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LTC4270 Recommended for New Designs
The LTC4270/LTC4271 chipset is a 12-port power sourcing equipment (PSE) controller designed for use in IEEE 802.3at Type 1 and Type 2 (high power) compliant...
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LTC4270 on Analog.com

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Artwork of LT4270



		

			

									
					    Damon Ahn
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 22, 2020 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    hi team
    

    My customer asked me the following.

    600 mA load applied to the poe output, measured at 620 mA.
    

    This is the reading of the register.
    There is a difference from the actual load of the electric loader.
    EVboard is measured in the same value as the electric loader.
    

    If you raise the load value a little more, the board is shutdown.
    

    Looking at PCB designs, the difference in current measurement of output in the order that is close to the device decreases slightly.
    

    

    The circuit diagram is the same as the LTC4270 EVB.
    

    https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/DC1840C.pdf
    My customer has a strong suspicion of artwork.
    Please review the circuit diagram and Artwork.
    

    Also, could you tell me if there is a mandatory in the artwork?
    

    PDF
    

    3857.poe_pcb.zip
    

    Thanks
    

    Damon
    
										

    
				add mandatory in the artwork
    
[edited by: Damon Ahn at 7:59 AM (GMT 0) on 6 Jul 2020]
				
    
						
			        
		
    

				
						
        

    
    Tags: 
                                            
                 PoE Power Sourcing Equipment (PSE)
                
                                                    
                 LTC4270
                
                                                    
                 Power-over-Ethernet (PoE) Interface Controllers
                
                                
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 13, 2020 1:14 AM
            
            
					
      
	
      

		
		
      
					
      Hi Damon,
      

      Can you confirm the circumstances of the test you described? Is this a Class 4 power allocation that is drawing the 600mA / 620mA? This is right up to the maximum of the specification. The LTC4270/LTC4271 will cut off the current when it senses a voltage between 152mV and 168mV across the 0.25 Ohm sense resistor, this means a current as low as 608mA could cause the port to be disconnected.
      

      In regards to the artwork on the schematic, yes, it is important. The twelve sense resistors must be kelvin sensed and they all share the same low-side sense point. Please review the DC1840C Demo Manual and Layout files for an example layout for the sense resistors.
      

      https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/DC1840C.pdf
      

      

      Best Regards,
      

      Eric
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Jul 13, 2020 1:14 AM
            
            
					
      
	
      

		
		
      
					
      Hi Damon,
      

      Can you confirm the circumstances of the test you described? Is this a Class 4 power allocation that is drawing the 600mA / 620mA? This is right up to the maximum of the specification. The LTC4270/LTC4271 will cut off the current when it senses a voltage between 152mV and 168mV across the 0.25 Ohm sense resistor, this means a current as low as 608mA could cause the port to be disconnected.
      

      In regards to the artwork on the schematic, yes, it is important. The twelve sense resistors must be kelvin sensed and they all share the same low-side sense point. Please review the DC1840C Demo Manual and Layout files for an example layout for the sense resistors.
      

      https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/DC1840C.pdf
      

      

      Best Regards,
      

      Eric
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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