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LT4293 Recommended for New Designs
The LT4293 is an LTPoE++/IEEE 802.3af/at/bt-compliant powered device (PD) interface controller. The T2P output distinguishes between LTPoE++ and IEEE 802...
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LT4293 on Analog.com

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[LTPoE LT4293] Implementation and configuration when LT4293 works Ultramode



		

			

									
					    feelyoursoul
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Feb 18, 2021 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    To whom may it concern,
    

    

    Hi I'm HS.
    

    

    LTPoE PSE(LTC4279) works in ultamode and it will source power to LTPoE PD(LT4293).
    

    

    But the datasheet denotes that LT4293 supports up to 90W.
    

    

    I would appreciate if you elaborate how to configure and design the LT4293 with respect to ultra power mode and DCDC .
    

    

    Thank you!
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		
	
    















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
			                            
                        
                on Mar 4, 2021 2:04 AM
            
            
					
      
	
      

		
		
      
					
      Hi HS,
      

      UltraPWR is a specific mode of the LTC4279. It should only be used in a closed system. It will aggressively power any valid PDs, and it will set the current limit to 2950mA typical. The LT4293 will identify an LTC4279 in UltraPWR mode as an LTPoE++ PSE, but since this is a closed system the PD could assume it will always receive an UltraPWR allocation.
      

      An UltraPWR PD should have a very low RDSON Hotswap FET, and we highly recommend using an ideal diode bridge such as the LT4321 in this application, with low RDSON FETs. The PSMN4R8-100BSE or similar low RDSON FET with good SOA can be used for the Hotswap FET, and the PSMN040-100MSE should work for the ideal diode FETs.
      

      Best Regards,
      

      Eric
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
			                            
                        
                on Mar 4, 2021 2:04 AM
            
            
					
      
	
      

		
		
      
					
      Hi HS,
      

      UltraPWR is a specific mode of the LTC4279. It should only be used in a closed system. It will aggressively power any valid PDs, and it will set the current limit to 2950mA typical. The LT4293 will identify an LTC4279 in UltraPWR mode as an LTPoE++ PSE, but since this is a closed system the PD could assume it will always receive an UltraPWR allocation.
      

      An UltraPWR PD should have a very low RDSON Hotswap FET, and we highly recommend using an ideal diode bridge such as the LT4321 in this application, with low RDSON FETs. The PSMN4R8-100BSE or similar low RDSON FET with good SOA can be used for the Hotswap FET, and the PSMN040-100MSE should work for the ideal diode FETs.
      

      Best Regards,
      

      Eric
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
				
						
						
				
				
		
		
      
			
		
      
	
      

      

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