Having transferred the 'Synchronous Rectification' circuit from the datasheet to a PCB, I find that it doesn't seem to work. Plugging in a POE cable causes a voltage between UVLO and UVLORTN of 2.7V, which I think means that it was correctly recognised as a PD. My understanding is that the next step involves RTN being 1.5V below VEE, which doesn't seem to happen. There's mention of a charging load capacitor that has something to do with this but no description of where this capacitor is so I might have missed something.
I notice that VCC to local ground is 7.8V, COMP is seeing a sawtooth waveform of around 1.25V mean and that OUT is emitting a series of pulses at ~250kHz. I mention this because I might have completely misunderstood the order in which the IC starts up and the actual issue might be something else. I should clarify that there appears to be no significant voltages on the other side of the transformers and total output is zero volts.
Obviously there's a mistake or a fault somewhere, could anyone help me by pointing out where it's likely to be?
Thanks for your time.