I saw the data sheet of the LTC3703 and there was a design example on page 27, i followed the same procedure.
LTC3703 Data Sheet
VIN = 24V to 100V, VOUT = 12V, IOUT(Max) = 10A, f = 250kHz
As per the formula in the data sheet
RSET(kOhm) = 7100/(250 - 25) = 31.5KOhm -> eq1
2. Inductor value for about 40% ripple current at maximum VIN
L = 12/250K*0.4*10(1 - 12/100) = 10.56uH. -> eq2
3. Minimum On-time
ton(min) = 12/(100*250kHz) = 480nS -> eq3
which is above LTC3703's 200ns Minimum on-time.
4. Top and Bottom MOSFET switch
Since the drain of each MOSFET will see the full supply voltage 100V (max) plus any ringing, choose a 125V MOSFET to provide a margin of safety.
PMAIN = 1.32W -> eq4
=1.84 -> eq5
TJ = 70 + 1.84*20 = 106.8
5. Current Limit Resistor
RDS(ON) = (25mOhm)/2 [1 + 0.009(105 - 25)] = 21.5mOhm
IMAX pin voltage = 10*0.0215 = 0.215V
RMAX = 0.215/12uA = 18k -> eq6
6. CIN is chosen for an RMS current rating of 5A (IMAX/2) at 85DegC.
7. For the output capacitor 2 low ESR OS-CON capacitors (18mF) are used.
The LTSPICE model is in progress, i have completed to the below level, the work is still in progress, i also need to choose the MOSFET. But based on the above steps, could you please provide comments.