UCC21222: How many volts is the VBUS limited when using a UCC21222 drives the half-bridge IGBT?

Hi,

That is a complex question, the bus voltage is influenced by a lot of variables, like the creepage, clearance, isolation voltage, PCB materials, and safety standards. The VIOWM spec for this part is 990V, which is upper limit that the part can take continuously across the isolation barrier and over a long period of time. Please take this into account for your application. Typically this part is used in applications with a 400V bus driving 650v FETs, which would be my recommendation. 

Regards,

Krystian