Precharge bootstrap capacitor for three phase inverter(MOSFET based)

[VV.12]

I want to switch the low side mosfets in a particular manner to charge the bootstrap capacitor in driver IC. I wanted generate three 120 degree phase shifted square pulses of same frequency.

Can three phase shifted signals be generated by timer in MAster Slave mode.?

Any suggestions for precharging boot strap capacitor, whether pulses to be given for charging or continuous signal for a minimal time?