Probably they won't fire you if you give 30 day notice too, cause it's some decent work on management side to prepare documents for involuntary termination, espically if they are large company . They have to make sure they are not exposing them self to libiality and law suit. Unless there is something exposed during your background check and they don't want you on their campus or something is there related to criminal charges.

But also down side of volutntary termination is that you can't claim unpmoyment benefits.