UCC28700 Designed, application in Low Vin 40VDC~56VDC

Hi all,

I currently use UCC28700 to design DC/DC power
spec as below
Vin = 40VDC~56VDC, Vout = 12VDC, Iout = 1A,
fs = 100kHz,
NP/NS = 7~9,

But need consider Brown in/out problem, and VDD Start-Up Resistance RSTR
Can suggest me how to first consider designed parts, thanks.