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ADV7343 Not Recommended for New Designs
The ADV7342/ADV7343 are high speed, digital-to-analog video encoders in a 64-lead LQFP package. Six high speed, 3.3 V, 11-bit video DACs provide support...
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ADV7343 on Analog.com

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ADV7343 Test Pattern Issue



		

			

									
					    ranaya
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 5, 2017 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi All, We're using ADV7343 video encoder to convert 24bit RGB video to a single ended CVBS signal. For testing first we generated the test patterns as per the data sheet by successfully writing I2C data. But the LCD display at the other end does not have a sign of the video signal (nor for 24bit RGB signal). I'm pretty sure that the I2C writing and register settings are okay, specifically the following addresses loaded with the bold color values :
    
 
    0x17 --> 0x02
    
 
    0x00 --> 0xFC 
    
 
    0x82 --> 0xC9 
    
 
    0x84 --> 0x40
    
 
    The retrieved CVBS signal from DAC4 (low drive) for the test pattern is shown below :
    
 
    And the schematic we use is attached herewith. A 27MHz of clock signal is fed to the CLKIN_A of the encoder !
    
 
    What could cause this issue ? I read somewhere that a termination resistor has been used to workaround a similar issue. Any suggestions would be appreciated !
    
 
    Thanks in Advance
    
 
    Anuradha
    
 
    PS: More to this, I checked a BOSCAM with the same LCD (that's SEETEC) through CVBS. The screen displays the camera input without any issue. 
    
								
    

				
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      •  Analog Employees  
      
            
			                            
                        
                on Jan 18, 2017 6:09 PM
            
            
					
      
	
      

		
		
      
					
      Hi Anuradha,
      
 
      To answer your questions:
      
 
      1. So according to what you say, the timing should be compliant with NTSC standard, not the lcd parameters ? I am using a 800x480 generic lcd panel from SEETECH. 
      
 
      [AP]: Correct. The Encoder does not perform scaling of any kind so the timing you wish to see at the output should be the timing you supply at the input. The list of resolutions supported by the encoder can be found on p5 of the datasheet. Any resolutions outside this list are not supported.
      
 
      2. According to the datasheet, the sync signals should be in 'active low' mode, in otherwords the inverted version of the signals in the oscilloscope view right ? 
      
 
      [AP]: Correct
      
 
      3. Where can I find these full timing parameter list for NTSC 525i ?
      
 
      [AP]: NTSC is a very common analog video standard, timing of all the different variants can be easily obtained online. 
      
 
      Best Regards,
      
 
      Anthony
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Jan 18, 2017 6:09 PM
            
            
					
      
	
      

		
		
      
					
      Hi Anuradha,
      
 
      To answer your questions:
      
 
      1. So according to what you say, the timing should be compliant with NTSC standard, not the lcd parameters ? I am using a 800x480 generic lcd panel from SEETECH. 
      
 
      [AP]: Correct. The Encoder does not perform scaling of any kind so the timing you wish to see at the output should be the timing you supply at the input. The list of resolutions supported by the encoder can be found on p5 of the datasheet. Any resolutions outside this list are not supported.
      
 
      2. According to the datasheet, the sync signals should be in 'active low' mode, in otherwords the inverted version of the signals in the oscilloscope view right ? 
      
 
      [AP]: Correct
      
 
      3. Where can I find these full timing parameter list for NTSC 525i ?
      
 
      [AP]: NTSC is a very common analog video standard, timing of all the different variants can be easily obtained online. 
      
 
      Best Regards,
      
 
      Anthony
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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