We are using the LT4293 for 90W PoE, along with the LT4321 ideal diode bridge. The circuit works normally at 25C ambient temperature. At around 55C ambient temperature, the output voltage shuts off unexpectedly. For this test, the PoE circuit is sourcing 90W into a test load.
Monitoring the signals during the expected shutdown reveals the following sequence of events:
1) HSGATE (violet) starts dropping, from ~10V above HSSRC (Teal) to ~0V above HSSRC (Teal) in about 10uS
2) This causes the HS MOSFET to turn off, and the output voltage (Teal) to fall. The HS Mosfet drain (Dark blue) increases slightly because the load was removed.
This behavior would be consistent with the overtemperature protection on the LT4293 kicking in and pulling HSGATE down, but the highest temperature visible using a thermal camera is about 60C.... way below the LT4293's rated 125C.