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AD8145 Production
The AD8145 is a triple, low cost, differential-to-single-ended receiver specifically designed for receiving red-green-blue (RGB) video signals over twisted...
Datasheet
AD8145 on Analog.com

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AD8145 Reference Schematics Required

		            
		

			

									
					    qt5nt6
					
							


			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 20, 2011 
				
			
			
		
    
		
     
				
		
    
		    		    
		    
		    	
			
    Hello Experts,
    
 
             I am new user of Analog devices and I need your help in designing my system. I am in urgent need of AD8145 reference schematics; kindly share it as I could not find it on the internet.
    
 
    Also i need to know the following:
    
 
    a)       The Differential input of AD8145 is 3 that is VGAR+, VGAR-, VGAB+, VGAB-, VGAG+, VGAG- please suggest how can i convert the differential HSync and Vsync signals through the same chip? Do I need to use another chip for converting these HSync and VSync signals or I can use the same chip, please suggest how can I do that.
    
 
    The digital signals from AD8145 is than feed to ADV 7403 for further digitization where I need Hsync and Vsync.
    
 
    Your kind help and expert suggestions are highly required. Please find some time to reply me.
    
 
    Take care and have a nice day.
    
 
    Kloon
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Video Amplifiers and Analog Video Functions
                
                                                    
                 CAT-5 Video Receivers
                
                                                    
                 ad8145
                
                                
            
    
    
    

		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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							FormerMember
					
      
		
      
			
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									FormerMember
							        
			
			
			
    
            
						
                            
            
            				
            
                on Mar 28, 2011 4:09 PM
            
                                    
					
    
	
    

		
		
    
					
    Hi Kloon,
    
 
    1) You should terminate the incoming video signals.  Check out Figure 37 and 38 on the data sheet.  If you're running twisted pair then the nominal termination should be 100 Ohms.  If you don't have the correct termination all kinds of problems will exist.
    
 
    2) Decoupling capacitors are required.  Fig 37 and 38 show 0.01uF although I would recommend using 0.1uf plus a 0.01uF (ceramic, X7R are good) in parallel as close to the supply pins with the0.01uF being the closest component.  The capacitors should connect directly to the ground and power planes if  possible.  The bigger these loops are, the more noise will get injected into the receiver.  A bulk capacitor (around 10-33uF electrolytic) for the supplies is always good.  It should be of the low ESR type.
    
 
    3) ESD protection depends on you environment,  Check out the input clamping on page 17 for recommendations.  Personnally I would never design a product with out ESD protection or for common mode voltage clamping.  If either of these exceed the devices rating it can and will damage the part.
    
 
    4) Assuming you are going with a 75 Ohm single ended impedance the output should have a gain of 2 with a 75 resistor in series with each output.  It really depends on the video sink, connector and wiring to the sink.  RGB out are analog signals, not digital. 
    
 
    5) If you're not using the comparators I suggest that you tie the positive input thru a 1k resistor to +5V and the negative input through a 1k resistor to -5V.  As a general rule of thumb never let comparator or amplifier inputs float, they'll have a tendency to oscillate causing all kinds of problems like extra noise and/or extra heat dissipation.
    
 
    6) Tying Vref to ground is OK.  You might want to tie it to ground with a zero Ohm resistor in case in the future you want to shift the reference voltage, you can remove the zero Ohm resistor and inject what ever voltage you want.
    
 
    7) Don't select the gain through the connector.  This will cause all kinds of problems.  If you want to change the gain I'd put a zero Ohm resistor on the gain pin to ground, so for a gain of 2, install the resistor else leave it out for a gain of 1.  The gain loop must be very cleam and very close to the part.  Again review the layout information for the AD8143.  If you absolutely must have a selectable gain then there are other ways to do this.
    
 
    Pay very close attention to the PCB layout.  I'd look at the AD8143 for a recommended layout.
    
 
    Hope this helps
    
 
    Guenter
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    


	



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							FormerMember
					
      
		
      
			
													0
							
			
				
									FormerMember
							        
			
			
			
    
            
						
                            
            
            				
            
                on Mar 28, 2011 4:09 PM
            
                                    
					
    
	
    

		
		
    
					
    Hi Kloon,
    
 
    1) You should terminate the incoming video signals.  Check out Figure 37 and 38 on the data sheet.  If you're running twisted pair then the nominal termination should be 100 Ohms.  If you don't have the correct termination all kinds of problems will exist.
    
 
    2) Decoupling capacitors are required.  Fig 37 and 38 show 0.01uF although I would recommend using 0.1uf plus a 0.01uF (ceramic, X7R are good) in parallel as close to the supply pins with the0.01uF being the closest component.  The capacitors should connect directly to the ground and power planes if  possible.  The bigger these loops are, the more noise will get injected into the receiver.  A bulk capacitor (around 10-33uF electrolytic) for the supplies is always good.  It should be of the low ESR type.
    
 
    3) ESD protection depends on you environment,  Check out the input clamping on page 17 for recommendations.  Personnally I would never design a product with out ESD protection or for common mode voltage clamping.  If either of these exceed the devices rating it can and will damage the part.
    
 
    4) Assuming you are going with a 75 Ohm single ended impedance the output should have a gain of 2 with a 75 resistor in series with each output.  It really depends on the video sink, connector and wiring to the sink.  RGB out are analog signals, not digital. 
    
 
    5) If you're not using the comparators I suggest that you tie the positive input thru a 1k resistor to +5V and the negative input through a 1k resistor to -5V.  As a general rule of thumb never let comparator or amplifier inputs float, they'll have a tendency to oscillate causing all kinds of problems like extra noise and/or extra heat dissipation.
    
 
    6) Tying Vref to ground is OK.  You might want to tie it to ground with a zero Ohm resistor in case in the future you want to shift the reference voltage, you can remove the zero Ohm resistor and inject what ever voltage you want.
    
 
    7) Don't select the gain through the connector.  This will cause all kinds of problems.  If you want to change the gain I'd put a zero Ohm resistor on the gain pin to ground, so for a gain of 2, install the resistor else leave it out for a gain of 1.  The gain loop must be very cleam and very close to the part.  Again review the layout information for the AD8143.  If you absolutely must have a selectable gain then there are other ways to do this.
    
 
    Pay very close attention to the PCB layout.  I'd look at the AD8143 for a recommended layout.
    
 
    Hope this helps
    
 
    Guenter
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    





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