DC2583A (LT4294) does not supply enough power to the load

Question

I've arranged the DC2583A (LT4294) and DC2660A as DCDC (LT8646S) boards as shown: 
 
 Then I've connected the SW-525 PoE switch + 48V/100W Power Supply and an electronic load for the LT8646S 5V output. 
 
 Jumper selection are set to JP11 and JP12 (40W PD Class 5) 
 PoE Auxiliary input is not used (left unnconnected) 
 LT4294 PWRGD is connected to LT8646S EN enable pin 
 
 The problem is I'm not able to get 5V@8A (40W) from the whole system as expected. In my case the maximum power I can deliver to the load is 22W. Why? 
 Any help from ADI support? 
 regards, gaston

EHorsma · Accepted Answer

Can you measure the voltage or waveform of the /T2P pin? It sounds like your PoE switch is only allocating 25.5W of power to your PD. You can confirm the number of classification events by looking at the /T2P pin. If it is near zero volts, then the PSE is providing three or two classification events instead of four that indicates it has allocated 40W to this PD. 
 Best Regards, 
 Eric)

Electronic Design Services - PartnerZone

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DC2583A (LT4294) does not supply enough power to the load