated.
    
 
    BTW: nice capture and comparisons on the attachment.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    


	



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							FormerMember
					
      
		
      
		    
		    		    
			
				
									FormerMember
							        
			
			
			
    
            
						
                            
            
            				
            
                on May 28, 2013 4:47 PM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    Hi Tamu,
    
 
    According to SMPTE-170M the color burst is suppose to start 19 subcarriers after the falling edge of Hsync.  One subcarrier is ~226ns.  Depending on the phase of the subcarrier the actual count down may begin at slightly different times.  What  is important that the subcarrier begins at approxiametly the right time and last long enough for the monitor to phase lock to the frequency so the correct color can be generated.
    
 
    BTW: nice capture and comparisons on the attachment.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    





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