Hello, I've re-created the UCC28720-EVM on my own circuit card, emulating everything "almost" exactly - placement and layout is very very close. I am even using the Wurth transformer called out in the design. Only difference is the transistor Q1, which I chose ST Micro ST13003, because the transistor in the original design shows to be EOL.
I am targeting a 5W USB charger.
I get no output voltage, and indeed no VS either. VDD is a nice triagngle wave between 13V and 20V, which I'm assuming is the device trying to charge and turn on through the HV port? But, because there is no VS voltage the part isn't coming on?
Please let me know what else to try and measure - a I said I did everything like the EVM sample circuit.