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ADV7180 Not Recommended for New Designs
The ADV7180 automatically detects and converts standard analog baseband television signals compatible with worldwide NTSC, PAL, and SECAM standards into...
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ADV7180 on Analog.com

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(ADV7180)Burst signal level

		
	
				

			

									
					    donadona999s
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Sep 18, 2017 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user reports an issue with the ADV7180 in an automotive application where one unit fails to detect color with a long cable, despite the burst signal level being within the 5% to 200% range (76mVpp). The final answer suggests the ADV7180 may be incorrectly detecting the video standard as NTSC 4.43, and recommends checking if the issue resolves after startup, using fast switch mode, or forcing the video standard. The user will also consider modifying the resistor divider circuit to boost the signal, ensuring it does not exceed 1Vpp.
                        	    

                
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Hi !

 
Our customer have some problem at their application.

 
The project is already MP and it is automotive application.

 
One of their unit was fail at their OEM test line.

 
It looks like there is no color.

 
* Sorry I can't attach the picture here because it include confidential information.

 
We asked them to read back the register.

 
And the different was this.

 

 
So it is not color kill mode.

 
But it look like ADV7180 miss detect the video standard.

 
* Just only one ADV7180 has this problem.

 
   They already did cross check at their PCB.

 
And when they use short cable from camera, The color looks OK.

 
But when they use long cable(5m) , the picture change to no color.

 
The NTSC waveform is this.

 
With short cable.

 

 
With long cable.

 
.

 
It looks burst signal level is very low.

 
So my questions are these.

 
Q1)

 
At ADV7180 datasheet, it says ADV7180 can detect 5%~200% burst signal level.

 

 
I think color burst signal 100% for NTSC is 285mVpp.

 
Does this specification mean ADV7180 can detect the color burst signal if the burst signal level is 285*5%=14.275mVpp even if other signal level is 100% level( Ex. sync signal = 40IRE).

 

Q2)

 
Do you think this problem reason is ADV7180?

 
Q3)

 
Do you have any comment to debug this problem?

 
Our is it faster way send this device to quality team?

 
Best regards

 
Kawa

			

			
									
		                             
                        

    

                                            
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                on Sep 19, 2017 4:43 AM
            
            
						
			            		
    
		
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    Hi Robert 
    
 

    Thank you for your reply.
    
 
    As you said , the device which has problem detect analog input as NTSC4.43.
    
 
    
  
    Does this issue occur directly after startup?
    
 
    
 
    =>I think yes.
    
 
        But I have to confirm this to my customer.
    
 
    
  
    Could you leave the part in this setup for a few minutes to see if the ADV7180 corrects itself? Keep polling User map register 0x10.
    
 
    
 
    => I have to ask this to my customer.
    
 
         Do you mean you are think if our customer leave this device few minutes maybe the problem will fix?
    
 
    
  
    It is also possible that after a few frames the ADV7180 goes back to NTSC-M and determines that it is not able to lock to the color subcarrier. After this point the ADV7180 will set the color kill bit. 
    
  
     
    
 
    
 
    => Do you mean that if ADV7180 detect NTSC-M after few minutes , the status will be NTSC-M and also color kill mode?
    
 
    
  
    Q1) Yes you are correct. It the color subcarrier is below 14.275mVpp before the resistor divider circuit, then the ADV7180 will not be able to lock to the color subcarrier and will output a black and white image. This is true regardless of the Horizotnal sync depth.  I would expect the color kill bit to go high if this were the case.
    
  
     
    
 
    
 
    They are using color kill but the status bit show that ADV7180 didn't detect color kill.
    
 
    Also I asked them to change the color kill detect level by changing the register but nothing changed.
    
 
    
  
    Q2)  Yes if the amplitude of the color subcarrier is too low then the ADV7180 will never be able to lock to it. They could try using an amplifier to boost the signal. They could also try replacing the resistor divider circuit on the ADV7180 with a single 75 Ohm resistor to ground. This will increase the amplitude of the signal to the ADV7180. However they need to ensure that the CVBS signal never exceeds 1Vpp at the input to the ADV7180 or else the signal will become clipped. This will result in video artifacts.
    
  
     
    
 
    
 
    I got it.
    
 
    I will ask them to change the divider circuit.
    
 
    
  
    Q3) I don't think that this is a Failure Analysis issue, but doing the experiments above should give some insight on the issue
    
  
     
    
 
    
 
    I am asking to my customer to check the burst signal peak to peak voltage.
    
 
    If the value is in 5% to 200%, do you think something is wrong in ADV7180?
    
 
    We worried that if we send the sample to ADI , we are not sure that ADI can find the problem inside the device.
    
 
    So I want to ask my customer everything what we can do now and our customer agree that.
    
 
    So if you have any other advice, please let us know.
    
 
    Best regards
    
 
    Kawa
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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Reply

    


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                on Sep 19, 2017 4:43 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    Hi Robert 
    
 

    Thank you for your reply.
    
 
    As you said , the device which has problem detect analog input as NTSC4.43.
    
 
    
  
    Does this issue occur directly after startup?
    
 
    
 
    =>I think yes.
    
 
        But I have to confirm this to my customer.
    
 
    
  
    Could you leave the part in this setup for a few minutes to see if the ADV7180 corrects itself? Keep polling User map register 0x10.
    
 
    
 
    => I have to ask this to my customer.
    
 
         Do you mean you are think if our customer leave this device few minutes maybe the problem will fix?
    
 
    
  
    It is also possible that after a few frames the ADV7180 goes back to NTSC-M and determines that it is not able to lock to the color subcarrier. After this point the ADV7180 will set the color kill bit. 
    
  
     
    
 
    
 
    => Do you mean that if ADV7180 detect NTSC-M after few minutes , the status will be NTSC-M and also color kill mode?
    
 
    
  
    Q1) Yes you are correct. It the color subcarrier is below 14.275mVpp before the resistor divider circuit, then the ADV7180 will not be able to lock to the color subcarrier and will output a black and white image. This is true regardless of the Horizotnal sync depth.  I would expect the color kill bit to go high if this were the case.
    
  
     
    
 
    
 
    They are using color kill but the status bit show that ADV7180 didn't detect color kill.
    
 
    Also I asked them to change the color kill detect level by changing the register but nothing changed.
    
 
    
  
    Q2)  Yes if the amplitude of the color subcarrier is too low then the ADV7180 will never be able to lock to it. They could try using an amplifier to boost the signal. They could also try replacing the resistor divider circuit on the ADV7180 with a single 75 Ohm resistor to ground. This will increase the amplitude of the signal to the ADV7180. However they need to ensure that the CVBS signal never exceeds 1Vpp at the input to the ADV7180 or else the signal will become clipped. This will result in video artifacts.
    
  
     
    
 
    
 
    I got it.
    
 
    I will ask them to change the divider circuit.
    
 
    
  
    Q3) I don't think that this is a Failure Analysis issue, but doing the experiments above should give some insight on the issue
    
  
     
    
 
    
 
    I am asking to my customer to check the burst signal peak to peak voltage.
    
 
    If the value is in 5% to 200%, do you think something is wrong in ADV7180?
    
 
    We worried that if we send the sample to ADI , we are not sure that ADI can find the problem inside the device.
    
 
    So I want to ask my customer everything what we can do now and our customer agree that.
    
 
    So if you have any other advice, please let us know.
    
 
    Best regards
    
 
    Kawa
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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