What I said was according to the circuit of FAN7390 in page 3, the two outputs HO(High Side) to drive an IGBT and LO(Low Side) to drive another IGBT, and normally two Output Sides will connected together similar as the last output stage of the amplifier, and they also need the input square waves, if you don't want the clock to drive then why don't you just use the MOSFET to be the driver for IGBT?Still not clear to me what your asking. I'm just wanting to "pre-charge" the bootstrap capacitors of two separate half bridges so the circuit will work when called on. This circuit will be totally sequential, no clock signal involve, so the bootstrap caps need to be pre-charged.
If you just want the bootstrap function and you want two half bridges working separated then you will need the RBoot, DBoot and CBoot, you can try to pull the inputs HIN and LIN to High, the ic was designed to working with clock, so if you choose to work with your own way then you just try it.
You may refer to the Application Note below --
Design and Application Guide of Bootstrap Circuit for High-Voltage Gate-Drive IC_AN-6076.pdf