We busted EPC2034, MP6908 along with TPS724xx device in an implementation using UCC28782 controller.
It gives output as desired: but very fast , all secondary ICs popped!
Pl see the schematic screenshot attached.
The reason for the convoluted biasing of MP6908 is the datasheet does not specifically give any table for VG output values!
So we suspected that with HVC at any unknown voltage, VDD max could be 9V which is clear from datasheet. But nowhere any mention is made for VG value. Since they only show applications with MOSFET, most of which will take 12V, we assumed VG will be 9V- not acceptable for EPC GaN.
So we drop Vout from 20V to 5V & set up MP6908 with 5V.
Clearly, TPS724xx LDO cannot sustain charging current to VDD.
We won’t have to use this scheme if VG pin value under all VDD conditions is specified to be 5V.
Any help will be highly appreciated.